Innovations for Economic and Environmental Improvement

#### **Chapter 4**

## Innovative Greenhouse to Improve Economic and Environmental Conditions

*Zainab Abdel Mo'ez Mansour Embaby*

#### **Abstract**

Together with the World Bank and the Food and Agriculture Organization (FAO), a number of international organizations are promoting innovation in agricultural systems to combat natural disasters like extreme weather, drought, floods, rising sea levels, increased snowmelt, and changes in the amount and timing of water used for irrigation. The impacts of climate change on food security are undeniably significant, and they are expected to get worse over the coming years as a result of population growth, economic development, urbanization, and the recurrence of natural disasters. In today's agribusiness, particularly horticultural agribusinesses such as vegetables and decorative plants, climate-smart greenhouse is not a novel concept. In terms of GHG (greenhouse gas) emissions, CSA (Climate Smart Agriculture) can contribute. These days, climate-smart greenhouse (CSG) can actually connect adaptation and mitigation at all scales and helps farmers take the lead in combating climate change. The research on CSG emphasizes the need for innovative thinking to harmonize policy and practices in a way that is complementary. Additionally, CSG has to have a better grasp of how well-equipped the consultants or extension services are in each nation to assist with training farmers in climate-smart practices. Additionally, new financial tools are required to enable global, national, and local transformations.

**Keywords:** greenhouse, climate change, food security, adaptation, mitigation, innovative thinking, climate smart emissions, climate smart agriculture

#### **1. Introduction**

The world is currently dealing with a difficult, complex, but solvable set of issues as part of its ambitious attempt to achieve self-sufficiency in food production. Climate change modifies agricultural production and food systems, posing hazards of vulnerability and unpredictability to farmers and those who create policy. Planning for adaptation can take into account scientific data from both assessments of adaptable capability and estimates of climatic consequences, **Figure 1** ([1], pp. 8537-8362) clarified Impact approaches ([2], pp. 2775-2789; [3], pp. 607-610; [4], pp. 4422-4443). In view of analyzing global climate forcings and circulation models, they suggested that the main factors

#### **Figure 1.**

*Impact and capacity approaches to adaptation planning. Source: https://www.researchgate.net/figure/impactand-capacity-approach.2013.*

influencing crop yield are the connections between simulation and real-world adaptation to comprehend and predict climate change.

Climate change is harmful. The studies [5, 6] affirmed that climate change and variability (CCV) affect crop harvesting, including decreased rainy days, prolonged dry spell, sea-level rise, drought frequency and severity, heat stress, wind, pest, and disease outbreaks activities resulting in changes in rainfall patterns around the world with increasing flood. According to United Nations Environmental Protection Agency [7], climate forcing refers to a change in the Earth's energy balance, and a variety of natural and human variables can affect the Earth's energy balance and contribute to climate change. Burning fossil fuels, destroying forests, and preparing land for towns, roads, and farmland are all examples of human activity. It was concluded that all of these actions contribute to the atmospheric emissions of greenhouse. However, the Intergovernmental Panel on Climate Change [8] predicts that global warming will exceed the 1.5C upper limit this century, without rapid and significant cuts in greenhouse gas emissions. **Figure 2** clarifies adaptation plans and actions that keep global warming to 1.5 degrees Celsius with little to no overshoot ([8], pp. 13-14).

A chart (**Figure 2**) shows GHG emission reduction needed to keep 1.5 degrees C within reach. (IPCC AR6). Since fossil fuels are the primary source of GHG emissions and one of the causes of global warming, the phase-out of these fuels must be accelerated throughout society. Climate change impacts on agriculture will make it difficult to meet the key Sustainable Development Goals (SDGs) of ending hunger, achieving food security, and ensuring sustainable food production systems by 2030. In the longer term, facing the challenges to the quantity and quality of foods, urgent action is urgently needed to achieve food security. Agriculture is the affected sector of food security in all dimensions, especially food availability, through extreme weather events. On the other

#### **Figure 2.**

*GHG emission reductions consistent with 1.5°C from 2019 emissions to 2040 emissions. Source: [9].*

hand, climate extremes are considered one of the challenges to the quantity and quality of foods people can access. Food Agriculture Organization ([10]; [11], pp. 521-546) released agriculture is a sector contributing both carbon emissions and capture uniquely susceptible to climate and extreme weather. In addition, agricultural innovations can combat climate change through both mitigation and adaptation (World Bank group [12]). To accommodate climatic conditions, agricultural activities will need to be modified to reduce greenhouse gas (GHG). Climate change is the only one of the major forces which will affect the future of agriculture. Others include population growth and increases in income as well as changes in human capital, knowledge, and infrastructure. Much of the changes in agriculture will stem from new innovations. The previous studies [13, 14] affirmed the role of Climate Smart Agriculture (CSA) in response to climate change. CSA plays a prominent role in facing increased demand for food. The CSA approach has been considered an essential mechanism for achieving the Sustainable Development Goals.

#### **2. The significance of the chapter**

With a share of 560 m3 of water per person, Egypt has become one of the most waterscarce nations in the world (United Nations International Children's Emergency Fund [15]. Additionally, Egypt may soon run out of water, with climate change being the primary cause. CSG contributes significantly to the community's revenue in rural areas, even in the absence of population growth and the race to enhance agricultural productivity. As a result, the emphasis of this analysis is on the significance of climate-smart greenhouse (CSG) as a cutting-edge remedy for food insecurity both globally and in Egypt.

#### **3. Methodology**

The current review study focused on numerous data found in English-language peer-reviewed papers worldwide with searches using terms relevant to CSA practices and CSA outcomes. The objective of this ongoing review is to give a first appraisal of the evidence for CSG as an innovative one contributing to improving economic and environmental conditions. This review highlighted Egypt, aiming to offer effective supporting information to decision-makers and policy makers as well as overall professionals and end-users in introducing new techniques, artificial intelligence, and communication infrastructure in agriculture sector. Then it focuses on:


#### **3.1 Development of greenhouses and technologies worldwide**

A number of significant factors, including population growth; urbanization; wealth development; changes in human capital, knowledge, and infrastructure; as well as climate change, have resulted in the introduction of novel characteristics to traditional agricultural farming methods [16]. The study conducted to release in Qatar to boost the local food and achieve its National Vision 2030, particularly the food security, environmental, and sustainability challenges, focused on differentiating innovations based on their forms, such as technological, managerial, and institutional innovations, in line with the economic growth hypothesis. It also clarified that technical innovation takes the form of new tools, mechanical innovations (like tractors), biological innovations (like seeds), chemical innovations (like fertilizers), better practices like Integrated Pest Management, enhanced pruning methods, and crop rotation serve as better practices' equivalents to managerial innovations, which are not physically represented in capital. Institutional innovations can refer to novel organizational structures, like cooperatives, and trading agreements, like futures markets and contract farming [17]. Due to the variety and irrationality of the effects of climate change, there are many different sorts of innovations. Sapkota et al. [18] propose that a way forward to address food security, climate change adaptation, and mitigation challenges faced by current agriculture is to widely promote suitable conservation agriculture (CA) practices by integrating them into national agriculture development strategies. The benefits of CA in terms of food security, climate change adaptation, and mitigation have been demonstrated in the Indo-Gangetic Plains (IGP) based on the findings of numerous farm and station trials. Due to greater accessibility and availability of food, there will be an increase in farm productivity and income for household food security. Similar improvements in crop yield; higher energy, water, and nutrient usage efficiency; as well as the least amount of heat stress show

#### *Innovative Greenhouse to Improve Economic and Environmental Conditions DOI: http://dx.doi.org/10.5772/intechopen.113335*

adaptability to climate change and unpredictability. It's still early to adopt and integrate new CSA technologies, like drones, and big data applications, including artificial intelligence and machine learning. Although multidisciplinary CSA research in Africa has advanced significantly, there is still a vacuum in the application of policies. Barasa et al. [19] made it clear that in order for the sub-Saharan region to achieve benefits from CSA, concrete steps must be taken to, among other things, encourage farmers to implement context-specific CSA technologies, make funds available to them, encourage investments, and create policy frameworks that support CSA.

#### **3.2 Overview of effects of climate change on agriculture in Egypt**

Along with others, [20] stated in light of the severe effects of climate change on the agricultural sector in Egypt, it was made clear that climate adaptation is a major national priority to preserve food security. In order to address the dispersion of funding schemes, it was further underlined that the Ministry of Environment should create a specific Climate Financing and Resource Mobilization Unit for adaptation in agriculture. International Monetary Fund (IMF) [21] clarified that as a result of climate change, the nations in the Middle East and Central Asia (ME&CA) have similar macroeconomic policy problems. The past economic effects of the region's main climate stressors—lower growth, shifting GDP and employment shares, and larger fiscal and external imbalances—will likely get worse with the predicted intensification of the region's climate stressors, especially where current weaknesses in climate resilience persist. Therefore, even under the assumption of mild global warming and ambitious global mitigation measures, regional policymakers must acknowledge that climate change would have an influence in the past three decades: variations in temperature and precipitation patterns have decreased per capita earnings and changed the sectoral composition of the economy, as econometric study claims. However, climate adaptation is an urgent priority for the region and requires significant additional spending and hence financing.

#### **3.3 CSG and emissions reductions**

The studies [6, 19] agreed upon empirically identifying factors that affect the intensity of participation in emission practices in Ghana and determining if adopting climate-smart agriculture practices decreases participation in emission practices. The study used inverse-probability-weighted regression adjustment (IPWRA) to achieve its goals, and empirical findings indicated that CSA can be applied as a method to lower GHG emissions from agricultural sources. Additionally, the government should take into account CSA technology installation as part of its policy. Also, it confirmed that the methodological approach is regarded as a robust one because it produces estimates that are nearly uniform across the IPWRA, the generalized Poisson model, and both Poisson and Poisson models. On the other hand, the studies affirmed that CSA increases profit, and minimizes vulnerability by reducing greenhouse gas emissions, by smart and advanced technological knowledge.

#### **3.4 Economic and environmental benefits of application CSG**

A case of Villages Around Songe-Bokwa Forest, Kilindi District, Tanzania [22] revealed that there was rainfall variability, shift in rainfall patterns, and increase in temperature in the study area. **Figure 3** shows impacts of climate change on household

**Figure 3.** *Impacts of climate change on households. Source: The results of the study Nkumulwa & Pauline [22].*

livelihoods, showing that 38.7, 18.6, and 12.8% of households perceived that climate change variability (CCV) resulted in food shortage, decreased income, increased disease outbreaks, youth emigration, and rise of food price.

A notable increase in crop harvest after farmers engaged in CSA was recorded in **Table 1**. The findings show farmers were food secured and gained more income through sales of their crops, and they used part of their income for paying school fees, buying production tools, supporting medical services, purchasing livestock, and paying for house construction. Consequently, CSA farmers became more resilient to negative climate effects. The study used random and purposive sampling designs to collect quantitative and qualitative data. Data in this study on the contribution of CSA to farmers livelihoods. Data in this study, on the contribution of CSA to farmers livelihoods, was subjected to analysis of variance(ANAVO) using the SPSS software package for Windows. Were more food secured and gained more income. In response to the decline in crop productivity and deforestation, the findings showed that farmers engaged in CSA practices such as agroforestry (i.e. agrisiliviculture), conservation agriculture, integrated nutrient management, and agronomic techniques such as cover crops, improved crop varieties, drought-resistant crops, intercropping, and crop rotation. Also, the production of crops after the introduction of CSA was higher than before the practice (α = 0.05, df = 5, p = 0.028).


