Using fruit and vegetable waste to generate hydrogen through dark fermentation

Abstract

Fruit and vegetable waste (FVW) are sugar-rich substrates that can result in hydrogen through dark fermentation. The success of dark fermentation depends on changing operation parameters, which vary based on the characteristics of the substrate. This study aimed to determine how FVW from a central horticultural wholesaler should be fermented to produce the maximum amount of hydrogen. The following goals were listed as determining the pre-treatment method (chemical, thermic, and acid) for brewery sludge and evaluating the fermentation of the liquid fraction of FVW in an anaerobic structured bed reactor (AnSTBR). The AnSTBR operation started with sucrose as substrate at a hydraulic retention time (HRT) of 6 h. Then, the sucrose was gradually replaced by FVW at the HRT of 6 h. The FVW was fed as the sole carbon source (5 g COD/L) at HRTs of 6, 12, and 3 h for at least 20 days on each condition. The heat treatment resulted in the highest cumulative hydrogen production and hydrogen production rate (HPR) (90 mL H2 and 6.6 mL H2/h). In the AnSTBR operation, the highest values of HPR were observed at 6 h (2094 L H2/m3 reactor.d). The attempt to decrease the HRT to 3 h caused a reduction in the HPR to 216 L H2/m3 reactor.d. It is highly encouraging the increase of the organic loading rate and the use of co-fermentation, aiming to reduce the size of the reactor and water expended on dilution by increasing substrate concentration in future studies.