return to main project page
Feasibility Study of Methanol as Transportation Fuel
Methanol Conversion Group
Project Advisor: Richard Herz, Ph.D.March 18, 2001
The Methanol Conversion Group has performed a literature review of four methods for the use of methanol as an alternative fuel for transportation. These four alternatives are: direct use of methanol, as a blend with gasoline, methanol to gasoline and methanol to hydrogen in transportation. The group recommends that for immediate application, methanol blends starting at 5% and rising up to 15% be introduced into the transportation sector. As methanol production from biomass or natural gas sources increase over time, higher percentage methanol fuel blends will be introduced eventually up to 100%, taking advantage of technological development of methanol fueled automobiles. This will enable the US to meet increasingly stringent greenhouse emission reduction goals as well as decreasing the need for what surely will be decreased global oil reserves in the next few decades. In the future, fuel cell technology will advance to the point of being a viable alternative to the internal combustion engine, as the methanol to hydrogen, MTH, process is ideal for sustainable transportation needs in the future. The MTH process and fuel cell use has the lowest estimated carbon emissions, zero particulate and NOx emissions, as well as the highest energy efficiencies, of the four alternatives researched for the use of methanol as a transportation fuel.
In the past 100 years oil has played a vital role in fueling the energy and transportation needs of the United States and other countries around the world. In fact, oil was so vital to a nationís success in the emerging global economy of the mid 20th century that in World War II, Japan, starving for oil, joined the Axis powers in order to secure a steady supply. The importance of oil has not diminished since then, with the Arab Oil Embargo in 1973 and 78, and later in 1990-91 when the United States fought the Gulf War in order to secure the free flow of oil to the rest of the world. The importance of oil stems from its use not only for energy production, but also for transportation, i.e. the internal combustion engine. Two thirds of the oil used in the US is for transportation and is increasing in proportion (Krupnick and Walls, 1992). With this increased use of oil comes increased greenhouse gas emissions and economic impacts resulting in a situation that soon may be unsustainable.
In order to address this situation, goals have been established by the National Energy Strategy, Energy Policy Act and Clean Air Amendments in order to study and develop alternatives that could reduce environmental and economic problems of petroleum fuels (Borgwardt, 1998). Methanol is one of these alternative fuels being studied and can be used for transportation in four main applications: direct substitution, as a blend with gasoline, conversion to gasoline for internal combustion engines and conversion to hydrogen for use in fuel cells. The Methanol Conversion Group has performed a literature review of the feasibility, environmental and safety/health (ESH) issues, and economic impacts of the four main applications of methanol use in transportation.
Methanol was first isolated in 1823 by condensing gases from burning wood into a liquid, hence the common name, "wood alcohol." It can be produced from biomass and coal, but the main method of production in the US is with natural gas:
CH4 + 0.5 O2 → CO +2 H2 (syn gas)
CO + 2 H2 →CH3OH (methanol)
Currently, the US produces 2.6 billion gallons of methanol per year (AMI, 2001) and if all sources of methanol were collected for production, including biomass and waste natural gas, methanol could provide 37% of fuel demands in the US (Black, 1991). Additionally, production from biomass is considered to be a CO2 emission neutral process, which means the CO2 released from conversion of biomass to methanol results in no net increase in CO2 concentration in the atmosphere due to living biomass reabsorbing the CO2 (Gustavsson, 1995). While methanol has various benefits as a transportation fuel, including higher octane than gasoline, it does have some safety drawbacks when compared to gasoline. The flammability limits of methanol are wider than gasoline making it more dangerous to handle and transport, and it burns almost invisibly. Additives are being studied in order to produce color when burned in order to decrease the danger.
