Alternative Energy Sources

Beyond Oil and Gas: The Methanol Economy**George A. Olah*

Keywords:environmental chemistry · hydrocarbons ·hydrogen · methanol

Oil and natural gas together with coal,the main fossil fuels, not only remain ourmajor energy sources but they are alsothe feedstocks for a great variety ofmanmade materials and products thatrange from gasoline and diesel oil tovaried petrochemical and chemicalproducts, including synthetic materials,plastics, and pharmaceuticals. What na-ture gave us as a gift, formed over thecourse of eons, is being used up ratherrapidly. Fossil fuels continue to besignificantly depleted and will becomeincreasingly costly. Thus we need tosearch for new sources and solutions.

All fossil fuels are mixtures of hy-drocarbons, which contain varying ratiosof carbon and hydrogen. Upon theircombustion, they are irreversibly usedup: carbon is converted into carbondioxide and hydrogen into water. On arelated note, the increase of the CO2

content of the atmosphere is considereda major manmade cause of globalwarming.

Coal and the IndustrialRevolution

Coal is considered to have beenformed during the so-called carbonifer-ous period some 300 million years agofrom the anaerobic decomposition ofthen-living plants. Its use for heating

purposes began slowly and becamemore widespread in the 16th and 17thcenturies mainly in England as a re-placement for wood, which was becom-ing scarcer. Coal became dominant inthe 18th century with the invention ofthe steam engine and the industrialrevolution, which was also fueled bycoal, that followed. In the 19th and 20thcenturies, coal continued to satisfy theever-increasing energy demand of man-kind, and today it is used primarily forgenerating electricity.[1] Whereas ourcoal reserves may last for another twoor three centuries, the mining of coal(except in areas suited for surface stripmining) is increasingly affected by socio-economical, safety, and environmentaldifficulties.

Oil and Natural Gas

Since the latter half of the 19thcentury, petroleum oil and natural gashave become increasingly important anddominant energy sources and raw ma-terials for chemicals and manmade ma-terials. They are certainly the mostconvenient fossil-fuel sources.

Much has been said over the yearsabout the extent of our available oil andgas resources. At first glance, estimatedworld oil and gas reserves look impres-sive. These reserves seem not to havediminished in the last 50 years[2] owingto continuous developments and im-proved technologies that have allowedexploration, production, and recoveryfrom increasingly difficult-to-accessareas, such as the depths of the seasand inhospitable land areas from desertsto the Arctic. Conservation of energyand secondary and tertiary recoveryfrom previously exploited fields are

significant, but will not fundamentallychange the long-range outlook.

Besides petroleum oil and naturalgas (and also coal), we have additionalsources of “heavy” hydrocarbons, suchas heavy-oil deposits in Venezuela, oilshales in various geological formationsincluding the US Rocky Mountains, andvast tar sand deposits in the Canadianprovince Alberta. The relatively stablehydrates of methane, as found under theSiberian tundras and along the conti-nental shelves of the oceans, representsignificant possibilities for natural gasdeposits in the future. They will alleventually be exploited, although thedifficulties and expense involved areextensive.

Besides the size of oil reserves (1–1.5trillion barrels or some 200 billionmetric tons), one must also considerour expanding world population, whichexceeds 6 billion now and will probablyapproach 9–10 billion by the mid-21stcentury, as well as increasing standardsof living and demand in countries suchas China and India if one wants topredict how long the estimated oilreserves may last. Present estimates ofour proven oil reserves reveal that theywould last for some 40 years at thecurrent rate of consumption. Naturalgas reserves are comparable but some-what larger. New developments andimproved recovery methods, however,could extend these estimates significant-ly.

Alternative Energy Sources

To satisfy mankind�s ever-increasingenergy needs, one has to consider allfeasible alternative energy sources. Hy-dro- and geothermal energy are usedwhere Nature makes it feasible, but no

[*] Prof. Dr. G. A. OlahLoker Hydrocarbon Research Institute andDepartment of ChemistryUniversity of Southern CaliforniaLos Angeles, CA 90089-1661 (USA)Fax: (+ 1)213-740-5087E-mail: olah@usc.edu

[**] An identically titled monograph that dis-cusses various aspects of the methanoleconomy is being published by Wiley-VCH.

