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The methanol economy is a suggested future economy in which methanol and dimethyl ether replace fossil fuels as a means of energy storage, ground transportation fuel, and raw material for synthetic hydrocarbons and their products. It offers an alternative to the proposed hydrogen economy or ethanol economy, although these concepts are not exclusive. Methanol can be produced from a variety of sources including fossil fuels (natural gas, coal, oil shale, tar sands, etc.) as well as agricultural products and municipal waste, wood and varied biomass. It can also be made from chemical recycling of carbon dioxide.
Nobel prize laureate George A. Olah advocated a methanol economy. [1] [2] [3] [4]
Methanol is a fuel for heat engines and fuel cells. Due to its high octane rating it can be used directly as a fuel in flex-fuel cars (including hybrid and plug-in hybrid vehicles) using existing internal combustion engines (ICE). Methanol can also be burned in some other kinds of engine or to provide heat as other liquid fuels are used. Fuel cells, can use methanol either directly in Direct Methanol Fuel Cells (DMFC) or indirectly (after conversion into hydrogen by reforming) in a Reformed Methanol Fuel Cell (RMFC).
Methanol is already used today on a large scale to produce a variety of chemicals and products. Global methanol demand as a chemical feedstock reached around 42 million metric tonnes per year as of 2015. [8] Through the methanol-to-gasoline (MTG) process, it can be transformed into gasoline. Using the methanol-to-olefin (MTO) process, methanol can also be converted to ethylene and propylene, the two chemicals produced in largest amounts by the petrochemical industry. [9] These are important building blocks for the production of essential polymers (LDPE, HDPE, PP) and like other chemical intermediates are currently produced mainly from petroleum feedstock. Their production from methanol could therefore reduce our dependency on petroleum. It would also make it possible to continue producing these chemicals when fossil fuels reserves are depleted.
Today most methanol is produced from methane through syngas. Trinidad and Tobago is the world's largest methanol producer, with exports mainly to the United States. [10] The feedstock for the production of methanol comes natural gas.
The conventional route to methanol from methane passes through syngas generation by steam reforming combined (or not) with partial oxidation. Alternative ways to convert methane into methanol have also been investigated. These include:
All these synthetic routes emit the greenhouse gas carbon dioxide CO2. To mitigate this, methanol can be made through ways minimizing the emission of CO2. One solution is to produce it from syngas obtained by biomass gasification. For this purpose any biomass can be used including wood, wood wastes, grass, agricultural crops and their by-products, animal waste, aquatic plants and municipal waste. [11] There is no need to use food crops as in the case of ethanol from corn, sugar cane and wheat.
Methanol can be synthesized from carbon and hydrogen from any source, including fossil fuels and biomass. CO2 emitted from fossil fuel burning power plants and other industries and eventually even the CO2 contained in the air, can be a source of carbon. [12] It can also be made from chemical recycling of carbon dioxide, which Carbon Recycling International has demonstrated with its first commercial scale plant. [13] Initially the major source will be the CO2 rich flue gases of fossil-fuel-burning power plants or exhaust from cement and other factories. In the longer range however, considering diminishing fossil fuel resources and the effect of their utilization on Earth's atmosphere, even the low concentration of atmospheric CO2 itself could be captured and recycled via methanol, thus supplementing nature's own photosynthetic cycle. Efficient new absorbents to capture atmospheric CO2 are being developed, mimicking plants' ability. Chemical recycling of CO2 to new fuels and materials could thus become feasible, making them renewable on the human timescale.
Methanol can also be produced from CO2 by catalytic hydrogenation of CO2 with H2 where the hydrogen has been obtained from water electrolysis. This is the process used by Carbon Recycling International of Iceland. Methanol may also be produced through CO2 electrochemical reduction, if electrical power is available. The energy needed for these reactions in order to be carbon neutral would come from renewable energy sources such as wind, hydroelectricity and solar as well as nuclear power. In effect, all of them allow free energy to be stored in easily transportable methanol, which is made immediately from hydrogen and carbon dioxide, rather than attempting to store energy in free hydrogen.
