Internal combustion engines and gasoline have dominated transportation systems for three generations. In fact, the internal combustion engine has been so successful that until recently prospects for radical alternatives have been considered dim, and little research has been directed to the search for alternatives. Not only would a shift to new kinds of vehicles and new fuels affect the business practices of vehicles manufacturers and petroleum companies, two of the world’s largest economic sectors, but also a shift to a new fuel would require massive investment in new infrastructures, as filling stations, pipelines, and fuel storage facilities are replaced.

Such obstacles should not be viewed as impossible to overcome. Starting in late 1970, Brazil has shifted about half of its automotive fleet to ethanol. Recent volatility in transportation markets increases the likelihood that renewable fuels will find major markets in other countries too.

In addition, environmental reform is likely to transform world-wide markets for new fuels and propulsion systems. Already, acute air quality problems are creating markets for innovative transportation systems in some urban areas. Planners in these areas have come to realise that the solution is not as simple as mandating further incremental restrictions on tailpipe emissions and so are beginning to explore more radical changes. Research and development are now underway on zero emission propulsion alternatives, both battery-powered electric vehicles and fuel cells vehicles. Also under investigation are fuel alternatives such as reformulated gasoline, compressed natural gas, alcohol fuels (ethanol and methanol), electricity, and hydrogen.

In response to air quality concerns, California has mandated that by 2003, 10% of the vehicles sold in the state must have zero emissions. Other USA states are considering similar requirements.
The search for alternative transportation strategies is motivated largely by environmental concerns. However, technologies that are superior to existing internal-combustion-engined vehicles in the areas of cost, reliability, driving performance, and noise generation could emerge. The challenge for policy-makers is to construct policies that facilitate the introduction of new transportation systems that offer consumers multiple benefits while meeting the environmental goals of society.

New vehicle technologies
To date, the battery-powered electric vehicle is the zero-emission vehicle that has received the most attention. But its market share is likely to be small unless there is a breakthrough in the battery storage technology, because its range is limited and its batteries require several hours for recharging. Moreover, if the electricity for these vehicles comes from conventional fossil fuel-powered generators, air quality problems are not eliminated, only shifted from one site to another.

Fuel-cell-powered electric vehicles are at an earlier stage of development but are likely to be attractive alternatives to battery-powered vehicles. Fuel cells convert hydrogen directly into electricity without first burning it to produce heat. Hydrogen fuel-cells vehicles are perhaps three times as energy-efficient as comparable vehicles powered by gasoline-burning internal-combustion engines. The electricity produced by the fuel cell drives electric motors that provide power to the wheels. It is likely that a fuel-cell vehicle will use a battery (or perhaps a capacitor) to store electricity for starts and to provide extra power for passing and long uphill climbs. Fuel cell vehicles are refuelled quickly, either with hydrogen or with a hydrogen carrier such us methanol that is converted into hydrogen on board. They also have excellent environmental characteristics. Hydrogen-powered vehicles emit only water vapour and methanol vehicles only carbon dioxide and tiny amounts of local air pollutants, along with water vapour. If the methanol is produced from biomass grown on a sustainable basis, this carbon dioxide would be absorbed by growing biomass, so that net carbon dioxide emissions would be zero.

Alternative fuels
During the next few decades, several fuels will be competing for markets now dominated by gasoline. In the near term, the most important renewable transportation fuels are likely to be ethanol and methanol used in internal-combustion-engined vehicles. In the longer term methanol and hydrogen used in fuel-cell vehicles may be preferred.

Methanol is produced from biomass via a thermochemical process that begins with the gasification of biomass at high temperature. The products of gasification, which include carbon monoxide, hydrogen, and methane, are then converted to methanol via well-established industrial process developed originally for making methanol from natural gas and coal.

