Induced land use emissions due to first and second generation biofuels and uncertainty in land use emissions factors

Much research has provided estimates of induced land use change and emissions for first generation biofuels. Relatively little has estimated land use change for the second generation cellulosic biofuels. In this paper we estimate induced land use change and emissions for these biofuels. Estimated emissions due to land use changes induced by biofuels production are uncertain not only because their associated land use changes are uncertain, but also because of uncertainty in the land use emissions factors (EFs). This paper also examines uncertainties related to these EFs and their assumptions. Three emissions factors including EFs obtained based on Woods Hole (WH) data, EFs developed by California Air Resources Board (CARB), and EFs obtained from the Terrestrial Ecosystem Model (TEM) are examined. Using these three EFs, induced land use emissions are calculated for several biofuel pathways under alternative assumptions. The land use change results suggest that corn stover (and by implication other crop residues) have no significant induced land use change associated with biofuel production, but that is not the case for dedicated energy crops. Use of dedicated energy crops induces land use change and transfers natural land (in particular forest) to crop production. Producing bio-gasoline from miscanthus generates the lowest land requirement across all alterative pathways. The largest land requirement is associated with the switchgrass. The difference is due largely to the assumed yields of switchgrass and miscanthus in this analysis. The two major conclusions from this emissions analysis are: 1) inclusion or exclusion of cropland pasture makes a huge difference; and 2) there is wide divergence among the emission factor sources, especially for dedicated crop conversion to ethanol. Inclusion of cropland pasture emissions doubles or triples the emissions obtained using the WH EFs. The estimated induced land use emissions for ethanol and bio-gasoline produced from dedicated crops are essentially the same using the WH EFs, but vastly different using the CARB or TEM EFs factors, with cellulosic ethanol producing substantially more emissions.