Review of the RTI jatropha study

Dr. David Shonnard, Ph.D.

Professor and Robbins Chair in Sustainable Use of Materials

Jiqing Fan, Ph.D. Candidate

Department of Chemical Engineering and

Sustainable Futures Institute

Michigan Technological University

Houghton, MI 49931 USA

Dec 12, 2012

Report to:  Tom Kalnes, UOP‐Honeywell, Des Plaines, IL USA

   
Introduction: The purpose of this report is to provide feedback on the report “GHG Assessments of

Jatropha Oil Production: Literature Review and Synthesis‐Draft Report” from RTI International (project

number 02013142.000.005).  We conducted a spot check on several of the cited references on the

inputs reported in several of the tables and concluded that the numbers are accurately reported in the

RTI report.  Some of the inputs are compared to those assumed in GREET (Wang 2012) and GHGenius

((S&T)2 2004). We focused our evaluation on the inputs that are expected to have the strongest

influence on the GHG emissions; jatropha seed yield, nitrogen fertilizer inputs per unit mass jatropha

seed, co‐products from oil extraction and allocation, land use change, and plantation lifetime.  

Jatropha Seed Yield: In 2011, MTU conducted a LCA (Life Cycle Assessments of Hydro‐Renewable Jet

and Diesel from Jatropha Grown in Mexico, submitted to EPA on Nov 9th) on jatropha‐based biofuels

production in Mexico and as part of that study, evaluated the impacts of seed yield on GHG emissions of

green jet fuel.  Although it was not possible to include the effects of seed yield and oil content in the LCA

model because of lack of data, that study analyzed likely results from these variants.  When considering

a reduction of jatropha seed yield from 10 to 5 tons seed/ha/yr, that analyses also assumed oil content

remains at 40% and that the full commercial tons oil were still required to be converted to HRJ.  To

achieve this oil production target, twice as many hectares would be needed.  But we assumed further

that fertilizer application rate per ha would be reduced by 50% because the application rate is linked to

the jatropha yield through the N, P, and K composition of the biomass.  Therefore, total N, P, and K

application amounts would not change from the basecase.  This expansion of plantation area would

have three main effects.  The first effect would be to increase the fuel use in cultivation and harvesting,

thereby increasing the cultivation/harvest stage by approximately 0.5 g CO2 eq/MJ of GJ.  The second

effect would be to increase distance of truck transport from plantations to location of oil extraction.  We

conservatively assumed that transport distance is doubled for this variant and therefore doubled the

emissions for transport from 0.5 to 1 g CO2 eq/MJ of GJ.  The third effect would be to change the dLUC

calculation, then dLUC emissions would increase by 0.2 g CO2 eq/MJ.  These combined causes would

likely increase the GJ GHG emission by approximately 1 to 1.5 g CO2 eq/MJ compared to the HRJ

basecase analysis.   

We performed a similar analysis on effect of seed oil content from 40‐30%, and when combining the two

effects we can conclude that even for a worst case situation, that the HRJ emissions would not increase

more than 1‐2 g CO2 eq/MJ.  These results are very preliminary, but do indicate that assumptions on

seed yield and oil content are not major drivers of GHG emissions, unless yield and oil content factor

into dLUC and iLUC as suggested in Figure 3‐3 in the RTI report.  

Nitrogen Fertilizer: The studies listed in the review show a wide range NPK fertilizer inputs while the

values provided by GCEH and assumed in GHGenius are on the lower end (Table 1). GCEH envisions the

use of jatropha meal and husk as green fertilizer to offset the synthetic fertilizer use, thus the fertilizer

inputs are lower compared to other studies. Bailis and Baka also explored the scenario where jatropha

meal and husk are used as fertilizer, offering a GHG credit to the oil extraction step.  It is important to

note the relation between jatropha yield and plantation management (land, irrigation and fertilizers).

The high yields generally requires fertile agricultural land and irrigation, which results in negative land

use change impacts and water issues.   However, the MTU (2011) study assumes high jatropha yield (10

tonne/ha) on Mexico marginal agricultural land unsuitable for food production, which results in positive

LUC impact because jatropha helps the soils to store carbon. Lower yields from marginal lands

unsuitable for food cultivation may avoid detrimental land use change emissions as well.   
Table 1: Chemical and energy inputs of jatropha cultivation

