Valorization of cassava residues for biogas production in Brazil based on the circular economy: An updated and comprehensive review

Abstract

Biorefining is an essential component for achieving a sustainable economy. This approach makes use of zero-waste technologies and generates renewable energy. Besides converting organic waste into profit, the technology also avoids competition with biomass and different food-based feedstocks, water use, and impacts on biodiversity, making it a viable alternative to energy crops. In this context, anaerobic digestion (AD) allows proper waste management through controlling pollution/waste accumulation and converting organic matter into higher-value products: biogas and biofertilizer. Considering these points, Brazil has substantial agricultural productivity and generates a significant amount of waste residues that has enormous potential for biogas and bioenergy production. Cassava is an important staple crop for the country, particularly in northern and northeastern regions, where it is produced and processed mainly by families on a small-scale. It produces solid residues (peels, stems, and leaves) and wastewater, known as cassava wastewater, which is characterized by a high chemical oxygen demand, many mineral nutrients and cyanide. Nonetheless, all of these residues are usually disposed of in the vicinity without any treatment, rather than being used to produce higher value-added products. Hence, this review explored the potential role of anaerobic digestion for cassava residues management in association with the bio-based circular economy. Overall, the current manuscript emphasized cassava waste residue's potential for biogas generation, process intensification, scale scale-up strategies, and challenges. • In Brazil, cassava is a valuable staple crop that generates a lot of waste. • Anaerobic digestion of cassava residues is promising but has not yet been widely applied. • Co-digestion with animal manure or sewage sludge is a practical option. • The economic viability of biogas output from cassava residues is still required.