“If biofuels benefit the climate, it’s not when they’re burned.”
John DeCicco writes at the Energy Collective:
… The core of this debate and a basic tenet of the lifecycle view is the fact that the carbon in a biofuel was recently absorbed from the atmosphere and so exactly cancels out the CO2 released when the biofuel is burned. This “renewability shortcut” in carbon footprint calculations presumes that biofuels are inherently carbon neutral. As an accounting convention, it implies that if feedstocks are grown and converted into fuels efficiently enough, then replacing a fossil fuel with a renewable fuel such as ethanol from biomass cuts GHG emissions overall.
It’s the big “if” about the net GHG emissions of the biofuel production chain — from the need for land and nutrients to the emissions during processing, refining and distribution — that is so difficult to ascertain. In trying to patch over the carbon neutrality assumption, lifecycle analysis becomes inordinately complex and too unreliable to yield sound answers. A new paper concludes that evaluating biofuels through lifecycle analysis is a lost cause, overwhelmed by scientific uncertainties and undone by the intractable system boundaries involved when accounting for GHG impacts throughout the global and dynamic commodity markets that supply feedstocks and fuels. A legal critique of such flaws in carbon footprinting is one basis for the recent court decision blocking California’s LCFS.
There is an easier way to look at the issue and that is to focus not on the carbon neutrality of biomass, but rather on the fact that the CO2 released when burning a biofuel for energy is essentially the same as the CO2 released when burning an equivalent amount of fossil fuel. This simple function of chemistry bears emphasis because we’ve become so accustomed to thinking that the carbon in biofuels doesn’t count. In round numbers, burning a gallon of gasoline directly releases 19 pounds of CO2 and so does burning an equivalent amount of ethanol. As a finer point of chemistry, the exact numbers differ by 0.4 percent and similarly, the CO2 directly released by biodiesel differs from that of petroleum diesel by roughly one percent…