Or with electric energy:
Total:
The necessary CO2 would be captured from fossil fuel burning power plants and other industrial flue gases including cement factories. With diminishing fossil fuel resources and therefore CO2 emissions, the CO2 content in the air could also be used. Considering the low concentration of CO2 in air (0.04%) improved and economically viable technologies to absorb CO2 will have to be developed. For this reason, extraction of CO2 from water could be more feasible due to its higher concentrations in dissolved form. [14] This would allow the chemical recycling of CO2, thus mimicking nature's photosynthesis.
In large-scale renewable methanol is mainly produced of fermented biomass as well as municipal solid waste (bio-methanol) and of renewable electricity (e-methanol). [15] Production costs for renewable methanol currently are about 300 to US$1000/t for bio-methanol, about 800 to US$1600/t for e-methanol of carbon dioxide of renewable sources and about 1100 to US$2400/t for e-methanol of carbon dioxide of direct air capture. [11]
Methanol which is produced of CO2 and water by the use of electricity is called e-methanol. Typically hydrogen is produced by electrolysis of water which is then transformed with CO2 to methanol. Currently the efficiency for hydrogen production by water electrolysis of electricity amounts to 75 to 85% [11] with potential up to 93% until 2030. [16] Efficiency for methanol synthesis of hydrogen and carbon dioxide currently is 79 to 80%. [11] Thus the efficiency for production of methanol from electricity and carbon dioxide is about 59 to 78%. If CO2 is not directly available but is obtained by direct air capture then the efficiency amounts to 50-60 % for methanol production by use of electricity. [11] [17] When methanol is used in a methanol fuel cell the electrical efficiency of the fuel cell is about 35 to 50% (status of 2021). Thus the electrical overall efficiency for the production of e-methanol with electricity including the following energy conversion of e-methanol to electricity amounts to about 21 to 34% for e-methanol of directly available CO2 and to about 18 to 30% for e-methanol produced by CO2 which is obtained by direct air capture.
If waste heat is used for a high temperature electrolysis or if waste heat of electrolysis, methanol synthesis and/or of the fuel cell is used then the overall efficiency can be significantly increased beyond electrical efficiency. [18] [19] For example, an overall efficiency of 86% can be reached by using waste heat (e.g. for district heating) which is obtained by production of e-methanol by electrolysis or by the following methanol synthesis. [19] If the waste heat of a fuel cell is used a fuel cell efficiency of 85 to 90% can be reached. [20] [21] The waste heat can for example be used for heating of a vehicle or a household. Also the generation of coldness by using waste heat is possible with a refrigeration machine. With an extensive use of waste heat an overall efficiency of 70 to 80% can be reached for production of e-methanol including the following use of the e-methanol in a fuel cell.
The electrical system efficiency including all losses of peripheral devices (e.g. cathode compressor, stack cooling) amounts to about 40 to 50% for a methanol fuel cell of RMFC type and to 40 to 55% for a hydrogen fuel cell of LT-PEMFC type. [22] [23] [24] [25]
Araya et al. compared the hydrogen path with the methanol path (for methanol of directly available CO2). [22] Here the electrical efficiency from electricity supply to delivery of electricity by a fuel cell was determined with following intermediate steps: power management, conditioning, transmission, hydrogen production by electrolysis, methanol synthesis resp. hydrogen compression, fuel transportation, fuel cell. For the methanol path the efficiency was investigated as 23 to 38% and for the hydrogen path as 24 to 41%. With the hydrogen path a large part of energy is lost by hydrogen compression and hydrogen transport, whereas for the methanol path energy for methanol synthesis is needed.
Helmers et al. compared the well-to-wheel (WTW) efficiency of vehicles. The WTW efficiency was determined as 10 to 20% for with fossile gasoline operated vehicles with internal combustion engine, as 15 to 29% for with fossile gasoline operated full electric hybrid vehicles with internal combustion engine, as 13 to 25% for with fossile Diesel operated vehicles with internal combustion engine, as 12 to 21% for with fossile CNG operated vehicles with internal combustion engine, as 20 to 29% for fuel cell vehicles (e.g. fossile hydrogen or methanol) and as 59 to 80% for battery electric vehicles. [26]
In German study "Agora Energiewende" different drive technologies by using renewable electricity for fuel production were examined and a WTW efficiency of 13% for vehicles with internal combustion engine (operated with synthetic fuel like OME), 26% for fuel cell vehicles (operated with hydrogen) and 69% for battery electric vehicles was determined. [27]
If renewable hydrogen is used the well-to-wheel efficiency for a hydrogen fuel cell car amounts to about 14 to 30%.