#### **Table 1.**

*Comparison of crop harvest per acre in a bag of 90 kg for climate-smart farmers before and after engaging in CSA interventions.*


#### **Figure 4.**

*Smart agriculture benefits over traditional agriculture. Source: https://www.researchgate.net/publication/35782463*

Benefits of CSG include scheduling productions so as to maximize output, improve quality, and minimize waste. **Figure 4** shows the tremendous benefits of smart agriculture compared to traditional agriculture. ([23], pp. 1-45) concise the benefits of CSA as water conservation; optimization of the use of fertilizers and pesticides making products are more toxin-free and nutrient-rich. In addition to, the benefits include increased crop production efficiency; reduction of operational costs; opening up of unconventional farming area in cities, deserts; lower greenhouse gas emissions; reduced soil erosion; real time data availability to farmer. Also, production and distribution of food will be in economically efficient way as never before.

The automation of greenhouses has advanced significantly in recent years, largely due to environmental sensors that are essential to its programmed operation. In fact, modern sensor technologies integrated into smart greenhouse solutions are now frequently utilized to track the environment for crop growth. Using DHT 11 sensors to collect temperature and humidity data, it is possible to compare the conditions inside and outside a smart greenhouse for fruitful crops. While assuring effectiveness and sustainability, the integration of smart systems can decrease reliance on labor and boost profitability.

#### **4. Application of climate-smart greenhouse and challenges**

According to a survey, the majority of studies concurred on the key attributes of the smart greenhouse. It is [2, 16, 23] clarified a climate-controlled indoor space

designed specifically for plants. It is a self-contained farm monitoring environment with IoT, AI, and ML technologies integrated. The farm is shielded from wind, storms, and floods. It boosts productivity effectiveness without requiring manual labor. For humans to have access to sustainable food sources, the smart greenhouse is crucial. The climate-smart greenhouse (CSG) application is a structural system used to develop a range of fruits, vegetables, flowers, and other plants that need particular temperature and humidity conditions to thrive. This is required so that the smart greenhouse can adjust the environment to meet the needs of its plants. To track the movement of dangerous insects that have entered the greenhouse farm, we employ a motion sensor. We can reduce insecticide waste by using insecticides just where they are identified, avoiding unnecessary spraying in other areas. Nkumulwa and Pauline, [22]; Sapkota et al. [18] highlighted the main factors: high population growth, and limited support from the government that drive farmers to practice unsustainable farming practices. Food security represents one of the agricultural productivity challenges. It is the greatest risks that requires implementing CSA as a proposed solution. On the other hand, to address triple challenges of present agriculture: food security, climate change adaptation, and GHG mitigation, wide-scale promotion of CA-based production system could be an important government strategy. Contrasting views about implementation indicate that CSA's focus on the "triple win" (adaptation, mitigation, and food security) needs to be assessed in terms of science-based practices [24].

#### **5. Implications of climate-smart greenhouse research**

CSG focuses especially on agriculture. It refers to an approach that sustainability increases productivity, enhances resilience (adaptation), reduces GHGs (mitigation) where possible, and enhances achievement of food security and development goals. CSA approach assessment is based on science-based practices. CSG can only be achieved in the long term after understanding and mitigating any challenges as the new paradigm shifts. Innovative thinking is required in order to reconcile policy and practices along complementary lines. CSG implementation also faces a better understanding of the capacity of extension services or consultants in each country to help train farmers on climate-smart practices. It is well-known that innovative technologies require specific extension support, sometimes not readily available. It's also important to comprehend the attitudes and behaviors of farmers regarding CSA activities. It all boils down to whether or not individual farmers are prepared to make the necessary adjustments or have the skills and knowledge to do so. Additionally, new financial tools are required to facilitate changes at all scales, including local, national, and global [20]. Along with the UNFCCC negotiations and the COP27 - Agriculture & Climate Change, new funding mechanisms are being developed for both climate change and agriculture. The recently concluded COP27 (November 23) of the United Nations Framework Convention on Climate Change (UNFCCC) offers a chance to start the shift to regenerative agriculture, under a whole food systems approach, which can bring various benefits for climate, health, resilience, biodiversity, and social justice. It concentrated on the need to see a 10-fold increase in climate finance to change agriculture and food systems for food and economic security by 2030. Innovative finance has a significant role to play in this.

Egypt performed a super job encouraging climate-smart agriculture to respond to the region's urgent agri-food and climate change requirements. It focused on the necessity of a 10-fold increase in climate finance to transform the food and

#### *Innovative Greenhouse to Improve Economic and Environmental Conditions DOI: http://dx.doi.org/10.5772/intechopen.113335*

agricultural systems for both economic and food security by 2030. Innovative finance can play a big part in this. Also, it can reduce food loss and waste and deal with the deterioration of irreplaceable natural like soil and water, and use ways to deal with heat, drought, and water scarcity under forecasted climate change scenarios. FAO Egypt at COP27 Hybrid Event, Sharm El-Sheikh (Egypt), 6–18 November, 2022. FAO Egypt at COP27 FAO in Egypt Food and Agriculture Organization of the United Nations.

#### **6. Conclusions**

In this chapter, we have seen how CSG is both a technical and a political concept that requires multidisciplinary work. We have also demonstrated how difficult it is to simultaneously implement the three pillars of CSG. We have discussed the main obstacles to CSA's adoption as well as its major policy and decision-making ramifications. Globally, rising temperature trends, an increase in the frequency of weather extremes, and an increase in seasonal variability have all been identified as new dangers to agriculture. Due to direct greenhouse gas emissions, agriculture has now been identified as one of the causes of climate change. Due to its potential involvement in GHG mitigation, agriculture is now starting to be seen as a way to combat climate change. A climate-smart greenhouse can aid in the creation of land-use plans that make the connectivity of adaptation and mitigation possible at all scales, thereby assisting farmers in taking the lead in the fight against climate change. The main takeaways from this chapter are as follows: (1) CSG meets sustainability, productivity, mitigation, food security, and development goals; (2) creative thinking is necessary; (3) a deeper comprehension of farmers' perspectives is also necessary; (4) additional financial instruments are required; and (5) a deeper comprehension is required of how well-equipped extension services or consultants are in each nation to assist in educating farmers about climate-smart practices. There is still room for improvement in policy implementation at the level of small farmers. To benefit from CSG, concrete steps must be taken to encourage farmers to use CSG technologies, provide them with the right funding, and encourage investment.

#### **Acronyms and abbreviations**



### **Author details**

Zainab Abdel Mo'ez Mansour Embaby Department of Environmental and Economic Assessment, Agriculture Research Center, Giza, Egypt

\*Address all correspondence to: zainab.embaby@yahoo.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Innovative Greenhouse to Improve Economic and Environmental Conditions DOI: http://dx.doi.org/10.5772/intechopen.113335*

#### **References**

[1] Vermeulen S et al. Addressing uncertainty in adaptation planning for agriculture. Proceedings of the National Academy of Science. 2013;**110**:8357- 8362. DOI: 10.107/pnas.1219441110

[2] Challinor AJ, Ewart F, Arnold S, Simelton E, Fraser E. Crops and climate change: Progress, trends and challenges in simulating impacts and informing adaptation. Journal of Experimental Botany. 2009;**60**(10):2775-2789. DOI: 10.1093/jxb/rep062

[3] Lobell DB, Bure ME, Tebaidi C, Masterandrea MD, Naylor R. Prioritizing climate change adaptation for food security in 2030. Science. 2008;**319** (5865):507-610. DOI: 10.1126/ science.1152339

[4] Nashwan MS, Shahid S. A novel framework for selecting general circulation model based on the spatial patterns of climate. International Journal of Climatology. 2020;**40**:442-4443. DOI: 10001002/joc.6463

[5] Fakan ST. Causes of climate change: Review article. Global Journal of Pure and Applied Sciences. 2020;**20**(2), Version 1:6-12

[6] Israel MA, Amikuzuno J, Abbeam GD. Assessing farmers contribution to greenhouse gas emission and the impact of adapting climate-smart agriculture on mitigation. Ecological Process. 2020; **9-51**:1-10

[7] EPA, 2014, United States Environmental Protection Agency Plan (EJ) 2014. USEPA. Available from: www.epa.gov/environmentaljustice/ plan-ej-2014

[8] IPCC. Intergovernmental Panel on Climate Change. AR6 Synthesizes

Report: Climate Change. IPCC. 2023. Available from: https://www.IPCC.ch/ report/six

[9] World Resources Institute. 1o Big Finding from 2023 IPCC Report on Climate Change by Sophine Boem and Clea Schumer. Cover Image by Arinut Thailand/Shutterstock. World Resources Institute; 2023

[10] FAO. In: FAO, editor. FAO; IFAD; UNICF; WEP; WHO Serial. The State of Food Security and Nutrition in the World. 2022. DOI: 10.4060/cc0639en/report

[11] FAO. FAO Egypt at COP27 FAO in Egypt Food and Agriculture Organization of the United Nations. FAO; 2022

[12] World Bank Group. AADAPT: Agriculture Adaptation and Natural Resource Management, World Bank Group. 2023. Available from: https:// www.worldbank.org/en/research/dime/ brief/agriculture

[13] Paul M et al. A review of climatesmart agriculture research and applications in Africa. Agronomy. 2021; **11**(6):1255. DOI: 10.3390/agronomy 11061255

[14] Theodora K et al. Smart greenhouses as the path towards precision agriculture in the food-energy and water nexus: Case study of Qatar. Environment System and Decisions. 2022;**42**:521-546. DOI: 10.10071s 10669-022-0966-2

[15] UNICEF, United Nations International Children's Emergency Fund. Water Scarcity in Egypt, UNICEF, 2021. Available from: https://www.uncif. org/egypt/documents/water-scarcity

[16] Karanisa T et al. Smart greenhouse as the path towards precision agriculture in the food-energy and water-nexus: Case study of Qatar. Environment Systems and Decisions. 2022;**42**:521-546

[17] Ziberman D et al. Innovation to response to climate change. Climate smart agriculture: Chapter. In: PART of the Natural Resource Management and Policy Book Series. Vol. 52. NRMP; 2018 First online: 21 October 2017

[18] Sapkota TB et al. Climate change adaptation, greenhouse gas mitigation and economic profitability of conservative agriculture. Some examples from cereal systems of Indo-Gangetic plans. Journal of Integrative Agriculture. 2015;**14**(8):1524-1533

[19] Barasa PM et al. A review of climatesmart agriculture research and applications in Africa. Agronomy. 2021; **11**(1255):1-26. Available from: https:// www.mdpi.com/journal/agronomy

[20] Barakat F et al. From Policy to Implementation: Adaptation to the Impact of Climate Change on Agriculture on Egypt. Egypt: The American University in Cairo; 2022

[21] International Monetary Fund (IMF). Climate Adaptation for MF&CA. IMF; 2022

[22] Nkumulwa HO, Pauline NM. Role of climate-smart agriculture on enhancing farmers 'livelihoods and sustainable forest management: A case of livings around song-Bokwa Forest, Kilindi District, Tanzania. Frontiers in Sustainable Food Systems. 2021;**51**: 6714190. DOI: 10.3389/

[23] Alakananda M et al. Everything you wanted to know about smart agriculture. arXiv. 2021.04754vI[cs CY]. DOI: 10.48550

[24] Torquebiau E et al. Identifying climate-smart agriculture research needs. Cahiers Agriculture Cultures. 2018;27: 26001, DOI: 10.1051/cagri/2018010. Available from: www.cahieragricultures.fr

#### **Chapter 5**

## A Review of Controlled Environment Agriculture (CEA) Vegetable Production in Africa with Emphasis on Tomatoes, Onions and Cabbage

*Taiwo Bintu Ayinde, Charles Fredrick Nicholson and Benjamin Ahmed*

#### **Abstract**

This chapter reviews the available information about performance indicators for controlled environment agriculture (CEA) and conventional production systems in Africa with an emphasis on those arising from tomatoes, onions and cabbage production. We identified a small number of studies that reported, yields per land area, costs, cumulative energy demand (CED), global warming potential (GWP) and water use for either CEA or field-based production systems. The available information does not allow robust comparisons of CEA and field-based production for any of these indicators, which suggests the need for expanded and improved crop-specific data collection from existing operations and the usefulness of alternative approaches such as economic engineering.