Direct use of Methanol in Transportation
As mentioned previously, one of the major benefits of using "neat" methanol (100% methanol), as a transportation fuel is it has a higher octane number than gasoline. This creates an internal combustion engine with a higher compression ratio (Kowalewicz, 1993). This ratio relates to efficiency of the engine, where a higher compression ratio allows for more work per unit of fuel. A neat methanol engine has 30% more efficiency than a regular engine, not only due to the higher compression ratio but also due to methanolís higher heat of vaporization (MacDougall, 1991; Hancook, 1985). Methanolís greater heat of vaporization cools the air in the engine to a larger extent, thus lowering the density and allowing more air in. This results in a leaner fuel mixture, possibly lowering emission of CO due to more complete combustion. Another benefit to the use of methanol is it has a low combustion temperature, which results in less formation of NOx, a precursor to smog in urban settings (Kowalewicz, 1993).
Many benefits arise with the use of methanol, yet there are some shortcomings. Because of gasolineís composition, it has a boiling point that varies from 31° C to 221° C. In contrast, methanol has a boiling point of 65° C, creating a problem in cold-starting applications. Other problems include corrosion of car parts that are made from lead, magnesium or aluminum, and a possibility of explosion since saturated methanol-air mixes are explosive at ambient temperatures (Another Look, 1984). A main concern, however, is methanolís heat of combustion, which is half that of gasoline. This means a car would need a tank twice as large and more heat in the intake system to run only on methanol (Ingamells and Lindquist, 1980). With the combination of increased efficiency and methanolís lower energy density, it is estimated that the fuel tank for methanol would have to be 1.5 to 1.8 times larger in volume compared to a gasoline fuel tank (Poulton, 1994). Additional adjustments required for a neat methanol fueled internal combustion engine include a larger injection system and a heating system for evaporation of neat methanol (Kowalewicz, 1993).
ESH issues with the use of neat methanol in transportation start with the tendency for methanol to form aldehydes during combustion, unlike gasoline. Specifically, formaldehyde is formed, which is toxic and possibly carcinogenic in nature, but the formaldehyde can be removed by catalytic conversion. Toxic substances released by gasoline combustion however, such as benzene and 1,3-butadiene, are nearly eliminated with methanol use. It has also been found that compared to emissions from the combustion of gasoline, methanolís HC emissions have one-fifth the reactivity, signaling a potential for lower ozone formation. However, one group has shown that even with a significant replacement of conventional cars with neat methanol cars, the reduction of ozone is small, on the order of a few percent (Krupnick and Walls, 1992). Therefore the benefit of ozone reduction from methanol use is still unclear at this time.
The full economic impact of direct methanol use in transportation involves a multitude of variables and is beyond the scope of this review, therefore; only general qualitative issues are discussed. In examining the issues, it was discerned that not only are production costs important, but also methods of distribution, costs of renovating or building new fueling stations, and costs for the production of vehicles optimized for methanol. Comparison of methanol versus gasoline also depends on the current price of gasoline. In 1987, the IEA estimated that compared to the production cost of a barrel of gasoline, methanol produced from natural gas would be 11% to 148% higher (this is adjusted for equivalent amounts of energy). When methanol is produced from coal or biomass, the costs increase significantly. Methanol from natural gas seems economically viable, and it could be more competitive when methods to increase conversion to methanol are developed (Poulton, 1994). At this time, the ability of the US to produce the amount of methanol required to have a significant impact upon emission reductions and gasoline consumption is minimal. Krupnick and Walls state that by 2004, 6 billion gallons (current production, 2.6) of methanol would be required. Therefore, a significant increase in production would be required to supply enough methanol, which would entail large capitol investments for plant construction. As for automobiles that can use neat methanol as a fuel, Ford and General Motors testified to the US Congress in 1989 that dedicated methanol vehicles, if produced in quantities of at least 100,000 per year, would have a cost comparable to a conventional car (Poulton, 1994).
Methanol as a Blend in Transportation
As a solution to neat methanolís shortcomings, methanol blends with gasoline have been considered. Blends up to 15% methanol require only minor engine modifications to operate. Higher concentration blends, such as M85, 85% methanol blend, used in studies for California require significant modifications. The addition of methanol has comparable emissions to gasoline, but it boosts the octane rating. Thus, the efficiency of the engine increases with the increase in methanol concentration (Kowalewicz, 1993). Blends also solve the major problem of cold-starting a car. Although methanol blends solve many of neat methanolís problems in the internal combustion engine, other problems unique to blends arise.
The mixture of gasoline and methanol has a tendency to deviate from an ideal solution, and the resulting vapor pressure of the mixture is higher than both methanol and gasoline. This can create a situation called vapor lock, where there is evaporation in the fuel lines (Ingamells and Lindquist, 1980). Another major problem is water absorption, which causes methanol and gasoline to separate into two different phases. The amount of water present in the blend affects the temperature of phase separation. A 10% blend at 20° C can have phase separation with as little as 0.1% water content (Another Look, 1984). Some groups have studied this problem and have found that blending agents, also termed "solubility enhancers", such as aliphatic alcohols can reduce the problem by hydrogen bonding to water. As little as 5% blending agent can lower the temperature to which the blend phase separates below winter condition temperatures (Osten and Sell, 1983).
The ESH issues involved in methanol blend use tend to vary with the concentration of methanol in the blend. As the fraction of methanol in gasoline increases, hydrocarbon emissions decrease while methanol and formaldehyde emissions increase. Basically, the environmental benefits and disadvantages of the use of methanol are commensurate with the percentage of methanol in the fuel. With the use of methanol, there is a reduced amount of moles of carbon emitted per mile. With gasoline, it is 0.12 moles C/mi, while with M85 and M100; it is 0.04 and 0.02 moles C/mi respectively (Black, 1991).
The economic impact of methanol blends also varies with methanol concentration. A World Bank Technical Paper in 1989 reported that it would cost 350 dollars to convert a conventional passenger car to one that would be able to use up to 85% methanol (1989). California, in partnership with several auto manufacturers, has sponsored demonstration programs to test "flex-fuel" cars that utilize M85 blend. By 1996, 13,000 cars in California were flex-fuel, mostly fleet vehicles. Ford has charged approximately 500 to 1,200 additional dollars for the M85 usable cars (Energia, 1999). Of course, depending once again on the amount of methanol blended with gasoline, production of methanol would have to be increased in the US. This would result in similar initial capitol outlays of money as for direct use of methanol. A method to introduce methanol use for transportation and yet keep costs down involves producing fuel with 5% methanol content, then increase to 15% after a few years. At this point, very little if any engine modifications would be necessary, and production and distribution costs could be slowly introduced. Then higher percentage blends would be made available, finally resulting in 100% methanol cars after a number of years (Kowalewicz, 1993).
Methanol to Gasoline in Transportation
The methanol-to-gasoline (MTG) process was initially discovered in the mid 1970ís and has received renewed interest in the past couple of years due to increasing gasoline costs. The discovery of the MTG process by Clarence D. Chang in 1976 came about from his study of selective zeolite catalysts and was rapidly developed into a 14,000 bbl per day plant in New Zealand in the early 1980ís. The MTG process can use natural gas or biomass as feedstocks and produces gasoline higher in octane than gasoline produced from oil. The true reaction pathway is still unknown, but hotly debated. The generally accepted reaction pathway is:
2 CH3OH → CH3OCH3 + H2O (Dimethyl Ether, DME)
DME → (C2 ñ C5)n → C6+ olefins, aromatics and paraffins up to C10
The final composition formed over the zeolite catalyst is 60% saturated hydrocarbons, 10% olefins and 30% aromatics (Meyers, 1984). When compared to gasoline from oil, the MTG process produces gasoline comparable to high quality oil derived gasoline and would not require engine modifications for use. The only drawback to the composition of the MTG product compared to gasoline from oil is the formation of Durene, a C10 molecule that needs to be separated out as it decreases engine performance.
ESH issues for the use of gasoline from the MTG process are no different than with the use of normal gasoline. As far as emissions are concerned, however, unless the methanol for the process is formed from biomass, the MTG product has nearly the same emissions in transportation as gasoline from oil.