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2636 � 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/anie.200462121 Angew. Chem. Int. Ed. 2005, 44, 2636 –2639

major new sources have been found.Energy from the sun and wind, andwaves and tides of the seas all have realpotential and are increasingly exploited,but their use on such a large scale so asto substitute fossil fuels is not likely tosignificantly affect our energy outlook inthe foreseeable future.[3]

Atomic Energy

Probably the greatest technologicalachievement of the 20th century was toharness the energy of the atom. Regret-fully, as it was first achieved by buildingthe atomic bomb, in subsequent yearspublic opinion increasingly turnedagainst atomic energy, even for peacefuluses. Over the last few decades, rela-tively few new atomic power plants wereconstructed. There is even strong senti-ment to close them down altogether insome countries, although others such asFrance depend on them for some 80%of their electricity needs. Progress hasbeen made to limit the use of atomicenergy to only peaceful uses and toimprove its safety aspects, including thestorage and disposal of radioactivewaste. I believe that our society, whichwas able to build the atomic bomb, canand will solve these problems. In myopinion, the decline of the atomic en-ergy industry is most regrettable.Whether or not one supports atomicenergy, in the long term it is the mostfeasible and massive energy source formankind.[4] Conservation and use ofalternate energy sources are most desir-able, but they cannot replace, by them-selves, the “classic” energy sources infulfilling mankind�s enormous energydemand.

Energy Storage and Distribution

Despite their nonrenewable natureand diminishing resources, fossil fuelsand particularly oil and gas will maintaintheir leading role as the most convenientsource of transportation fuels and en-ergy sources as long as they last. A vastinfrastructure exists for their transportand distribution. As transportation fuelsfor our cars, trucks, and airplanes, theycan be used in the form of their con-venient products (liquid gasoline, diesel

fuel) or as compressed natural gas. Theyare also the basic raw materials forchemical products and materials thatare essential to our everyday life. How-ever, the bulk of fossil fuels is utilized inpower plants to generate electricity.From whatever source electricity isgenerated, its storage on a large scaleis still unresolved; for example, batteriesare inefficient and bulky. It is thusnecessary to also find, besides newenergy sources, efficient means to storeand distribute energy.

The Hydrogen Economy andIts Difficulties

With our diminishing resources offossil fuels, there is urgent need todevelop feasible new and safe ways tostore and distribute energy from what-ever sources it is generated (atomic oralternate) as well as to produce effi-ciently manmade hydrocarbons.

One approach that was proposedand has been much discussed recently isthe generation of hydrogen and its useas a clean fuel—the so-called “hydrogeneconomy”. Hydrogen is not a naturalenergy source on earth as it is incom-patible with the high oxygen content ofour atmosphere. Whereas it is indeedclean burning to form water, its gener-ation is a highly energy-consumingprocess, which itself is not necessarilyclean. Presently it is mainly produced bythe reforming of fossil fuels to give syn-gas (synthetic gas), a mixture of CO andH2. The generated CO can also be usedin the water gas shift reaction to yieldmore hydrogen. In this process, how-ever, at least 20% of the energy of thefossil fuel is lost as heat. Hydrogen canalso be produced by the electrolysis ofwater, a process that does not produceCO2 nor involve a source of fossil fuels.Our oceans represent inexhaustible wa-ter sources that can be split by atomicenergy or any of the alternate energiesto produce hydrogen. Despite this, hy-drogen is not convenient either as ameans to store energy or for its subse-quent use as a fuel. The handling ofvolatile (b.p.: �253 8C) and potentiallyexplosive hydrogen gas necessitates spe-cial conditions: high pressure, use ofspecial materials to minimize diffusionand leakage, and extensive safety pre-

cautions. Even so, any leaks couldrepresent explosion hazards, which lim-its its potential use. Regardless, theU.S.[5] and other governments as wellas major industries seem to be increas-ingly committing themselves to developthe hydrogen economy. Besides thementioned difficulties of hydrogen stor-age and distribution, the development ofthe needed infrastructure for the hydro-gen economy, in my view, is also eco-nomically prohibitive, although this in-frastructure may eventually be devel-oped. The volumetric power density ofliquid hydrogen is also a drawback atonly one-third of that of gasoline, whileliquefying hydrogen requires consider-able amounts of energy.[6]

The Methanol Economy andIts Advantages

Methanol, which is presently pre-pared from fossil-fuel-based syn-gas, canalso be prepared by direct oxidativeconversion of natural gas (methane) orreductive conversion of atmosphericcarbon dioxide with hydrogen(Scheme 1). In this way, hydrogen can

be stored by converting it into metha-nol—a convenient liquid fuel and rawmaterial for synthetic hydrocarbons andtheir products—with carbon dioxidefrom industrial effluents or the atmos-phere. This opens up the possibility of analternative energy source to diminishingoil and gas resources and would lead to afeasible “methanol economy”.