**Keywords:** controlled environment agriculture, economic analysis, GHG emissions, vegetable production, Africa

#### **1. Introduction**

More than 25% of the world's population suffers from micronutrient deficiencies and related health problems [1, 2]. Increased vegetable consumption has been proposed as a mechanism to reduce the prevalence of non-communicable diseases (NCD) in low and middle-income countries [1]. However, increasing vegetable consumption faces the challenge of increasing availability (production) at affordable costs [2, 3]. Total conventional (field-based) vegetable production increased in Africa from 2001 to 2021, with both tomatoes (*Solanum lycospersicum L.*) and onions (*Allium cepa L.*) production increasing by 59%, and cabbage (*Brassica oleracea var. capitata L.*) by 65% [4]. Field-based vegetable production in Africa is often practiced close to water supply points, in swampy areas or along the littoral band with easy access to water. In such areas, farmers operate within an informal economy and cultivate plots generally less

than 1 hectare in size [3]. Production practices are characterized by the use of limited machinery and other inputs and hand-powered technology such as the use of cutlass, hoe and irrigation boxes [3]. African vegetable farmers generally have access to limited information about technical recommendations [4, 5]. This contributes to a wide range of negative impacts on the environment that include reduction in crop yield and subsequently income and revenue, biodiversity loss, deterioration of water catchments, declining plot sizes, land degradation and greenhouse gas (GHG) emissions [5, 6].

The increased demand for affordable and nutritious food in urban areas has resulted in more demand for land and high migration from rural to urban areas, with workers willing to carry out conventional vegetable farming. Supply chains for vegetables produced in the open fields of rural are usually informal with low levels of coordination [1]. Disruptions in international food supply chains due to COVID-19 and economic and political instability in the region have also compounded the inability to attain regional self-sufficiency in vegetable consumption.

Recent years have seen increased discussion about whether alternatives to fieldbased vegetable production such as controlled environment agriculture (CEA) provide a mechanism to increase supply in urban areas. CEA comprises multiple types of approaches at alternative scales, including the production of plants, fish, insects, or animals using in- (home production or indoor gardens), medium- (e.g., community gardens), or larger-scale commercial operations, e.g., rooftop greenhouses, plant factories (PF) or vertical farms (VF) often using hydroponics, aquaponics or aeroponics, and growth chambers. These technologies control to varying degrees environmental parameters such as humidity, light, temperature and CO2 to create optimal growing conditions [6–16]. CEA technologies are classified according to the type of facility and growing systems [16]. Soil-based CEA systems use regular soil or compost as the plant growth medium and the predominant type of greenhouses in Africa [5, 7, 12–16]. In contrast, hydroponic systems are soilless culture in which solutions containing nutrients are applied directly to the roots of the plants. Aquaponic systems combine fish cultivation and hydroponics plant production. In aquaculture, microbial activity converts fish excreta into nutrients. The nutrient-rich wastewater is then pumped through the hydroponic area for use as the plant nutrient. The plants take up the nutrients and clean the water, which is then cycled back into the fish tank.

There has been significant rise in global CEA production for over the past two decades; the primary crops in CEA production focus on vegetables that form part of the local diet across all income groups (e.g., tomatoes, peppers, spinach, cabbage, and other leafy greens). Whether sold on local markets or to 'niche' markets such as hotels, the price is the same as for soil-grown produce [17]. The global–defined here as including vegetables that are important in diets across all income groups (e.g., tomatoes, peppers, spinach, cabbage, and other leafy greens)—has increased by ∼80% from \$ 0.4 billion in 2013 to \$8.5 billion in 2022, and it is projected to reach about \$20 billion in 2026. The main production regions in 2022 were North America (\$1.4 billion), Europe (\$1.4 billion) and Asia-Pacific (\$1.3 billion). Africa and the rest of the world contributed about 14% of the global total, \$665 million [17, 18]. CEA operations can often use fewer pesticides, land and water per unit of product [1], and reduce susceptibility to pests, diseases and adverse weather conditions. CEA has the potential to produce year-round yields of high-quality produce with yields as much as 20 times higher [7, 8, 17]. Depending on the technologies compared, CEA can use considerably less water and with the use of renewable energy sources could reduce GHG emissions per kg of product [1, 8]. CEA has received particular attention for production in urban areas where demand is large, but land is limited. CEA may play

#### *A Review of Controlled Environment Agriculture (CEA) Vegetable Production in Africa… DOI: http://dx.doi.org/10.5772/intechopen.113249*

a beneficial role in the production of vegetables, for which Africa's per capita consumption is the lowest in the world although demand is increasing. Africa's vegetable imports amounted to US\$ 1.9 billion in 2013. Most of the vegetables imported (tomato, lettuce, and onion) can be produced in the region [17].

In addition to the potential impacts on the supply of vegetables, peri-urban CEA development in low-income counties could provide opportunities for young people migrating to cities from rural areas who are in search of more profitable and less physically demanding work than traditional farming or because rural livelihoods are now less viable [16]. Growers in Kenya, Nigeria and India who provide training in hydroponics or aquaponics identified four common categories of people who are interested in starting commercial CEA ventures: young people looking to start their own business; conventional farmers wanting to try a new approach or boost insufficient income; people in other professions seeking additional income; and white-collar workers who are close to retirement.

Despite the advantages of higher yields and lower use of some inputs [8–11] some CEA production systems (e.g., plant factories or vertical farms) do not appear to be particularly "climate-smart" in the sense that they can have high production costs, and use more energy and emit more GHG per unit product [8–11]. CEA activity based primarily on soil-based greenhouses is growing in parts of Africa [16]. Egypt and South Africa have seen development of large-scale greenhouse projects in cooperation with Dutch businesses, greenhouses have a 'considerable' presence in Kenya, and a few cases in other countries exists (Nigeria, Namibia, and Somaliland). Efforts to promote increased production of fruits and vegetables with CEA on small farms in low-income countries have achieved limited success. The uptake of CEA technology particularly has been limited in low and middle-income countries, particularly in Africa, with high costs for installation and maintenance cited as constraints [1, 11, 12]. However, distance to market, having government support and access to social media, additional information are key positive determinants of awareness that would help inform the potential role for CEA in Africa (e.g., [19–22]). To date, there are few empirical studies that carry significant ecological impacts, food insecurity, nutrition-related problems, farmer livelihood challenges, and persistent food systemrelated inequities on CEA production in Africa [16, 17].

The objective of this chapter is to review the available evidence about the costs and selected environmental performance indicators for CEA and field-based irrigated production systems in Africa with an emphasis on tomatoes (20.7 million tonnes) and onions (15.50 million tonnes) for being some of the predominant vegetables grown in 2021 [4]. Literature search showed up no public data to demonstrate the economic and environmental viability of large-scale CEA production of cabbages and other crops of the cabbage family (4.00 million tonnes) [2, 17].

The evidence is derived from previous studies that reported information about the costs per unit, yields per land area, cumulative energy per unit, GHG emissions an global warming potential (GWP) and water use for CEA and conventional vegetable production. This will provide more information on the potential role for CEA production systems in Africa and highlight the priority needs for additional research.

#### **2. Materials and methods**

This review considers six performance indicators per unit of product: cost of output, yields per land area, cumulative energy, GHG and GWP and water use for three crops (cabbage, onions, and tomato) in Africa. The information derives from studies with a Life Cycle Inventory (LCI) and Life Cycle Assessment (LCA) perspectives. LCI and LCA are related in the sense of providing accounting of comprehensive and systematic documentation of the impacts, processes and material flows of production but LCI focuses on current operational inputs and impacts (like energy use in a greenhouse) whereas LCA includes the inputs and impacts of 'embedded inputs' (for example, the energy to manufacture and dispose of steel used in a greenhouse). Previous reviews (e.g., [23, 24]) have adopted a similar approach to synthesis of the available information.

We developed a database with information about the six performance indicators using two approaches. For the first approach, we identified literature published from January 2000 to January 2023 using Scopus and Web of Science with search terms 'life cycle inventory' AND ('greenhouse' OR 'CEA') AND ('tomatoes') and evaluated which studies had information on production systems in Africa. Fifty-four articles were obtained from the initial search for tomato production. An additional three studies were identified from the literature cited by the articles identified through the database searches. The second approach employed a search in Google scholar for 'Africa' AND ('onions' OR 'cabbage' OR 'tomatoes') AND 'irrigated' and 'CEA production'. This search resulted in seven studies on irrigated and CEA production, of which three [15, 16, 25] contained multiple data points (for either for different crops or production systems).

Although 64 studies were reviewed, the number of observations for which specific values of the six indicators per unit of the product were reported or could be calculated was considerably smaller. Many studies reported ranges of values for aggregations of multiple crops (e.g., [15, 25]), which we deemed insufficiently specific for this review. We thus excluded the observations derived from these studies. Our review identified four observations for unit costs per (2 for tomatoes from [26] and two for general vegetables [5, 15]), and two values for each of Cumulative Energy Demand (CED; MJ/kg [26]), Global Warming Potential (GWP; kg CO2eq/kg [26]) and water use (lts/kg [7, 16, 26]).

One possible reason for the limited number of studies with information for specific crops is the predominance and importance of "mixed vegetable" production systems with multiple crops grown throughout the year. In some sense, it is the overall performance of these systems that is important for the farms producing them, which are often of smaller scale. Thus, studies of the overall performance metrics of costs, yields and water use [15, 26] are more common than studies reporting that information for individual crops. In addition, most studies did not report all metrics of costs, yields, CED, GWP and water use; production indicators were more commonly reported than estimates of energy or GWP. In some cases, we made conversions of available data to estimate appropriate metrics. For example, water use was sometimes reported in units of liters per m<sup>2</sup> per day, which required an estimate of the length of the growing season in addition to the conversion of yields to kg/m2 .

The functional unit for our analysis (a measurement that is normalized across all systems for comparative purposes) was 1 kg of product (multiple vegetables or tomato) grown each year. We undertook conversion calculations (e.g., total yields to yields/ha or total GHG to GHG/kg or total water per ha to water/kg product) that were specific to each study. Yields were estimated in kg/m2 [7] were converted to hectare by multiplying by 10,000 kg ha−1. We converted values in local currencies to USD using exchange rates at the time data were collected in previous studies.

Revenues (\$/ha) were calculated based on product yield (kg/ha) and output price, when available. Total costs of production include both variable and field costs, *A Review of Controlled Environment Agriculture (CEA) Vegetable Production in Africa… DOI: http://dx.doi.org/10.5772/intechopen.113249*

converted to \$/kg when needed using information on yields per hectare and costs per ha. The value of water used was converted to water per kg using volume and yield factors in [26]. Cold greenhouse vegetable was 20.0 kg/m3 yield/water use, where 1 m3 was equivalent to 1000 liters.

Quantities of energy in the standard unit of energy were expressed based on the International System of Units (SI), the joule (symbol J), is equal to 3600 kilojoules or 3.6 MJ. It was converted to megajoules (MJ) based on specific energy density for fuel (36 MJ l\_1 in [26]) and later MJ/kg and was adapted for this review.

