The change in the level of emis ol carbon dioxide(CO) resulting ch toward biofuels is much more debatable. The EPA(2002 ted that they were not able to identify an unambiguous difference in exhaust CO, emissions between conventional fuel and biodiesel. Other research suggest that there is a 10 percent increase in the tailpipe emissions of CO, when using biodiesel, but thai the sequenration efi of growing the plants to start with is calculated to oma this incre(Dr T, 2007). Indeed the EPA state that it should be noted that the benefits commonly attributed to biodiesel are the result of the renew ability of the biodiesel itself, rot the comparative exhaust CO, Thi ery interesting given the arguments now looming over the land-use change effects of the push towards biofuels(see section on'The land take issue' below). The nel effect on life cycle emissions of CO, (but see below) is purported to be a reduction of between 10 per cent and 100 per cent, depending on what exactly is included in the calculation(eg the source of the biofuel the amount and type of fertilizer used in the crop production and the energy used in the production process), the blend of fuel used and the type of conventional diesel to which the biodiesel is added(EPA, 2002), Emissions savings from biofuels can vary widely The use of wheat-based ethanol produced CO savings from as little as 7 per cent to as much as 77 per cent in the United Kingdom(Defra, 2007) Turning to energy efficiency, the EU estimates that fuel consumption increases by about 10 per cent with the use of biofuels. The IEA argues that because of the higher cetane number of biodiesel, it has a higher burning efficiency and this, combined with the fact that the lubricity of biodiesel is higher, means that the energy efficiency is just a little below raditional diesel.