Biotechnological Exploitation of Lignocellulosic Wastes for Biomethane Production and Algae Cultivation in the Digestate

Abstract

—The use of renewable energy sources and applying appropriate conditions for realization of anaerobic digestion of agricultural waste is carried out for obtaining higher yields of biomethane as an energy carrier. The influence of substrate type, quantity and pretreatment, together with temperature regime on biomethane production was estimated. Both substrates generated higher biogas yields at the higher temperature regime and after pretreatment. The organic loading of 35 g/L was found to be most appropriate. The obtained liquid phase of anaerobic digestate was utilized as medium to maintain and enhance green microalgal growth. The ability of microalgae to photosynthetically fix carbon dioxide producing various biologically active substances, their short growth cycle and easy accummulation of biomass was involved. Due to their ability to colonize different environments these microorganisms represent promising sources for new products and applications. Good growth and development was observed for the microalga Scenedesmus acutus in digestate after adsorption with active carbon, using the macro and micronutrients present. This approach may lead to reducing costs and environmental impacts. Accumulated algal biomass (5 g/L) was afterwards introduced back in the reactor, realizing twice increased quantity of biogas on the second day of the anaerobic digestion process