#### **3. Results and discussion**

As noted above, the number of observations with sufficient information for inclusion in this review is small (**Table 1**). Thus, it is difficult to make direct comparisons of revenues and profitability between operators who are cultivating the same crop in different systems and countries. Some studies [15, 26] provide insights about the impacts on the profitability of alternative irrigation systems for vegetable products, but do not allow comparisons of field and CEA production. More evidence is needed to understand the economic feasibility of CEA vegetable production in low-income countries and the extent to which experience from high-income countries is relevant for low-income countries. That is, no analyzes comparable to [11] have been conducted yet for low- and middle-income countries. Differences in costs and profitability for CEA and conventionally-grown produce may narrow as the initial investment is amortized, productivity increases, and new, cost-effective technologies become available [21, 22, 25, 26] but it is difficult to predict when this might occur.

There is anecdotal evidence that hydroponic systems may be more economically viable for vegetable production, including in dry land climates due to their minimal water use [https://bicfarmsconcepts.com]. In these systems, inexpensive, locally-available materials were used as substrates [23, 25, 26]. Where electricity was expensive or its supply irregular, pumps that do not need to lift or spray water on to the roots, such as the gravity-driven Kratky or ebb and flow technologies may be


#### **Table 1.**

*Summary of observations from review.*

preferred. Where there is sufficient water and reliable electricity, aquaponics can be a viable form because it has two outputs—vegetables and fish—that provide complementary sources of income [26].

There was some evidence that enclosed structures using shipping containers and re-purposed buildings can house financially, socially and environmentally viable. CEA operations, partly because they have enabled entrepreneurs to set up in built-up urban locations where there is no space for greenhouses [16]. The higher operating costs compared to greenhouses, due to the need for LED lighting and air conditioning, could be offset by reduced fuel costs to transport produce to market. The risk of losing crops due to occasional electricity outages can be less than the risk of losing crops in transport from rural areas to urban markets due to fuel shortages or absence of adequate cold storage. Another reason why completely enclosed structures could viable is that parameters can be set to provide optimum conditions year-round, enabling the higher running costs to be offset by higher, and more consistent yields [16].

We identified only two values from one specific study that provided estimates of energy consumption and GWP per kg [26] (**Table 2**). In this case, more energy (0.01/0.46 MJ/kg) are required during the dry season for irrigation than the seasonal systems for cold greenhouse and open field vegetables, respectively. The difference in the values of energy consumption is much less for the cold greenhouse than the open field because Beninese have no access to electricity for irrigation and use generators fueled with oil with a higher GWP [26]. This is in contrast to [11] who found that both energy and GWP were higher for heated greenhouses. The higher mineral and organic nitrogen fertilizer rate as well as irrigation efficiency were reported to have contributed to the difference of GWP due to both production of fertilizers and field emissions of 0.37 CO2eq/kg in cold greenhouse and open field (0.11 kg CO2eq/kg) vegetable production. The more water supplied, the higher the leaching rate and soil moisture content. The higher the maximal soil moisture, the higher the denitrification rate. The more nitrogen supplied, the more Nr emitted and soil pH that will increase the rate of volatilization. Overall, the nature and amount of energy consumed per volume of irrigation water applied were critical to the climate change potential.

The maintenance of water pumps would limit the quantities of energy consumed as well as the irrigation efficiency. Second, it could also enhance crop yields at the edge of rivers where soils present a greater water retention capacity, lowering the need for irrigation water. Better irrigation management taking soil properties and local climate (evapo-transpiration) into account could improve the water use efficiency and also reduce (water losses by drainage).

Water use per kg product was based on ranges of water use per m<sup>2</sup> per day for tomatoes [26] and multiple vegetables [15, 25] (**Table 3**). These estimates are for vegetable production in Ghana where water is conveyed in 15-liter watering cans to irrigate. The range of values is large, 153–840 lts/kg, but it is consistent with estimates


#### **Table 2.**

*Yield, cumulative energy demand and global warming potential for tomatoes, greenhouse and open field.*

*A Review of Controlled Environment Agriculture (CEA) Vegetable Production in Africa… DOI: http://dx.doi.org/10.5772/intechopen.113249*


#### **Table 3.**

*Estimated water use for open field [tomatoes and multiple vegetables].*

for field-based lettuce production in the USA of 201 lts/kg [11]. Both values are considerably larger than the 21 lts/kg reported by [11] for CEA leaf lettuce. The GWP of urban garden tomatoes in Benin were reported to be 4–23 times larger than the impacts of tomatoes grown in European cropping systems, due to low and variable crop yields (high fuel consumption for irrigation, large nutrient flows and use of insecticides [26]).

Given the very limited information on costs in most reviewed studies (e.g., [14–16, 18, 21]), improvements in data collection and reporting would be helpful to improve our understanding of the potential for CEA compared to fieldbased production systems. First, it is relevant to collect and report data for specific crops to facilitate comparison between production systems. CEA operations often focus on one or a few crops, so crop-specific data (i.e., not 'vegetables') is needed for adequate comparisons. Reporting of both yield per crop and yield per year when those are different would better represent total production for the purposes of calculating costs, revenue and input requirements per unit of product. CEA operations typically produce multiple crops per year, but this can also be true for field products (e.g., cabbage entries that have multiple cropping periods per year). Reasonably accurate cost data are also needed to make relevant comparisons. Future studies can usefully distinguish better between costs (both variable and fixed) and revenues. For example, some studies (e.g., [15, 16, 21]) report only price information (which can be used to calculate revenues) or total revenue information, but not cost data. Most of the studies reviewed reported no specific costs, either in aggregate (for a ha or for a cropping season) or per unit. It would also be helpful if additional disaggregation of cost categories (especially for energy inputs like fuel and electricity) were reported because they would facilitate improved estimates of environmental impact. In general, it would be helpful if future studies were also more comprehensive, reporting information on all performance metrics we considered: yields, costs, and input use for energy and water.

More studies of CEA are needed for Africa, especially for sub-Saharan Africa. This can include both less technologically advanced systems (e.g., greenhouses without full temperature or humidity control), and more advanced (and expensive) systems such as greenhouses with more environmental controls—and similar systems such as plant factories and vertical farms. Generally, greenhouses and polytunnel structures were readily obtained locally [16], except in Nigeria, where greenhouses are not yet popular (they are imported and relatively expensive [6, 16, 20–23, 25–28]). Variations

the combine different characteristics may be relevant. For example, hydroponic units have been installed outside of greenhouses in Nigeria, influenced by crop varieties and space constraints. In Kenya, suppliers offer hydroponic units that can be installed in a variety of enclosed or open settings, including a small unit that can be mounted on the wall of a building for those with no land.

#### **4. Conclusions**

The uptake of CEA production technology has been limited in low and middleincome countries, particularly Africa. This means that we have very limited information to evaluate the potential of CEA and to make comparisons to field production. That is, until we have more examples—and data—to evaluate it will be difficult to understand the potential role for, and impacts of, different types of CEA production systems in the region. One requirement is expanded and improved data collection from existing operations. Improved data collection would include a broad range of relevant indicators collected in a consistent manner across farms and studies. Another approach is to develop more 'synthetic' approaches based on economic engineering approaches used for other food production technologies [28]. This approach can suggest the conditions under which CEA operations may be successful even in locations where they do not currently exist. The long-term success and economic viability of CEA in Africa will also depend on future trends in consumer preferences and market demand for vegetables (e.g., [25, 28]), so studies on the costs would be complemented by consumer preference studies. Together, this information will inform decisions about private investors and governments.

#### **Authors contributions**

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [Taiwo Ayinde], [Charles Fredrick Nicholson] and [Benjamin Ahmed]. The first draft of the manuscript was written by [Taiwo Ayinde] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

#### **Conflict of interest**

The authors declare no conflict of interest.

#### **Ethical approval**

All due consents have been sought.

#### **Consent to participate**

All due consents have been sought.

*A Review of Controlled Environment Agriculture (CEA) Vegetable Production in Africa… DOI: http://dx.doi.org/10.5772/intechopen.113249*

#### **Consent to publish**

All due consents have been sought.

### **Author details**

Taiwo Bintu Ayinde1 \*, Charles Fredrick Nicholson2 and Benjamin Ahmed3

1 Samaru College of Agriculture, Ahmadu Bello University (ABU), Zaria, Nigeria

2 Departments of Animal and Dairy Sciences and Agricultural and Applied Economics, University of Wisconsin-Madison, Madison, Wisconsin, USA

3 Department of Agricultural Economics, Ahmadu Bello University (ABU), Zaria, Nigeria

\*Address all correspondence to: taiyeayinde2006@yahoo.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

[1] Pinstrup-Andersen P. Is it time to take vertical indoor farming seriously? Global Food Security. 2018;**17**(September 2017):233-235. DOI: 10.1016/j. gfs.2017.09.002

[2] Nicholson CF, Monterrosa E. Application of participatory systems modeling to identify intervention priorities for vegetable consumption in Nairobi Kenya. In: Revision for Public Health Nutrition. 2023

[3] Mondédji AD, Silvie P, Nyamador WS, Martin P, Agboyi LK, Amévoin K, et al. Cabbage production in West Africa and IPM with a focus on plant-based extracts and a complementary worldwide vision. Plants. 2021;**10**(3):1-36. DOI: 10.3390/ plants10030529

[4] FAOSTAT. Crops and Livestock Products [Internet]. 2021. Available from: https://www.fao.org/faostat/ en/#data/QCL [Accessed: May 4, 2023]

[5] Robert K, Kara HA, Adamu MM, Muhammad B. Analysis of dry season vegetable production among Kiri dam users in Adamawa state, Nigeria. Journal of Agripreneurship and Sustainable Development (JASD). 2021;**4**(4):173-179

[6] Dorr E, Sanyé-mengual E, Gabrielle B, Grard BJ, Aubry C. Proper selection of substrates and crops enhances the sustainability of Paris rooftop garden. Agronomy for Sustainable Development. 2017;**37**:51. DOI: 10.1007/s13593-017-0459-1

[7] Wachira JM, Mshenga PM, Saidi M. Comparison of the profitability of smallscale greenhouse and open-field tomato production systems in Nakuru-North district, Kenya. Asian Journal of Agricultural Sciences. 2014;**6**(2):54-61

[8] Dorais M, Antón A, Montero JI, Torrellas M. Environmental assessment of demarcated bed-grown organic greenhouse tomatoes using renewable energy. Acta Horticulturae. 2014;**1041**:291-298. DOI: 10.17660/ ActaHortic.2014.1041.35

[9] Fan Y, Luo Z, Hao X, Li S, Kang S. Potential pathways to reduce environmental impact in a greenhouse tomato production: Life cycle assessment for different irrigation and fertilization treatments. Scientia Horticulturae. 2022;**305**(March):111411. DOI: 10.1016/j. scienta.2022.111411

[10] Fisher S. A Case Study of Urban Agriculture: A Life Cycle Assessment of Vegetable Production. Faculty of the Graduate School of the University of Colorado, ProQuest LLC; 2014

[11] Nicholson CF, Harbick K, Gómez MI, Mattson NS. An economic and environmental comparison of conventional and controlled environment agriculture (CEA) supply chains for leaf lettuce to US cities. In: Aktas E, Bourlakis M, editors. Food Supply Chains in Cities. Cham: Palgrave Macmillan; 2020. DOI: 10.1007/978-3-030-34065-0\_2

[12] Aboaba KO, Sanusi RA, Akamo AA, Bello B. Double hurdle approach to consumer awareness, perception of, and willingness to pay for greenhouse vegetables. International Journal of Vegetable Science. 2022;**28**(1):15-24. DOI: 10.1080/19315260.2020.1819929

