Rethinking Biofuels: Alternative Feedstocks Switchgrass and Miscanthus Predicted to Outperform Corn Grain Concerns over the potential effects of climate change on energy and food production in the last ten years have created a new market for alternative fuels. In the United States, corn-based ethanol, likely due to the political clout of the US corn lobby, has dominated biofuels research to date. However, corn may be ill-suited for ethanol production because oil is used in the production, transport, and application of the large amounts of nitrogen fertilizer necessary to boost corn yields. The nitrogen fertilizers have a detrimental effect on the environment by decreasing soil productivity and leaching into neighboring soils and water tables. With the advent of the US Energy Independence Act of 2007, the US government created demand for up to 15 billion gallons of corn derived ethanol per year, mandating any amount beyond that be produced from other feedstock sources. Although high in energy yield, corn's dependence on oil makes it less efficient overall if environmental damage and GHG emissions are considered. The cap on corn ethanol production initially stimulated research into alternative feedstock, with preliminary research showing great promise from perennial grasses like switchgrass and miscanthus. The initial studies on the relative energy yield efficiency of corn and alternative feedstock prompted Parton et al. to develop a model capable of estimating the benefits of switching ethanol feedstock from corn to perennials. By using regression analysis of the DAYCENT model, they found that by substituting miscanthus and switchgrass for corn on lands already designated for ethanol production food productivity would increase by 4% and available feedstock for ethanol by 82% all while avoiding the GHG releases associated with the conversion of uncultivated land for agricultural production (known as ILUC, indirect land-use change).—Michael Gazeley-Romney Davis, S., Parton, W., Del Grosso, S., Keough, C., Marx, E., Adler, P., DeLucia, E., 2011. "Impact of second-generation biofuel agriculture on greenhouse-gas emissions in the corn-growing regions of the US". Frontiers in Ecology and the Environment; doi:10.1890/110003 Davis et al. simulated the effects of substituting 30% of the central US regional corn crop with three alternative biofuel crops: (1) switchgrass, (2) switchgrass with fertilizer treatments, and (3) miscanthus. Using the model they were able to calculate the feedstock production potential in each case as well as related GHG emissions, soil carbon sequestration, and nitrogen leaching over a ten year period. Their model is version of the CENTURY model that operates on a daily time step simulating exchanges between soil, plants, and the atmosphere as well as the affects of management practices like prescribed burning, grazing, and fertilizer use. To verify the accuracy of the model, the simulations were compared to test results from biofuel feedstock test plots already present in the study region finding close correlations for crop yields, GHG emissions, and nitrogen leaching. Using a simulation of ethanol corn production as a baseline, the researchers were able to calculate the differences in outputs between the growth scenarios. Possible imperfections in the model stem from the unknown effects of ILUC on GHG emissions. Although it is generally understood that large amounts of GHGs are produced in the tilling of virgin soil for agriculture, the amounts are hard to predict and can vary greatly. In order to compensate for this, Davis et al. calculated the effects of converting 30% of central US corn acreage to ethanol production using ILUC accounting from the California Air Resources Board finding emissions of 4.7--5.3 Tg C. When computed with the model results, the ILUC emissions did not have a significant effect on the large net differences between emissions for corn and those for the perennials. This is significant because the ILUC calculations should not apply to the test scenarios as no new land is being converted; the crops are simply being rotated. Controversy over outcrossing and slow investment realization (three years needed to establish perennial grass crops) are also omitted from the model analysis. However, both switchgrass and miscanthus present a low outcrossing risk because switchgrass is native to the US and miscanthus is a sterile hybrid. The results of the modeling showed significant environmental benefits from switching to perennial cellulose feedstock. These findings are more significant because the model was constructed to only consider the conversion of land already being used in ethanol production. In this way, the environmental benefits realized by switching feedstock crops comes absent the usual concerns about ethanol land use competing with food production. By limiting the model to a 30% corn-to-perennial land-use switch, the researchers hoped to simulate the complete transition from corn to perennial feedstock in US ethanol production (30% of all corn grown in the US is used in ethanol production). By avoiding the effects of ILUC entirely and only substituting feedstock within the existing production capacity of 30%, the study reduces foreseeable land use pressure from ethanol production on the 8% of US corn grown for food. Modeling of soil organic carbon (SOC) showed increases under fertilized switchgrass and miscanthus cultivation of 27 and 173 Tg Ceq yr-1 respectively. Compared to corn, fertilized switchgrass increased SOC by 1.9% and miscanthus by 19%. The conversion from corn to perennial feedstock changed also altered the regional output of GHGs--in terms of the re-appropriated cropland--from 27 Tg Ceq yr–1 for corn to 17 Tg Ceq yr–1 for switchgrass, –0.05 Tg Ceq yr–1 for fertilized switchgrass, and –97 Tg Ceq yr–1 for miscanthus. While the switchgrass succeeded in reducing agricultural GHG emissions, the substitution of miscanthus effectively transformed the entire region into a massive carbon sink. Davis et al. attributed the reduction in GHG emissions to less fertilizer use and increased carbon sequestration in the perennial crops compared to corn. Davis et al. reinforce the magnitude of this finding by citing a recent study that shows the reduction in GHGs from ethanol use (in the place of fossil fuel) are wholly offset by the heavy application of nitrogen fertilizers on corn. Using other research to interpret the significance of the modeling results, Davis et al. found that switching to perennial grasses would reduce nitrogen use overall, resulting in 0.7--0.8 Tg N yr–1 less nitrogen leaching through the soil. With 52% of the nitrogen polluting the Gulf of Mexico stemming from US corn and soybean production, the savings on environmental mitigation measures in the Gulf alone would be significant. To further demonstrate the relative benefits of switching feedstock, the researchers calculated the CO2 emissions from harvests of the corn and grasses, with the grasses producing 74% less CO2 during the harvest cycle. In a second run, Davis et al. altered the model constraints to substitute the perennials for corn on only the least productive 30% of the ethanol corn grown in the region. In this model the differences in efficiencies between corn and the perennials were even more pronounced with miscanthus producing 82% more biomass for ethanol feedstock than the corn baseline scenario, the equivalent of about twelve billion gallons of ethanol. As we continue to wean ourselves from foreign oil, energy efficiency within national production systems will take on a higher priority for policy makers. Choosing a low N-input, high energy-output feedstock over traditional corn has been shown under comprehensive modeling by Davis et al. to be much more efficient. When considering biofuels, it cannot be forgotten that they are meant to be a low-impact replacement for fossil fuels. With its dependence on oil for growth in the current agricultural system, corn has become an unsuitable and highly inefficient ethanol feedstock compared to perennial grasses. The findings of the study with regard to the yield efficiency and environmental benefits of miscanthus make it the clear choice for future feedstock use. In light of the findings of Davis et al., national production capacity for cellulose feedstock like miscanthus needs to be addressed in order to realize its benefits. Replacing corn ethanol feedstock in the central US region could increase the regional productivity of food by 4% and feedstock biomass 82% all while avoiding additional ILUC, making ethanol a truly environmentally friendly substitute to fossil fuel.

