Economic theory
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.
Uses.
Fuel.
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).
Green methanol.
Green methanol is a liquid fuel that is produced from combining carbon dioxide and hydrogen () under pressure and heat with catalysts. It is a way to reuse carbon capture for recycling. Methanol can store hydrogen economically at standard outdoor temperatures and pressures, compared to liquid hydrogen and ammonia that need to use a lot of energy to stay cold in their liquid state. In 2023 the Laura Maersk was the first container ship to run on methanol fuel. Ethanol plants in the midwest are a good place for pure carbon capture to combine with hydrogen to make green methanol, with abundant wind and nuclear energy in Iowa, Minnesota, and Illinois. Mixing methanol with ethanol could make methanol a safer fuel to use because methanol doesn't have a visible flame in the daylight and doesn't emit smoke, and ethanol has a visible light yellow flame. Green hydrogen production of 70% efficiency and a 70% efficiency of methanol production from that would be a 49% energy conversion efficiency.
Feedstock.
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. 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. 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.
Production.
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. 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. There is no need to use food crops as in the case of ethanol from corn, sugar cane and wheat.
Biomass → Syngas (CO, CO2, H2) → CH3OH
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. It can also be made from chemical recycling of carbon dioxide, which Carbon Recycling International has demonstrated with its first commercial scale plant. 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 at atmospheric pressure 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. 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). 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.
Efficiency for production and use of e-methanol.
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% with potential up to 93% until 2030. Efficiency for methanol synthesis of hydrogen and carbon dioxide currently is 79 to 80%. 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. 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. 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. If the waste heat of a fuel cell is used a fuel cell efficiency of 85 to 90% can be reached. 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.
Araya et al. compared the hydrogen path with the methanol path (for methanol of directly available CO2). 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.
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.
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).
Cost comparison methanol economy vs. hydrogen economy.
Fuel costs.
Methanol is cheaper than hydrogen. For large amounts (tank) price for fossile methanol is about 0.3 to 0.5 USD/L. One liter of Methanol has the same energy content as 0.13 kg hydrogen. 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). 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 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, 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.
Infrastructure.
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