Life Cycle Assessment of Carbon Dioxide–Based Production of Methane and Methanol and Derived Polymers

Previous studies showed that using carbon dioxide (CO2) as a raw material for chemical syntheses may provide an opportunity for achieving greenhouse gas (GHG) savings and a low†carbon economy. Nevertheless, it is not clear whether carbon capture and utilization benefits the environment in terms of resource efficiency. We analyzed the production of methane, methanol, and synthesis gas as basic chemicals and derived polyoxymethylene, polyethylene, and polypropylene as polymers by calculating the output†oriented indicator global warming impact (GWI) and the resource†based indicators raw material input (RMI) and total material requirement (TMR) on a cradle†to†gate basis. As carbon source, we analyzed the capturing of CO2 from air, raw biogas, cement plants, lignite†fired power, and municipal waste incineration plants. Wind power serves as an energy source for hydrogen production. Our data were derived from both industrial processes and process simulations. The results demonstrate that the analyzed CO2†based process chains reduce the amount of GHG emissions in comparison to the conventional ones. At the same time, the CO2†based process chains require an increased amount of (abiotic) resources. This trade†off between decreased GHG emissions and increased resource use is assessed. The decision about whether or not to recycle CO2 into hydrocarbons depends largely on the source and amount of energy used to produce hydrogen.