**1.3 The energy consumption and emission discharge in green space maintenance**

The maintenance work in urban green space includes the consumption of energy resources and the discharge of waste to the environment, with annual cycles [9]. In daily maintenance, most trimming work and plant waste transportation depend on machine use. This machine work mainly consumes fossil energy and emits harmful gases (including CO2, NOx, CH4, etc.) into the atmosphere. Irrigation mainly consumes urban tap water. The fertilizer and pesticide consumed in fertilization and pest control work can produce soil carbon residues. Besides, the trucks responsible for fertilizer transportation and drug spraying also need to consume fossil energy and generate exhaust gas [10, 11].

The fossil energy (gasoline, diesel, etc.) consumed in green space maintenance is named direct energy (DE) consumption, which can be converted with standard coal that releases the same amount of heat during combustion. The use of water resource, fertilizer, and pesticide is named indirect energy (IDE) consumption. The IDE consumption also has the equivalent conversion coefficient with the calorific value of standard coal, and ultimately all show the consumption of heat energy [12, 13]. Among the harmful gases emitted by green space maintenance, greenhouse gases (GHG) have been recognized as the main source of atmospheric pollution, which account for more than 83% of the total emissions [14]. This energy consumption and exhaust emissions persist with the annual cycle of maintenance tasks.

Although the purpose of maintenance is to provide a safe and healthy development for the green space, which is able to continue the service for the urban public, this long-term human intervention in the green space itself also violates the basic requirements for the sustainable development: maximization of self-renewal and

most parts of the world has changed from "quantity" to "quality" [2]. Take China as

many urban reservations were filled with woodland and lacked maintenance.

*The increase of maintenance equipment used in Chinese urban green space (2000–2018).*

*The increase of urban built-up and green space area in China (2000–2018).*

*Sustainability in Urban Planning and Design*

reducing resource consumption to save on maintenance budgets.

The extensive growth period of the urban green space was from 1990 to 2004. With the intention of the "garden city" proposed by the Ministry of Construction, most cities began to expand the green area and pursue high greening rates [3]. During this period,

From 2005 to 2014, urban green space growth began to focus on the richness of vertical plant layers. This dramatically increases the maintenance workload. With the goals of the "National Forest City" and "Ecological Garden City" proposed by the State Forestry Administration and the Ministry of Construction, the development of urban green space has turned to forest vegetation as the main body, enriching the vertical plant level to improve ecological functions [4]. Multilevel plant communities require more maintenance tasks to maintain the shape or function of each plant layer than traditional woodland green spaces [5]. During this time, the growing maintenance workload has forced city managers to consider increasing productivity and

In the year 2015, the General Office of the State Council issued the "Guiding Opinions on Promoting the Construction of Sponge City" [6]. This framework

an example.

**220**

**Figure 2.**

**Figure 1.**

minimization of the artificial disturbance [15]. Therefore, reducing the environmental impact caused by maintenance tasks will contribute to the sustainable development of urban green space.

the potential environmental impact of human behavior from the beginning to the end by collecting the life cycle inventory (LCI) [24]. The LCA method includes four steps (**Figure 3**): goal and scope definition; analysis of life cycle inventory; environmental impact assessment; and interpretation of results [25]. It is mainly used to quantitatively study the negative environmental impacts (i.e., resource energy consumption and waste discharge) on the LCI list and seek ways to decrease the

LCA was initially applied primarily to research on resource consumption and environmental impacts of product packaging. In the early 1980s, due to the global energy crisis, environmental problems mainly focused on fossil energy consumption and combustion pollutant emissions, and the life cycle assessment method also entered the stage of academic discussion. At the same time, with the global solid waste problem that emerged from the late 1970s to the mid-1980s, the life cycle method has gradually become a resource analysis tool and has entered the field of scholars. Research at that stage mainly focuses on the assessment method construction, with limited case studies. The earlier LCA research was concentrated in the

