CO2
Waste CO2 streams from industrial facilities (e.g., steel, cement) can be converted into synthetic fuels and chemicals. Direct Air Capture technologies can remove ambient CO2.
Biomass
Sugars - either simple (starch) or complex (cellulose) - and lipids (fats & oils) are the most basic components in biomass for conversion to produce a range of renewable fuels.
Biochemical Route
Biochemical conversion processes use bacteria, microorganisms and enzymes to break down biomass into gaseous or liquid fuels, such as ethanol (fermentation) and biogas (anaerobic digestion).
Chemical Route
The chemical route relies on a chemical reaction by mixing three types of reactants: pre-treated* fatty acids, alcohols and a catalyst (typically a strong base or strong acid). Transesterification is a common chemical conversion process that converts the fatty acids into biodiesel and glycerol. *Pre-treatment can include water removal, oil refining, degumming and other processes to improve the input lipids.
Thermochemical Route
Thermochemical conversion processes generally involve the controlled heating or oxidation of biomass, utilizing a range of technologies including pyrolysis, gasification, and combustion which, in varying configurations, produce gaseous or liquid precursors for upgrading to liquid fuels or chemical feedstocks, as well as outputs of heat and electricity.
Hydrolysis
Sugars from lignocellulosic materials (e.g. straw and woody fibre) and lignin, etc can be extracted by enzymes under moderate pressure and temperatures. Sugars can be fermented into biofuels, such as ethanol, and ethanol can be used in gasoline or converted into a synthetic jet fuel using catalytic processes like those employed in petroleum refineries.
Extraction
Soybeans, canola seeds, and other vegetable oils are ‘crushed’ to remove the oils; this also produces a co-product of protein meal that is a main nutritional source for the dairy, livestock, and aquaculture sectors. Used cooking oils and rendered products are the other main source of feedstocks and are extracted primarily by rendering companies.
Pyrolysis/Liquefaction
Pyrolysis broadly describes the thermal decomposition of biomass under high temperature conditions to produce - in the case of biomass - a ‘bio-oil,’ and a ‘biochar.’ Hydrothermal liquefaction processes specifically convert wet biomass into a ‘biocrude’ oil under moderate temperature and high pressure; this biocrude can be further converted to renewable gasoline, diesel, and jet fuel in an upgraded conventional refinery.(See Ensyn - pyrolysis, and Steeper Energy - liquefaction.)
Gasification
Gasification is a process that converts biomass and other carbonaceous materials into gases: nitrogen (N2), carbon monoxide (CO), hydrogen (H2), and carbon dioxide (CO2). The resultant ‘syngas’ is converted to fuels (and other products).
Engineered CO2 capture, dehydration, compression
Aqueous direct air capture (DAC) processes remove CO2 when ambient air makes contact with chemical media (first cycle), typically an aqueous alkaline solvent. A second ‘cycle’ uses calcium to regenerate first cycle media. (See Carbon Engineering.) H2 can be added to the CO2 and the gas converted to fuels.
Gas Conditioning
CO and CO2 rich gases (e.g., steel mills, chemical plants, refineries) are diverted from flaring and conditioned so that they can be used directly in gas fermentation. Industrial waste gasses that can be fermented are composed of combinations of CO, CO2 and hydrogen. (See LanzaTech)
Fermentation
Yeasts, in the absence of oxygen, anaerobically convert sugars such as glucose, fructose, and sucrose into ethanol, with carbon dioxide as a by-products. Corn starch is a common source of fermentable sugars.
Transesterification
In a simple chemical process, fatty acids (i.e. fats and oils) are reacted with alcohol in the presence of a catalyst to produce biodiesel (‘fatty acid methyl ester’), and a glycerol by-product.
Hydrotreating
The hydrotreating process upgrades vegetable oils or biocrude oils to hydrocarbons by removing oxygen, nitrogen, and sulfur and saturating olefins and some aromatics present in biomass. Hydrocarbon oils can be further refined with the hydrocracking process, which breaks down complex hydrocarbon molecules into simpler ones by using a catalyst and an elevated partial pressure of hydrogen gas.
Gas Fermentation
Bacterial syngas fermentation uses biocatalysts (also called acetogens, which may be metabolically engineered[JH1] ) to produce a range of biofuels (e.g. ethanol) and biochemicals (e.g. isopropanol, acetone, proteins). Ethanol can be used in gasoline or converted into a synthetic jet fuel using catalytic processes like those employed in petroleum refineries. (See LanzaTech)
Catalysis (FT/MeOH)
These gas to liquids processes convert carbon monoxide and hydrogen into liquid hydrocarbons in the presence of metal catalysts (under high pressure and temperatures). Biomass or synthetic gases can be used as feedstocks for the Fischer-Tropsch (FT) and Methanol (MeOH) processes. Distillate fuels (diesel, jet) are common products from FT. Methanol can be converted to gasoline or olefins.
Gas Fermentation
Bacterial syngas fermentation uses biocatalysts (also called acetogens, which may be metabolically engineered[JH1] ) to produce a range of biofuels (e.g. ethanol) and biochemicals (e.g. isopropanol, acetone, proteins). Ethanol can be used in gasoline or converted into a synthetic jet fuel using catalytic processes like those employed in petroleum refineries. (See LanzaTech)
Bioethanol
Bioethanol is ‘fuel alcohol’ made from sugars (see Fermentation) that is a ‘drop-in’ gasoline substitute at 15% blends (E15) in any 2001 or later light duty vehicle, and in ‘flex fuel’ vehicles up to 85% blends (E85.)
Biodiesel
Biodiesel is a renewable diesel fuel produced from fats, oils, and greases (see Transesterification) that is a ‘drop-in’ diesel fuel substitute at blends typically up to 20% (B20.)
Transport Fuels
Transport fuels as described here are broadly hydrocarbon fuels that are fully fungible, and can include hydrogenated ‘renewable diesel,’ co-processed renewable gasoline/diesel/jet fuels, or ‘alcohol-to-jet’ fuels that can be used in a 50% blend with conventional kerosene jet fuel.
Transport Fuels
Transport fuels as described here are broadly hydrocarbon fuels that are fully fungible, and can include hydrogenated ‘renewable diesel,’ co-processed renewable gasoline/diesel/jet fuels, or ‘alcohol-to-jet’ fuels that can be used in a 50% blend with conventional kerosene jet fuel.
Transport Fuels
Transport fuels as described here are broadly hydrocarbon fuels that are fully fungible, and can include hydrogenated ‘renewable diesel,’ co-processed renewable gasoline/diesel/jet fuels, or ‘alcohol-to-jet’ fuels that can be used in a 50% blend with conventional kerosene jet fuel.
Transport Fuels
Transport fuels as described here are broadly hydrocarbon fuels that are fully fungible, and can include hydrogenated ‘renewable diesel,’ co-processed renewable gasoline/diesel/jet fuels, or ‘alcohol-to-jet’ fuels that can be used in a 50% blend with conventional kerosene jet fuel.