On January 11, new journal Nature Energy published a study in its inaugural edition, ‘Impacts of a 32-billion-gallon bioenergy landscape on land and fossil use in the US.’ In the study, researchers used economic and ecological modeling to calculate how land use change and gasoline replacement from renewable fuels impact greenhouse gas emissions under three scenarios; no policy, the Renewable Fuel Standard as-is, and the Renewable Fuel Standard (RFS) plus a cellulosic biofuel tax credit. 

Researchers at the University of Idaho, the University of Illinois, the University of Georgia, and Colorado State University compared the effects of the three scenarios. Under an RFS as-is scenario, the researchers found that domestic GHG emissions were reduced by seven percent, even when accounting for potential land use change and a rebound effect in gasoline consumption due to lower gasoline prices from increased use of biofuels.  

This is counter to some previous studies, which used ecological models to find that the RFS led to an increase in GHG emissions. The researchers note that these studies, “did not consider the market response of land use and gasoline consumption to changes in crop and fuel price due to biofuel production.”

With the RFS and a $1.01/gallon cellulosic ethanol production tax credit, the study found that GHG emissions could be reduced by 12 percent. This additional reduction in GHG would largely come from providing a tax credit to incentivize cellulosic biofuel production, driving it to become more cost-competitive with corn ethanol, currently the cheapest source of ethanol. This would help fulfill the cellulosic mandate, and the researchers estimate it could even drive farmers to switch less productive acres of corn to perennial feedstocks.

While producing corn ethanol has become much more energy efficient than even a few years ago, corn is still more resource intensive to grow than cellulosic feedstocks such as perennial grasses, corn stover (corn cobs and husks), and other agricultural residues. Growing perennial grasses on less productive, marginal lands makes sense. Perennial feedstocks can sequester additional carbon, are less resource intensive to grow, and offer additional benefits such as improving water quality by acting as nutrient filters.   

While there has been great interest in the growth of perennial grasses as both a biofuels and bioenergy feedstock, the number of acres devoted to their cultivation has been slow-growing. This is for a number of reasons – perennials cannot be harvested in the first year, and may require different expertise or even harvesting equipment.

Even for agricultural residues, their collection is more challenging and they can be expensive to transport – making local cellulosic ethanol facilities key for farmers to be able to tap into this market.  Three such facilities made this a reality last year, both POET’s Project Liberty in Emmetsburg, Iowa, and DuPont’s facility in Nevada, Iowa. A third plant, Abengoa Bioenergy’s in Hugoton, Kansas, was recently shuttered due to bankruptcy filings by the parent company, Abengoa SA, a global solar and bioenergy company.

Without policy drivers like the RFS and other renewables policies, the researchers note that the effort to continue making progress on low-carbon fuels won’t continue. Policy remains especially critical as rock bottom oil prices continue to hammer the renewable fuels industry.


For more information see:

Impacts of a 32-billion-gallon bioenergy landscape on land and fossil fuel use in the US, Nature Energy 

Study: Second-generation biofuels can reduce emissions, University of Illinois