If trucks ran on hydrogen instead of fossil fuels, carbon dioxide emissions from heavy-duty road transport could be significantly reduced. At the same time, a new study from Chalmers University of Technology in Sweden shows that differences in how the gas is produced, distributed and used greatly affect its climate benefits. Locally produced green hydrogen is the best option for the climate – with the additional benefit of enabling all countries to become self-sufficient in energy and fuel, even in times of crisis and war.
Heavy-duty road transport currently account for one fifth of global oil consumption and, in the EU, heavy-duty diesel trucks are the largest source of emissions of the transport-related greenhouse gas carbon dioxide. In the future, the need for road transport is expected to increase, and consequently also the sector’s demand for fossil fuels from oil.*
Replacing fossil fuels with hydrogen in the heavy-duty vehicle sector is an essential part of strategies to reduce carbon dioxide emissions worldwide. The Chalmers study, which has been published in iScience, provides a full overview of hydrogen’s potential as a fuel: from production and transport to choice of materials in truck manufacturing and the actual use of the fuel.
“Hydrogen does not produce carbon dioxide when used in fuel cells, but we need to make sure that we do not shift emissions from one part of the life cycle to another. Therefore, we built different scenarios of what future supply chains might look like in Sweden, and evaluated different technologies at each life cycle stage,” says lead author Jorge Enrique Velandia Vargas, who was a postdoctoral researcher at Chalmers when the study was conducted.
The main conclusion of the study is that running heavy-duty vehicles on hydrogen instead of diesel significantly reduces carbon dioxide emissions. However, different methods of producing and handling hydrogen lead to significant differences in climate emissions, and the study provides important tools for navigating the options.
Questions about blue hydrogen
One of the clearest findings is that blue hydrogen (which is made from natural gas, and the carbon dioxide produced during the process is captured and stored instead of being released into the atmosphere) can have a higher climate impact than green hydrogen, which is produced from water and renewable electricity.
“In theory, the production of blue hydrogen is climate neutral, but in reality it is not. It is not possible to capture all CO2 after the conversion process, but 5 to 10 percent leaks out to the atmosphere. The supply chain including the manufacturing process also leaks methane, which has 30 times the greenhouse effect of carbon dioxide,” says Maria Grahn, Associate Professor at the Department of Mechanics and Maritime Sciences at Chalmers.
The researchers also point out that biomethane could replace natural gas in the same process. Biomethane is a renewable gas produced from organic waste such as manure or food waste. In theory, it can be used to produce hydrogen in a way that absorbs more carbon dioxide from the atmosphere (through the photosynthesis of plants) than is emitted, i.e. hydrogen production with negative emissions. However, the process still requires carbon capture and storage infrastructure, and each step requires energy. According to the researchers, it may therefore be more efficient to use biomethane directly as a fuel in trucks, rather than first converting it into hydrogen.
Green hydrogen is the best option for the climate, according to the study. Water is used as the raw material, and the energy required to extract hydrogen from the water comes from renewable sources. Maria Grahn points out that, in addition to the fact that its production and use generate very low emissions of carbon dioxide, hydrogen is an energy carrier that can be produced anywhere in the world, regardless of the natural resources available.
“These days, we talk a lot about resilience, i.e. the ability of a community or country to cope in an uncertain world. Energy self-sufficiency is as important as reducing carbon emissions, which we in particular have seen in Russia's war of aggression against Ukraine. And hydrogen can be produced anywhere in the world using water and energy from the sun or wind,” says Maria Grahn.
Local beats large-scale production
The study also shows that it is better for the climate to produce hydrogen close to refuelling stations than to build large central production facilities. If the gas is produced at the refuelling station itself, long-distance transport of hydrogen can be avoided. This would otherwise require a great deal of energy and cause emissions.
“Hydrogen is the lightest of all the elements and does not ‘like’ to be transported. In gaseous form it requires powerful compression and in liquid form extreme cooling. Both options involve energy losses, and with liquid hydrogen you also have to deal with the problem of evaporation during transport,” says Jorge Enrique Velandia Vargas.
Overall, the researchers argue that the right conditions are needed for hydrogen to maximise its contribution to reducing emissions, and to avoid time and resources being wasted. The study was based on Swedish conditions, but the overarching results can be transferred to the rest of the world.
“The transport sector is changing rapidly and every decision made has long-term consequences. Therefore, it is desirable for decision-making to be supported by thorough evaluations and life cycle analyses. Our research, which is at a high system level, is very suitable for decision-makers to use as a basis for decisions,” says Maria Grahn.
Facts: Different paths to hydrogen
Green hydrogen: Produced by electrolysis when water is divided into hydrogen and oxygen using electricity. The electricity used must come from renewable sources such as solar, wind or hydroelectric power for the process to be labelled ‘green’. However, the production of green hydrogen demands precious metals such as iridium and platinum.
Blue hydrogen: Produced by natural gas reacting with water vapour at high temperatures; the carbon dioxide released is captured and stored underground. It is not possible to capture all carbon dioxide, and in some places the risk of methane leakage is high during the extraction and transport of natural gas.
Hydrogen from biomethane: By replacing natural gas with biomethane, it is technically possible to achieve negative carbon dioxide emissions. However, it is uncertain whether the volumes of biomethane required are available. A simpler alternative, although one that does not create negative emissions, may be to use biomethane directly as fuel in trucks.
*
IPCC (2023): Climate Change 2023: Synthesis Report
IEA (2017): The Future of Trucks.
Source: Chalmers University