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The environmental impact of biodiesel is diverse. == Greenhouse gas emissions == An often mentioned incentive for using biodiesel is its capacity to lower greenhouse gas emissions compared to those of fossil fuels. Whether this is true or not depends on many factors. Especially the effects from land use change have potential to cause even more emissions than what would be caused by using fossil fuels alone.〔 ''Related news articles:'' * *〕 Carbon dioxide is one of the major greenhouse gases. Although the burning of biodiesel produces carbon dioxide emissions similar to those from ordinary fossil fuels, the plant feedstock used in the production absorbs carbon dioxide from the atmosphere when it grows. Plants absorb carbon dioxide through a process known as photosynthesis which allows it to store energy from sunlight in the form of sugars and starches. After the biomass is converted into biodiesel and burned as fuel the energy and carbon is released again. Some of that energy can be used to power an engine while the carbon dioxide is released back into the atmosphere. When considering the total amount of greenhouse gas emissions it is therefore important to consider the whole production process and what indirect effects such production might cause. The effect on carbon dioxide emissions is highly dependent on production methods and the type of feedstock used. Calculating the carbon intensity of biofuels is a complex and inexact process, and is highly dependent on the assumptions made in the calculation. A calculation usually includes: * Emissions from growing the feedstock (e.g. Petrochemicals used in fertilizers) * Emissions from transporting the feedstock to the factory * Emissions from processing the feedstock into biodiesel Other factors can be very significant but are sometimes not considered. These include: * Emissions from the change in land use of the area where the fuel feedstock is grown. * Emissions from transportation of the biodiesel from the factory to its point of use * The efficiency of the biodiesel compared with standard diesel * The amount of Carbon Dioxide produced at the tail pipe. (Biodiesel can produce 4.7% more) * The benefits due to the production of useful by-products, such as cattle feed or glycerine If land use change is not considered and assuming today's production methods, biodiesel from rapeseed and sunflower oil produce 45%-65% lower greenhouse gas emissions than petrodiesel.〔 *''Summary:'' (【引用サイトリンク】title=Biodiesel Life Cycle Assessment ) 〕〔 〕〔 〕〔 〕 However, there is ongoing research to improve the efficiency of the production process.〔〔 Biodiesel produced from used cooking oil or other waste fat could reduce CO2 emissions by as much as 85%.〔 As long as the feedstock is grown on existing cropland, land use change has little or no effect on greenhouse gas emissions. However, there is concern that increased feedstock production directly affects the rate of deforestation. Such clearcutting cause carbon stored in the forest, soil and peat layers to be released. The amount of greenhouse gas emissions from deforestation is so large that the benefits from lower emissions (caused by biodiesel use alone) would be negligible for hundreds of years.〔〔 Biofuel produced from feedstock such as palm oil could therefore cause much higher carbon dioxide emissions than some types of fossil fuels. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Environmental impact of biodiesel」の詳細全文を読む スポンサード リンク
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