[13] Adams F, Etuah S, Appiah GB, Aidoo R, Osei J, Nyekyeyel J, et al. Do consumer opinions matter? Consumer perception and purchasing decisions of greenhouse vegetables in

*A Review of Controlled Environment Agriculture (CEA) Vegetable Production in Africa… DOI: http://dx.doi.org/10.5772/intechopen.113249*

Ghana. Journal of International Food & Agribusiness Marketing. 2022. DOI: 10.1080/08974438.2022.2145536

[14] Oyediran W, Omoare AM, Shobowale AA, Onabajo AO. Effect of socio-economic characteristics of greenhouse farmers on vegetable production in Ogun state, Nigeria. Sustainability, Agri, Food and Environmental Research. 2020;**8**(1):76- 86. DOI: 10.7770/safer-v0n0-art1593

[15] Obuobie E, Keraita B, Danso G, Amoah P, Cofie OO, Raschidsally L, et al. Irrigated Urban Vegetable Production in Ghana Production in Ghana: IWMI-RUAF-CPWF. Accra, Ghana: IWMI; 2006

[16] Halliday J, von Kaufmann R, Herath KV. An Assessment of Controlled Environment Agriculture (CEA) in Low- and Lower-Middle Income Countries in Asia and Africa, and Its Potential Contribution to Sustainable Development. Colombo, Sri Lanka: Commission on Sustainable Agriculture Intensification. CGIAR Research Program on Water, Land and Ecosystems (WLE); 2021. 86p

[17] de Janvry A, Sadoulet E. Agriculture for development. Development Economics. 2nd ed. Issue No 34. 2021. pp. 448-476. DOI: 10.4324/9781003024545-19

[18] Asongwe GA, Yerima PKB, Tening AS. Vegetable production and the livelihood of farmers in Bamenda municipality, original research article vegetable production and the livelihood of farmers in Bamenda municipality, Cameroon. International Journal of Current Microbiology and Applied Science. 2014;**3**(12):682-700

[19] Paucek I, Durante E, Pennisi G, Quaini S, Gianquinto G, Orsini F. A methodological tool for sustainability and feasibility assessment of indoor vertical farming with artificial lighting in Africa. Scientifc Reports. 2023;**13**:2109. DOI: 10.1038/s41598-023- 29027-8

[20] Jones OE, Tham-Agyekum EK, Ankuyi BF, Ankrah DA, Akaba S, Shafiwu AB, et al. Mobile agricultural extension delivery and climate-smart agricultural practices in a time of a pandemic: Evidence from southern Ghana. Environmental and Sustainability Indicators. 2023;**19**:100274

[21] Kabiru F, Nina C, Kosgei B. Feasibility Study of the Best CEA System for School Feeding in Mukuru Informal Settlement, Nairobi. Berlin: TMG Research; 2023

[22] Gómez C, Currey CJ, Dickson RW, Kim HJ, Hernández R, Sabeh NC, et al. Controlled environment food production for urban agriculture. HortScience. 2019;**54**(9):1448-1458. DOI: 10.21273/ HORTSCI14073-19

[23] Verteramo L, Nicholson CF, Gómez MI. A meta-analysis of life cycle assessments for tomato, lettuce and strawberry supply chains. Revision Submitted to Journal of Cleaner Production. 2023

[24] Li J, González W, Monterrosa E, Gómez MI, Nicholson CF. Choice experiments and value-chain modeling of attribute improvements to increase vegetable consumption in Kenya. Submitted to Food Policy. 2023

[25] Drechsel P, Keraita B, editors. Irrigated Urban Vegetable Production in Ghana: Characteristics, Benefits and Risk Mitigation. 2nd ed. Colombo, Sri Lanka: International Water Management Institute (IWMI); 2014. DOI: 10.5337/2014.219

[26] Perrin A, Basset-Mens C, Huat J, Benoit G. The variability of field emissions is critical to assessing the environmental impacts of vegetables: A Benin case-study. Journal of Cleaner Production. 2017;**153**:104-113. DOI: 10.1016/j.jclepro.2017.03.159

[27] BIC Farm Concepts. BIC Farm Concepts. 2023. Available from: https:// bicfarmsconcepts.com

[28] Risner D, Li F, Fell JS, Pace SA, Siegel JB, Tagkopoulos I, et al. Preliminary techno-economic assessment of animal cell-based meat. Food. 2021;**10**(3):10010003. DOI: 10.3390/ foods10010003

#### **Chapter 6**

## Simulation of a Novel Cooling System for a Closed Greenhouse

*Geordie Zapalac*

#### **Abstract**

A simulation of a cooling system for a closed greenhouse is described. The cooling system relies upon cool ambient temperatures during the night and morning to discharge heat accumulated within the greenhouse during the day. Radiative heat into the greenhouse is transferred to a large reservoir of water inside the greenhouse using an unpressurized droplet system. During the night and morning the accumulated reservoir heat is discharged to ambient air using the same droplet system to transfer reservoir heat into a restricted volume of air above the reservoir, while simultaneously circulating the heated air through an air-to-air heat exchanger comprised of thinwalled plastic tubes.

**Keywords:** closed greenhouse, simulation, convective cooling, heat exchanger, water savings

#### **1. Introduction**

Climate change is creating a crisis for food security. Grain yields are threatened by elevated temperatures and drought stress that shorten the grain filling period and impair starch biosynthesis [1]. Increasing irrigation to counter high temperatures and drought is a progressively less likely option because climate change impacts other aspects of the hydrological cycle in addition to precipitation, including glaciers, river flows, and aquifer replenishment, increasing competition to agriculture for freshwater resources required for wild ecosystems, consumption and sanitation, industry, and cooling [2]. Climate change also reduces arable land by desertification of drylands [3], soil erosion from extreme precipitation events [4], and saltwater intrusion into river deltas [5].

Mitigating climate change will require removing gigatonnes of CO2 annually from the atmosphere [6]. It is generally assumed that captured CO2 will be liquified under pressure and geologically sequestered. For schemes where CO2 is not mineralized underground and where no fluid is produced from the well, it has been argued that the increase in well pressure precludes underground sequestration of CO2 at scales required to mitigate climate change [7]. Storage in saline formations would be possible by simultaneously producing brine to relieve the pressure, but this would require desalinating the produced brine and pumping the highly concentrated waste brine

back into the formation for disposal [8]. Storage of CO2 in oil wells during enhanced oil recovery (EOR) is possible because oil is produced to relieve the pressure. The CO2 sequestered by EOR could be managed to exceed the CO2 emitted by combusting the produced oil [9].

Use of captured CO2 to enhance greenhouse yields provides a potentially profitable route of sequestration into biomass such as biochar, woody products, or humus, and CO2 could be provided at ambient pressure from the output stream of the CO2 capture facility. The greenhouses must be closed or unventilated so that the CO2 is confined until it is consumed by the plants. Water is also conserved and recycled because it is confined within the greenhouse with the CO2. Closed greenhouses can enhance yields of C3 crops by maintaining a high concentration of CO2 during the afternoon period of maximum photosynthesis, when other greenhouses are normally ventilated for cooling. High CO2 concentrations might increase the temperature for optimal photosynthesis [10–14], increasing the yield while reducing the cooling load for the greenhouse.

Cooling a closed greenhouse generally requires much more energy than evaporatively cooling a ventilated greenhouse. However, renewable energy and energy storage costs are falling while freshwater resources are diminishing, and CO2 will need to be sequestered at scale. Therefore an important engineering challenge for addressing food security and CO2 sequestration in a changing climate is the problem of economically cooling a closed greenhouse.

Different solutions to the closed greenhouse cooling problem have been prototyped and commercialized in the past. Closed greenhouses sited in northern climates have used borehole heat exchangers to access cold ground temperatures that are recharged to low temperatures during the winter [15]. Closed greenhouses have been sited over aquifers to access seasonal storage of cold water temperatures [16]. The closed greenhouse cooling system for the Watergy prototype operated on a diurnal cycle using a water-to-air heat exchanger that accessed a reservoir of water outside the greenhouse that was cooled by low ambient nighttime temperatures [17, 18]. The Novarbo Oy Company commercialized a closed greenhouse that cools and dehumidifies the greenhouse air using water droplets, returning the water to an outside reservoir that is cooled with a heat pump [19, 20].

The closed greenhouse design described in this report relies upon cool ambient nighttime and morning temperatures to discharge heat removed from the greenhouse air during the day and stored in a reservoir of water inside the greenhouse [21]. During the day heat entering the greenhouse from solar radiation is transferred to a reservoir of water by an unpressurized droplet system. The novelty of the proposed design is the method of discharging the accumulated reservoir heat to the ambient air. During the night and morning heat in the reservoir is discharged to ambient air by using the same droplet system to transfer reservoir heat into a restricted volume of air above the reservoir, while simultaneously circulating the heated air through an air-toair heat exchanger composed of thin-walled plastic tubes. This design avoids the cost and maintenance of a chiller as well as the supported weight and risk of leaks using a water-to-air heat exchanger. The design requires a climate with a low minimum ambient temperature during the morning, preferably 13°C or less. Because the greenhouse is convectively cooled, it could be sited equally well in deserts and in high humidity climates.

The greenhouse cooling simulation described here uses a "well-stirred" energy balance model where the temperature and humidity are assumed to be uniform throughout the greenhouse volume. Heat and mass transfers are modeled with

correlation formulas developed for forced convection applications that are based upon dimensionless Nusselt numbers. These formulas have an accuracy of about 20% [22].

Experiments were performed on small components of the cooling system: a single plastic heat exchanger tube and droplet dispensers [21]. These experiments confirmed the air-to-air heat transfer properties of the plastic tube, and informed the simulation on the effective droplet surface temperature for simulating the heat and mass transfer to a falling droplet. The droplet surface temperature is modeled using a linear combination of the bulk temperature in the droplet and the surrounding air temperature [21].

The simulation advances in time steps of Δ*t* ¼ 90 seconds for a 24-hour period. More refined time steps are required to model the reservoir and heat exchanger system during the heat discharge period. The 24-hour simulation is repeated iteratively until the total heat within the greenhouse at the end of the 24-hour cycle is within 10 kJ of the total heat at the beginning of the cycle.

#### **2. Components and operation of the cooling system**

**Figure 1** shows a schematic of four greenhouse modules taken from an array of closed greenhouses, where the cover is not shown for one of the modules in the drawing. The green cultivated regions in this example have an area of 20 m by 50 m or 0.1 ha. Adjacent to each cultivated region is a reservoir of water with a depth *dr* of 1 m and an area *Ar* of 10 m by 50 m. Above each reservoir is a restricted volume of air or "tunnel" that is optionally open to a bank of plastic tubes located above the tunnel that serves as an air-to-air heat exchanger. The individual heat exchanger tubes are not shown.

During the day the reservoir water is cool, the sides of the tunnels are open to the cultivated regions in the greenhouses on either side, and the ends of the tunnels are

#### **Figure 1.**

*Four modules from a greenhouse array that share a common volume of air. One of the modules has the cover removed from the drawing. White outlined arrows show the direction of airflow during the day, when warm greenhouse air is circulated through cool reservoir droplets to transfer heat and water vapor from the air into the reservoirs. Blue arrows show the direction of airflow during the night through the heat exchanger tube bank, when cool tunnel air is circulated through warm reservoir droplets to transfer reservoir heat into the air-to-air heat exchanger.*

closed off from the C-shaped ducts that lead to the outside heat exchanger. 1.6 m above the reservoir surface, below the roof of the tunnel, there are trays with a pattern of short tubes that comprise the droplet dispensers.

