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Biofuels, Solar and Wind as Renewable Energy Systems_Benefits and Risks Episode 2 Part 10

Tham khảo tài liệu 'biofuels, solar and wind as renewable energy systems_benefits and risks episode 2 part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 466 S. Ulgiati et al. 18.1 Introduction Two kinds of biofuels are generally considered available and feasible i.e. bioethanol and biodiesel although some expectations are also being placed on future bio-hydrogen generation. Bio-ethanol is obtained through fermentation and distillation of sucrose-producing plants sugar cane sugar beet or cereals mostly maize and is usually mixed with petrol either directly at the pump splash blends or before distribution tailor blends . New production methods for bio-ethanol are also being developed which make use of ligno-cellulosic biomass. This is however still at the R D stage and is currently referred to as a second-generation biofuel. The second type of biofuel named biodiesel or Vegetable Oil Methyl Esters -VOME is produced from vegetable oils and the crops that are most widely employed in Europe and in the USA are sunflower rapeseed canola and soy. Palm trees are also a very promising raw material in tropical countries. Biodiesel is obtained through a chemical process called trans-esteriflcation which consists of making the vegetable oil react with methanol thus yielding biodiesel and glycerine as co-products and can only be mixed with fossil diesel. Biofuels raise increasing hopes as substitutes for fossil fuels and therefore as a contribution towards the reduction of the associated problems of greenhouse effect high energy expenditures and energy dependency. Moreover it is often claimed that biofuels are not only green on a global scale reducing of greenhouse effect but also on a local scale reducing urban pollution . Finally biofuels are seen by many as a motor of rural development. The European Union transportation sector is responsible for about 20 of total greenhouse gas emissions AA. VV. 2005 . The 2001 European Commission White Paper on Tranport Policy AA. VV. 2001 estimated that between 1990 and 2010 European CO2 emissions from transportation sector are likely to increase up to 50 reaching about 1.1 Gt and that road