Full Title: Rural African renewable fuels and fridges: cassava waste for bioethanol, with stillage mixed with manure for biogas digestion for application with dual-fuel absorption refrigeration.Short Title: Rural African cassava waste for bioethanol and biogas for refrigeration.Authors: M P McHenry, D Doepel, K de Boer.
Biofuels, Bioproducts, & BiorefiningThe growth and processing of cassava (Manihot esculenta) in Africa produces a range of waste streams which are proving problematic due to their current mismanagement. Although a range of technical solutions exist to convert these waste streams into valuable products there has been very little progress made in applying these solutions. This review provides a broad picture of the cassava waste issue in the context of African agriculture and bioprocessing. As an outcome of the review process the authors propose a simple and scalable two-step process that biologically converts the waste streams into valuable products. The first step in the process is fermentation and distillation of the cassava waste to produce ethanol. The second step is the anaerobic digestion of the fermentation byproducts with other waste streams including animal manure and human excrement to produce biogas and biological fertilisers. Despite the scalability of this system, the focus of this paper is the development of a conceptual system for rural smallholders to achieve multiple beneficial outcomes including: treatment of multiple troublesome waste streams, production of a liquid biofuel, the provision of refrigeration through biogas powered absorption chillers and the coproduction of organic fertilisers.Keywords: Cassava; bioethanol; biogas; waste; sub-Saharan Africa.
IntroductionRural agricultural production is a livelihood that directly engages most of the population in sub-Saharan Africa, 1 and new technology and institutional capacity will likely underpin transformation in the sector. 2 In parallel, around 70% of African nations are dependent on energy imports, predominantly liquid fuels, making domestically produced biofuels an attractive option, particularly to stimulate employment and wider economic benefits.
3,4Alternative energy sources are necessary for various reasons, including strategic energy security and also fiscal stability. 4 Unfortunately, sub-Saharan Africa suffers from a combined effect of declining value of their export (primarily agricultural products), and the loss of market share to competitors. 3 Thus, a major challenge is adding value to existing domestic production, and cost-effectively securing domestic energy supplies while stimulating smallscale agricultural system productivity. 1 Parallel sustainable energy development and agricultural productivity gains are fundamental to rural development goals, and great attention is needed to successfully link existing crop production requirements with processes and technologies that best fit local social, economic, and ecological needs.
1, 3Current biofuel support policies remain a concern in relation to sub-Saharan imple...