Sequential dark fermentation of municipal solid waste using Starch-Derived volatile fatty acids for lignocellulose pretreatment and biohydrogen production

A multi-stage approach was evaluated for biohydrogen production from organic fraction of municipal solid waste and pruning, including pine, cypress, and mulberry wastes. The process consists of three stages: "starchy dark fermentation", "intermediary autogenous acidic pretreatment", and "lignocellulosic dark fermentation". These stages synergistically contribute to the efficient conversion of organic waste into biohydrogen, offering an innovative solution for waste management while promoting sustainable energy production. In the first stage, easily degradable materials (starch) were utilized and converted into biohydrogen, underscoring the necessity of preventing their loss during the subsequent pretreatment stage. In the first stage, 72-78 % of starch was consumed, yielded 494-2,274 mL biohydrogen per 100 g waste. The second stage involved improving the structure of lignocellulose-rich solids through the application of volatile fatty acid-rich liquor generated in the first stage for pretreatment. In the second stage, the substrate was subjected to 120-180 degrees C for 60 min to pretreat the lignocelluloses catalyzed by the volatile fatty acids generated in the first stage. The third stage produced 119-3,154 mL biohydrogen from 100 g waste. At optimum conditions, the three-stage process yielded an overall of 5,228 mL hydrogen from 100 g of untreated substrate, 2.4-fold higher than one-stage dark fermentation.