If renewable e-methanol is produced from directly available CO2 the well-to-wheel efficiency amounts to about 11 to 21% for a vehicle with internal combustion engine which is operated with this e-methanol and to about 18 to 29% for a fuel cell vehicle which is operated with this e-methanol. If renewable e-methanol is produced from CO2 of direct air capture the well-to-wheel efficiency amounts to about 9 to 19% for a vehicle with internal combustion engine which is operated with this e-methanol and to about 15 to 26% for a fuel cell vehicle which is operated with this e-methanol (status of 2021).
Methanol is cheaper than hydrogen. For large amounts (tank) price for fossile methanol is about 0.3 to 0.5 USD/L. [28] One liter of Methanol has the same energy content as 0.13 kg hydrogen. [5] [6] Price for 0.13 kg of fossile hydrogen is currently about 1.2 to 1.3 USD for large amounts (about 9.5 USD/kg at hydrogen refuelling stations). [29] For middle scale amounts (delivery in IBC container with 1000 L methanol) price for fossile methanol is usually about 0.5 to 0.7 USD/L, for biomethanol about 0.7 to 2.0 USD/L and for e-methanol [30] from CO2 about 0.8 to 2.0 USD/L plus deposit for IBC container. For middle scale amounts of hydrogen (bundle of gas cylinders) price for 0.13 kg of fossile hydrogen is usually about 5 to 12 USD plus rental fee for the cylinders. The significantly higher price for hydrogen compared to methanol is amongst others caused by the complex logistics and storage of hydrogen. Whereas biomethanol and renewable e-methanol are available at distributors, [31] [32] green hydrogen is typically not yet available at distributors. Prices for renewable hydrogen as well as for renewable methanol are expected to decrease in future. [11]
For future it is expected that for passenger cars a high percentage of vehicles will be full electric battery vehicles. For utility vehicles and trucks percentage of full electric battery vehicles is expected to be significantly lower than for passenger cars. The rest of vehicles is expected to be based on fuel. While methanol infrastructure for 10 000 refuelling stations would cost about 0.5 to 2.0 billion USD, cost for a hydrogen infrastructure for 10 000 refuelling stations would be about 16 to 1400 billion USD with strong dependence on hydrogen throughput of the hydrogen refuelling station. [22] [33]
While for vehicles with internal combustion engine that are fuelled with methanol there are no significant additional costs compared to gasoline fuelled vehicles, additional costs for a passenger car with methanol fuel cell would be about -600 to 2400 USD compard with a passenger car with hydrogen fuel cell (primarily additional costs for reformer, balance of plant components and perhaps stack minus costs for hydrogen tank [34] and hydrogen high-pressure instruments).
In the process of photosynthesis, green plants use the energy of sunlight to split water into free oxygen (which is released) and free hydrogen. Rather than attempt to store the hydrogen, plants immediately capture carbon dioxide from the air to allow the hydrogen to reduce it to storable fuels such as hydrocarbons (plant oils and terpenes) and polyalcohols (glycerol, sugars and starches). In the methanol economy, any process which similarly produces free hydrogen, proposes to immediately use it "captively" to reduce carbon dioxide into methanol, which, like plant products from photosynthesis, has great advantages in storage and transport over free hydrogen itself.
Methanol is a liquid under normal conditions, allowing it to be stored, transported and dispensed easily, much like gasoline and diesel fuel. It can also be readily transformed by dehydration into dimethyl ether, a diesel fuel substitute with a cetane number of 55.
Methanol is water-soluble: An accidental release of methanol in the environment would cause much less damage than a comparable gasoline or crude oil spill. Unlike these fuels, methanol is biodegradable and totally soluble in water, and would be rapidly diluted to a concentration low enough for microorganism to start biodegradation. This effect is already exploited in water treatment plants, where methanol is already used for denitrification and as a nutrient for bacteria. [35] Accidental release causing groundwater pollution has not been thoroughly studied yet, though it is believed that it might undergo relatively rapid.
