# ICCT comments on the RTI draft review on Jatropha for EPA

Soil Carbon

Papers included in the RTI review

Based on our review, n one of the papers referenced in this section on changes in soil carbon actually report values of soil carbon stocks or accumulation. Reinhardt et al. (2007) discussed carbon accounting but did not provide any estimates of changes in soil carbon with Jatrop ha cultivation. Srivastrava et al. (2011) reported on soil carbon concentrations on several Jatropha plantations (p3939). They did not report on changes in soil carbon concentration over time or compare to soil carbon on land other than Jatropha plantation s. This paper did not provide estimates of soil bulk density, so it would not even be possible to calculate soil carbon stocks (t soil C ha - 1 ) from this paper. Axelsson & Franzen (2010 ; p45 ) prov ide estimates of carbon stocks o n Jatropha plantations but do not provide estimates of soil carbon stocks or changes.



### Additional papers that were not included

Ogunwale et al. (2008) estimated that Jatropha cultivation on degraded land in India could increase soil carbon concentration by 1.33 gC kg - 1 (note: this cann ot be extrapolated to area

- based increases in carbon stocks without bulk density measurements). Wani et al. (2012) showed that the soil carbon concentration was higher on a Jatropha field (on agricultural land and on degraded land in India) than a grasslan d. These studies suggest that Jatropha may sequester carbon on some soils.



## Biomass carbon

Papers included in the RTI review

Skutsch et al. (2011) did estimate carbon stocks on Jatropha plantations but reported numbers that are different from those quoted i n the RTI review. RTI writes: “In Mexico jatropha plantations were estimated to have a biomass carbon stock of 1.6 tons of CO2e per acre (moderate assumption) or 4.04 tons of CO2e per acre (optimal assumption) by the tenth year assuming no pruning had take n place (Skutsch et al. 2011). ” In fact, Skutsch et al. (2011) actually writes on page 11: “ Assuming a steady growth rate (the correlation between age and weight was strong, r2 = 0.80) and a planting density of 1600 per hectare, which is thestandard used in the Mexican jatropha program, this would imply carbon stocks of 10 and 4 tons per hectare for fast and moderate

- growth, respectivel y, after 10 years (Table 4).” This converts to 14.7

– 36.7 tCO 2 ha - 1 . It should be noted that the “optimal assumption” app ears to refer to Jatropha grown on prime agricultural land, a nd that these are rough estimates relying on assumptions.

This review also cited Achten (2010) for finding that the average biomass carbon stock on Jatropha plantations was equivalent to that on grassland. While this is true, Achten’s calculations rely partly on shaky estimates from other papers (Appendix 4, pLXVIII). Achten starts with a figure of 18.3 tCO 2 ha - 1 (5 tC ha - 1 ) for 3.5 year

- old Jatropha plantations from Reinhardt et al. (2008). He th en applies sequestration rates quoted from Henning (in Benge, 2006) and calculated from Francis et al. (2005) for plant ages 1

- 5 years and 5

- 10 years respectively, and then guesses what the sequestration rate would be for plants ages 10

- 20 years. He then t akes an average of carbon stocks across the different age groups. It should be noted that the Henning estimate is an industry

- provided estimate that Benge stipulated was likely “extremely high” (Benge, 2006; p16). Achten calculated a sequestration rate from Francis et al. (2005; p21) based on estimates of the total area that could be used for Jatropha cultivation and of the total CO 2 sequestration that could be expected from cultivating this area

– these estimates were un cited and not explained in the text. Because most of these extrapolations are not based on real data, we advise that the estimate in Achten (2010) not be included in this review.

We presume that the reference to biomass yields of 5,000 t ha - 1 cited to Hou et al. is marked with the wrong units.



### Additional papers that were not included

Here are literature estimates of carbon stocks in Jatropha biomass that we were able to find, but we do not necessarily recommend that they be included in the review.

Reinhar dt et al. (2008) was included in the RTI review but not for biomass carbon stocks. B ased on figures from CSMCRI (2007; we were unable to access this publication)

, they calculated that 3.5 year

- old Jatropha plants had an average carbon stock ( above

- and bel ow

- ground biomass) of 5 tC ha - 1 (18.4 tCO 2 ha - 1 ) . The type of land and location are not given.

As mentioned above, Axelsson & Franzen (2010) was also included in the RTI review, but not for biomass carbon stocks. In fact, they do provide estimates of carbo n stocks in Jatropha biomass of 1.07

– 5.03 tC ha - 1 (3.9

– 18.5 tCO 2 ha 1 ) for 5

- year

- old plants in Egypt and India (p45

- 46). It should be noted that these estimates are based on interviews with government officials and on unspecified literature research ( p23).

Struijs (2008) estimated biomass stocks of 39.6 tC ha - 1 (145.1 tCO 2 ha 1 ) for 6

- year

- old plants in Tanzania (p28). This estimate was based on an unsubstantiated assumption of growth rates coupled with visual inspection of a plantation (p23).

## Land use competition

Skutsh et al. (2011) is included in the RTI review but not for land use competition. In fact, they report that farmers in Mexico have been converting agricultural land previously used for maize , other food crops, and pasture (p6)

.