Thermophilic biohydrogen production from sugarcane molasses under low pH: Metabolic and microbial aspects

Abstract

By-products from sugarcane mills have a considerable energy potential, and therefore have been studied aiming to generate biogas emphasising biohydrogen (bioH2). Sugarcane molasses, a byproduct from sugar production, are rich in carbohydrates, thus easily biodegraded by anaerobic microorganisms. This study evaluated the production of bioH2 in unfavorable pH (3.80) using molasses as a feedstock in an anaerobic structured bed reactor (AnSTBR-A) under thermophilic conditions (55 °C). The AnSTBR-A operated with an organic loading rate (OLR) of 60 g L−1 d−1 was able to produce bioH2 under long-term operation (392 days). The hydrogen yield (HY) was 1.18 mol H2 mol total carbohydrates−1. The results highlighted HY variation concomitant with metabolite concentrations. The main role to bioH2 production in AnSTBR-A was acetate + lactate → butyric + bioH2, with a predominance of the organism belonging to the Thermoanaerobacterium genus.