The economic impact of the MTG process must take into account the huge initial capitol investment for conversion plants, ~750 million in 1980ís dollars. As mentioned earlier, New Zealand has already built such a plant. At the time New Zealand, an energy importer, desired to reduce the costs and insecurities of dependence on oil imports. After a study of the available synthetic fuel processes, they decided on MTG due to the availability of natural gas fields within the country (Maiden, 1988). Similar plants in the US would invariably have the same results, although the same issues with methanol production, as stated earlier, would need to be addressed. If the methanol is
formed from biomass, the cost would be 0.30 to 0.55 $ per gallon higher than from natural gas (Kowalewicz, 1993), but this may be necessary if Kyoto emission reduction protocols are to be met in the future.
Methanol to Hydrogen in Transportation
Methanol to hydrogen, MTH, while not a relatively new process, has been garnering renewed interest with the advent of fuel cell technology being adapted to transportation. The general reaction:
CH3OH + H2 → 3 H2 + CO2
takes place over a copper based catalyst using a quartz reactor. One of the more promising methods for hydrogen production is the Hynol process. This process uses natural gas in conjunction with biomass to form methanol or hydrogen, resulting in a net 20% reduction in CO2 emissions relative to separate processes and has the additional benefit of being easily switched from methanol to hydrogen production (Borgwardt, 1998). The hydrogen is then utilized in fuel cells to produce electricity for powering an electric vehicle.
The type of fuel cell most commonly considered for use in transportation is the solid polymer fuel cell (SPFC). The basic method of operation begins with hydrogen being fed into the fuel cell where a catalyst on the anode converts the gas into negatively charged electrons (e-) and positively charged ions (H+). The electrons (e-) then flow through an external load to the cathode. The hydrogen ions (H+) then migrate through the electrolyte to the cathode where they combine with oxygen and the electrons (e-) to produce water. Individual cells produce a small voltage. They are arranged in 'stacks' to provide the required level of power for transportation. Alternative designs would carry methanol on board, which would then be reformed into hydrogen for use by the cell.
Shortcomings of the MTH process include the formation of CO, which poisons the SPFC. The CO must therefore be removed from the hydrogen to less than 1% by volume. Additionally, even with the high energy efficiency of the SPFC, many cells need to be stacked together to provide the necessary power and range to operate an electric car, increasing size and weight of the vehicle. Lastly, the SPFC car has a long warm-up period before operation, although several companies, including the company Xcelsis, owned by Daimler-Chrysler, are currently working on improving cold starting applications for fuel cells.
ESH issues for MTH and use in fuel cell cars start with the extreme flammability and explosion hazard of hydrogen. The fuel cell car must be engineered to carry large quantities of pressurized hydrogen in vessels that must both be lightweight and able to withstand impacts typical in auto accidents. Of course, if methanol is used as a liquid hydrogen carrier for the SPFC instead of hydrogen gas, the risk of catastrophic accidents is reduced. Moving on to environmental issues, the Hynol process mentioned earlier utilizes a biomass-natural gas mixed feed for production of either methanol or hydrogen. This method, as previously mentioned, reduces CO2 emissions by 20%. Additionally, emissions from fuel cells are greatly reduced compared to gasoline engines. Particulate, CO and NOx emissions reduce to zero and HCís from 0.50 to 0.04 g/mile (DOE, 1999).
As it stands today, all inclusive economic analysis related to the MTH process and fuel cell use are still in preliminary stages of study. Iceland, in partnership with Ballard Power and Daimler-Benz has stated a preliminary effort to switch to a hydrogen economy in 15 to 20 years, which will provide excellent data for the continued study of hydrogen use in transportation (Hoffman, 1998). Some aspects of MTH and fuel cell use, however, can be discussed at this time. Currently, as with methanol production, the US is not capable of producing enough hydrogen to fuel the needs of a fuel cell economy or transportation sector (Borgwardt, 1998). The fuel cell car still has its own hurtles to overcome, including power issues and CO poisoning as previously mentioned, as well as the major problem of creating a distribution network of hydrogen refueling stations.
The comparison of the four different areas of methanol use in transportation involves a myriad collection of information from scientific, technological and economic sources. It is difficult to rank one as a better choice than another since all of the alternatives are currently in their infancy in regards to development. In addition, other factors come into play such as US foreign policy dealing with oil imports, global and US acceptance of emission reduction protocols such as the Kyoto agreement and unforeseen technological advancement such as the Mobil MTG process. The Methanol Conversion Group therefore recommends an approach that combines the best of three of these alternatives, and is based upon an idea set forth by Kowalewicz, that is, the slow introduction of methanol blends into the transportation sector.
