Biochar Production

Introduction

Biochar is a carbon-rich, highly stable soil amendment produced as a by-product of pyrolysis, which generates energy from biomass in the absence of oxygen. When biomass decomposes, carbon and methane escape into the atmosphere. Biochar retains most of the carbon. If we bury it, that carbon can be held for centuries in the soil. Applying biochar to soils can reduce other soil greenhouse gas emissions (though this emissions reduction impact is not modeled in this study). In infertile soils, biochar can reduce loss of nutrients through leaching.

Project Drawdown’s Biochar Production solution involves tapping this process to produce energy, improve soils, and store carbon. This solution provides an alternative to disposing of unused biomass through burning or decomposition.

Biochar production is something of a new solution and is not precisely replacing a current practice, but can be seen as an alternative to other uses of biomass, such as burning. Theoretically, biochar could sequester billions of metric tons of carbon dioxide every year.

Methodology

Total Addressable Market

Biochar is both land- and technology-based, so we define its total addressable market in terms of the feedstock that may be allocated for conversion. Our biomass integrated model calculates future availability of various biomass types and allocates feedstocks to the solutions that need them. Within the integrated biomass model we allocate feedstock to biochar only after demand by all other bio-based solutions has been satisfied. Our modeled total addressable market, which serves our theoretical upper limit to biochar adoption, ranges from 215 million metric tons of biomass in 2020 to 1.0 billion metric tons in 2050. These figures can be expressed in terms of potential biochar production using our modeled yield of 0.298 metric tons biochar per metric ton of feedstock to arrive at 64.0 million metric tons and 298 million metric tons of biochar potential in 2020 and 2050, respectively.

We projected future adoption of biochar production based on the biochar sales data from 2013 to 2015 (International Biochar Initiative, 2015).

Adoption Scenarios

We calculated impacts of increased adoption of biochar production from 2020 to 2050 by comparing two growth scenarios with a reference scenario in which biochar production from available biomass was fixed at current levels.

• Scenario 1: 63.05 million metric tons of biochar are produced (21 percent of the total addressable market).
• Scenario 2: 117.95 million metric tons of biochar are produced (40 percent of the total addressable market).

Emissions, Sequestration, and Yield Model

We estimated avoided emissions from biochar to be 0.95 metric tons of carbon dioxide equivalent emissions per metric ton of feedstock based on meta-analysis of 13 data points from five sources.

Financial Model

All monetary values are presented in 2014 US$.

We estimated the net first cost to implement a biochar production facility at US$21.63 million, based on meta-analysis of 11 data points from three sources. Operating costs were US$194 per metric ton of biochar produced, based on meta-analysis of 14 data points from three sources.

Integration

We used Project Drawdown’s integrated biomass model to integrate the Biochar Production solution with other solutions. This allowed us to avoid double-counting input feedstock and resulting emissions results.

Results

Adoption of Scenario 1 sequesters 1.36 gigatons of carbon dioxide equivalent greenhouse gas emissions. The net first cost to implement is US$123.54 billion, and the lifetime operational cost is US$333.20 billion.

Adoption of Scenario 2 sequesters 3.00 gigatons of carbon dioxide equivalent sequestered from 2020 to 2050. The net first cost to implement is US$244.94 billion, and the lifetime operational cost is US$663.11 billion.

Discussion

Benchmarks

Climate impacts produced by our model (0.1–0.2 gigatons of carbon dioxide equivalent per year in 2050) were much lower than a benchmark reported by the Intergovernmental Panel on Climate Change (IPCC) of 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. The IPCC benchmark also included soil sequestration from biochar application, which we concluded lacks sufficient data to model effectively.

Limitations

This review likely does not capture small-scale developments that may be advancing the biochar industry. The spectrum of implementation scales presents challenges from a modeling perspective, though it may be advantageous from an implementation perspective. Industry data on production across all scales would enable modeling to better capture such developments.

Both technological scale-up and scale-out processes may come with cost reductions from learning. We have not yet modeled these because we found no significant differences in financial inputs between this updated model and our previous version. There is currently an apparent paradox in development in which the technological sub-processes are relatively mature, implying low potential for further learning, but deployment to date has been limited, implying that scale-out could in fact reduce costs.

Conclusions

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 sequestering carbon and improving soil fertility.

References

International Biochar Initiative (2015). State of the Biochar Industry Report. https://biochar-international.org/state-of-the-biochar-industry-2015/

Lal, R. (2005). World crop residues productions and implications of its use as a biofuel. Environment International 31, pp. 575-584. DOI: 10.1016/j.envint.2004.09.005

Woolf, D., Amonette, J. E., Street-Perrott, F. A., Lehmann, J., and Stephen, J. (2010). Sustainable biochar to mitigate global climate change. Nature Communications. 1(1), 56-65. DOI: 10.1038/ncomms1053