Carbon footprint of synthetic natural gas through biogas catalytic methanation

Abstract

The carbon footprint of synthetic natural gas production from biogas catalytic methanation was determined. The material and energy data inputs required to produce 1 kWh of synthetic natural gas were experimentally collected from a pilot plant operating in a waste water treatment plant as a relevant environment. The experimental plant had a capacity of 37 kW and consisted of biogas and water conditioning, water electrolysis and 2-step carbon dioxide catalytic methanation unit, by compact technology of micro-reactor and micro-size catalysts al mild pressure conditions. The technology evaluated in this study is ready for scalability to MW-scale. The carbon footprint was evaluated by means of the Global Warming potential impact in kg CO2-eq/kWh. Life Cycle Assessment methodology was used according to ISO:14040 and ISO:14067 thorough Ecoinvent data. The carbon footprint analysis showed that producing synthetic natural gas using the current electricity mix led to high carbon impact. However, the utilization of renewable electricity sources and a more efficient electrolyzer technology is able to reduce the carbon footprint to 0.100 kg CO2-eq/kWh. This value represents an interesting reduction of the climate change impact of 57%, using currently available technologies. Therefore, synthetic natural gas from biogas catalytic methanation process represents a feasible option to partially decarbonize the gas grid infrastructure. In this way, synthetic natural gas can support the penetration of random renewable sources by allowing its seasonal storage, as well as, to provide a low-carbon gas alternative.