Biomethane use for automobiles towards a CO2-neutral energy system

Abstract

Abstract To pursue the goal of sustainable mobility, two main paths can be considered: the electrification of vehicles and the use of biofuels, replacing fossil fuels, in internal combustion engine (ICE) vehicles. This paper proposes an analysis of different possible scenarios for automobiles towards a CO2-neutral energy system, in the path of the use of biofuels and the production, distribution and use of biomethane. The study, an update of work presented previously, focuses on different scenarios that take into account numerous parameters that affect the overall efficiency of the production-and-use process. A Well-to-Wheel analysis is used to estimate the primary energy savings and reduction in greenhouse-gas emissions compared both to the use of fossil-based methane and to other fuels and automotive technologies. In particular, the study shows that the Non-Renewable Primary Energy Consumption (NRPEC) for biomethane is slightly higher (+9%) than that of biodiesel, but significantly lower than those of all the other power trains analysed: –69% compared to the battery electric vehicle (BEV) and –55% compared to bioethanol. Compared to the use of fossil natural gas, the NRPEC is reduced to just over a third (2.81). With regard to CO2 emissions, biomethane has the lowest values: –69% compared to BEV, –176% compared to bioethanol and –124% with respect to biodiesel. Compared to the use of fossil natural gas, the CO2 emissions are reduced over a third (3.55). Moreover, the paper shows that biomethane can completely cover the consumption of fossil methane for vehicles in Italy, proposing two different hypotheses: maximum production and minimum production. It is evident, therefore, that biomethane production can completely cover the consumption of fossil methane for vehicles: this means that the use of biomethane in the car can lead to a reduction in NRPEC equal to 28.9 × 106 GJ/year and a reduction of CO2 emissions equal to 1.9 × 106 t/year.