Synthetic fuel made from carbon dioxide, often referred to as e-fuel or power-to-liquid fuel, represents an innovative approach to energy production. This type of fuel is engineered by combining captured carbon dioxide (CO2) with hydrogen. The aim is to create a combustible liquid that can serve as an alternative to conventional fossil fuels. This technology seeks to address energy demands while potentially mitigating environmental impacts.
The Conversion Process
Synthetic fuel production begins with obtaining carbon dioxide, which can be sourced directly from the atmosphere through Direct Air Capture (DAC) or captured from industrial emissions. These methods isolate CO2 for fuel synthesis.
Hydrogen, the other primary component, is produced by splitting water molecules (H2O) into hydrogen and oxygen through electrolysis. This process requires electricity. For the resulting fuel to be considered sustainable, the energy powering this electrolysis must come from renewable sources such as wind, solar, hydropower, or even nuclear energy.
The captured CO2 and produced hydrogen are then chemically combined to form liquid hydrocarbons. This synthesis occurs under high pressure and temperature, with a catalyst. A widely known method for this conversion is the Fischer-Tropsch process, which transforms a mixture of carbon monoxide (derived from CO2) and hydrogen into various synthetic fuels like gasoline, diesel, and jet fuel.
Carbon Neutrality Potential
Synthetic fuels offer potential for carbon neutrality, based on a “closed carbon loop.” When combusted, synthetic fuel releases CO2 into the atmosphere, similar to fossil fuels. However, because the CO2 used to produce the fuel was originally captured from the atmosphere or industrial sources, the net addition of new carbon to the atmosphere can be zero over the fuel’s lifecycle.
Achieving carbon-neutral status depends on the energy source used during the production process. If the electricity for hydrogen production via electrolysis, and other energy demands for carbon capture and synthesis, are derived from renewable sources, the fuel is carbon neutral. Conversely, if fossil fuels power any part of this process, the overall carbon footprint increases, diminishing the environmental benefit. This highlights that the sustainability of synthetic fuels is linked to their production pathway, not just their end-use emissions.
Applications in Transportation and Industry
Synthetic fuels are promising due to their “drop-in” nature, meaning they are chemically similar to conventional petroleum products. This characteristic allows them to be used in existing engines and fuel infrastructure, including pipelines, storage tanks, and pumps, without extensive modifications or new vehicle purchases. This compatibility offers a pathway for immediate decarbonization efforts in sectors that are challenging to electrify directly.
These fuels show promise for long-haul transportation, such as aviation and maritime shipping. Aircraft and large vessels require high energy density fuels for extended ranges and heavy loads, which current battery technologies cannot provide. Synthetic fuels offer a solution for these hard-to-abate sectors, helping them reduce greenhouse gas emissions while maintaining operational capabilities.
Current Production Hurdles
Widespread adoption of synthetic fuels faces several practical challenges, related to the energy demands and associated costs of their production. The manufacturing process is energy-intensive, especially the electrolysis required to produce hydrogen. This substantial electricity requirement is a bottleneck, as it demands vast amounts of renewable energy generation.
Due to the high energy consumption and the complexity of the underlying technologies, synthetic fuels are currently more expensive than traditional fossil fuels. They can be multiple times the cost of conventional fuels, making them less competitive in today’s market. Reducing these costs requires further technological advancements and economies of scale.
Scaling up production to a meaningful level presents another challenge. Building carbon capture facilities, renewable energy infrastructure, and fuel synthesis plants to meet global demand for aviation and shipping fuels requires large investment and time. For instance, achieving a 10 percent share of e-fuels in aviation and shipping by 2030 would necessitate 2,100 terawatt-hours per year of additional renewable electricity, equivalent to about half of the annual electricity consumption in the United States.