CONVERSION OF LIGNOCELLULOSIC BIOMASS (SUGAR BEET BYPRODUCTSAND COW MANURE) INTO VOLATILE FATTY ACIDS

Resumen

Anaerobic digestion (AD) has been widely applied for lignocellulosic biomass treatment. However, recently the production of high value-added bio-products from the acidogenic AD of lignocellulosic biomass is gaining interest with respect to biogas production. Volatile fatty acids (VFAs) are intermediates generated in the acidogenesis step of the AD process, and could be obtained together with hydrogen in a dark fermentation process. In addition, VFAs are considered as the main precursors for the production of biopolymers (e.g. polyhydroxyalkonates). Moreover, lignocellulosic biomass from agri-food and livestock industries is an abundant feedstock for the production of bio-based products and renewableenergy. In this study, dark fermentation of sugar beet by-products (SBB) individually and in co-digestion with cow manure has been performed in a thermophilic semi-continuous reactor. Comparison of VFAs yields and profiles has been assessed. Hydrogen productions have also beencompared. The obtained results showed that VFAs yield was similar in both tests with values of 13.6 g/L and 12.1 g/L, respectively for individual digestion and co-digestion assays. Nevertheless, the VFAs distribution was different. The ratio of the main VFAs, acetic, propionic, butyric and valeric acids was 59:14:26:1 and 74:5:18:3 in individual digestion and co-digestion tests, respectively. Moreover, the hydrogen production rate in co-digestion was 2.08 LH2/Lr*d, which was 1.7 fold higher than for the SBB individual digestion. Co-digestion has been widely considered as an improvement strategy for methane generation. However, this study shows that co-digestion may also benefit hydrogen production. Likewise,substrates characteristics may influence the VFAs profiles.