Methanol economy advantages compared to a hydrogen economy:
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 a fuel. Historically, it has been used as a replacement for gasoline, when gasoline supply has been limited; for example, wood gas was used to power cars in Europe during WWII.
Gasification is a process that converts biomass- or fossil fuel-based carbonaceous materials into gases, including as the largest fractions: nitrogen (N2), carbon monoxide (CO), hydrogen (H2), and carbon dioxide (CO2). This is achieved by reacting the feedstock material at high temperatures (typically >700 °C), without combustion, via controlling the amount of oxygen and/or steam present in the reaction. The resulting gas mixture is called syngas (from synthesis gas) or producer gas and is itself a fuel due to the flammability of the H2 and CO of which the gas is largely composed. Power can be derived from the subsequent combustion of the resultant gas, and is considered to be a source of renewable energy if the gasified compounds were obtained from biomass feedstock.
Ethanol fuel is fuel containing ethyl alcohol, the same type of alcohol as found in alcoholic beverages. It is most often used as a motor fuel, mainly as a biofuel additive for gasoline.
Alternative fuels, also known as non-conventional and advanced fuels, are fuels derived from sources other than petroleum. Alternative fuels include gaseous fossil fuels like propane, natural gas, methane, and ammonia; biofuels like biodiesel, bioalcohol, and refuse-derived fuel; and other renewable fuels like hydrogen and electricity.
Methanol fuel is an alternative biofuel for internal combustion and other engines, either in combination with gasoline or independently. Methanol (CH3OH) is less expensive to sustainably produce than ethanol fuel, although it is more toxic than ethanol and has a lower energy density than gasoline. Methanol is safer for the environment than gasoline, is an anti-freeze agent, prevents dirt and grime buildup within the engine, has a higher ignition temperature, and produces horsepower equivalent to that of super high-octane gasoline. It can readily be used in most modern engines. To prevent vapor lock due to being a simple, pure fuel, a small percentage of other fuel or certain additives can be included. Methanol may be made from fossil fuels or renewable resources, in particular natural gas and coal, or biomass respectively. In the case of the latter, it can be synthesized from CO2 (carbon dioxide) and hydrogen. The vast majority of methanol produced globally is currently made with gas and coal. However, projects, investments, and the production of green-methanol has risen steadily into 2023. Methanol fuel is currently used by racing cars in many countries and has seen increasing adoption by the maritime industry.
The hydrogen economy is an umbrella term for the roles hydrogen can play alongside low-carbon electricity to reduce emissions of greenhouse gases. The aim is to reduce emissions where cheaper and more energy-efficient clean solutions are not available. In this context, hydrogen economy encompasses the production of hydrogen and the use of hydrogen in ways that contribute to phasing-out fossil fuels and limiting climate change.
The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures and pressures in the presence of a nickel catalyst. It was discovered by the French chemists Paul Sabatier and Jean-Baptiste Senderens in 1897. Optionally, ruthenium on alumina makes a more efficient catalyst. It is described by the following exothermic reaction:
Synthetic fuel or synfuel is a liquid fuel, or sometimes gaseous fuel, obtained from syngas, a mixture of carbon monoxide and hydrogen, in which the syngas was derived from gasification of solid feedstocks such as coal or biomass or by reforming of natural gas.
Various alcohols are used as fuel for internal combustion engines. The first four aliphatic alcohols are of interest as fuels because they can be synthesized chemically or biologically, and they have characteristics which allow them to be used in internal combustion engines. The general chemical formula for alcohol fuel is CnH2n+1OH.
Waste-to-energy (WtE) or energy-from-waste (EfW) is the process of generating energy in the form of electricity and/or heat from the primary treatment of waste, or the processing of waste into a fuel source. WtE is a form of energy recovery. Most WtE processes generate electricity and/or heat directly through combustion, or produce a combustible fuel commodity, such as methane, methanol, ethanol or synthetic fuels, often derived from the product syngas.
