Know your sustainable fuels Sustainable fuels differ by feedstock, application, and production methods. Conventional biofuels Biofuels produced from organic matter, including food crops and organic- residue materials, are typically blended with conventional fossil fuels at low percentages (given the constraints of engines to accommodate fuel with certain properties). Ethanol is produced through fermentation of plant-based materials. First-generation ethanol uses feedstocks such as corn, while second- generation ethanol is produced from residues such as bagasse, which requires more processing. Ethanol is used primarily in gasoline blends (for example, E10) and additives (for example, ethyl tert-butyl ether), improving fuel characteristics such as octane number and lowering greenhouse gases (GHGs) at a modest cost (for first-generation ethanol). Fatty acid methyl ester (FAME) is a type of biodiesel derived from renewable sources such as vegetable oils or animal fats. FAME is commonly blended with fossil diesel fuel (such as B7 and B20). Traded products on the market reflect the underlying feedstock: for example, FAME and cooking oil can combine to create used cooking oil methyl ester, or UCOME.
score, these fuels typically have lower particulate-matter and nitrogen oxide emissions. Products currently on the market or expected to go to market soon include renewable diesel (hydrotreated vegetable oil) or e-diesel, sustainable aviation fuel (such as HEFA 1 and e-SAF), biomethane and synthetic methane (sustainable natural gas), and e-gasoline. These fuels are often traded and blended with conventional fuels in the country of use. E-fuels or hydrogen-based fuels (non-drop-in) E-fuels are manufactured using hydrogen from low-carbon electricity sources (such as renewable or nuclear energy) and captured carbon. The production of low-carbon hydrogen through electrolysis based on renewable or nuclear energy can be traded as gaseous hydrogen or liquid hydrogen. When hydrogen is combined with acceptable sources of carbon (such as biogenic carbon 2 or carbon derived from direct air capture) or nitrogen, it can form e-fuels such as e-methanol or e-ammonia. However, some hydrogen derivatives are not compatible with existing engines and infrastructure.
Biomethanol is a type of methanol produced from biomass or renewable feedstocks, such as agricultural residues, woody biomass, or side-stream extracts from pulp mills. It can be used as a fuel in dedicated engines—for example, as a gasoline additive (methyl tert- butyl ether)—or as a feedstock for the production of chemicals. Biogas is produced through the anaerobic digestion of waste streams such as corn stover, manure, wastewater sludges, or food waste. It is often produced on a small scale, contains roughly two-thirds methane and one- third other gases, and can be combusted to produce electricity and heat. When upgraded to biomethane, it becomes a drop-in fuel and tradable commodity. Drop-in sustainable fuels Drop-in sustainable fuels can be produced from edible or residue biomass sources by using low- carbon hydrogen or by synthesizing sustainable captured carbon and low-carbon hydrogen. They are compatible with existing engines and fossil-fuel infrastructure. Drop-in fuels have already been a replacement for diesel, jet fuel (currently, the blend limit is 50 percent), and compressed and liquefied natural gas. In addition to having a positive impact on GHG emissions and a low carbon-intensity
1 Hydrotreated esters and fatty acids (synonymous with the hydrotreated-vegetable-oil process). 2 Biogenic carbon is CO2 sequestered from the atmosphere during the growth of feedstock and released during biofuel combustion.
Accelerating the journey to net zero
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