Owing to the serious limitations ofthe hydrogen economy, I have beenproposing for some time now the meth-anol economy as a reasonable alterna-tive.[7] Methanol provides an efficientmeans to store energy and can be used

Scheme 1. Production of methanol fromatmospheric carbon dioxide or from naturalgas (methane), and its use as a fuel. DMFC:direct methanol fuel cell.

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as a convenient fuel as well as a rawmaterial for manmade hydrocarbonsand their products.

Methanol is an excellent fuel in itsown right and it can also be blendedwith gasoline, although it has half thevolumetric energy density relative togasoline or diesel. It is also used in thedirect methanol fuel cell (DMFC) thatwe developed jointly with the Jet Pro-pulsion Laboratory of Caltech.[8] In thiselectrochemical cell, methanol is direct-ly oxidized with air to carbon dioxideand water to produce electricity, withoutthe need to first generate hydrogen. Thisgreatly simplifies the fuel-cell technol-ogy and makes it available to a widescope of applications: for example, toprovide power to cellular phones andcomputers (already under development)and eventually to motor scooters andcars, or even to use it in large electricity-generating facilities. It was also foundthat methanol can be conveniently con-verted into ethylene or propylene in theMTO (methanol-to-olefins) process(Scheme 2). In turn, these olefins can

be used to produce hydrocarbon fuelsand their products,[9] which are presentlyobtained from oil and gas. UOP, basedon the earlier work of Jule Rabo and co-workers,[9d] developed an industrialprocess for the production of ethylenefrom methanol using acidic zeolite cata-lysts, and industrial plants based on thisprocess are now under development.[9e]

In contrast to hydrogen gas, meth-anol is a convenient and safe liquid (b.p.:64.7 8C). Whereas it is toxic when inter-nally ingested and is frequently quotedas a poison, so are gasoline and dieselfuel. Some suggestions were made to useethanol as a fuel as it can be made byfermentation from agricultural products.However, its use as a fuel has manydrawbacks, and even Brazil is limiting itsambitious program to convert sugarcane into ethanol fuel. The overalleconomics to produce agriculture-based

ethanol to replace fossil fuels is also notfavorable. In fuel cells, ethanol encoun-ters further difficulties as cleavage of C�C bonds is more difficult than cleavageof C�H bonds. Interestingly, it wasLenin that supported the industrial useof agricultural alcohol after the Bolshe-vik Revolution, but even the Russiansresisted the “misuse” of their belovedvodka and the plan was abandoned.

At present, methanol is producednearly exclusively from syn-gas, which isobtained by catalytic reforming of fossilfuels.[9b] As long as natural gas remainsquite abundant, it seems reasonable toconvert it directly (without first produc-ing syn-gas) into methanol. In ourresearch, much progress was made inthe direct oxidative conversion of meth-ane into methanol. As mentioned ear-lier, large resources of methane are tiedup as gas hydrates in vast areas of sub-Arctic tundras and under the seas in theareas of the continental shelves.

Chemical Recycling of CO2

As mentioned earlier, methanol canbe also obtained by the reduction ofcarbon dioxide with hydrogen. Fluegases of coal- or fossil-fuel-burningpower plants may be an abundantsource of readily isolable carbon dioxidefor the foreseeable future. Many indus-trial exhausts also contain considerableconcentrations of carbon dioxide. Watercan provide the required hydrogen.Instead of just sequestration, this proc-ess would recycle carbon dioxide intouseful fuel and provide a source ofhydrocarbons.

For the long-range solution to man-kind�s hydrocarbon needs as well as forefficient storage of energy that willeventually be generated from nonfossilfuel sources, the utilization of atmos-pheric carbon dioxide itself through itsreduction to methanol offers a feasiblenew alternative. However, the contentof carbon dioxide in the atmosphere islow at 0.037%. Thus, new efficient waysto separate CO2 are needed. One way ismembrane separation technology, an-other is the use of selective absorptionmethods; here our ongoing research hasled to significant advances to allowpractical separation of atmosphericCO2 from air. Besides, in the conversion

of CO2 to methanol, volatile hydrogengas is converted into a convenient, safeliquid. If we can produce methanolefficiently on a large scale from atmos-pheric carbon dioxide and hydrogen, itcould replace oil and gas both as a fueland as a chemical raw material.

