Sustainable management of cassava processing waste for promoting rural development

Cassava is the third-most important food source in the tropics after rice and maize. Cassava is the staple food for about half a billion people in the World. It is a tropical crop grown mainly in Africa, Asia, and South America. It can be cultivated on arid and semiarid land where other crops do not thrive. During the processing of cassava into chips, flour or starch, enormous amount of wastes are generated ca. 0.47 tons for each ton of fresh tubers processed. This waste consists of peels, wastewater and pulp that contain between 36 to 45% (w/w) of starch and from 55 to 64% (w/w) of lignocellulosic biomass. An innovative processing system is therefore essential to take into account the transformation of this waste into value added products. This will address both the environmental pollution and inefficient utilization of these resources. The starch and lignocellulosic cassava processing waste can be converted into renewable energy carriers such as biogas through anaerobic digestion (AD), bio-ethanol through fermentation and bio-hydrogen through dark fermentation. In the case of AD, the waste can be used directly as substrate while for fermentation; the waste must be pre-treated to release monomeric sugars, which are substrates for bioethanol and bio-hydrogen production. There is possibility of sequential fermentation for either bio-ethanol or bio-hydrogen and AD for biogas production thereby making use of all the fractions of the cassava waste. Generation of renewable energy from cassava waste could benefit rural populations where access to electricity is very poor. This would also reduce the dependence on firewood and charcoal that are known to provide almost 90 percent of domestic energy requirements. Such a development could help save trees, lower emissions that cause climate change and reduce the fumes from millions of tons of firewood that threaten human health, especially the health of women and children. Although deforestation and land degradation are well-known, the charcoal and firewood consumption that causes them is still on the rise. This chapter, therefore, explores the use of cassava waste for production of fuel energy with a focus for use as domestic cooking fuel. It also proposes an efficient approach to cassava processing to ensure efficient resource utilization in which every part of the tuber is converted to value added products mitigating environmental pollution and improving human health