Life Cycle Greenhouse Gas Emissions Analysis Report of Hydrogen Supply Chain
Mizuho Information & Research Institute, Inc.
- With the launch of commercial fuel cell vehicles (FCVs), new propulsion options have emerged alongside conventional gasoline and hybrid vehicles. In addition, automotive fuels are becoming increasingly diversified. While hydrogen-powered FCVs present the advantage of not emitting greenhouse gases (GHGs) during driving, GHGs are emitted during hydrogen production pathways. This study was conducted to quantitatively evaluate the GHG emissions of different hydrogen production pathways, and to consider future possibilities for reducing the emissions. The reference flow was set as the refueling of an FCV fuel tank with 1 Nm3 of hydrogen.
- GHG emissions over the entire life cycles of the hydrogen production pathways were resulted in between 0.16 to 1.86 kg-CO2e/Nm3-H2. Production pathways that produce hydrogen from fossil fuels have a tendency to have the highest GHG emissions, followed by hydrogen production pathways as by-product. A tendency for production pathways that produce hydrogen from renewable energy (solar or wind power generation) to have the lowest GHG emissions was observed.
- When looking at a breakdown of the GHG emissions, it was confirmed that the parameters associated with significant impact for overall GHG emissions in the respective pathways are: "energy consumption at the production stage and direct emissions from the feedstock" for hydrogen production pathways that are fossil fuel-used; "energy consumption at the transport, storage, and refueling stages" for hydrogen production pathways as by-product; and, "energy consumption at the refueling stage" for production pathways where hydrogen is produced from renewable energy. It was also established that "power consumption over the entire life cycle" is an important parameter for every hydrogen production pathway, with this being especially prominent for production pathways that produce hydrogen from renewable energy. These results indicate that reductions in energy consumption by improving efficiency for the devices used in the respective processes, implementing Carbon Capture and Storage (CCS) for fossil fuel-used pathways, and reducing GHG emission intensity for grid electricity are important to reduce total GHG emissions for each hydrogen production pathway.
- Although processes that form the life cycle of devices comprising the respective hydrogen production pathways lie outside of the system boundary of this study, a sensitivity analysis was conducted to refine this system boundary. As a result, it was demonstrated that GHG emissions due to facility construction for the feedstock production process are extremely low for production pathways that produce hydrogen from fossil fuels, and hardly contribute to the total emissions of these pathways. On the other hand, for hydrogen production pathways using renewable energy, it was demonstrated that the GHG emissions due to the construction of power generating facilities increase the total emissions of the entire hydrogen production pathway by approximately 13 to 110%. This study did not include emissions due to the construction of facilities for the production of hydrogen or due to the transport, storage, and refueling processes, as the relevant data could not be obtained. Accordingly, including such emissions remain a challenge for future study.
- This study assumes that excess by-product hydrogen that is not utilized effectively is put to use as FCV fuel, and environmental burdens are not allocated, in principle. However, a sensitivity analysis to apply different allocation procedures was carried out by taking into consideration the case in which by-product hydrogen that is already being utilized effectively is diverted for use as FCV fuel, and results indicated that GHG emissions increase by 2 to 3-fold when alternative fuels are considered. When burdens are allocated according to mass, there is an emissions increase of roughly 1.2-fold, and when burdens are allocated according to economic value, there is an increase of roughly 1.3 to 3.7-fold. In this manner, although wide variation was found regarding the extent of the increase in emissions depending on the selected allocation procedures, GHG emissions were found to increase in every case where allocation was adapted. From these results, it needs to be noted that using by-product hydrogen in the future as a fuel for FCVs will be accompanied by the risk to increase GHG emissions.
- The results of this study should provide useful implications to organizations involved in the production, supply, and use of hydrogen, as well as FCV users, when developing technologies aimed at reducing the environmental burdens and selecting hydrogen with the lowest environmental burdens. However, the results given in this report are produced under certain preconditions for only the environmental aspect of climate change, and therefore do not demonstrate the superiority of particular hydrogen production pathways, when all environmental aspects and other preconditions are considered.
- In the future, it will be necessary to conduct as many studies as possible to examine environmental aspects and preconditions aside from those covered, in order to refine this study and make it possible to provide organizations involved in the production, supply, and use of hydrogen, as well as FCV users with more accurate information.
- This report is an executive summary produced by Mizuho Information & Research Institute, Inc. using extracts of a report verified by Bureau Veritas as an independent third party. However, this executive summary has not itself received third-party verification by Bureau Veritas.
- Goal of the study
- Scope of the study
- Life Cycle Inventory (LCI) Analysis
- Life Cycle Impact Assessment (LCIA)
- Life cycle interpretation