Life cycle assessment of two alternative biorefinery processes

A biorefinery process applied to cheese whey is evaluated from the enviormental point of view, starting from laboratory test results. The process is based on a first step of dark fermentation (DF) or integrated bio-electrochemical system (IBES) and followed by hydrothermal carbonization (HTC). The preliminary environmental evaluation, by Life Cycle Assessment (LCA), showed that the climate change indicator results favourable for the IBES case, thanks to the reduced impacts of the biological process. Cheese whey (CW) is an agro-industrial liquid effluent generated by the precipitation and removal of the milk casein during the cheese-making process, being the main by-product of the dairy industry (Zotta et al., 2020). Within the BBCircle project1, funded by the Lazio Region (IT), it was proposed to feed the CW to an integrated biorefinery process. The focus of this work is on the first part (Figure 1) of a previously proposed biorefinery wider scheme (Costa et al., 2022). The CW is fed to a first step base either on dark fermentation (DF) or integrated bioelectrochemical system (IBES), to produce a gas mainly composed by H2 and CO2. The H2/CO2 gas is processed by physical/chemical absorption, with the aim of producing an almost pure H2 stream for further use. The fermentate, exiting the DF/IBES as well, is still rich in organic content and can be further exploited by other steps. Here hydrothermal carbonization (HTC) is considered for producing hydrochar, to be used as biofuel. HTC process water is assumed to be disposed of.