*3.1.3 Crop residue*

In every crop harvested, the residue obtained is 25-50% (Residue to Product ratio) of the product and sometime is above 100%. These organic parts mostly are left behind to regenerate the soil, as animal feed and source of energy. In 2010, agricultural residues with an energy content of some 90 EJ were reported to have been generated worldwide and is expected to reach 128 EJ in 2050 [19]. These materials


*\*\*The assumption made is that biowastes are used at small percentages; hence energy contributed by biomass mostly comes from fresh biomass.*

### **Table 2.**

*Example of biowaste energy potentials.*

are potential for energy although compete with animal feed and soil stabilization. The analysis of 19 crops mostly grown found that crop wastes of production rate of 697.87 million tons per year can generate 10.52 EJ. This potential is enough to support 366 million population (around 33% of 2019 Sub-Saharan Africa population) that had 28.76 GJ per capital [20]. If this energy from crop residue is well utilized and assuming mean biomass energy of 20 GJ/t, the wood biomass that can be saved is around 526 million tons of wood which is equal to 122 million hectare of forest area saved. The controversy of utilizing these wastes is the removal of nutrients from the soil. Currently, uncontrolled burning of these wastes onsite leads to the nutrients loss. A good control of burning and generating energy can generate ashes that can be used as fertilizers.

**Table 2** has summarized available data of biowaste from crop, forest and animal residue and MSW of six countries according to reported estimations. Furthermore the primary energy consumption for 2017 has been also recorded. Since the incorporation of biowaste analyzed is almost negligible, it can be said that the biomass contribution comes from fresh biomass. The use of biowastes can reduce this dependency.

### **3.2 Current management and utilization of biowastes in Africa**

Biowaste resources are important for energy, animal feed, and soil stabilization. The level of utilization depends on the investment and technology. In developed countries, the collection, treatment, and conversion have been a priority for incorporation in renewable energies and protection of environment. In Africa, the utilization of biowastes is still at low level. Very small investment and conversion technologies have been implemented. In rural areas, biowastes have been little used as animal feed and sources of energy. Due to poor technology and investment, biowastes use as sources of energy has been poor. The availability of fresh biomass for animal feed, biowastes have also found little use. These wastes have been accumulating continuously. The main method of handling has been unplanned dumping and uncontrolled combustion. Crop residue burning is more regular feature and a source of greenhouse gas emissions. Crop residue burning is driven by factors like labour scarcity, short turn-around time, socio-economic constraints, ignorance of farmers towards public health issues, and low nutritive value of crop residues. Crop residue burning causes loss of valuable soil nutrients, pollution episodes, and public health issues [28]. Unplanned damping may cause pollution especially when decomposition takes place and produces methane. Improper use of biowastes such as animal wastes especially cooking and heating leads to health problems. It has

*Biowastes as a Potential Energy Source in Africa DOI: http://dx.doi.org/10.5772/intechopen.99992*


### **Table 3.**

*Some of biowaste to energy conversion plants.*

been reported by WHO that 4.3 million deaths have occurred due to use of these wastes in cooking and heating [29]. The only advantage of poor handling of biowastes in rural area is to maintain soil quality. In rural areas, the generation of MSW is low while forest, animal, and crop wastes are high. Animal waste is commonly used as organic fertilizer and hence maintain soil ecosystem.

In urban area, the production of MSW is high while animal, forest, and crop residue is low. The big problem has been handling of MSW. Some efforts have been made in the collection and dumping of MSW. In Africa, most of collected MSW are unsorted and hence if energy conversion is decided to be done gets the challenge. In Africa, only a small amount of MSW is collected and dumped in landfill with no plan of energy recovery. There has been uncontrolled dumping and combustion which all lead to energy loss and environmental pollution.

Although there has been little effort to effectively utilize biowastes in Africa, some uses such as cooking, electricity generation, and transport fuel have been realized [30]. **Table 3** summarizes some of the plants generating electricity. Energy recovery technologies, such as landfill gas recovery and bio digesters for the organic fraction of MSW and industrial biomass are currently very limited in their implementation in Africa [31]. Gasification, direct combustion, and carbonization technologies have been in low utilization. Only noticeable biowaste waste to energy conversion has been in the use of bagasse in sugar plantation. In Tanzania, Kilombero, Mtibwa, TPC, and Kagera sugar companies have daily generation of 21,914 tons per day of bagasse and electricity installation of 40 MW [32]. The use of forest residue and sisal in Tanzania has led to the production of 21 MW. Currently, African only recycles 4% of waste produced and the African Union plans by 2023, 50% should be recycled. Other ways of managing biowaste have been producing composite manure, and animal feed.

### **3.3 Challenges of utilizing biowastes in Africa**

The use of biowastes in energy mix has not been fully done. Lack of appropriate technologies, investment, knowledge, and policy has hindered its utilization. Poor realization of biowaste potential has led to low investment and hence utilization. The wide large of properties of biowaste due to low level of farming, production of variety of biowastes, still brings challenges in the choice of universal technology and hence need segregation stages. Furthermore, government and financial institution have little interest in funding of innovation, purchasing, and utilization of appropriate technologies [33]. Therefore, efforts are needed to increase investment, education, and introduction of appropriate conversion technology.

To increase the use of biowastes in energy mix, the following can be done. The government should have appropriate policy that promotes use of biowastes. These includes; increase of incentives, removal of fossil fuel subsides, promotion of a net zero emission, and promotion research and development of appropriate technology. Education should be made to population on the need of using biowastes, separation of components of MSW in the disposal, discourage uncontrolled burning, introduction of simple and cheap conversion technology at household level. The peasants and farmers should be educated on the effective ways of preparation, collection, disposal, and utilization of wastes. To reduce variation obstacle, the co-generation and small processing plants should emphasized. To increase awareness, organization or companies that add value should be created.
