E-diesel is a synthetic diesel fuel for use in automobiles. Currently, e-diesel is created at two sites: by an Audi research facility Germany in partnership with a company named Sunfire, and in Texas. The fuel is created from

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

, water, and electricity with a process powered by

renewable energy Renewable energy (also called green energy) is energy made from renewable resource, renewable natural resources that are replenished on a human lifetime, human timescale. The most widely used renewable energy types are solar energy, wind pow ...

sources to create a liquid

energy carrier An energy carrier is a substance (fuel) or sometimes a phenomenon (energy system) that contains energy that can be later converted to other forms such as mechanical work or heat or to operate chemical or physical processes. Such carriers inclu ...

called blue crude (in contrast to regular

crude oil Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring u ...

) which is then refined to generate e-diesel. E-diesel is considered to be a

carbon-neutral fuel Carbon-neutral fuel is fuel which produces no net-greenhouse gas emissions or carbon footprint. In practice, this usually means fuels that are made using Carbon dioxide, carbon dioxide (CO2) as a Raw material, feedstock. Proposed carbon-neutral fu ...

as it does not extract new carbon and the energy sources to drive the process are from carbon-neutral sources.

Catalytic conversions

Sunfire, a

clean technology Clean technology, also called cleantech or climate tech, is any process, product, or service that reduces negative environmental impacts through significant Efficient energy use, energy efficiency improvements, the sustainable use of resources, o ...

company, operates a pilot plant in

Dresden, Germany Dresden (; ; Upper Saxon German, Upper Saxon: ''Dräsdn''; , ) is the capital city of the States of Germany, German state of Saxony and its second most populous city after Leipzig. It is the List of cities in Germany by population, 12th most p ...

. The current process involves

high-temperature electrolysis High-temperature electrolysis (also HTE or steam electrolysis, or HTSE) is a technology for producing hydrogen from water at high temperatures or other products, such as iron or carbon nanomaterials, as higher energy lowers needed electricity to ...

sources to split water into

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

and

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

. The next two chemical processes to create a liquid

called blue crude are done at a temperature of and a pressure of . In a conversion step, hydrogen and carbon dioxide are used to create

syngas Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide in various ratios. The gas often contains some carbon dioxide and methane. It is principally used for producing ammonia or methanol. Syngas is combustible and can be used as ...

with water as byproduct. The syngas, which contains

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

and hydrogen, reacts to generate the blue crude. * Sunfire power-to-liquids system: Base products are carbon dioxide (CO₂) and water (H₂O) :1st step: Electrolysis of Water ( SOEC) −water is split into hydrogen and oxygen. :2nd step: Conversion Reactor ( RWGSR) −hydrogen and carbon dioxide are inputs to the Conversion Reactor that outputs hydrogen, carbon monoxide, and water. :3rd step: F-T Reactor −hydrogen and carbon monoxide are inputs to the F-T Reactor that outputs paraffinic and olefinic hydrocarbons, ranging from methane to high molecular weight waxes. The third step is also known as

Fischer–Tropsch process The Fischer–Tropsch process (FT) is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen, known as syngas, into liquid hydrocarbons. These reactions occur in the presence of metal catalysts, typically at te ...

which was first developed in 1925 by German chemists Franz Fischer and Hans Tropsch. After the blue crude is produced, it can be refined to create e-diesel on site, saving the fuel and other infrastructure costs on crude transportation. As of April 2015, Sunfire has a capability to produce a limited amount of fuel at a day. There is a plan to increase the production to an industrial scale. Audi also partners with a company named

Climeworks Climeworks AG is a Switzerland, Swiss company specializing in direct air capture, direct air capture and sequestration (DACCS) technology. The company's plants filter directly from the ambient air through an adsorption-desorption process that r ...

which manufactures Direct Air Capture technology. Climeworks technologies can absorb atmospheric carbon dioxide which is chemically captured at the surface of a

sorbent A sorbent is an insoluble material that either absorbs or adsorbs liquids or gases. They are frequently used to remove pollutants and in the cleanup of chemical accidents and oil spills. Besides their uses in industry, sorbents are used in comm ...

