But what exactly are alternative fuels, and how will new technology affect daily commutes in the decades to come? The future fuels that scientists are working on could come from a variety of sources. They may be blended with conventional gasoline, or could be 100 percent pure. Some offer reductions in CO2 emissions.
To better understand the wide range of different “alternative” fuels that are being developed, here’s an overview of what may some day fill your gas tank:
1. Gas-to-Liquids (GTL) – Made from natural gas, GTL fuel is a cleaner-burning diesel fuel that’s clear, odorless, sulfur-free and compatible with today’s diesel engine. GTL can be used on its own or blended with diesel and has been cited by the California Energy Commission as the most cost-effective “alternative fuel” in reducing tail pipe emissions and our dependence on petroleum.
2. Conventional or “First Generation” Biofuels – Currently, available biofuels are made from food crops (e.g. corn, vegetable oil). Today’s most common biofuel, ethanol, is usually made from sugar cane, corn or wheat. While these biofuels can be blended into gasoline and diesel at low concentrations, high concentrations of biofuels require fuel tank and injection system modifications.
3. “Second Generation” Biofuels – Made with non-food plant materials, such as wood chips, straw and algae, these fuels have the potential to be produced in high volumes. Currently they are expensive to research and develop and it may be difficult to convince people to pay for their key environmental benefit, CO2 reduction. However, they show real promise as an alternative fuel. For example:
* Cellulosic ethanol – Cellulosic ethanol has the same properties as ethanol that is already being blended with gasoline in many regions of the United States, but is made from non-food crops like wheat straw and corn stalks.
* Biomass-to-Liquid (BTL) – This second generation biofuel takes a woody feedstock, gasifies it and converts the gas into a high quality diesel fuel. The product has potential to be a low-carbon transportation fuel and is produced from a renewable source of energy.
4. Hydrogen – Hydrogen is the most plentiful element in the universe. Hydrogen fuel is a new form of transport fuel that can be used in modified combustion engines, but the best results are achieved through the use of “fuel cell vehicles.” These engines generate electricity through an electrochemical reaction that produces just water and heat as by-products. Since hydrogen is not commonly found in its pure form, it must be produced from different energy sources, usually fossil fuels. If the full environmental benefits of hydrogen-powered vehicles are to be realized, a critical challenge is to produce, and make widely available, hydrogen fuel with a low, or potentially zero CO2 footprint.
What are the CO2 benefits of biofuels?
A key advantage of biofuels compared with conventional gasoline and diesel is that they generally produce less CO2 on a life-cycle basis. This is because plants used in biofuels have absorbed CO2 from the air while growing, which is then released when the biofuel is burnt. In theory, this leaves the balance neutral. However, energy is required to grow and harvest the plants, convert them into biofuel and distribute them, and this all produces CO2. Since the amount and sources of energy used in production vary considerably, the CO2 emissions of different fuels need to be compared on a life-cycle basis.
It will take some time to develop “Second Generation” biofuels in significant commercial quantities. Until that time, companies should work to ensure the raw materials and conversion processes used today result in genuinely beneficial, low-carbon biofuels. That means accelerating the pace of international sustainability and CO2 certification systems for the supply chain for “First Generation” biofuels.
To learn more about fuel technology and the development of future fuels, visit www.shell.com/technology.