Indirect emissions from biofuels: land-use change: introduction

Zamboni et al. (2011) and Gnansounou et al. (2011) articles, which will be the focus of this post, briefly raise some important issues regarding land-use change emissions of biofuels.

Biofuel cultivation often entails indirect GHG emissions through causing an increase in the global total cultivated lands e.g. forest to biofuel crop conversion; even in cases where biofuels are grown on previously-cultivated lands, it may still mean that uncultivated carbon-storing lands will have to be converted to agricultural in other parts of the world, which may produce substantial net GHG emissions (Zamboni et al., 2011). This is important as land-use changes arising from activities such as deforestation account for ~20% of global GHG emissions (Lange, 2011).

However, not all land-use change results in net GHG emissions from biofuel cultivation, due to spatial and temporal variations:

1. Biofuel cultivation may occur through cultivation of set-aside lands, which may make the emissions from land-use change insignificant (Zamboni et al., 2011).
2. Biofuel production may create useful by-products which further increase their efficiency and thus effectively decrease emissions per unit production e.g. DDGS for heat and power generation, or food for cattle  (Zamboni et al., 2011)
3. Land-use change taking place on degraded lands, which store little carbon, will likely have beneficial GHG saving effects (Gnansounou et al., 2009).
4. Emissions thus also depend on how much land is used for biofuel growth e.g. in EU substitution of ~10% of transport fuel with domestically-grown biofuels should not result in extra conversion of agricultural lands, while substituting any more than this will mean that food crops would have to be imported, increasing transport emissions, land-use change effect and thus biofuel emissions (JRC, 2008); this limits GHG saving potential of biofuels.

All these factors result in biofuel GHG emissions variations from land-use change of up to 6.4 times; the GHG emissions compared to gasoline may vary from -112% to +120% for the same production process (Gnansounou et al., 2009).

There are other problems with suggesting that emissions from land-use change should be included in biofuel emissions alculation; for example, the issues may prove to be highly controversial (Zamboni et al., 2011).