until it becomes saturated. At that point, the sorbent is introduced with heat in a

desorption Desorption is the physical process where Adsorption, adsorbed atoms or molecules are released from a surface into the surrounding vacuum or fluid. This occurs when a molecule gains enough energy to overcome the activation barrier and the binding e ...

cycle to drive out the high-purity carbon dioxide that can be used during the conversion step of the blue crude generation process. The atmospheric carbon dioxide capturing process has 90% of energy demand in the form of low-temperature heat and the rest from electrical energy for pumping and control. The combined plant of Climeworks and Sunfire in Dresden became operational in November 2014. As of April 2015, an

Audi A8 The Audi A8 is a full-size luxury vehicle, luxury sedan (car), sedan manufactured and marketed by the German automaker Audi since 1994. Succeeding the Audi V8, and now in its fourth generation, the A8 has been offered with either front-wheel dri ...

driven by Federal Minister of Education and Research in Germany is using the e-diesel fuel. A plant on

Herøya Herøya is a peninsula in Porsgrunn Municipality in Telemark county, Norway. It is located between the fjords of Frierfjord to the west and Gunnekleivfjord to the east, at the mouth of Porsgrunn River. The name stems from the Old Norse word ...

in Norway, producing 10 million liters per year, is being considered, as from a fertilizer plant is readily available and electricity is relatively cheap in Norway. An E-diesel plant in Texas started in 2024.

Properties

As much as eighty percent of blue crude can be converted into e-diesel. The fuel contains no

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

aromatics Aromatic compounds or arenes are organic compounds "with a chemistry typified by benzene" and "cyclically conjugated." The word "aromatic" originates from the past grouping of molecules based on odor, before their general chemical properties were ...

, and has a high

cetane number Cetane number (cetane rating) (CN) is an indicator of the combustion speed of diesel fuel and compression needed for ignition. It plays a similar role for diesel as octane rating does for gasoline. The CN is an important factor in determining t ...

. These properties allow it to be blended with typical fossil diesel and used as a replacement fuel in automobiles with

diesel engine The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...

Oxygen by-product

In future designs, the oxygen

by-product A by-product or byproduct is a secondary product derived from a production process, manufacturing process or chemical reaction; it is not the primary product or service being produced. A by-product can be useful and marketable or it can be cons ...

may be combined with

renewable natural gas Renewable natural gas (RNG), also known as biomethane, is a renewable fuel made from biogas that has been upgraded to a quality similar to fossil natural gas and has a methane concentration of 90% or greater. By removing carbon dioxide and other ...

in the

oxidative coupling of methane The oxidative coupling of methane (OCM) is a potential chemical reaction studied in the 1980s for the direct conversion of natural gas, primarily consisting of methane, into value-added chemicals. Although the reaction would have strong economics ...

ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...

: : 2 + → + 2 The reaction is

exothermic In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e ...

(∆H = -280 kJ/mol) and occurs at high temperatures (750–950 ˚C). The yield of the desired products is reduced by non-selective reactions of

methyl radical Methyl radical is an organic compound with the chemical formula (also written as •). It is a metastable colourless gas, which is mainly produced ''in situ'' as a precursor to other hydrocarbons in the petroleum cracking industry. It can act as ...

s with the reactor surface and oxygen, which produces carbon monoxide and carbon dioxide by-products. Another ethylene production initiative developed by the European Commission through the Seventh Framework Programme for Research and Technological Development is the OCMOL process, which is the Oxidative Coupling of Methane (OCM) and simultaneous Reforming of Methane (RM) in a fully integrated reactor.

Biocatalytic conversions

Audi also partnered with a now-defunct United States company,

Joule The joule ( , or ; symbol: J) is the unit of energy in the International System of Units (SI). In terms of SI base units, one joule corresponds to one kilogram- metre squared per second squared One joule is equal to the amount of work d ...

