ARS Comment Overview:

Chris –

A couple of our staff from the ARS service provided comments – Dave Archer’s comments are in the body of the 

attached document –Paul Adler agrees with Dave’s comments (Dave is actually and economist) and I agree with 

them as well. Paul also has provided some general comments on jatropha below.

Paul’s general comments:

Overall, jatropha will be challenging because there is so much uncertainty surrounding the main factors affecting the 

GHG LCA i.e. soil N2O emissions, the direct soil carbon changes, the type of land in which it will be grown and the 

expected yield over this range of soils and climate, and the indirect effects of this land use change, all of which have 

large impacts on the LCA, and this review does little to reduce that uncertainty.

I think this is going to be a very challenging crop to consider. The most important drivers of the LCA are soil N2O 

emissions and changes in soil carbon. As this report pointed out, there is very little land in the US where jatropha 

would grow well, so most feedstock would be coming from outside the US. This will lead to much uncertainty. As the 

review suggested, there is large variability in the type of lands which have been considered and the yields that have 

been observed and the inputs and costs of production.

To perform a very basic tier 1 analysis for estimating soil N2O emissions, one needs to know the required N 

application rates. From this review, that kind of basic information seems lacking (Table 2.3 NPK fertilizer application -

how much needed per unit expected yield and does this vary with site productivity), however, if the authors can 

extract this information on N rates per unit seed yield, this would be very helpful for the LCA. If there are no 

generalizations, this will be problematic to estimate N2O emissions.

Without knowing the types of lands where jatropha is expected to be grown, one cannot estimate expected direct 

changes in soil carbon. Indirect effects will even be harder to determine, but these effects will drive the EPA analysis. 

More certainty in crop production costs and how they vary with production region and land productivity will also be 

important in determining what crops jatropha will displace and this review is very weak in this area. Maybe the 

authors can organize their review to better address these important issues.

Considering the important factors driving the GHG LCA, the metrics which will be most important for the EPA LCA will 

be N application rate per unit production, expected yield and how this varies with climate and soil productivity, crop 

economics and how they vary across regions and soil productivity, and what types of land jatropha is expected to 

compete for on the landscape and how this translates into direct and indirect effects on soil carbon. Without more 

certainty in this type of information, conducting a LCA to meet the rigors of the analysis required by EPA will be 

problematic.

Chris – feel free to touch base directly with Dave Archer or Paul Adler or you have any further questions or need 

clarification. If you do, please copy me.

Happy Thanksgiving

Harry

Harry S. Baumes Ph. D.

Director

Office of Energy Policy and New Uses

Office of the Chief Economist

(O) 202-401-0463

(C) 202-423-9378

(F) 202-401-0533