Cool reservoir water pumped into the trays returns to the reservoir as 1.5 mm diameter droplets that exchange heat and water vapor with the air above the reservoir. Warm greenhouse air is circulated by fans across the width of the tunnel and through the falling droplets in the direction of the white outlined arrows, shown for one the modules, transferring both heat and water vapor to the reservoir to cool and dehumidify the air. A complete greenhouse array would be configured to return the airflow through a similar string of greenhouses in the opposite direction so that the airflow is cycled through all the greenhouse modules.

During the night the reservoir water is warm, the sides of the tunnel are closed, and the ends of the tunnel are opened to the ducts that lead to the heat exchanger tube bank. The same droplet system is activated and fans move saturated air down the length of the tunnel through the falling droplets, and then through the heat exchanger tube bank in the opposite direction, shown by blue arrows in **Figure 1**, where the forced convection of greenhouse air transfers both sensible and latent heat to the ambient air. Outside fans also pull a crossflow of cool ambient air through the tube bank.

The tube bank is comprised of 900 PETG tubes that are 30 m in length and in contact with the ambient air. Each tube has an outer diameter *D*<sup>1</sup> of 10 cm and a wall thickness of 0.5 mm. The tubes are arranged in a staggered configuration of 30 rows with 30 tubes per row, with a pitch of *a* ¼2 within a row and a pitch of *b* ¼1.25 in the vertical direction. The tubes may be slightly angled to allow condensed water to drain back into the reservoir. **Figure 2** is a closer view of one end of the cooling system showing the surface of the reservoir, the top of the tunnel where the droplet dispensers are located, the duct leading to the heat exchanger, and the region occupied by the heat exchanger tube bank.

**Figure 3** shows the solar radiation into the 1000 m<sup>2</sup> greenhouse in the simulation. The integral of this curve is the heat load that must be transferred during the day to

#### **Figure 2.**

*View of one end of the cooling system schematic from Figure 1, where the cover was removed from the drawing. Adjacent to the cultivated region is the primary heat exchanger system comprising a reservoir of water, a tunnel with droplet dispensers to transfer heat to or from the reservoir, and a C-shaped duct that leads to a bank of 900 thin-walled plastic tubes.*

**Figure 3.** *Model of the daily radiative heat load into the 1000 m2 greenhouse.*

the reservoir or to the soil and plants, or conducted to the ambient air through the cover. If the integrated outside radiation is 9.5 kWh m<sup>2</sup> day<sup>1</sup> , then the transmission of the greenhouse cover must reduce the incoming insolation by 50% to achieve the radiation heat load shown in **Figure 3**. During the day the reservoir water temperature is roughly 15°C cooler than the greenhouse air. The reservoir droplet dispensers are activated to flow 100 L s<sup>1</sup> of droplets to transfer both latent and sensible heat into the reservoir. During the night the reservoir droplet dispensers flow 450 L s<sup>1</sup> to transfer heat from the reservoir to the air.

**Figure 4** is a plot of temperature versus distance through 50 m in the tunnel, shown to the left of the vertical dashed line, and through 30 m of the heat exchanger tubes, shown to the right of the dashed line. It is assumed that the air temperature

#### **Figure 4.**

*Air temperature versus distance in the heat exchanger system. During the first 50 m the temperature rises in the tunnel as reservoir heat is transferred by warm reservoir droplets to the air. During the last 30 m the air cools as it passes through the heat exchanger and transfers heat originally stored in the reservoir into the cool ambient air.*

does not change within the ducts; the distance through the ducts is not shown in **Figure 4**. As cooled air moves through the warm reservoir droplets down the length of the tunnel the temperature increases and the humidity remains saturated. When the air moves through the heat exchanger the temperature falls as reservoir heat is transferred to the ambient air. Water condenses inside the tubes and eventually drains back into the reservoir.

During the night heat is conducted through the walls and roof of the cultivated regions and the air temperature falls, increasing the relative humidity. A second airto-air heat exchanger, denoted as the condenser, is positioned on the apex of each greenhouse roof as shown in **Figure 2** to reduce the relative humidity at night. The condenser has the same tube arrangement as the primary heat exchanger over the tunnel, but the PETG tubes are smaller, with an outside diameter of 2.5 cm and a wall thickness of 0.3 mm. Indoor fans pull air through the condenser tubes, while outside fans pull a crossflow of cool ambient air through the condenser tube bank.

Water is completely recycled within the closed greenhouse. All the water that evaporates into the air, including water transpired by the plants, eventually condenses on the falling reservoir droplets or on the inner surfaces of the heat exchanger tubes and returns to the reservoir.

#### **3. Simulation**

#### **3.1 Daytime cooling**

During the day radiative heat must be transferred to the reservoir by the droplet system at approximately the same rate that it enters the greenhouse. The plants also transpire and the additional water vapor must be removed by the droplet system to maintain an acceptable vapor pressure deficit (VPD) for the plants. **Figure 5** shows the model for plant transpiration over a 24-hour cycle, assuming a transpiration rate of 3 L m<sup>2</sup> day<sup>1</sup> in the cultivated region. The simulated transpiration rate at any

**Figure 5.** *Transpiration rate from plants cultivated in the greenhouse.*

*Simulation of a Novel Cooling System for a Closed Greenhouse DOI: http://dx.doi.org/10.5772/intechopen.113135*

given time depends upon the insolation and VPD. Because the VPD depends upon the solution for the greenhouse temperature and humidity, the time dependence of the transpiration is iterated together with the simulated temperature and humidity to provide a self-consistent result after the simulation converges [21].

During a time step Δ*t* the reservoir droplets absorb the heat Δ*Qr* and the water vapor mass Δ*Mr* from the greenhouse air. These are signed quantities: Δ*Qr* and Δ*Mr* are positive when heat and water vapor are transferred from the greenhouse air to the reservoir droplets, and negative when heat and water vapor are transferred from the reservoir droplets to the greenhouse air. During Δ*t* the reservoir temperature increases by:

$$
\Delta T\_r = \frac{\Delta Q\_r}{A\_r d\_r \rho\_w C\_{pw}} \tag{1}
$$

where *ρ<sup>w</sup>* and *Cpw* are the density and specific heat capacity of water. The mixing ratio *Xa* (grams of water per grams of dry air) for the total greenhouse air volume *Va* changes by:

$$
\Delta X\_a = \frac{\Delta \mathcal{M}\_{Tr} - \Delta \mathcal{M}\_r}{V\_a \rho\_a} \tag{2}
$$

where Δ*MTr* is the mass of water vapor transpired by the plants during Δ*t*. During Δ*t* the radiative heat Δ*QS* enters the greenhouse, and conductive heat Δ*QC*> 0 (< 0) also enters (leaves) the greenhouse through the cover over the cultivated region. The greenhouse air temperature *Ta* changes by:

$$
\Delta T\_{\rm{at}} = \frac{\Delta Q\_{\rm{S}} + \Delta Q\_{\rm{C}} - H\_{\rm{v}}\Delta M\_{\rm{Tr}} - (\Delta Q\_{\rm{r}} - H\_{\rm{v}}\Delta M\_{\rm{r}})}{V\_{\rm{a}}\rho\_{\rm{a}}C\_{\rm{pa}} + m\_{\rm{s}}C\_{\rm{pv}}} \tag{3}
$$

where *Hv* is the enthalpy of vaporization for water, *Cpa* is the specific heat capacity of air, *ms* is the mass of the soil in the cultivated region (g), and *Cps*is the specific heat capacity of the soil (0.92 J °C�<sup>1</sup> g�<sup>1</sup> ). The simulation assumes that heat transfers instantly to the soil mass and neglects any heat transfer to the plants or other objects in the greenhouse.

#### **3.2 Discharging reservoir heat to the ambient air**

Ninety percent of the energy required to operate the greenhouse is used to discharge the accumulated reservoir heat to the ambient air during the night and morning. The simulation discharges reservoir heat between 19:00 in the evening and 9:00 in the morning. During this period the sides of the tunnel are closed to the remainder of the greenhouse volume and the ports to the heat exchanger on either end of the tunnel are open. The tunnel and heat exchanger form an isolated system that is simulated independently from the remainder of the greenhouse. **Figure 6** shows the model of ambient temperature *To* used by the simulation. The most critical feature for discharging heat is the minimum diurnal temperature, assumed to be 11.8°C in this example, at 7:00.

If the ambient temperature is at least 2°C less than the reservoir temperature, pumps are activated to circulate 450 L s�<sup>1</sup> into the droplet dispensers and fans are

#### **Figure 6.**

*Model of the ambient temperature for the simulation over 24 hours. The temperature reaches a minimum of 11.8° C at 7:00.*

activated to pull air through the heat exchanger tubes and to push the cool, saturated air through the falling droplets down the length of the tunnel. The fan power is adjusted so that the airspeed in the heat exchanger tubes *vx* is linearly proportional to the difference between the reservoir water temperature *Tr* and the ambient air temperature *To*, reaching a maximum of 5 m s�<sup>1</sup> during the morning. The airspeed *vT* in the tunnel is a factor 2.20 less than *vx* and determined by the ratio of cross-sectional areas of the tunnel and heat exchanger tubes.

The air circulating through the tunnel and heat exchanger is always saturated. As cool air moves down the tunnel the warm reservoir droplets transfer both heat and water vapor to the air at the surface of the droplet, but as the water vapor diffuses away from the warm surface of the droplet it is assumed to recondense as fog, so that both the sensible and latent heat contributed from the droplet raise the temperature of the tunnel air. When the warmed air at the end of the tunnel enters the heat exchanger, it loses heat to the ambient air through the wall of the heat exchanger tube, and water condenses within the tube as the temperature and saturation vapor pressure fall. The simulation follows a Lagrangian air parcel through the tunnel to calculate the heat transfer from the reservoir water to the air, and a second Lagrangian parcel through a heat exchanger tube to calculate the transfer of heat from the air in the heat exchanger tube to the outside.

The tunnel Lagrangian parcel is a lamina of tunnel cross section with volume Δ*VT* ¼ *h*Δ*W*Δ*Z*, where *h* = 1.54 m is the height between the reservoir water surface and the bottom of the droplet dispenser trays, Δ*Z* = 10 m is the width of the tunnel, and Δ*W* = 5 cm is the thickness of the lamina along the direction of tunnel airflow. During the small time step *dt* ¼ Δ*W=vT* < < Δ*t*, the heat *dQT*,Cnv that is transferred convectively from the falling droplets to the tunnel air is calculated within the parcel volume Δ*VT*. The time step *dt* that is used to update the Lagrangian parcel is much smaller than the simulation time step Δ*t* that is used to update Eqs. (1)–(3). The reservoir droplets also release the water vapor mass �*dMr* into the parcel air. The temperature increase *dTT*,*<sup>a</sup>* of the parcel air due to both sensible and latent heat is then:

*Simulation of a Novel Cooling System for a Closed Greenhouse DOI: http://dx.doi.org/10.5772/intechopen.113135*

$$dT\_{T,a} = \left(dQ\_{T,\text{Crv}} - H\_v dM\_r\right) / \left(\Delta V\_T \rho\_a \mathcal{C}\_{pa}\right) \tag{4}$$

After the parcel has traversed the entire length of the tunnel it has accumulated the heat *δQT* so that heat is removed from the reservoir at the rate *δQT=dt*. Therefore, during the simulation time step Δ*t* the reservoir temperature changes by:

$$
\Delta T\_r = -\left(\frac{\Delta t}{dt}\right) \frac{\delta Q\_T}{A\_r d\_r \rho\_w C\_{pw}}\tag{5}
$$

Within the heat exchanger tube the simulation follows a cylindrical Lagrangian parcel with volume Δ*Vx* ¼ *πD*<sup>0</sup> 2 Δ*L=*4 where Δ*L* ¼ 3 cm is the length of the parcel and *D*<sup>0</sup> is the inner diameter of the tube. The time step for the heat exchanger tube simulation is *dt* ¼ Δ*L=vx* < < Δ*t*.

