**6. Utilization of rice husk for energy**

In 2014, it was estimated that Sub-Saharan Africa produces about 22.1 million tonnes of paddy, which represent about 4.6% of the total global production [5]. Structurally, paddy consists of about 72% kernel, 5–8% bran and 20–22% husk [62]. Therefore, when 22.1 million tonnes of paddy are subjected to milling, it produces about 4.8 million tonnes of husk [11]. With the increased production of paddy in Africa over the last 2 decades, the annual production of rice husk has also proportionally increased. The utilization of rice husk for economic purposes hitherto in Africa especially SSA is very low even though by-products such as rice husk is suitable raw material for energy generation and bran is a nutritive ingredient for food formulation [11, 63]. The high amount of silica in rice husk even when mixed with bran as obtained from village mills (Engelberg type mill) is not suitable for animal feeding purposes. In SSA, significant proportion of rice husk produced is disposed of by burning in open fields or abandoned around rice milling facilities [11]. These practices have resulted in the pollution of air, land and water through the generation of greenhouses gases and particles in water and air [64]. This situation calls for urgent and innovative technique to economically utilize the husk and improve rice postharvest handling for sustainable environment.

Rice husk, a by-product of rice milling is about 20% by weight of paddy and chemically contains about 20% SiO2. Gasification technique for rice husk as energy for rice parboiling and household cooking has been recently developed and is being commercialized across the continent of Africa [65]. Five different rice husk top-lit updraft (TLUD) gasifier household cooking stoves for use in rice processing clusters of Africa has been evaluated under a study to select technically feasible rice husk stove for rural and semi urban household cooking and artisanal rice processing in Africa. Ndindeng, *et al*. [65] study demonstrated that fan-assisted cook stoves especially PO150 recorded better thermal and emission indices and are safer to use than the natural draft gasifiers stove and is therefore recommended for household cooking in rice processing communities of Africa.

Gasification is the process of converting biomass such as rice husk into a combustible gas through thermo-chemical reaction of oxygen in the air and carbon available in the biomass during combustion. In other to gasify rice husk therefore, about 4.7 kg of air per kg of rice is needed [66, 67] and has resulted in the development of several models of fan-assisted rice husk gasifier [65]. The energy obtained are environmentally friendly and the technology easy to use by rural households. Using biomass such as rice husk in Africa for energy generation offers several advantages, including the mitigation of gaseous emissions such as CO2, SOx, and NOX [68]. This is probably due to low amount of sulphur and nitrogen present in

**219**

*Advances in Rice Postharvest Loss Reduction Strategies in Africa through Low Grade Broken Rice…*

agricultural residues as well as minimal chlorine content [69]. But the question arises as to whether some components of emitted gasses by the stove during burning can contaminate the food being processed and exert toxic effects on consumers. Germaine *et al*. [70] evaluated in vivo toxicity of rice husk used as fuel for household cooking and indicated significantly non toxicity of water boiled with rice husk gasifier. The results obtained by Germaine *et al*. [70] suggested that rice husk used as fuel in household cooking using a fan-assisted rice husk stove is not toxic at 0.5, 1.0 and 2 ml/100100 g body weight and did not produce any evident symptoms in the acute and sub-chronic oral toxicity studies. Even though no evident symptom of toxicity was observed, Quispe *et al*., [69] suggested that the use of agricultural residues such as rice husk for energy purpose require the performance of integral assessment considering all stage of its life cycle and comparing same with the use of fossil fuels as a means of identifying the conditions and scenarios for a lower environmental impact. Ndindeng, *et al*., [65], McKendry, et al., [71, 72] illustrated the following as the main advantages of the innovative rice husk gasification cook-

1.Newly introduced rice husk stove had better performance metrics than

2.Rice husk mixed with palm kernel shell or other biomass significantly increase

3.Data from end-user evaluation were in conformation with stove performance

4.If the rice husks are completely burned, the amount of CO2 produced is equal to the amount taken from the environment during the growing stage, making it husk gasification and environmentally sustainable practice.

5.Another advantage is the diversification of energy supply avoiding nonrenewable resources depletion which is challenging African forest and

Significant improvement has been made in Africa in terms of rice production mainly as a results of the development of new improved varieties, expansion of area under rice cultivation and huge public and private sector investments. This increased production has resulted in increased by-products such as broken rice fractions and husk. Poor utilization of the broken fractions resulted in reduction of productivity of rice and the husks have become of huge environmental and health changes. The high postharvest losses recorded in Africa has become of great concern to research and development experts, and new innovative methodologies were developed to use broken rice fractions for the production of high quality rice flour that could be used to produce high nutrients and consumer acceptable value added products that improve income and food security of smallholder rice value chain actors. The utilization of rice husk for energy generation has also become a fast moving technology where fan-assisted cooking stoves are developed and provide efficient alternative to fossil fuel. Both qualitative and quantitative postharvest losses in rice are being aggressively managed as a strategy to improve food and nutrition security, environmental sustainability and overall productivity of rice

*DOI: http://dx.doi.org/10.5772/intechopen.94273*

ing stove introduced in Africa:

farming lands.

**7. Conclusion**

that of existing brands in the region.

metrics determined instrumentally.

burning time but not flame temperature.

*Advances in Rice Postharvest Loss Reduction Strategies in Africa through Low Grade Broken Rice… DOI: http://dx.doi.org/10.5772/intechopen.94273*

agricultural residues as well as minimal chlorine content [69]. But the question arises as to whether some components of emitted gasses by the stove during burning can contaminate the food being processed and exert toxic effects on consumers. Germaine *et al*. [70] evaluated in vivo toxicity of rice husk used as fuel for household cooking and indicated significantly non toxicity of water boiled with rice husk gasifier. The results obtained by Germaine *et al*. [70] suggested that rice husk used as fuel in household cooking using a fan-assisted rice husk stove is not toxic at 0.5, 1.0 and 2 ml/100100 g body weight and did not produce any evident symptoms in the acute and sub-chronic oral toxicity studies. Even though no evident symptom of toxicity was observed, Quispe *et al*., [69] suggested that the use of agricultural residues such as rice husk for energy purpose require the performance of integral assessment considering all stage of its life cycle and comparing same with the use of fossil fuels as a means of identifying the conditions and scenarios for a lower environmental impact. Ndindeng, *et al*., [65], McKendry, et al., [71, 72] illustrated the following as the main advantages of the innovative rice husk gasification cooking stove introduced in Africa:

