kimerajamm
Joined: 28 Nov 2010
Posts: 785
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 Posted: Thu Feb 24, 2011 2:41 pm Post subject: Environment Protection Agency |
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Various biodiesel schemes exist at present, and as with most renewables, interest is growing in the subject. Westray Development Trust operate a biodiesel vehicle fueled by the residual vegetable oils from the Orkney archipelago fish and chip outlets.[65] On a larger scale Argent Energy's plant in Motherwell recycles tallow and used cooking oil to produce 50 million litres of biodiesel per annum.[66]
A major benefit of biodiesel is lower carbon emissions, although the energy balance of liquid biofuels is a matter of controversy.[67] Research is being undertaken into converting rapeseed oil into biodiesel,[65] and the European biofuels directive intends to ensure that 5.75% Europe's transport fuel comes from renewable sources by 2010. However, there is only enough used vegetable oil in the UK to contribute 0.38% of current road fuel demand and if all the arable land in the UK were turned over to biofuel crops this would still only satisfy 22% of the existing requirement for road transport. Serious concerns regarding the ethics of growing biodiesel in developing countries and importing the fuel to Europe have been raised on the grounds that they may replace much needed food crops.[5] Converting any mainstream transport system to a renewable one also involves the conundrum that for consumers to use it the infrastructure must be in place, but high levels of use may be required to finance the infrastructure.[5] Developments are thus slow at present and renewably powered vehicles very much the exception.
Due to the relatively short growing season for sugar producing crops, ethanol is not commercially produced as a fuel in Scotland at present.[68] However there are encouraging developments in cellulosic decomposition that might enable grass or tree crops to be used to this end in future and which may prove to have lower net carbon emissions than other production techniques.[69][70]
[edit] Biogas, anaerobic digestion and landfill gas
Biogas, or landfill gas, is a biofuel produced through the intermediary stage of anaerobic digestion consisting mainly of 45–90% biologically produced methane and carbon dioxide. In early 2007 a thermophilic anaerobic digestion facility was commissioned in Stornoway in the Western Isles. The Scottish Environment Protection Agency (SEPA) and the Renewable Energy Association are also leading the way towards the establishment of a digestate standard to facilitate the use of solid outputs from digesters on land. Anaerobic digestion and mechanical biological treatment facilities have been planned at a number of other locations in Scotland, such as Westray.[71]
It has been recognised that biogas (mainly methane) – produced from the anaerobic digestion of organic matter – is potentially a valuable and prolific feedstock. It is estimated that 0.4 GW of generating capacity might be available from agricultural waste in Scotland.[2] The Scottish Executive and SEPA has funded seven small scale farm trial plants with the British anaerobic digestion company Greenfinch in Southwest Scotland.[72] Landfill sites have the potential for a further 0.07 GW with sites such as the Avondale Landfill in Falkirk already utilising their potential.[73]Psychic
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