The heat exchanger tube enables the forced convection of heat to the ambient air through the total heat transfer coefficient *hc*. There are three contributions to *hc* that each represent a resistance to heat transfer out of the tube [22]:

$$\frac{1}{D\_0 h\_\epsilon} = \frac{1}{D\_0 h\_0} + \frac{\log(D\_1/D\_0)}{2k\_{01}} + \frac{1}{D\_1 h\_1} \tag{6}$$

The first term on the right hand side with heat transfer coefficient *h*<sup>0</sup> computes the convection across the boundary layer of air flowing within the tube. The third term with heat transfer coefficient *h*<sup>1</sup> computes the convection across the boundary layer of the outside crossflow air stream flowing through the heat exchanger tube bank. Outside fans pull air across the tube bank at the same speed *v*<sup>1</sup> ¼ *vT* as the airspeed through the tunnel.

The second term with thermal conductivity coefficient *k*<sup>01</sup> computes the heat conduction through the wall of the tube. For PETG tubing, *<sup>k</sup>*<sup>01</sup> <sup>¼</sup> <sup>0</sup>*:*0029W cm�<sup>1</sup> <sup>K</sup>�<sup>1</sup> . Although the thermal conductivity of plastic tubing is very low, metal tubing for the heat exchanger was rejected as impractical because of cost. Because the 0.5 mm tube wall is very thin, the thermal conductivity through the wall contributes only about 3% of the total resistance to heat transfer in Eq. (6).

The heat transfer coefficients are calculated from dimensionless Nusselt numbers: *h*<sup>0</sup> ¼ Nu0*ka=D*<sup>0</sup> and *h*<sup>1</sup> ¼ Nu1*ka=D*1, where *ka* is the thermal conductivity for air. For turbulent air flow [23, 24]:

$$\begin{aligned} \mathbf{Nu}\_0 &= \mathbf{0.023} \,\mathrm{Re}\_0^{0.8} \mathrm{Pr}^{0.33} \\ \mathbf{Nu}\_1 &= \mathbf{0.33} \,\mathrm{Re}\_1^{0.6} \mathrm{Pr}^{1/3} \end{aligned} \tag{7}$$

Re <sup>0</sup> ¼ *D*0*vxρa=μ<sup>a</sup>* is the Reynolds number for air flow inside the tube, where *μ<sup>a</sup>* is the viscosity of air, and Re <sup>1</sup> ¼ *D*1*v*<sup>1</sup> *ρa=μ<sup>a</sup>* is the Reynolds number for the outside cross flow of air within the tube bank. The Prandtl number is given by Pr ¼ *Cpaμa=ka*. Note that the temperature loss down the tube is only a weak function of the airspeed *vx*: although the residence time for a parcel of air within a tube section of length Δ*L* is *dt* <sup>¼</sup> <sup>Δ</sup>*L=vx*, the heat transfer coefficient is proportional to *<sup>v</sup>*<sup>0</sup>*:*<sup>8</sup> *<sup>x</sup>* . Hence the total rate of heat transfer roughly scales with *vx* so that high speed turbulent flow through the heat exchanger tubes is preferred.

The temperature drop Δ*T* within a tube parcel during a time step *dt* depends upon the heat *dQw* transferred from the air through the wall of the tube and on the heat of

fusion *dQm* released into the volume of the parcel as water vapor in the saturated air condenses due to the drop in temperature:

$$
\rho\_a \mathbf{C}\_{pa} \Delta V\_{x} \Delta T = d \mathbf{Q}\_w - d \mathbf{Q}\_m \tag{8}
$$

In Eq. (8), the temperature drop Δ*T*, *dQw*, and *dQm* are all unsigned positive quantities. *dQw* and *dQm* are given by:

$$\begin{aligned} dQ\_w &= h\_c (\pi D\_0 \Delta L)(T - T\_o) dt \\ dQ\_m &= \left(\pi D\_0^2 \Delta L/4\right) \rho\_a H\_v \Delta T \frac{d\mathbf{X}}{dT} \end{aligned} \tag{9}$$

where *X* and *T* are the mixing ratio and temperature of the tube parcel air. Eqs. (8) and (9) may be combined to solve for the temperature drop Δ*T* during the time interval *dt*:

$$
\Delta T = \frac{4h\_c(T - T\_o)dt}{\rho\_a D\_0 \left(C\_{pa} + H\_v \frac{dX}{dT}\right)}\tag{10}
$$

The derivative *dX=dT* is obtained by differentiating the expression for the mixing ratio in terms of the saturation vapor pressure *Ps*ð Þ *T* :

$$X(T) = \frac{M\_w P\_s(T)}{M\_a(P\_{\text{atm}} - P\_s(T))} \tag{11}$$

where *Ma* and *Mw* are the gram molecular weights of air and water and *P*atm is one atmosphere of pressure [21].

#### **3.3 Greenhouse temperature, humidity, and VPD over a 24 hour cycle**

**Figure 7** shows the temperature of the greenhouse air and reservoir over a 24-hour cycle. The sun sets at 19:00 and the reservoir water is warm from the previous day. The sides of the tunnel are closed off from the remainder of the greenhouse volume and the tunnel is opened at each end to the ducts that lead to the heat exchanger tube bank in preparation for discharging the accumulated reservoir heat. The ambient temperature decreases (**Figure 6**) and the temperature of the greenhouse air also decreases as heat is conducted through the greenhouse cover. At 22:47 the ambient air temperature has fallen to 2°C less than the reservoir temperature and the fans and dispensers are activated in the tunnel to discharge the reservoir heat. The temperature in the reservoir continues to drop until 9:00 when the heat discharge period ends. During this time the sides of the tunnel are opened to the remainder of the greenhouse volume and the ports to the heat exchanger at the ends of the tunnel are closed. Droplets are dispensed to cool the greenhouse air and the reservoir temperature begins to rise.

The sun rises and begins to heat the greenhouse at 7:00. The temperature begins to climb rapidly until the daytime droplet activation period begins at 9:00. After 9:00 the temperature continues to climb more slowly as the insolation increases and the reservoir temperature increases, reducing the efficacy of the droplet system. At 15:30 the air temperature begins to gradually subside as the solar insolation drops. At 17:00 the droplet flow is reduced by 60% from 100 L s�<sup>1</sup> to 40 L s�<sup>1</sup> and there is a cusp in the air *Simulation of a Novel Cooling System for a Closed Greenhouse DOI: http://dx.doi.org/10.5772/intechopen.113135*

**Figure 7.** *Greenhouse air and reservoir water temperatures over a 24-hour cycle.*

temperature curve when the temperature starts to rise. At 18:00 the droplets are turned off entirely creating a second cusp in the curve.

**Figure 8** is a plot of the relative humidity (RH) of the greenhouse air. During the night the RH gradually drops because the drop in air temperature is more than compensated with the removal of water vapor by the condensing tubes on the roof of the greenhouse. At 7:00 light begins to enter the greenhouse and the plants transpire, overwhelming the condensing tubes and causing the RH to rise rapidly. The humidity drops sharply at 9:00 when the droplet dispensers are activated for daytime cooling. The rising greenhouse temperature and falling efficacy of the droplet cooling compensate one another to keep the RH roughly constant until 15:00, when the RH begins to rise. At 17:00 the droplet flow is reduced by 60%, causing a small jump in RH that is

**Figure 8.** *Greenhouse relative humidity over a 24-hour cycle.*

#### **Figure 9.**

*Sensitivity of the vapor pressure deficit to the daytime droplet flow in the greenhouse over a 24-hour cycle. The previous plots were created for a daytime droplet flow of 100 L s*�*<sup>1</sup> .*

quickly counteracted by the rise in temperature. At 18:00 when the droplets are shut off the RH rises rapidly, but this is counteracted by the steep drop in plant transpiration as the sunlight disappears, so that the condensing tubes begin reducing the humidity after 20:00.

The greenhouse temperature and relative humidity may be combined to compute VPD. The VPD controls the transpiration of the plants, and it has been argued that the VPD is the parameter most relevant to the comfort of the plants [25, 26]. **Figure 9** is a plot of the greenhouse VPD for several values of the daytime droplet flow, demonstrating that the VPD may be tuned for this greenhouse design by adjusting the daytime droplet flow. VPD values in the range of 0.4–1.3 kPa are optimal for greenhouse cultivation [25].

#### **4. Discussion and conclusions**

The simulation predicts that 191.5 kWh are required to operate the fans and pumps during a 24-hour cycle to cool a 1000 m<sup>2</sup> greenhouse, assuming the conditions specified in **Figures 3** and **6** for the incoming solar radiation and the ambient temperature. 62.4% of this energy is used to operate the pumps. Once the reservoir is cold, the greenhouse air may be cooled during the day with a smaller expenditure of energy. 90.3% of the energy required to operate the greenhouse is used to discharge the accumulated reservoir heat using the air-to-air heat exchanger, or 173 kWh. The strategy to leverage the ambient temperature difference between the morning and afternoon significantly reduces the energy cost compared to using an air-cooled chiller, which requires 6.9 times the energy for a coefficient of performance of 4 [21]. The maintenance of the proposed cooling system would be simpler than the maintenance of a chiller, requiring the occasional replacement of pumps, fans, heat exchanger tubes, and tiles for the dispensers.

The energy cost per cultivated area for the closed greenhouse is far greater than using a conventional ventilated greenhouse cooled by a fan-pad system. Cooling a

#### *Simulation of a Novel Cooling System for a Closed Greenhouse DOI: http://dx.doi.org/10.5772/intechopen.113135*

1000 m<sup>2</sup> greenhouse evaporatively with a fan-pad system for 8 h during the day would require 14.8 kWh for the fans, assuming an airflow of 60 m<sup>3</sup> s �<sup>1</sup> [21], a factor 13 less than the closed greenhouse design proposed here. Furthermore the conventional greenhouse does not require the costs for constructing the closed greenhouse cooling system including pumps, extra fans, reservoirs, dispensers, and heat exchanger tubes. The significant additional costs of constructing and operating a closed greenhouse enable conserving fresh water, maintaining an arbitrarily high concentration of CO2 during the afternoon period of peak photosynthesis, and sequestering captured CO2 into biomass.

Civilization is entering an era of abundant renewable energy but diminishing freshwater resources. Photovoltaics and battery storage have enormous potential for future innovation, and renewable energy costs will continue to fall from economy of scale as solar and wind replace fossil fuels. However freshwater resources are increasingly precious. The conventional fan-pad greenhouse used in the comparison above consumes 7.9 m<sup>3</sup> d�<sup>1</sup> of water for evaporative cooling assuming an ambient temperature of 33°C and ambient relative humidity of 37% [21]. For a limited number of greenhouses this amount of water may not be a concern, but for many square kilometers under greenhouse cultivation in the desert a water loss this high becomes impractical.

It may be possible to reduce the cost of cooling system components by using recycled plastic. The reservoirs, heat exchanger tubes, and dispensers are made from thermoplastics that may be melted and reformed repeatedly. Recycling used plastic products into new products is the most desired means of disposal [27], so that extensive closed greenhouse construction might become a useful output stream for plastic waste.