Atmospheric carbon dioxide is avail-able to everybody on earth. The meth-anol economy thus eventually can lib-erate mankind from reliance on fossilfuels. The required hydrogen can beobtained from the electrolysis of waterof the seas—an unlimited source. Theelectrical energy will be provided byatomic energy, which will be made saferand solved of problems pertaining toradioactive waste disposal, as well as byall suitable alternate energy sources(sun, wind, and hydroelectric). Alterna-tively, direct aqueous electrochemicalreduction of CO2 can be used,[7b] andphotochemical reduction of CO2 is alsofeasible. I believe that it is reasonable toconsider the methanol economy as apractical and sensible approach to even-tually replace fossil fuels. It can providea feasible and safe way to store energy,to make available a convenient liquidfuel, and assure mankind an unlimitedsource of hydrocarbons, while at thesame time mitigating the dangers ofglobal warming owing to the greenhouseeffect of carbon dioxide. In contrast tohighly volatile hydrogen, methanol is aconvenient liquid. Its use does notnecessitate the development of a newand extremely costly and unproven in-frastructure, nor does it suffer the greatdifficulties of safety as with the use ofhydrogen.

The hydrogenation of carbon diox-ide either by catalytic conversion withH2 or by electrochemical reduction,including the reverse use of the directmethanol fuel cell,[7b] produces formicacid and formaldehyde besides metha-nol. It is possible, however, to furtherconvert formic acid and formaldehydeinto methanol and allow an overall highyield of methanol to be obtained. Thedirect oxidation of methane, which isstill available from natural gas sources,into methanol also should be consid-ered. This also always produces signifi-cant amounts of formaldehyde and for-mic acid. Higher selectivities to obtainmethanol were reported only under low-conversion conditions.[10] With this in

Scheme 2. Conversion of methanol into ethyl-ene (or propylene) on the way to hydrocar-bons and their products.

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mind, we were successful in dramaticallyincreasing the yields of methanol by thesecondary conversion of formaldehyde/formic acid into methanol.

I suggest that carbon dioxide recy-cled by chemical reduction will providean essential source of methanol for useas a fuel as well as a raw material forsynthetic hydrocarbons and their prod-ucts. Nature, of course, recycles carbondioxide in the photosynthesis of plantsby using water and solar energy in aprocess catalyzed by chlorophyll. How-ever, the formation of hydrocarbonsfrom plant life is a very slow processthat requires hundreds of millions ofyears, although much faster bacterialconversion is feasible.

Methanol was suggested before as afuel and a bridge to a renewable energyfuture,[11] however, these suggestionswere never followed up by implementa-tion. The reason, besides economic andpractical factors, most probably was thatmethanol that originates from syn-gasgenerated from fossil fuel does notalleviate our dependence on fossil fuels.

The methanol economy throughchemical recycling of carbon dioxidewill eventually free mankind from de-pendence on diminishing natural fossilfuels. At the same time, recycling excessCO2 from industrial gases and theatmosphere will mitigate a major man-made cause of global warming. Thecollection and sequestration of CO2 insubterranean cavities or at the bottom ofthe seas is costly and does not provide apermanent solution, nor does it resolveour future needs for hydrocarbons. Thestill-controversial Kyoto agreement onglobal warming, which aims to limit CO2

emissions, would be made more feasibleby the availability of new technology,such as the chemical recycling of excessatmospheric carbon dioxide.

Ultimately all of our energy comesfrom the sun. As the sun will last for atleast 4.5 billion years, there is an enor-mous amount of time for mankind todevise methods for harnessing its en-

ergy. We cannot in any way imagineadvances of future generations. Discus-sion of what will happen beyond ourpresent oil and gas economy relates toonly the foreseeable future. Neverthe-less, to find efficient ways to storeenergy and to produce convenient hy-drocarbon-based fuels and productswhile mitigating global warming byrecycling carbon dioxide is essential toour life and has long-range significance.

In the suggested methanol economy,methanol will be used as 1) a convenientenergy-storage material, 2) a fuel, and3) a feedstock to synthesize hydrocar-bons and their products.

Published online: March 31, 2005

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[3] Energy Technologies for the 21st Cen-tury, International Energy Agency, Par-is, 1997.

[4] R. C. Morris, The Environmental Casefor Nuclear Power, Paragon House, St.Paul, MN, 2000.

[5] National Hydrogen Energy Road Map,US Department of Energy, November2002.

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