Methanol Production from Biogas-derived Syngas

"Green" hydrogen must gradually replace fossil fuel-based H 2 . The anaerobic digestion (AD) of sewage sludge or agro-industrial waste yields a CH 4 /CO 2 biogas and a NH 4 + digestate. Three ways to produce H 2 can be applied: (1) the Dry Reforming of CH 4 , and CO 2 , DRM (from biogas); (2) the Catalytic CH4 Decomposition, CDM (from biogas after CO 2 capture) and (3) the Catalytic Ammonia Decomposition (CDA, from digestate). DRM produces the ideal syngas at 700 °C and for a 50-50vol% CH 4 /CO 2 biogas. CDM with a selected catalyst produced 95% H 2 . The ammonia-rich digestate was stripped and NH 3 was catalytically decomposed into H 2 and N 2 at 650 °C. Considering the well known difficulties of storing H 2 , a conversion of syngas to methanol was studied for a wastewater treatment plant (WWTP) with A.D. of 300,000 person equivalent (PE) is examined; and simulated using Aspen Plus®. This AD process generates a daily feed rate of 4,485 m 3 CH 4 , 2,415 m 3 CO 2 and 320 kg NH 3 , resulting in a CH 3 OH production of 183 kg/hr. The additional CDA H 2 flow (631 m 3 /day) is not needed in the methanol production and can be co)fired in the Combined Heat and Power (CHP) normally associated with AD. CDA will produce more H 2 if NH 3 -richer manure would be digested.