For immediate application, methanol blends starting at 5% and rising up to 15% would be introduced into the transportation sector with little hardship as only minor modifications to the internal combustion engine would be necessary. Also, methanol production levels could easily increase to meet the extra methanol need. After a few years, as methanol production from biomass or natural gas sources increased, higher percentage methanol fuel blends would be introduced, taking advantage of technological development of methanol fueled automobiles. This would enable the US to meet increasingly stringent greenhouse emission reduction goals as well as decreasing the need for what surely will be decreased global oil reserves in the next few decades.
Hopefully, at this point, enough time would have passed for the maturation of the fuel cell car as a viable alternative to the internal combustion engine, as the MTH process is ideal for sustainable transportation needs in the future. The MTH process and fuel cell use has the lowest estimated carbon emissions, zero particulate and NOx emissions, as well as the highest energy efficiencies, of the four alternatives researched for the use of methanol as a transportation fuel. It will take time to arrive at this final stage however, as processing, distribution and technical hurdles currently still remain for the establishment of hydrogen as transportation fuel. But in the end, the MTH process and fuel cell use would be the penultimate choice of the four methanol alternatives once a steady hydrogen economy is established in the US.
"Another Look At Alternative Fuels," Automotive Engineering, 92(1), 60 (1984).
American Methanol Institute, "Methanol Production," available athttp://www.methanol.org/methanol/fact/methpr.html (last accessed, January 2001).
Black, F., "An overview of the technical implications of methanol and ethanol as highway motor vehicle fuels," SAE Paper No. 912413, Society of Automotive Engineers, Warrendale, PA, (1991).
Borgwardt, R. H., "Hynol Process Evaluation," US EPA, Research and Development, available at http://www.epa.gov/ord/webpubs/projsum/600sr97153.pdf (last accessed, February 2001).
DOE, "High-Efficiency, Low-Emissions Fuel-Cell Technologies Used in GM Minivan," available at http://www.olt.doe.gov/pdfs/Gmminivan.pdf (last accessed, February 2001).
Energia, "Methanol Powered ñ Flexible Fuel Vehicles, Fuel and Vehicle History," available at http://www.energy.ca.gov (last accessed, March 2001).
Gustavsson, L. et al., "Reducing CO2 Emissions by Substituting Biomass for Fossil Fuels," Energy, 20,11, (1995).
Hancook, E.G. ed., Technology of Gasoline, Blackwell Scientific Publications, Oxford (1985).
Hoffman, P., "Iceland and Daimler-Benz/Ballard Start Plans for Hydrogen Economy," available at http://www.hfcletter.com/letter/june98/feature.html (last accessed, February 2001).
Ingamells, J. C., and R. H. Lindquist, "Methanol as a Motor Fuel or a Gasoline Blending Component," Alcohols as Fuels, Society of Automotive Engineers, USA (1980).
Kowalewicz, A., "Methanol as a Fuel for Spark Ignition Engines: A Review and Analysis," Proc Instn Mech Engrs, 207(D1), 43 (1993).
Krupnick, A. J. and M.A. Walls, "The Cost-effectiveness of Methanol for Reducing Motor Vehicle Emissions and Urban Ozone," Journal of Policy Analysis and Management, 11, 3, (1992).
MacDougall, L.V., "Methanol to Fuels Routes-The Achievements and Remaining Problems," Catalysis Today, 8(3), 337 (1991).
Maiden, C.J., "Project Overview," Chemtech, 18, 38 (1988).
Meyers, R., Handbook of Synfuels Technology, McGraw-Hill, New York (1984).
Osten, David W. and Nancy J. Sell, "Methanol-Gasoline Blends: Blending Agents to Prevent Phase Separation," Fuel, 62, 268 (1983).
Poulton, M.L., Alternative Fuels for Road Vehicles, Computational Mechanics Publications, Boston (1994).
return to main project page