, to develop ''Sunflow-D'' as e-diesel for Audi. Joule's planned plant in

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

involved the use of

genetically modified Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of technologies used to change the genetic makeup of cells, including th ...

microorganisms in bright sunlight to act as

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

for the conversion of carbon dioxide and salty water into

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

s. The process could be modified for longer molecular chains to produce

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in whi ...

s in order to create synthetic diesel. Joule was the first company to patent a modified organism that continuously secretes hydrocarbon fuel. The organism is a single-celled cyanobacterium, also known as blue-green algae, although it is technically not an algae. It produces the fuel using photosynthesis, the same process that multi-cellular green plants use, to make sugars and other materials from water, carbon dioxide, and sunlight.

Similar initiatives

There are other initiatives to create synthetic fuel from carbon dioxide and water, some are called e-diesel. The

water splitting Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen: Efficient and economical water splitting would be a technological breakthrough that could underpin a hydrogen economy. A version of water splitti ...

methods vary. *

Concentrated solar power Concentrated solar power (CSP, also known as concentrating solar power, concentrated solar thermal) systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight into a receiver. Electricity is generated whe ...

**2004 Sunshine-to-Petrol –

Sandia National Laboratories Sandia National Laboratories (SNL), also known as Sandia, is one of three research and development laboratories of the United States Department of Energy's National Nuclear Security Administration (NNSA). Headquartered in Kirtland Air Force B ...

. **2013 NewCO2Fuels – New Fuels Ltd ( IL) and

Weizmann Institute of Science The Weizmann Institute of Science ( ''Machon Weizmann LeMada'') is a Public university, public research university in Rehovot, Israel, established in 1934, fourteen years before the State of Israel was founded. Unlike other List of Israeli uni ...

. **2014 Solar-Jet Fuels – Consortium partners

ETH Zurich ETH Zurich (; ) is a public university in Zurich, Switzerland. Founded in 1854 with the stated mission to educate engineers and scientists, the university focuses primarily on science, technology, engineering, and mathematics. ETH Zurich ran ...

Royal Dutch Shell Shell plc is a British multinational oil and gas company, headquartered in London, England. Shell is a public limited company with a primary listing on the London Stock Exchange (LSE) and secondary listings on Euronext Amsterdam and the New ...

, DLR, Bauhaus Luftfahrt, ARTTIC. *

High-temperature electrolysis High-temperature electrolysis (also HTE or steam electrolysis, or HTSE) is a technology for producing hydrogen from water at high temperatures or other products, such as iron or carbon nanomaterials, as higher energy lowers needed electricity to ...

**2004 Syntrolysis Fuels –

Idaho National Laboratory Idaho National Laboratory (INL) is one of the national laboratories of the United States Department of Energy and is managed by the Battelle Energy Alliance. Historically, the lab has been involved with nuclear research, although the labora ...

and Ceramatec, Inc. (US). **2008 WindFuels – Doty Energy (US). **2012 Air Fuel Synthesis – Air Fuel Synthesis Ltd (UK). **2013 Green Feed –

Ben-Gurion University of the Negev Ben-Gurion University of the Negev (BGU) (, ''Universitat Ben-Guriyon baNegev'') is a public university, public research university in Beersheba, Israel. Named after Israeli List of national founders, national founder David Ben-Gurion, the unive ...

and Israel Strategic Alternative Energy Foundation (I-SAEF). **2014 Audi E-diesel The U.S. Naval Research Laboratory (NRL) is designing a power-to-liquids system using the Fischer-Tropsch Process to create fuel on board a ship at sea, with the base products carbon dioxide (CO₂) and water (H₂O) being derived from sea water via "An Electrochemical Module Configuration For The Continuous Acidification Of Alkaline Water Sources And Recovery Of CO₂ With Continuous Hydrogen Gas Production".

References

External links

Sustainable Transportation Fuels from Off-Peak Wind Energy, , and WaterOptions to dissociate for sustainable sunlight-to-fuel pathwaysPerspectives in electrolysis and recycling

Chemical Processes for a Sustainable Future - ch 8. Renewable Energy, {{chem, C, O, 2 and an Anthropogenic Carbon Cycle
Audi Synthetic fuels Renewable energy *