Enhancing in the advantage of organic waste by incorporating biochar and activated carbon during the anaerobic digestion

Abstract

A significant improvement in biomethane production from anaerobic digestion (AD) due to the use of activated biochar (AB) is shown in this work. Biochar (B) was produced from palm shells by pyrolysis at 350, 550 and 700 °C. The B produced at 550 °C was mainly microporous, and was activated, a process that increased the surface area of AB by 48% compared to the initial B and was mesoporous. In parallel, to determine the appropriate doses, triplicate Biochemical Methanogenic Potential (BMP) tests were performed in 1.1 L reactors using cellulose as substrate and commercial activated carbon (AC) to 10, 15, 20, 25, 30, and 35 g L⁻¹, as carbonaceous material that would allow to have a better control were tested. The results showed that a dose of 25 g L⁻¹ achieves 1.4 times more methane compared to cellulose alone. Finally, AC and AB were applied in a BMP trial with organic waste as substrate. The addition of AB increased methane production 4.1 times more than the residue alone, this difference was mainly attributed to the higher sorption potential and mesoporosity of AB which favor the processes of biofilm formation of microorganisms and diffusion at the molecular level involved in anaerobic digestion.