Kevin Steinberger
Internship with Princeton Environmental Institute –
Working with Dr. Eric Larson and the Energy Group
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Biochar (or agri-char) def:
“Stable, carbon-rich charcoal that
results from pyrolysis of
biomass”1
Slow pyrolysis: thermal
decomposition that is performed
at a low heating rate, and with a
low final temperature
Recent interest in biochar was
inspired by study of Terra Preta
soils in the tropics2
Recent studies have focused on
the application of biochar to soil:
◦ Soil improvement, carbon
sequestration, and energy by-products
Image taken from McGill University:
http://www.mcgill.ca/macdonald/alum
ni/newsletter/ebulletin/200912/research
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A group of researchers (Roberts et al) have performed a life
cycle analysis of the energy, Greenhouse Gas (GHG)
emissions, and economics of biochar production1
◦ “Life Cycle Assessment of Biochar Systems: Estimating the Energetic,
Economic, and Climate Change Potential” (2010)
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First goal: create Excel model to examine these findings, and
to be able to study the sensitivity of their results to certain
variables and assumptions
◦ Thorough literature review was performed to determine the range of cost
estimates for various aspects of the entire biochar production process
◦ Using Excel model, completed a separate analysis of the economics of
biochar production using data found in the literature
◦ Determined the impact of conflicting assumptions on the economic
viability of a project
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Second goal: write a scientific report to analyze the impact of
producing biochar at a slow pyrolysis facility and then
applying the biochar to agricultural soils
“Review and Assessment of Biochar Strategies for Climate
Change Mitigation” (still in progress)
Summarizes the current literature on biochar and identifies
needs for future research
Report focuses on understanding the conditions under which
favorable economic and environmental results can be
achieved, by discussing all of the economic factors involved
and examining the assumptions behind these factors
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Capital – Pretreatment and Pyrolysis
Costs
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Sensitivity to Capital Recovery Factor (CRF)
Comparison of estimates found in literature
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Stable C in soil
Reduced N2O and CH4 emissions
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Best and worst case estimates
Sensitivity to fuel prices
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Nutrient content of biochar
Increased soil efficiency
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Land Rent and Field Operations
Agrochemicals and lost nutrients
Operations and Maintenance
CO2 Offset: Varying emissions trading
prices
Energy Value
Fertilizer
Cost of biomass
Total Cost
Future Analysis
Figure 1: Biochar production/application process outline
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Many of the assumptions made by Roberts et al in their
analysis conflicted with other estimates found in the
literature:
◦ Cost of biomass collection and transportation
◦ Capital costs for pyrolysis plants
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Large uncertainties that need more research:
◦ Energy value of by-products of pyrolysis process
◦ Effects of biochar implementation on crop yields, and the
monetary value this would have for the farmer
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In reality, especially without an emissions trading
scheme, the production of biochar is not currently
economically favorable
Table 1: Baseline, best case, and worst case economic scenarios for biochar production/application
$/ton of biochar
produced
350
350
250
250
150
150
50
50
-50
-50
-150
-150
-250
-250
-350
-350
-450
-450
-550
-550
Baseline
Best case
Worst case
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Under current conditions and assumptions, the production of
biochar is not economically viable
However, with more research and improved technology, and
an emissions trading scheme, the economics could change
dramatically and biochar production may emerge as a
profitable strategy for climate change mitigation
Senior thesis: Design a gasification process, using Aspen
software, to improve the economics by optimizing energy and
char yields
This internship also confirmed my enthusiasm for the field of
renewable energy, and I plan on continuing my studies in
graduate school next year
Thanks so much to PEI and Dr. Larson for a great summer
internship!
1. Roberts, Kelli G., Gloy, Brent A., Joseph, Stephen, Scott, Norman B., and Johannes Lehmann. “Life Cycle
Assessment of Biochar Systems: Estimating the Energetic, Economic, and Climate Change Potential.”
Environmental Science and Technology.44. (2010): 827-833.
2. Woolf, D. et al. “Sustainable biochar to mitigate global climate change.” Nat Commun. (2010).
3. "Practitioner's Profile: Using Chicken Litter for Biochar | International Biochar Initiative." International
Biochar Initiative | International Biochar Initiative. Web. 14 July 2011. <http://www.biocharinternational.org/Frye/Poultry>.
4. Hooper, Troy. "Hope Mine Cleanup Banking on Biochar." Real Aspen 6 Oct. 2010. Web.
5. Pers. Communication