Prior land use and improving crop yields key to jatropha jet fuel benefits in Latin America, finds Yale study
Thu 7 Apr 2011 – Jatropha can deliver strong environmental and socio-economic benefits for Latin America, and can provide greenhouse gas reductions of up to 60 per cent when compared to petroleum-based jet fuel if the right farming and land use conditions are met. These are the findings of a Boeing-funded study conducted by Yale University’s School of Environmental Studies. The Yale team studied jatropha curcas projects in Brazil and conducted extensive interviews with jatropha farmers and used field measurements to develop the first comprehensive sustainability analysis of actual ventures, compared to previous theoretical studies. Prior land use issues and the quality of crop yields produced widely varying sustainability results relative to conventional jet fuel. Boeing says the study provides scientific guidance for aviation biofuel efforts in Brazil and Mexico.
Jatropha projects studied between 2008 and 2010 included small to large scale farms ranging from under ten hectares to more than several thousand hectares and used sustainability criteria developed by the Roundtable on Sustainable Biofuels. Yale researchers compared land conditions before and after jatropha cultivation, and identified prior land use as the most important factor driving GHG benefits of a jatropha-based jet fuel.
“Our team identified dozens of jatropha farmers willing to participate in our research, despite some challenges many encountered with this new crop. For most, this was the first time anyone had studied their efforts,” said Dr Rob Bailis, Assistant Professor, Yale School of Forestry and Environmental Studies. “Working with them allowed us to collect detailed data needed to build a comprehensive picture including both positive and negative aspects. Research like this is vital to helping developers to deliver better social, environmental and economic sustainability outcomes from jatropha cultivation.”
If the plant is grown on land previously covered in forest, shrubs or native grasses, those benefits may, unsurprisingly, disappear altogether. If, on the other hand, the crop is planted on land that was already cleared or degraded, then additional carbon is stored and emissions reductions can exceed the lifecycle baseline. This highlights that developers should pay particular attention to prior land use when deciding where to locate jatropha projects, says Boeing, which released details of the study last week.
Another important finding is that early jatropha projects suffered from a lack of developed seed strains, leading to poor crop yields and Boeing says advancing jatropha seed technology through private and government research is critical.
According to the abstract of the Yale study published in the journal Environmental Science & Technology, a baseline reference scenario that assumes a 20-year plantation lifetime with no direct land use change (dLUC) and a medium yield of four tons of dry fruit per hectare, results in emissions of 40kg CO2e per GJ of fuel produced, equivalent to a 55% reduction relative to conventional jet fuel.
However, dLUC based on observations of land-use transitions leads to widely varying changes in carbon stocks, ranging from losses in excess of 50 tons of carbon per hectare when jatropha is planted in native cerrado woodlands to gains of 10-15 tons of carbon per hectare when jatropha is planted in former agro-pastoral land. Thus, aggregate emissions vary from a low of 13kg CO2e per GJ when jatropha is planted in former agro-pastoral lands, an 85% decrease from the reference scenario, to 141kg CO2e per GJ when jatropha is planted in cerrado woodlands, a 60% increase over the reference scenario.
Boeing says the data is applicable to similar conditions in Mexico, where it is supporting a governmental roadmap assessment on aviation biofuels.
“The invaluable insights provided by this study will help our airline customers to better understand the sustainability of this potential jet fuel source, while also providing solid scientific data to governments and environmental organisations throughout the region,” said Boeing Commercial Airplanes’ Director of Environmental Strategy, Michael Hurd.