Project Drawdown defines biochar as a biosequestration process for converting biomass to long-lived charcoal (and energy) that can be used as a soil amendment. This solution provides an alternative to disposing of unused biomass through burning or decomposition.
Biochar is a carbon-rich, highly stable charcoal soil amendment produced as a by-product of pyrolysis, a bioenergy generation process. The production of biochar effectively stabilizes photosynthetic carbon by abating emissions that would occur if biomass feedstocks were allowed to follow their typical decomposition and disposal pathways, particularly for the great quantity of crop residues that are burned today.
Applying biochar to soils further stabilizes its carbon by protecting it from alternate loss pathways and can reduce other soil greenhouse gas emissions (though this emissions reduction impact is not modeled in this study). In infertile soils, such as sandy soils with low cation exchange capacity, biochar can reduce loss of nutrients through leaching.
Biochar is something of a new category and is not precisely replacing a current practice, but can be seen as an alternative to other uses of biomass, such as burning.
Total Addressable Market
Total demand for biochar in 2050 is estimated at 1615.57 million metric tons. Current biochar production is estimated at 0.0075 million metric tons. Biochar availability was calculated using the method (residue production = grain production * straw-to-grain ratio) given for crop residue estimation from the crop production by Lal (2005) and Woolf (2010). Crop production data were taken for the years 1991, 2001, and 2014, and future availability of biochar was estimated by the interpolation of this data set.
The implementation unit for this solution is biochar production facilities.
Future adoption of biochar production was based on interpolation of data from biochar sales data from 2013 to 2015 (International Biochar Initiative, 2015). Four custom scenarios were developed.
Impacts of increased adoption of biochar production from 2020 to 2050 were generated based on two growth scenarios. These were assessed in comparison with a Reference Scenario, in which the solution’s market share was fixed at the current levels.
- Scenario 1: This scenario leads to the production of 6,487.8 biochar production facilities.
- Scenario 2: Because the carbon benefits of biochar are much higher than those of crop residues left lying on the fields, an aggressive production of 12527.3 biochar production facilities was considered under this scenario.
Emissions, Sequestration, and Yield Model
Avoided emissions from biochar are estimated at 0.95 metric tons of carbon dioxide-equivalent per metric ton of feedstock. This reflects the amount of carbon dioxide-equivalent sequestered in the form of biochar that would otherwise have been emitted from the biomass used as feedstock if it had been burned or decomposed. This figure is the result of meta-analysis of 13 data points from five sources.
An 18 percent yield gain was modeled for biochar-amended soils, based on figures used by the Intergovernmental Panel on Climate Change (IPCC).
The first cost per biochar production facility is US$21.63 million. This is based on meta-analysis of 11 data points from three review sources. Operating costs are US$194 per metric ton of biochar produced, based on meta-analysis of 14 data points from three review sources. These figures are not comparable with a conventional practice, as biochar production represents a new industry.
A key constraint for this solution is the total availability of biomass feedstock. The model assumes that the maximum feedstock available is 50 percent of crop residues that are currently burned, with no dedicated feedstock production. This is because crop residues are utilized in solutions like conservation agriculture, and in the model all dedicated biomass feedstocks are used in biomass energy production, with none available for biochar production.
Total adoption in Scenario 1 is 6487.8 biochar production facilities producing 133 million metric tons of biochar by 2050. This represents 8 percent of the total addressable market. Climate impact is 2.22 gigatons of carbon dioxide-equivalent sequestered from 2020 to 2050. Net cost is US$195.87 billion and lifetime operational cost is US$734.05 billion.
Total adoption in Scenario 2 is 12,527.3 biochar production facilities producing 256.8 million metric tons of biochar by 2050. This represents 16 percent of the total addressable market. Climate impact is 4.39 gigatons of carbon dioxide-equivalent sequestered from 2020 to 2050. Net cost is US$383.30 billion and lifetime operational cost is US$1.4 trillion.
Climate impacts produced by the Project Drawdown model (0.1–0.2 gigatons of carbon dioxide-equivalent per year in 2050) are much lower than a benchmark reported by the IPCC, which estimates 3.67 gigatons of carbon dioxide-equivalent per year (2014). This is in part based on their estimate of 1.01 gigatons of biomass carbon, four times higher than our maximum feedstock estimate for the Project Drawdown scenario. This benchmark also includes impacts of soil sequestration from biochar application, which this study determined was lacking sufficient data to model effectively.
The biochar production solution has a number of limitations, most based in the nascent state of the industry. A key area is biomass feedstock availability, which would be useful to model across the many solutions that utilize it (e.g., clean cookstoves, biomass power, conservation agriculture). Availability of more robust data on the soil sequestration impact of biochar application would also be useful. More financial data, particularly revenues and profit margins, will be key to economic projections. Future studies could also model the energy production impact of biochar production.
For a period of time, biochar was billed as a “silver bullet” to mitigate climate change. While our model certainly does not show this to be the case, biochar production has an important role to play in biosequestration and soil fertility improvement.
 All monetary values are presented in 2014 US$.