Revaluation of agri-food waste to obtain bioethanol

Abstract

Objective: Bioethanol production from the alcoholic fermentation of agri-food waste.

Design/methodology/approach: Agri-food waste was collected for a month and separated into fruit and legume residues; their size was reduced, and they were washed with hot acetone. A batch of 100 g of residue underwent acid hydrolysis with 5% H₂SO₄ solution at 125 °C, the hydrolysate was fermented with Saccharomyces cerevisiae at 30 °C for 48 h; the ferment was distilled at 78° C. The amount of sugars was determined by phenol-sulfuric method. The °Brix, density and % w/w of ethanol were measured in a density meter.

Results: From the fruit residues an organic fraction was obtained with a total sugar amount of 53.3 g/100 g of residue and 9.6 °Brix, generating 45 mL of distillate with 3.8 % w/w of bioethanol. The organic fraction from the legume residues had a total amount of sugar of 19.4 g and 4.140 °Brix, generating 30 mL of distillate with 2.5 % w/w of bioethanol.

Limitations on study/implications: The rapid decomposition of waste by the attack of bacteria and fungi complicates its long-term storage.

Findings/conclusions: Fermentable sugars can be obtained from the evaluated agri-food waste to obtain bioethanol. In this way they can be integrated into the value chain as feedstock, reducing their accumulation and the environmental impact generated by their final disposal.