Hydrogen gas is produced by several industrial methods. Nearly all of the world's current supply of hydrogen is created from fossil fuels. Most hydrogen is gray hydrogen made through steam methane reforming. In this process, hydrogen is produced from a chemical reaction between steam and methane, the main component of natural gas. Producing one tonne of hydrogen through this process emits 6.6–9.3 tonnes of carbon dioxide. When carbon capture and storage is used to remove a large fraction of these emissions, the product is known as blue hydrogen.
Renewable fuels are fuels produced from renewable resources. Examples include: biofuels, Hydrogen fuel, and fully synthetic fuel produced from ambient carbon dioxide and water. This is in contrast to non-renewable fuels such as natural gas, LPG (propane), petroleum and other fossil fuels and nuclear energy. Renewable fuels can include fuels that are synthesized from renewable energy sources, such as wind and solar. Renewable fuels have gained in popularity due to their sustainability, low contributions to the carbon cycle, and in some cases lower amounts of greenhouse gases. The geo-political ramifications of these fuels are also of interest, particularly to industrialized economies which desire independence from Middle Eastern oil.
A methanol reformer is a device used in chemical engineering, especially in the area of fuel cell technology, which can produce pure hydrogen gas and carbon dioxide by reacting a methanol and water (steam) mixture.
Second-generation biofuels, also known as advanced biofuels, are fuels that can be manufactured from various types of non-food biomass. Biomass in this context means plant materials and animal waste used especially as a source of fuel.
Reformed Methanol Fuel Cell (RMFC) or Indirect Methanol Fuel Cell (IMFC) systems are a subcategory of proton-exchange fuel cells where, the fuel, methanol (CH3OH), is reformed, before being fed into the fuel cell.
Electrofuels, also known as e-fuels, are a class of synthetic fuels which function as drop-in replacement fuels for internal combustion engines. They are manufactured using captured carbon dioxide or carbon monoxide, together with hydrogen obtained from water split. Electrolysis is possible with both traditional fossil fuel energy sources, as well as low-carbon electricity sources such as wind, solar and nuclear power.
Carbon Recycling International (CRI) is an Icelandic limited liability company which has developed a technology designed to produce renewable methanol, also known as e-methanol, from carbon dioxide and hydrogen, using water electrolysis or, alternatively, hydrogen captured from industrial waste gases. The technology is trademarked by CRI as Emissions-to-Liquids (ETL) and the renewable methanol produced by CRI is trademarked as Vulcanol. In 2011 CRI became the first company to produce and sell liquid renewable transport fuel produced using only carbon dioxide, water and electricity from renewable sources.
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 (CO2) as a feedstock. Proposed carbon-neutral fuels can broadly be grouped into synthetic fuels, which are made by chemically hydrogenating carbon dioxide, and biofuels, which are produced using natural CO2-consuming processes like photosynthesis.
Power-to-gas is a technology that uses electric power to produce a gaseous fuel. When using surplus power from wind generation, the concept is sometimes called windgas.
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, water, and electricity with a process powered by renewable energy sources to create a liquid energy carrier called blue crude which is then refined to generate e-diesel. E-diesel is considered to be a carbon-neutral fuel as it does not extract new carbon and the energy sources to drive the process are from carbon-neutral sources.
The situation is much worse than this, however, because before the hydrogen can be transported anywhere, it needs to be either compressed or liquefied. To liquefy it, it must be refrigerated down to a temperature of −253 °C (20 degrees above absolute zero). At these temperatures, fundamental laws of thermodynamics make refrigerators extremely inefficient. As a result, about 40 percent of the energy in the hydrogen must be spent to liquefy it. This reduces the actual net energy content of our product fuel to 792 kcal. In addition, because it is a cryogenic liquid, still more energy could be expected to be lost as the hydrogen boils away as it is warmed by heat leaking in from the outside environment during transport and storage.
The cost of cryogenic storage – including the cost of the storage tank, the cost of the equipment to liquefy hydrogen, and the cost of electricity to run the equipment – remains high.
The infrastructure dilemma seems insurmountable. Onboard storage of hydrogen in either gaseous or liquid form, makes for incredibly expensive vehicles, and a large-scale shift to hydrogen entails supplementing or supplanting the existing liquid fuel delivery infrastructure. This is a tough proposition, to put it mildly.