Comprehensive analysis of ethanol production from coffee mucilage under sustainability indicators

Abstract

This article shows the results obtained by analyzing an emerging technology to produce bioethanol from coffee mucilage under sustainable development constraints. The investigation showed that the addition of an antibiotic is important to avoid contamination of the mucilage related to the presence of bacteria since these microorganisms can eat the sugars present in the biomass for their metabolism. On the other hand, for the conversion of cellulose and hemicellulose into simple reducing sugars present in coffee mucilage, the addition of the enzyme pectinase was necessary. The ANOVA analysis showed that the cellulase dose is the most significant factor in the hydrolysis process. The adequate doses of enzymes for the enzymatic hydrolysis process of coffee mucilage were obtained by the response surface method, finding an optimal value of 0,352 mL and 0,134 mL of cellulase and hemicellulase, respectively, per 100 mL of mucilage. From the logistics approach, the supply of coffee mucilage to a second-generation ethanol pilot plant with an installed capacity of 15.000 liters of mucilage per week was considered. Ideally, the pulping process must be carried out mechanically without water, ensuring a mucilage Brix content between 16 and 21, which would favor an ethanol yield close to 8% (v/v) in the must. A potential production of 4,137 liters of ethanol could be achieved with a total logistics cost of USD 305 if the available mucilage is collected. A potential reduction of 7,650 kg of carbon dioxide is possible if the ethanol produced is used to replace the same amount of gasoline in the trans portation industry