Material or fuel: comparative cradle-to-grave climate and material footprint analysis for the use of methanol from recycled CO2†
The European Commission as well as the German government favor an energetic use of methanol from CO2 recycling with their legislation and funding mechanisms. This study uses the product climate footprint and the product material footprint to assess the complete life cycle of fossil-based polypropylene, polyoxymethylene, heavy fuel oil, petrol and diesel compared to a functional equivalent product manufactured with methanol from recycled CO2. Assuming that renewable electricity from wind power feeds the electrolysis for the hydrogen production, the results confirm that the use of recycled CO2 reduces the climate footprint, but increases the material footprint as a trade-off. The substitution of polyoxymethylene provides the highest climate footprint reduction closely followed by the substitution of petrol, followed by polypropylene, heavy fuel oil and diesel. Solely for polyoxymethylene, petrol and heavy fuel oil the greenhouse gas emission savings are relatively higher than the additional material demand. Material recycling and energy substitution from plastics waste incineration provide a benefit to the footprints that is by a factor of three higher than for the substitution of fossil-based polymers alone. The analysis until 2050 reveals that the additional material demand is reduced due to the defossilization of the German electricity grid.