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With the discovery of oil and gas in the pre-salt Santos and Campos basin, the supply of natural gas (NG) is expected to increase considerably, so the use of compressed natural gas (CNG) in city buses will be an important option for reducing the overall consumption of fossil diesel fuel and a reduction in operating costs in São Paulo and Rio de Janeiro Metropolitan Areas in Brazil. A vehicle with an engine that can run on pure diesel or diesel and CNG has advantage over a vehicle that works exclusively with CNG, because when there is no availability or the lack of CNG, the vehicle / engine operates with diesel only. Another benefit of this technology is the resale value in Brazil, because after the life cycle of use in theses two big cities, Urban Buses are sold country side to small cities where CNG is not available.

With focus on reducing the Green House Gases emissions, the use of biodiesel as an alternative fuel, in special for buses that runs on the Brazilian metropolitan areas has been even higher. Additionally, with the introduction of the new legislation for diesel engines in 2012, CONAMA PROCONVE P7, that in order to attempt to its requirements uses different kinds of exhaust gases after treatment systems, the necessity of knowing the behavior of those “P7 engines” operating with different biodiesel contents on blends with regular fossil fuel or even pure biodiesel has been an important issue to ensure the benefits of using such alternative fuel. On this evaluation, blends of 5%, 10%, 20%, 30%, 50%, 75% and 100% of biodiesel content in ANP65/2011 A_S50 Diesel Fuel (50ppm Sulfur content) was experimented in a Mercedes-Benz OM926LA E5 engine with SCR (Selective Catalyst Reaction) exhaust gases after treatment system.

With the purpose of minimizing the gaseous emissions impacts on the metropolitan areas, many alternative fuel resources has been developed as alternatives to fossil fuels. An environmentally and economical interesting alternative for the Brazilian market is the diesel made from sugar cane (Farnesene - C15H32). The Farnesene, made by sugar cane juice fermentation in presence of a genetically modified yeast is basically a saturated hydrocarbon molecule (C15H32) with more than 98% purity and that presents properties comparable to fossil diesel and when used in regular diesel cycle engines can bring significantly reductions not only in soot levels (Particulate Matter - PM) but also on the Nitrogen Oxides (NOx), unlike the biodiesel, that is well known that it brings increases on NOx emission level due its physic-chemical properties. Reduction on CO2 levels on life cycle is another important benefit of using such fuel since it's made by renewable feedstock.