(Stratton et al. 2010) GREET 2012 Bailis and

Baka 2010

GHGenius GCEH

Low   Baseline High    

Yield (t/ha‐ yr) 5 2.5 1 2.5 4 2.38   

N (g/kg seed) 31.8 34 35.3 34 21 8.5 9.35

P2O5 (g/kg seed) 12.6 13 13.4 13 8.5 3.32 7.5

K2O (g/kg seed) 31.3 37.4 37.4 37.4 23.5 14.8 13.88

Diesel (L/kg seed) 0.034 0.039 0.041 0.039    0.036   

Electricity

(kWh/kg seed)

        0.02   

The fertilizers (NPK) assumed for the LCA study have significant impact on the total GHG emissions of

jatropha biofuels. Different N fertilizers have very different emission factors (e.g. ammonium nitrate vs

urea). The emission factors of N, P2O5 and K2O assumed in the GREET 2012 are 3.3, 0.66 and 0.64 g CO2

eq/g fertilizer, respectively. The emission factors of ammonium nitrate, urea in the Ecoinvent database

are 8.55 and 3.3 g CO2 eq/g fertilizer.  

Co‐products and Allocation: How to deal with the co‐products of jatropha oil extraction (meal, husk and

shell) has a significant impact of the life cycle GHG emissions.  If the co‐products credits are not

accounted for, it could result in less favorable GHG savings of jatropha biofuels, as the GHGenius

simulation result indicates (Fan 2012). Although other uses might be envisioned, the RTI study accounts

for the most important co‐product uses from the oil extraction step; energy use, fertilizer use, animal

feed use with suitable detoxification. For example, the energy application of the co‐products could yield

higher GHG credits, as shown by the Bailis and Baka study. The GREET 2012 (Wang 2012) assumes 99%

of the co‐products are combusted in biomass boiler with efficiency of 20.8% and the remainder 1% is

combusted in integrated gasification combined cycle ( IGCC) with efficiency of 40%. Total electricity

credit from the co‐products is 3.37 kWh/kg oil, which offers a GHG credit of 2.3 kg CO2 eq/kg oil (

emission factor of electricity is 677.53 g CO2 eq/kWh).   This electricity credit from the co‐products can

significantly reduce the life cycle GHG emissions of jatropha biofuels.  The importance of allocation to

GHG emissions from jatropha biofuels production has been demonstrated by many researchers.  

However, allocation methodology is a subject of debate and choice depending on regulatory

environment.  For example, the US EPA favors displacement (system expansion), the European Union

prefers energy allocation, and the Roundtable on Sustainable Biofuels recommends market value

allocation.  It is recommended to evaluate different allocation methods due to this uncertain

environment.    

Land Use Change: The RTI report does a good job on the discussion of land use decisions for jatropha

cultivation and on the topic of emissions of greenhouse gases associated with land use change.  The

study’s main conclusion is that the sustainability of jatropha biofuels largely depends on the choice of

land for cultivation and the circumstances of that prior land use.  Negative land use change impacts can

be avoided if the jatropha are planted on marginal agricultural land. LCA studies excluding LUC impacts

show that jatropha biofuels can offer >50% of GHG savings compared to the petroleum baseline.

However, studies have shown that dLUC can significantly change the total emissions when the jatropha

plantation land was converted from various land types, depending on the former land use such as

degraded pasture and tropical forests. Therefore, land use change depends on local situation of the
plantation. To achieve favorable GHG savings for the biofuels, the jatropha should be planted on low C

stock land (to gain a positive LUC impact) and land that are unsuitable for food production (to avoid

negative iLUC impact).   

Future Work: We are intending to continue to work with the information in the RTI report to develop a

base‐case jatropha‐based biofuel LCA using “average” values of inputs from this literature review on

jatropha and using the SimaPro 7.3 software tool.  Using those results, we will identify key inputs to the

life cycle GHG emissions and then conduct sensitivity analyses with uncertainty bounds for these key

inputs.  These results will provide important information on the relative importance of key life cycle

inputs for jatropha‐based biofuels.  This will focus further analysis on reducing uncertainty in predicting

GHG emissions for jatropha‐based biofuels.   

References

Shonnard DR, Donovan R, Fan J. Life Cycle Assessments of Hydro‐Renewable Jet and Diesel from

Jatropha Grown in Mexico: Greenhouse Gas Emissions and Fossil Energy Demand. April 30, 2011. p.38

Wang M. GREET_2012 transportation fuel‐cycle model.  Argonne National Laboratory 2012.

(S&T)2 Consultants Inc (2004). GHGenius 4.01, Natural Resources Canada

Fan J, Handler RM, Shonnard DR, Kalnes TN. A Review of Life Cycle Greenhouse Gas Emissions of

Hydroprocessed Jet Fuels from Renewable Oils and Fats. Submitted to IJESER, 2012