The enhancement of photosynthesis at higher temperatures in the presence of elevated levels of CO2 is fortuitous for closed greenhouses because of the energy demand by the cooling system to reduce the temperature and dehumidify the air. If the greenhouse temperature is allowed to increase, then the greenhouse relative humidity must also increase to maintain the same VPD for plant transpiration.

The photosynthesis enhancement at elevated temperature and CO2 has been investigated for tomatoes [11, 12] and other plants [10, 13, 14]. The biochemical mechanism for this enhancement, and the mechanism for inducing damage to photosynthesis under significant heat stress when elevated levels of CO2 are not present, remain active areas of investigation [12]. At the beginning of the Calvin cycle in photosynthesis, CO2 attaches to the sugar substrate RuBP (ribulose bisphosphate), catalyzed by the enzyme rubisco (ribulose bisphosphate carboxylase). As the temperature increases a competing reaction becomes more favorable, where oxygen attaches to RuBP instead of CO2, leading to photorespiration rather than photosynthesis. By increasing the concentration of CO2 the photorespiration reaction may be suppressed so that photosynthesis can take advantage of the increased activity of rubisco at higher temperature. This mechanism holds at all light intensities, although the effect is enhanced with increasing light intensity [11].

If the temperature increases too much it may damage plant photosynthesis if the CO2 concentration is not also increased. One hypothesis [12] argues that increased heat stress reduces the stomatal conductance, reducing the CO2 available to the Calvin cycle and effectively reducing or interrupting electron transport to rubisco and RuBP, reducing both the activity of rubisco and the regeneration of RuBP. Thylakoid electron transport away from the PSII reaction center (PSII RC) is effectively blocked or reduced, causing excessive reduction of the acceptor which damages the PSII RC.

Elevating ambient CO2 restores the flow of electrons from the PSII RC to the Calvin cycle, restoring the redox balance along the electron transport path so that damage to the PSII RC is prevented.

Closed greenhouses could extend agriculture in higher elevation deserts into regions far beyond what might be currently irrigated near a river or lake. In addition to enhancing yields for standard greenhouse crops such as tomatoes and peppers, closed greenhouses could cultivate woody plants to sequester CO2 into lumber and biochar. Bamboo for example is fast-growing and very responsive to enhanced concentrations of CO2 [28]. A large-scale program of CO2 sequestration into biomass might best be implemented in selected climates that are extremely favorable for deployment of the cooling system, such as the Altiplano plateau in Bolivia, Peru, and Chile.

The cooling system functions equally well in high humidity climates where evaporative cooling may be impractical. Coffee may be a suitable closed greenhouse crop because it prefers high humidity and shade, and a greenhouse would help protect the plants from unfavorable climate change induced conditions such as droughts, heat waves, and pests. Enhanced CO2 concentrations also allow coffee plants and bean quality to endure supra-optimal temperatures during the day and night [13]. The coffee plant shows both reduced photorespiration in the presence of elevated CO2 and increased thylakoid electron transport [14].

Future research will include building and testing a full prototype and further simulations to explore variations and improvements to the design. One variation under consideration is an aquaponic system, where cold water fish are raised in tall cisterns that serve as reservoirs, and nutrient rich reservoir water is circulated between the reservoirs and hydroponically grown vegetables or a deep water culture of lettuce or rice. Another variation is a closed greenhouse for northern climates, where the heat exchanger tubes are optionally enclosed within the greenhouse volume during the winter. Heat captured by the reservoir during the day is released by the heat exchanger into the cold greenhouse air at night to prevent the plants from freezing.

In summary, the simulation has demonstrated that it is possible to cool a closed greenhouse with a large reservoir of water and an air-to-air heat exchanger comprised of thin-walled plastic tubes. The reservoir volume used in the design is *A*/2 m<sup>3</sup> , where *A* is the area of the cultivated region in m<sup>2</sup> . The closed greenhouse requires about an order of magnitude more energy to cool than a conventional greenhouse cooled evaporatively using a fan-pad system. Hence the cooling system relies upon a high expenditure of electric power to conserve water and to maintain high concentrations of CO2 during the day to enhance yields. The summer insolation and minimum daily temperature are the most important parameters that decide the size and cost of the cooling system, so that regions where the greenhouse design may be deployed are restricted to climates with cool morning temperatures. The VPD within the greenhouse may be tuned by adjusting the droplet flow that cools the greenhouse during the day. Deployment of closed greenhouses in regions with very low minimum diurnal temperatures (< 8°C) during summer potentially allow profitably sequestering CO2 into biomass.

#### **Acknowledgements**

The author gratefully acknowledges the advice and encouragement of Professor J. Heiner Lieth at the University of California, Davis, and his consent to conduct heat and mass transfer experiments using a greenhouse on the Davis campus.

#### **Conflict of interest**

The author declares no conflict of interest.

### **Author details**

Geordie Zapalac Independent Researcher, Santa Clara, CA, USA

\*Address all correspondence to: geordie.zapalac@gmx.com

© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

[1] Mariem SB et al. Climate change, crop yields, and grain quality of C3 cereals: A meta-analysis of [CO2], temperature, and drought effects. Plants. 2021; **10**(6):1052-1070. DOI: 10.3390/ plants10061052

[2] Capon SJ, Stewart-Koster B, Bunn SE. Future of freshwater ecosystems in a 1.5°C warmer world. Frontiers in Environmental Science. 2021;**9**:784642. DOI: 10.3389/fenvs.2021.784642

[3] Burrell AL, Evans JP, De Kauwe MG. Anthropogenic climate change has driven over 5 million km<sup>2</sup> of drylands towards desertification. Nature Communications. 2020;**11**:3853. DOI: 10.1038/s41467-020-17710-7

[4] Lowery B et al. The 2008 Midwest flooding impact on soil erosion and water quality: Implications for soil erosion control practices. Journal of Soil and Water Conservation. 2009;**64**(6): 166A. DOI: 10.2489/jswc.64.6.166A

[5] Eslami S et al. Projections of salt intrusion in a mega-delta under climatic and anthropogenic stressors. Communications Earth & Environment. 2021;**8**:142. DOI: 10.1038/s43247-021- 00208-5

[6] Climate Change 2022: Mitigation of Climate Change. Working Group III Contribution to the IPCC Sixth Assessment Report. Geneva, Switzerland: Intergovernmental Panel on Climate Change; 2023

[7] Ehlig-Economides C, Economides MJ. Sequestering carbon dioxide in a closed underground volume. Journal of Petroleum Science and Engineering. 2010;**70**:123-130. DOI: 10.1016/ j.petrol.2009.11.002

[8] Akinnikawe O, Ehlig-Economides CA. Geologic model and fluid flow simulation of Woodbine aquifer CO2 sequestration. International Journal of Greenhouse Gas Control. 2016;**49**:1-13. DOI: 10.1016/j.ijggc.2016.02.014

[9] IEA. Storing CO2 Through Enhanced Oil Recovery. Paris: IEA; 2015. Available from: https://www.iea.org/reports/ storing-co2-through-enhanced-oilrecovery [Accessed: August 30, 2023], License:CC BY 4.0

[10] Jurik TW, Weber JA, Gates DM. Short-term effects of CO2 on gas exchange of leaves of Bigtooth Aspen (*Populus grandidentata*) in the field. Plant Physiology. 1984;**75**:1022-1026. DOI: 10.1104/pp.75.4.1022

[11] Nilsen S, Hovland K, Dons C, Sletten SP. Effect of CO2 enrichment on photosynthesis, growth and yield of tomato. Scientia Horticulturae. 1983;**20**: 1-14. DOI: 10.1016/0304-4238(83) 90106-1

[12] Pan C, Ahammed GJ, Li X, Shi K. Elevated CO improves photosynthesis under high temperature by attenuating the functional limitations to energy fluxes, electron transport and redox homeostasis in tomato leaves. Frontiers in Plant Science. 2018;**9**:1-11. DOI: 10.3389/fpls.2018.01739

[13] DaMatta FM, Rahn E, Läderach P, Ghini R, Ramalho JC. Why could the coffee plant crop endure climate change and global warming to a greater extent than previously estimated? Climate Change. 2019;**152**:167-178. DOI: 10.1007/ s10584-018-2346-4

[14] Ramalho JC et al. Sustained photosynthetic performance of *Coffea* *Simulation of a Novel Cooling System for a Closed Greenhouse DOI: http://dx.doi.org/10.5772/intechopen.113135*

spp. under long-term enhanced [CO2]. PLoS One. 2013;**8**(12):e82712. DOI: 10.1371/journal.pone.0082712

[15] Vadiee A, Martin V. Energy analysis and thermoeconomic assessment of the closed greenhouse–The largest commercial solar building. Applied Energy. 2012;**102**:1256-1266. DOI: 10.1016/j.apenergy.2012.06.051

[16] Opdam JJG, Schoonderbeek GG, Heller EMB, de Gelder A. Closed greenhouse: A starting point for sustainable entrepreneurship in horticulture. Acta Horticulturae. 2005; **691**:517-524. DOI: 10.17660/ ActaHortic.2005.691.61

[17] Zaragoza G, Buchholz M. Closed greenhouses for semi-arid climates: Critical discussion following the Watergy prototype. Acta Horticulturae. 2008;**797**:37-42. DOI: 10.17660/ ActaHortic.2008.797.2

[18] Buchholz M, Buchholz R, Jochum P, Zaragoza G, Para JP. Temperature and humidity control in the Watergy greenhouse. Acta Horticulturae. 2006; **719**:401-408. DOI: 10.17660/ ActaHortic.2006.719.45

[19] Novarbo. Heat Reuse™ [Internet]. Available from: https://www.novarbo. fi/en/greenhouse-technology/heat-reuse. html [Accessed: August 30, 2023]

[20] Huttunen J. Closed greenhouse cooling with water droplet curtain. Acta Horticulturae. 2011;**893**: 1043-1047. DOI: 10.17660/ ActaHortic.2011.893.118

[21] Zapalac G. Simulation of a convectively-cooled unventilated greenhouse. Computers and Electronics in Agriculture. 2022;**193**:106563. DOI: 10.1016/j.compag.2021.106563

[22] Bird RB, Stewart WE, Lightfoot EN. Transport Phenomena. New York: Wiley; 1960. p. 780. DOI: 10.1002/ aic.690070245

[23] Edward DK, Denny WK, Mills AF. Transfer Processes: An Introduction to Diffusion, Convection, and Radiation. New York: McGraw-Hill; 1979. p. 421. ISBN: 13: 9780070190412

[24] Khan WA, Culham JR, Yovanovich MM. Convection heat transfer from tube banks in crossflow: Analytical approach. International Journal of Heat and Mass Transfer. 2006;**49**:4831-4838. DOI: 10.1016/j.ijheatmasstransfer. 2006.05.042

[25] Shamshiri RR et al. Review of optimum temperature, humidity, and vapour pressure deficit for microclimate evaluation and control in greenhouse cultivation of tomato: A review. International Agrophysics. 2018;**32**: 287-302. DOI: 10.1515/intag-2017-0005

[26] Zolnier S et al. Psychometric and ventilation constraints for vapor pressure deficit control. Computers and Electronics in Agriculture. 2000;**26**: 343-359. DOI: 10.1016/S0168-1699(00) 00084-3

[27] Evode N et al. Plastic waste and its management strategies for environmental sustainability. Case Studies in Chemical and Environmental Engineering. 2021;**4**:100142. DOI: 10.1016/j.cscee.2021.100142

[28] Grombone-Guarantini MT et al. Atmospheric CO2 enrichment markedly increases photosynthesis and growth in a woody tropical bamboo from the Brazilian Atlantic Forest. New Zealand Journal of Botany. 2013;**51**:275-285. DOI: 10.1080/0028825X.2013.829502

### Section 3
