Development and evaluation of an acidogenic biorefinery for food waste valorisation

Joana Resende Ortigueira

Key information

Authors:

Joana Resende Ortigueira (Joana Resende Ortigueira)

Supervisors:

Carla Alexandra Monteiro da Silva (Carla Alexandra Monteiro da Silva); Patricia Maria Brito Madeira da Silva Moura (Patrícia Maria Brito Madeira da Silva Moura); Maria do Rosário Sintra de Almeida Partidário (Maria do Rosário Sintra de Almeida Partidário)

Published in

July 3, 2020

Abstract

Food waste (FW) is an organic, highly degradable residue which amounts for approximately 32% of the worldwide food production. Current strategies for FW processing focus on treatment and disposal in detriment of valorisation. This research explores the valorisation of non-avoidable FW and agro-industrial residues/byproducts through acidogenic fermentation for hydrogen production, strongly adapted to the Portuguese biomass availability and characteristics. The experimental stage focused on the selection of residues according to two typologies: agro-industrial residues or byproducts (AG) and catering industry waste (CIW). The agro-industrial residues and/or byproducts were selected from a process of cross-referencing between Portuguese data on waste production and the identification/characterisation of substrates appropriate for acidogenic fermentation. The fermentability of the agro-industrial residues was enhanced through optimised pretreatments for production of sugar-rich solutions. Small-scale assays were performed with the use of a well-known microbial H2 producer, Clostridium butyricum, for the selection of the most appropriate AG carbon source. The highest H2 production yield coupled with the simpler procedure for sugar solubilisation supported the selection of carob pulp (CP). CP and CIW were successfully tested in bench-scale pH-controlled batch fermentation under sterile conditions. CIW was used as a model substrate for the development of a simplified non-sterile conversion process with CO2 sequestration. The optimised settings of the batch system were used as the basis for the operation of a continuous FW conversion bioreactor (CSTR) during which continuous stable H2 and acid production were registered. Produced H2 was converted directly into electricity through the integration of a proton-exchange fuel cell. The quantification of valuable streams and the production efficiencies of the CSTR were used for the simulated scale-up and global warming impact evaluation, which culminated with the comparison between the new food waste biorefinery and the conventional food waste treatment and disposal pathway.