Valorizing by-products from primary coffee processing through anaerobic fermentation

Coffee production is a livelihood for more than 125 million people worldwide. Primary coffee processing is all about producing green coffee beans however it also generates huge volume by-products in the form of husk, pulp, mucilage and parchment. These by-products are often discarded to the hosting environment without any economic benefit. Thus, poses threats to human, animals and aquatic biota. This book is composed of three main sections.In the first section, the characterization of coffee husk, pulp, mucilage and parchments was determined. The biomethane formation potentials of the substrates were examined in a batch assay at 37 °C. Considering the annual generation of the by-products in Ethiopia, an estimate was made on the electricity and thermal generation potential of the bio-methane by recovering biogas from the coffee husks, pulp and mucilage. In the second section, the anaerobic performance and stability of coffee husks and pulp with and without the supplementation of trace elements (TE) was investigated using mesophilic continuous stirred tank reactors. The organic loading rates (OLR) of the digesters were increased stepwise in the course of the fermentation trials to identify the optimum OLR. The effect of TE supplementation coupled with the stability of the fermentation process was monitored.In the third section, the bio-methane formation potential of coffee husks, pulp and mucilage was examined in batch assays at 21 °C, 30 °C and 37 °C. The modified Gompertz and modified Logistic kinetic models were fitted to the respective dataset. Eventually these kinetic models were further modified to include temperature as an additional parameter to estimate the bio-methane yield of substrates at a given temperature.