After entering the 1990s, LCA entered a stage of rapid development. In 1990, for the first time, the International Society of Environmental Toxicology and Chemistry (SETAC) hosted an international seminar on LCA. The concept of "life cycle assessment" was first presented at the conference. In the following years, the SETAC hosted and held several academic seminars and conducted extensive research on the theory and methods of life cycle evaluation [28]. Although the current life cycle assessment methodology still has many issues worth studying, the SETAC and the International Standards Organization (ISO) have been actively promoting the international standardization of LCA. The ISO 14040 standard (Environmental Management—Principles and Framework for Life Cycle Assessment) was promulgated on 1997, and the corresponding series of standards ISO 14041 (list analysis), ISO 14042 (impact evaluation), and ISO 14043 (interpretation of impact statements) are also in the following [24]. The standard system has a great improvement to the standardiza-

Construction of the LCI database is a vital factor in the development of LCA. LCI database includes the total environmental impact data on every life cycle stage of the upstream product. The LCI database construction starts from the early 1990s.

environmental stress of production or behavior system [26].

United States and encouraged by the government [27].

tion steps of the LCA concept and the technical framework.

**2.2 The development of LCA**

*Sustainable Design in Urban Green Space DOI: http://dx.doi.org/10.5772/intechopen.90026*

**Figure 3.**

**223**

*The framework of LCA [24].*

## **1.4 The literature review of environmental impact in urban green space maintenance**

Few urban environment assessment systems are mentioned about the environmental impacts of green space maintenance. The University of Florida, in the "Florida-Friendly Landscaping Guidelines," proposed that the maintenance team should sign a contract with the green space owners and enact a detailed working plan before maintenance operations. The working plan should estimate the types of maintenance tasks and detail workload. This is important to improve working efficiency, save maintenance materials, and reduce environmental impacts [16]. The "Sustainable Sites Initiative" (proposed by the US Lady Bird Johnson Wildflower Center and US Botanic Garden) point out that during the complete life cycle of the urban landscape (design, construction, operation, maintenance, and disposal), the maintenance procedure occupied around 10–20% of the total environmental impact [17].

Some research point out reducing the maintenance workload can decrease the environmental impact and improve the ecological benefits of the green space. Zhao and Liu pointed out that the city managers should reduce the area of grassland and plant more native woodland to improve the adaptability and tolerance of urban green space. Extensive use of wildflowers and meadows can also benefit to the urban wildlife and reduce the maintenance requirement [18]. Guo in the renewable and recyclable landscape research indicated that the self-maintenance green space is able to maximize the utilization of energy and materials and reduce environmental pollution in the use process [19]. Min put forward that the conservation green space is to improve the utilization rate of maintenance resources and energy use and obtain the maximum ecological, environmental, and social benefits [20]. Shu-Hua pointed out that symbiotic cyclic urban landscape architecture should adopt the design of low environmental impact, including the selection of recyclable, lowconsumption, and high-durable building materials, and pay attention to reduce the maintenance material input in the later period [21].

The quantitative study on the environmental impact of urban green space maintenance is limited. After finishing 3 years of urban green space maintenance carbon emission data collection for the three major cities, Seoul, Chuncheon, and Gangneung, Hyun found that the annual increase of urban green space carbon emissions is between 10 and 20%. The average carbon (CO2-eq) emissions are 264.9, 37.0, and 67.9 t/ha/y<sup>1</sup> in Seoul, Chuncheon, and Gangneung, respectively. The annual carbon storage in the three urban green spaces (the amount of CO2-eq) is about 50% of the respective carbon emissions [22]. Lynch et al. believe that pruning, fertilization, pest control, and other works in green space maintenance can cause heavy carbon discharge. The design phase can directly influence the maintenance workload, such as the time investment, energy, and water consumption in urban green space [23].

#### **2. Life cycle assessment of the environmental impact**

#### **2.1 Introducing of LCA**

Life cycle assessment (LCA) is a comprehensive tool for evaluating the environmental impact of products or behaviors. This method can comprehensively analyze *Sustainable Design in Urban Green Space DOI: http://dx.doi.org/10.5772/intechopen.90026*

the potential environmental impact of human behavior from the beginning to the end by collecting the life cycle inventory (LCI) [24]. The LCA method includes four steps (**Figure 3**): goal and scope definition; analysis of life cycle inventory; environmental impact assessment; and interpretation of results [25]. It is mainly used to quantitatively study the negative environmental impacts (i.e., resource energy consumption and waste discharge) on the LCI list and seek ways to decrease the environmental stress of production or behavior system [26].
