tailieunhanh - Environmental Impact of Biofuels Part 2

Tham khảo tài liệu 'environmental impact of biofuels part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 12 Environmental Impact of Biofuels requirements under US Clean Air Act because concern about water contamination led to the state to ban MTBE. More recently concern about evaporative VOCs emission and combustion emissions of NOx led California to sue the US EPA twice for a waiver both times the waiver was denied 58 . But both the EPA and California Air Resources Board agreed during the process that ethanol increases NOx slightly in the on-road fleet 64 . Fulton et al 2004 on the other hand report that the impact of bio fuels on NOx emissions level are relatively minor and can actually be higher or lower than conventional fuel depending upon the conditions. In fact there is evidence that NOx level from low ethanol blends range from a 10 percent decrease to a 5 percent increase relative to pure gasoline emission 47 . Studies by US National Renewable Energy Laboratory NREL show inconsistent results with regard to biodiesel and NOx depending upon whether vehicle is driven on the road or in the laboratory. According to McCormick 2005 they have seen Nox reductions for testing of vehicles chassis dyno and Nox increases for testing of engines engine dyno . The former which involves driving an entire car on rollers rather than testing emissions directly from an engine removed from the vehicle is considered more realistic than the latter 65 . NREL studies of in-use diesel buses have found a statistical significant reduction in NOx emissions with biodiesel. A US auto-oil industry six year collaborative study examined the impact of E85 on exhaust emissions and found that NOx emission were reduced by upto 50 percent relative to conventional gasoline 66 . But India s Central Pollution Control Board has determined that burning biodiesel is a conventional diesel engine increases NOx emissions by about 13 57 . Fortunately newer vehicles designed to meet strict air standards such as those in California have very efficient catalyst system that can reduce VOC NOx and CO emissions .