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| Fig. 1: Methanol. (Source: Wikimedia Commons) |
Today, petroleum based fuels continue to predominate as the major global energy source. However, supplies of fossil fuels are finite. Fossil fuels are mixtures of hydrocarbons, mainly coal, oil, or natural gas, and contain varying proportions of carbon and hydrogen. The burning of fossil fuels releases water and carbon dioxide gas, which accumulates in the atmosphere. The Environmental protection agency estimates that fossil fuel production is responsible for 77% of U.S. greenhouse gas emissions, directly contributing to climate change. [1]
Several scientists support the transition to a methanol economy, first proposed by 1994 Nobel Prize winner George A. Olah. Olah purports that storing energy in the form of methanol (CH3OH) could alleviate global dependence on fossil fuels while sequestering harmful carbon dioxide emissions. The idea of a methanol economy briefly tested in the 1980s in America, but the effort was a largely considered a failure.
Methanol (Fig.1), the simplest oxygenated hydrocarbon may easily be used as a fuel source. It boasts a high octane rating, meaning it can withstand greater compression pressures at a lower risk of igniting. In addition, methanol has a latent heat of vaporization 3.7 times higher than gasoline, increasing the efficiency of engine heat removal. These two properties make methanol itself a suitable replacement, or additional component, of gasoline. [2]
Methanol itself can be manufactured from a variety of sources, such as biomass, municipal waste, natural gas and coal. At this time, methanol is predominantly produced through the catalytic reforming of fossil-fuel based synthesis gas, a mixture of CO and H2. [2] However, methanol can also be created through the direct oxidative conversion of methane, the major component of natural gas. This process is about 70% efficient, allowing the economics of methanol production to complete with gasoline. [3] Methanol can also be created through the reduction of carbon dioxide by hydrogen gas or water. [2,4] Methanol can then be utilized as a convenient liquid fuel, or used with fuel cells to generate electricity. In addition, methanol serves as raw material for synthetic hydrocarbons, as it can be converted into ethylene or propylene in the methanol-to-olefins process. [2] Olefins are typically extracted from oil, and used to produce hydrocarbon fuels. Thus, methanol represents a feasible alternative energy source over oil and gas.
In recent years, hydrogen has been proposed as a clean alternative fuel source since can be produced from water. A methanol economy presents several advantages over a hydrogen economy. Methane, unlike hydrogen gas, is an abundant natural energy source. Hydrogen gas is dangerously more volatile than methanol (64.7°C) with a boiling point of -253°C. [2] As a result, hydrogen gas is much more costly and complicated to store and transport. Importantly, methanol, as a liquid, can be seamlessly incorporated into present infrastructure; as it can even be easily mixed into gasoline and dispensed from present gas stations into flex-fuel vehicles. [5,6] Methanol is a particularly attractive alternative for conventional transportation fuels due to its low cost of implementation, low risk of flammability and toxicity, and potential to reduce pollution emissions and dependence. [6]
Recognizing the potential of methanol to become a significant component of transportation fuel, California established a test program that lasted from 1980 to 1990 and permitted drivers to convert their gasoline-powered cars to 85% methanol with 15% additives of choice (M85). [4] While the M85 vehicle users believed the cars performance was equal or superior, they were dissasifed by imposed limitations. Mainly, the small number of M85 refueling stations established, forcing drivers to plan routes based on proximity to fuel. Despite the early frustrations, M85 programs culminated in over 21,000 automobiles in 1997. In 2005, California abruptly ended the use of methanol in the transportation sector in order to shift focus to exploring ethanol-based options, which were quickly gaining recognition due to their agricultural basis. [6]
Although a methanol economy, by chemically recycling atmospheric carbon dioxide, would reduce the growing need for diminishing fossil fuel resources, early efforts to implement methanol as a transportation fuel did not succeed. However, methanol remains a practical replacement for petroleum-based fuels: it is environmentally friendly, economically competitive with gasoline, and can be simply incorporated into existing infrastructure.
© 2015 Alyssa Noll. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Inventory of U.S. Greenhouse Gas Emissions and Sinks" 1990-2013," U.S. Environmental Protection Agency, EPA 430-R-15-004, April 2015.
[2] G. Olah, "Beyond Oil and Gas: The Methanol Economy," Angewandte Chemie Int. Ed. 44, 2636 (2005).
[3] R. Nichols, "The Methanol Story: A Sustainable Fuel for the Future," J. Sci. Ind. Res. 62, 97 (2003).
[4] D. Sleiter, "Synfuel Cycle Efficiency," Physics 240, Stanford University, Fall 2010.
[5] K. Bullis, "The Methanol Economy, Technology Review, 2 Mar 06.
[6] L. Bromberg and W. K. Chen, "Methanol as an Alternative Transportation Fuel in the U.S.: Options for Sustainable and/or Energy-Secure Transportation," Massachusetts Institute of Technology, November 2010.
