Unlike conventional fossil fuels, such as coal and petroleum, bio-fuels are considered to be carbon neutral. In other words, they remove carbon dioxide from the atmosphere, and exude the same amount when burnt. This is what makes them a viable alternative to fossil fuels, which cause harmful carbon emissions.
Types of Bio-Fuels
Bio-fuels can be liquid, solid or gaseous. Different types of bio-fuels are available, and their use depends largely on the available feedstock and the energy that can be best used locally.
- Bio-Diesel is a clean burning alternative fuel, which is bio-degradable, non-toxic, and free of sulphur compounds and aromatics. It is manufactured by combining organically derived oils (vegetable oils, animal fats and recycled restaurant greases) with alcohol (usually methanol). The resultant chemical reaction creates fatty esters, such as methyl ester, which may be used neat or blended in any concentration with conventional diesel to create a bio-diesel blend. Bio-diesel, generally in the form of B20, is being used widely in the US today, in federal, state and transit fleets, private truck companies, ferries, tourist boats and launches, locomotives, power generators, home heating furnaces, and other equipment, especially in the agricultural sector. Regulated fleets are also being rewarded for implementing bio diesel use into their heavy-duty vehicles.
- Bio-ethanol, a similar product made from bio-mass, has proven efficiency and established economics. Many crops such as sugar cane, cassava, maize, potatoes, sorghum, sugar beet and wheat, have a high percentage of sugar or starch that may be fermented into ethanol. However, the conversion of their starch content into sugar has a high process energy demand, so that the cost of the product is quite high.
- Bio-Gas is being touted by environmentalists as a green alternative to Natural Gas. Both have nearly identical compositions, so the same burners can be used for both fuels. Bio-gas can be produced from plant or animal waste, or a combination of both. The animal waste produces the nitrogen needed for growth of the bacteria and the vegetable waste supplies most of the carbon and hydrogen necessary. Millions of cubic metres of methane in the form of swamp gas or bio-gas are produced every year by the decomposition of organic matter, both animal and vegetable.
The methane digester is a plant that converts plant and animal waste into methane. This is common in countries like India, but sorely neglected in others, even though the raw material is available everywhere.
- Biomass may be a practical option for small-scale heating schemes in rural areas. It comprises wood residue and excess straw from agriculture. The Pyrolysis (Gasification) of Bio-mass is a very old energy technology that is becoming interesting again among various systems for the energetic utilisation of bio-mass. Vehicles were run on gas produced by pyrolysis of wood in times of war to replace unavailable fossil fuels. Today, gasification plants produce a gas composed mainly of carbon monoxide and hydrogen. This has the advantage of being capable of transportation by pipeline or being filled into cylinders for distribution.
Pyrolysis has some distinct advantages over conventional combustion technologies. First, the combined heat and power generation from pyrolysis techniques connected to gas-fired engines or gas turbines can achieve significantly higher electrical efficiencies (22 per cent to 37 per cent) compared to bio-mass combustion technologies with steam generation and standard turbine technology (15 per cent to 18 per cent). Second, using the produced gas in fuel cells for power generation can achieve an even higher overall electrical efficiency in the range of 25 per cent to 50 per cent, even in small-scale bio-mass pyrolysis plants and during partial load operation.
- Sanitary landfills are now being used for the commercial production of methane in many areas, instead of simply flaring the gas for safety reasons. Methane continues to be produced in commercially viable quantities for many years after a landfill site has been closed. Nevertheless, there are still many landfill sites where the gas is being wasted. This source will dry up in time to come, since many countries are now finally emphasising the separation of waste and the need to recycle it, but there is gas for the next 20 years in the landfill sites which can be tapped.
Future Bio-Fuel Technologies
In the last decade, there has been a lot of research into new options for liquid bio-fuels. Two new fuels are currently in the pilot stage. They are different from conventional bio-fuels in two significant ways — first, in order to increase the amount of feedstock, the whole plant material is being used, not just the leaves. Second, these fuels are made using feedstock from non-food crop sources like tall grasses, woodchips from forest thinning and harvest residues and surplus straw from agriculture. These have the huge advantage of needing fewer agricultural inputs, which would bring the cost of these fuels down in the long run.
Research on gaseous biofuels has focussed on upgrading bio-gas to Substitute Natural Gas (SNG) so that it can be fed into existing natural gas pipeline systems (both locally, nationally, as well as for cross-border trade). Alternatively, it can be compressed into Compressed Natural Gas (CNG) to be used in gas-engine vehicles (buses, cars, trains, trucks, etc). Bio-gas derived SNG can be blended with natural gas in any proportion. Bio-gas could further be processed into a green GtL (gas-to-liquid), thus becoming directly available as a powerful and very clean-burning liquid fuel, although this route seems costly.
A third branch of research is studying the conversion of bio-mass into bulk and fine chemicals (or biomaterials), which are nearly equivalent to those derived from fossil hydrocarbons, and which may provide extra revenues than bio-fuels alone. These bio-refineries of the future would optimise the conversion of bio-mass feedstocks, so that its output mix reflects the highest revenues, and covers all attractive markets.
Who is using biofuel?
Air New Zealand
Air New Zealand is preparing to conduct its first trial of biofuel on one an upcoming Boeing 747 aircraft flight in December 2008. The biofuel to be used will be composed of 50% standard fuel jet and synthetic fuel made from oil extracted from seeds of the jatropha plant. This will fuel one of the four engines in the 2 hour test flight, which is a joint venture between Air New Zealand, Boeing, Rolls-Royce and UOP, a Honeywell company. According to Rolls Royce fuels specialist Chris Lewis, the properties of this fuel will hardly be distinguishable from conventional fuel - and is expected to make commercial aviation more sustainable in the coming future.
Boeing has announced its intention to phase in 30% biofuel blends over the next 5 years. And it increasingly looks like Boeing is doing much more than just agreeing to buy biofuels, or acknowledging the fact that planes can fly on biofuels. It is focusing particularly on making second-generation biofuels become a reality, specifically jatropha (and other oil-producing plants that grow in harsh conditions), and algae.
- The Environment Site
- Why make biofuels?