Although methanol from biomass may cost less than methanol from coal, it would probably be more costly as an internal-combustion-engine fuel than ethanol from the same biomass. But biomass-derived methanol would be an attractive fuel for fuel-cell vehicles. On a life-cost basis (cents per kilometre), a mass produced methanol fuel-cell vehicle may be competitive with gasoline internal-combustion vehicles. This is despite the fact that the price paid for methanol at the pump may be 50% higher than for gasoline, and that a methanol fuel-cell vehicle may cost 50% more than a gasoline internal-combustion-engine vehicle with comparable performance. This remarkable result arises from the fact that the methanol fuel-cell vehicle is likely to be 21/2 times as energy-efficient as the gasoline internal-combustion-engine vehicle and it is expected to last much longer and have lower maintenance costs.

Brazil launched the transition to an energy regime based on fuels from renewables in 1975 with its fuel-ethanol program. Under this program, ethanol from sugarcane (via the fermentation of sugar juice) has become a major fuel for Brazilian light-duty vehicles (automobiles and light commercial trucks). In 1989 Brazil’s entire fleet of light-duty vehicles consisted of 4.2 million fuelled with hydrated alcohol and 5 million fuelled with gasohol (a gasoline/ethanol blend that is 22% ethanol). Despite Brazil’s success in launching an ethanol industry, the cost of producing ethanol today, which is some 23 cents per litre, is higher than the value of neat ethanol as a gasoline substitute, which is about 20 cents per litre. However, Brazilian analyses indicate that the prospects for reducing the ethanol production costs over the next several years are good.

The prospects are auspicious for making alcohol competitively from sugarcane with technological improvements that are within reach. Other tropical countries where the conditions are suitable for growing sugarcane could adopt these advanced alcohol technologies.

The United States has a fuel-ethanol program based mainly on maize. At present, there are 50 fuel-ethanol facilities producing 3 billion litres of ethanol a year. The ethanol is used mainly in gasohol. In some years, maize-based ethanol will be competitive, but because the prices for maize and the coproducts of ethanol fluctuate widely from year to year, ethanol is profitable, on balance, only because of substantial subsidies.

A promising alternative involves shifting from maize to low-cost cellulosic feedstock, such as wood chips, which can be converted to ethanol via an enzymatic hydrolysis process now under development.

The production cost has fallen sharply, from about 95 cents a litre to 28 cents a litre.

Hydrogen produced electrolytically from wind or direct solar-power sources and used in fuel-cell vehicles can provide zero emission transportation. AS for any fuel, appropriate safety procedures must be followed. Although the hazards are different from those of the various hydrocarbon fuels now in use, they are no greater.

Electrolytic hydrogen may be attractive in regions such us Europe, South and East Asia, North Africa, and the Southwest United States, where prospects for biomass-derived fuels are limited, either because of high population density or lack of water. Land requirements are small for both wind and direct-solar sources, compared to those with biomass fuels. Moreover, as with wind electricity, producing electricity from wind would be compatible with the simultaneous use of the land for other purposes such as ranching and farming. Siting in desert regions, where land is cheap and insolation good, may be favoured for photovoltaic-hydrogen systems, because little water is needed for electrolyses: the equivalent of two to three centimetres per year of rain on the collectors, which represents a small fraction of the total precipitation, even for arid regions.

Electrolytic hydrogen will probably not be cheap. If cost goals for wind and photovoltaic electricity for the period shortly after the tear 2000 are met, the corresponding cost of pressurised electrolytic hydrogen to the consumer would be about twice that for methanol derived from biomass. Moreover, a hydrogen fuel-cell car would cost more than a methanol fuel-cell car, because of the added cost for the hydrogen storage system. Despite these extra costs, the lifecycle cost for a hydrogen fuel-cell car, in cents per kilometre, would be only 2 or 3 percent more than the gasoline engine car.

Hydrogen can be also produced thermochemically from biomass using the same gasifier technology that would be used for methanol production. Although the downstream gas-processing technologies would differ from those used for methanol production, in each case the process technologies are very well established. Thus, from a technological perspective, making hydrogen from biomass is no more difficult than making methanol.