Drop-in biofuels are hydrocarbon fuels substantially similar to gasoline, diesel, or jet fuels. These fuels can be made from a variety of biomass feedstocks including crop residues, woody biomass, dedicated energy crops, and algae. The goal for drop-in fuels is to meet existing diesel, gasoline, and jet fuel quality specifications and be ready to "drop-in" to existing infrastructure. This minimizes infrastructure compatibility issues, which are a barrier to fast commercialization of biofuels like ethanol and biodiesel. Drop-in fuels are in a research and development phase with pilot- and demonstration-scale plants under construction. The current focus is aimed at replacing diesel and jet fuel, which typically fuel vehicles that aren't good candidates for electrification.
There is more than one way to create a drop-in fuel. Researchers are exploring a variety of technology pathways. Production plants may be stand-alone or colocated at petroleum refineries where there are multiple places drop-in fuels can be inserted into the refinery process.
Potential technology pathways include:
- Upgrading alcohols to hydrocarbons
- Catalytic conversion of sugars to hydrocarbons (more information about this process from the National Advanced Biofuels Consortium - NABC)
- Fermentation of sugars to hydrocarbons (more information from NABC)
- Hydrotreating algal oils
- Upgrading of syngas (CO and H2) from gasification
- Pyrolysis or liquefaction of biomass to bio-oil with hydroprocessing
Drop-in fuels are expected to meet existing specifications for diesel, gasoline, and jet fuel. The benefits of drop-in fuels include:
- Engine and Infrastructure Compatibility—Drop-in fuels are expected to be substantially similar to their petroleum counterparts and therefore minimize compatibility issues with existing infrastructure and engines.
- Increased Energy Security—Drop-in fuels can be produced domestically from a variety of feedstocks and contribute to U.S. job creation.
- Fewer Emissions—Carbon dioxide captured by growing feedstocks reduces overall greenhouse gas emissions by balancing carbon dioxide released from burning drop-in fuels.
- More Flexibility—Drop-in fuels are replacements for diesel, jet fuel, and gasoline allowing for multiple products from various feedstocks and production technologies.
Research and Development
The National Advanced Biofuels Consortium (NABC), a Department of Energy (DOE) supported partnership of national laboratories, universities, and corporations, is working to make drop-in biofuels technologies cost-effective, sustainable, and infrastructure-compatible. The U.S. Navy, United States Department of Agriculture, and DOE plan to create a public-private partnership to develop drop-in fuels.
Another DOE sponsored consortium, the National Alliance for Advanced Biofuels and Bioproducts (NAABB), is developing the algal biofuels industry.
Currently there is one completed pilot-scale drop-in fuel plant (see Royal Dutch Shell's press release.)
- Advanced Biofuels Association (ABFA)
- Commercial Aviation Alternative Fuels Initiative (CAAFI)
- Fungible and Compatible Biofuels: Literature Search, Summary, and Recommendations
- Production of Gasoline and Diesel from Biomass via Fast Pyrolysis, Hydrotreating, and Hydrocracking: A Design Case
- Hydrogenation-Derived Renewable Diesel