Many cassava producing nations lack suitable energy availability and sufficiency. Just 10% of the population in Haiti receive power from the national electric grid. The proportion is 7% for Mozambique. In both countries, deforestation is extensive due to dependence on wood and charcoal for 70 and 85% of energy requirement respectively. In the case of Ghana, although biomass accounts for 64% of national energy supply, the dependence on primary biomass energy sources like wood and charcoal has led to increased loss of biodiversity, soil erosion and health problems. Prospects for the use of cassava peeling residues as a source of biomethane to mitigate these constraints have received little attention. In this chapter, the advantages and benefits of biomass energy, along with the potential for cassava as a feedstock and rationale for anaerobic digestion are highlighted. Depending on the quantity of cassava root processed by individual countries, the energy recovered from cassava peeling residues could satisfy up to 100% of national energy requirements.

Convenient energy sources like biomethane and electricity are scarce commodities in cassava producing countries that depend on wood and charcoal for energy supply. Combustion of wood and charcoal releases substances that impair human health. In 2016, about 30 million metric tons of cassava peeling residues (CPR) were generated worldwide and discharged into the environment. Apart from deforestation, loss of biodiversity and soil erosion caused by felling vegetation for wood and charcoal recovery, discharge of CPR into the environment exacerbates environmental pollution and health hazards. This study presented biogasification experiments with CPR in a simple, batch, leach‐bed, unmixed fermentor. Biofuel yield ranged from 180 to 310 (mean of 252) L CH4 kg−1 VS−1 while fermentation time ranged from 19 to 33 (mean of 27) days. The substrate contained on average 33% dry matter of which 96% was volatile, and 71% volatile solids reduction was achieved. Furthermore, all electrical and thermal energy required for producing three cassava root food products (flour, gari, and starch) could be generated on‐site using CPR as substrate for anaerobic digestion. Consequently, energy paucity, environmental contamination, health hazards associated with cassava processing effluent, and combustion of wood and charcoal, could be mitigated by biogasification of CPR. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13138, 2019

Circular economic paradigm applies residue from one process as input material for another, fostering sustainable benefits for humanity. Anaerobic digestion (AD) is an attractive technology for biogas production in a circular economy. Digestate is the residual organic matter generated as coproduct of biogas. Because digestate is nutrient rich and largely stabilized, it has varied management options. Digestate is suitable for direct use as bio-fertilizer and is a good amendment material to improve soil physical properties. However, the quality, safety, and utility of digestate are dependent upon the characteristics of feedstock, digester process, pre-and postdigestion treatments. Digestates emanating from AD of animal manure, energy crops, food processing residues, and other feedstocks have been reported in published literature. On the other hand, there is dearth of reports on digestate emanating from AD process that utilized cassava peeling residue (CPR) as sole feedstock. This chapter presents relevant information on digestates including production, feedstock, quality and safety requirements, processing and treatment technologies, regulatory aspects, applications management options, cost implications, as well as challenges and opportunities. In addition, new results of nitrogen (N), phosphorus (P), and potassium (K) compositions of liquid fraction of CPR digestate are reported.

Abstract. In conventional practice, starch is extracted and purified from a native source prior to glucose production using two steps: liquefaction and saccharification. Sequential protocols, liquefaction, and starch extraction and purification necessitate high-energy process conditions, material handling equipment, and other substantial cost inputs. In this work, native starch in ground fresh cassava root pulp and cassava flour was subjected to low-energy, simple single-step enzymatic hydrolysis at 37°C and 60°C for glucose production. Commercial purified cassava starch was similarly treated for comparison. Cassava root pulp reached a maximum of 30% starch conversion to glucose within 4 h of hydrolysis at 60°C and a maximum of 55% conversion within 96 h at 37°C. Cassava flour yielded mixed results, with slightly less conversion than root pulp at 60°C, reaching only 27%, but outperformed root pulp at 37°C, reaching 72% conversion. Purified cassava starch yielded 96% and 100% conversions at 60°C and 37°C, respectively. At 37°C, the reaction rate constants were 0.023 h-1, 0.021 h-1, and 0.025 h-1, respectively, for cassava root pulp, flour, and purified cassava starch, while at 60°C, the reaction rate constants were 0.816 h-1, 1.230 h-1, and 1.102 h-1, respectively. Activation energy for the substrates was similar at 134.6 kJ mol-1 for root pulp, 157.4 kJ mol-1 for flour, and 143.1 kJ mol-1 for purified starch. Keywords: Cassava root, Cassava starch, Enzymes, Glucose, Reaction kinetics, Synergistic enzymatic hydrolysis.