Beyond Oil and Gas: The Methanol Economy
When the world is racing to find scalable alternatives to fossil fuels, the methanol economy concept is presented as the energy storage and energy carrier solution to most pressing problems.
This third edition of the book is dedicated to the late author George A. Olah, a major proponent of the Methanol Economy concept together with his co-authors Alain Goeppert and Surya Prakash.
The Methanol Economy is introduced as a plausible, convenient solution (to replace oil and gas) which is laid out at the end of every chapter, making possible to build up the understanding of what is meant by captured and chemically recycled carbon dioxide (carbon capture and recycling, CCR) to methanol and derived products.
Facts about Methanol
Methanol is commonly referred as wood alcohol because it was first produced as a minor by-product of charcoal manufacturing by destructive distillation of wood. In the early days the synthesis of methanol and ammonia was so interrelated that they are often, even today, produced in the same plant.
Besides being an energy storage medium, methanol is an excellent fuel in its own right, with an octane number of 100, which can be blended with gasoline as an oxygenated additive. It can served as a convenient diesel substitute. Dimethyl ether, DME, readily produced from methanol by dehydration, is an excellent substitute for diesel as well as for household gas for cooking and heating.
Methanol is presently nearly exclusively produced by synthetic processes. Methanol is traditionally produced through steam reforming of natural gas and coal gasification. Liquid fuels and methanol in particular, produced from natural gas through direct oxidation, without going through syngas is a promising technology to reduce oil dependency. Methanol has the lowest cost and lower GHG emissions, but requires infrastructure modification and faces substantial acceptance challenge.
The fundamental difference between the production of bio-ethanol and methanol is that the latter does not rely entirely on agricultural resources but can also be readily produced from varied feedstocks including fossil fuels, waste products, and by chemical recycling of carbon dioxide from natural or industrial sources.
Applications
Today, methanol is mainly used as feedstock for the chemical industry. The use of methanol as a fuel by either blending into gasoline, for the production of biodiesel, or in the form of dimethyl ether has seen tremendous growth. Another application that is growing rapidly is the production of olefins through the MTO process as an alternative to more traditional petrochemical routes.
Hydrocarbons have and should continue to fulfil a major role in our lives. They should however be made environmentally CO2 neutral and regenerative through their chemical recycling in a technical carbon cycle.
Goals of the Methanol Economy:
New and more efficient ways of producing methanol and/or derived DME from fossil fuels sources, primarily natural gas, by either oxidative conversion, preferably without prior conversion to syngas.
Production of methanol by hydrogenative recycling of CO2 from natural and industrial sources and eventually from the air.
The use of methanol and derived DME as convenient energy storage media, transportation fuel for combustion engines and turbines, as well as new generations of fuel cells.
The use of methanol and DME as transportation fuels is one of the main aspects of the Methanol Economy.
Looking back at the history of methanol in the automotive sector, the fate of methanol fuel has been extremely dependant on economic aspects.
Going beyond, methanol produced efficiently from atmospheric CO2 and hydrogen generated from water can replace oil and gas as a convenient way to store energy, a suitable fuel, a chemical raw material for synthetical hydrocarbons and their products and even for protein production. Captured and chemically recycled carbon dioxide will be turned into a valuable, renewable and inexhaustible carbon source of the future. In a way, the proposed technological Methanol Economy can provide a viable alternative to nature´s own photosynthetic CO2 recycling.
Chemical recycling of carbon dioxide to methanol
A promising new approach is to convert CO2 chemically by catalytic of electrochemical hydrogenative methods to methanol or DME and subsequently to synthetic hydrocarbons and products using hydrogen obtained from water electrolysis or other cleavage methods. Methanol is most probably formed by hydrogenation of CO2 contained in the syngas on the catalyst surface. Heterogeneous catalyst are still the standard for preparation of methanol from CO2.
Methanol production from biomass and biogas
Depending on the nature of the feedstock, pyrolysis, liquefaction and gasification can be applied. For solid feedstocks technologies are similar to the ones applied to convert coal to methanol (gasification to syngas followed by methanol synthesis). Animal manure converts first to biogas followed by reforming to syngas and finally methanol synthesis.
The transportation of bulky biomass product with low energy density is not economical, its transformation to an easy to handle and store liquid intermediate through fast pyrolysis, which product is called biocrude, may be an option.
In Europe, the paper industry has also turned its attention to black liquor gasification as possible source for methanol and DME.
DME from biomass is one of the most energy efficient renewable fuels (well to wheel) the production costs of DME from black liquor is estimated to be equivalent to $65 per barrel of oil without subsidies.
Methanogenesis is the process where methanogenic bacteria generate biogas. In Europe was extensively used when energy supplies were reduce during and after WWII. Most common feedstocks are animal dung, sewage sludge and wastewater. The use of anaerobic digesters to treat industrial waste water has gained rapidly popularity. The biogas is mainly used to produce electricity or heat. After the removal of impurities (especially hydrogen sulphide), biogas could also be used directly for the production of methanol in the same way as natural gas.
Limitations: for the production of biomethanol, non-food crops selected specifically for energy purposes would therefore nave to be cultivated on a large scale if a significant amount of methanol were to be produced from biomass resources.
Hydrogen and why not hydrogen
Today hydrogen is used on a large scale as feedstock in the chemical and petrochemical industry to produce principally ammonia, refined petroleum products, and a wide variety of chemicals. Almost 96% of the world hydrogen needs are produced from fossil fuels, with almost half being generated by steam reforming of methane. Natural gas is the most suitable feedstock for hydrogen production.
Hydrogen energy is only as clean and environmentally friendly as the process used to produce it. Electrolysers allow both centralized and decentralized hydrogen production. It would be unreasonable to use fossil fuels to generate electricity and then use electricity to generate hydrogen. As each transformation involves energy losses, the overall efficiency would be lowered and much more CO2 would be emitted than if fossil fuels had been used directly or transformed by reforming.
Instead of using hydrogen in its highly volatile and inconvenient pure form, a feasible alternative for energy storage involves its conversion to a convenient, safe, and easy to handle liquid carrier.