The population of the Sub-Saharan region increased by 670 million between 1990 and 2005.  According to the latest global population projections published by the United Nations in 2007, 80% of the world's population growth will be concentrated in developing countries where pressures on food production due to climate change are also predicted to be highly intensified.  Due to the joint intensifications of climate change and population growth expected in these regions, studies of agricultural mitigation and its efficacy in boosting crop yields are now vital to future policy decisions.  Population and climate changes will increase food requirements and make growing those foodstuffs even more difficult.  With the Sub-Saharan population predicted to grow to between 1.5 and 2 billion between now and 2050, agricultural responses to climate change must begin now to maintain future food security in the region. Di Falco et al. analyzed geographic climate and yield data in a simultaneous equations model with endogenous switching to account for unobservable factors or skills that effect food productivity and individual farmers' decisions to adapt their techniques to changing climate.—Michael Gazeley-Romney

Di Falco, S., Varonesi, M., Yesuf, M., 2011. Does Adaptation to Climate Change Provide Food Security? A Micro-Perspective from Ethiopia. American Journal of Agricultural Economics. 93, 829—846.

          Di Falco et al. elected to use a pre-existingan Ethiopian database of climate values and crop yields of the five major annual crops (teff, maize, wheat, barley, and beans) in considering the future food security of the region.  Ethiopia, having less than 60% of observed farms employing irrigation, 95% of the national yield being produced on family farms, and 75% of that yield being consumed at the household level typifies the poor, rain-fed regions where production in rain-fed agriculture is predicted to fall 50% by 2020 according to a 2007 IPCC report.  This makes it an ideal sample population.  The team analyzed seasonally disaggregated climatic data at the individual farm level through a simultaneous equations model with endogenous switching using the thin plate spline method of spatial interpolation, inputting household specific rainfall and temperature data at the correct geographic coordinates.

An important distinction in this analysis is the use of real and predicted food production instead of land value in analyzing the economic effects of climate change.  Di Falco et al. insist that due to the high primary consumption of food crops and inconsistent property rights in the developing world, crop production is more readily linked to living conditions than to land value.  Subsistence farming exists somewhat separate from the market system, making land market analysis an unreliable indicator of well-being in the at risk regions.

          In the first phase of the analysis, the researchers surveyed 1000 households in 20 districts, sampling data from 50 farm units within each district.  In surveying the farmers, Di Falco et al. discovered a direct correlation between the availability of information on climate change, access to credit, and the decision to adopt climate-adaptive farming techniques.  Most respondents perceived rising temperature and falling annual precipitation, but 40—50% of households because of lack of concrete information failed to act on their perceptions of climate change.  The importance of education programs in the form of farmer-to-farmer education and government extension is clear; especially in the developing world where literacy and access to current climate research are low, education is the most important factor in the ability of the population to adapt.

          In the second phase of analysis, the team analyzed the effects on food production of the adoption of agricultural adaptation techniques including changing crop varieties, adoption of soil and water conservation strategies, and tree planting.  There was a statistically significant correlation between rainfall and food production only in the households that did not adapt—leading the researchers to conclude that adaptation techniques made farms less susceptible to the extreme weather conditions that make food-production in the Sub-Saharan region difficult in the first place.  Crop rotation, which might be a good adaptation strategy elsewhere is ineffective in Ethiopia because crops are already highly diversified.

          In comparing the expected food productivity of the four test conditions (households that did adapt, households that did not, and the production values for those conditions if the opposite had been true; i.e. the households that did not, had adapted) within the endogenous switching regression model Di Falco et al. concluded that adapted households grew more food than non-adapted ones, and that taking adaptive measures eliminated this discrepancy. 

          The analysis of Di Falco et al. suggests that future policy objectives should be to concentrate on farms that have not yet embraced climate-linked adaptation techniques.  The team points out the obvious need for further research to differentiate the most effective methods of adaptation, but the results demonstrate the importance in raising the productivity in the bottom 1% performers in raising national food-production, weather-proofing yield estimates, and increasing food security in the region.