Review of Lefebvre, et al., Biomass residue to carbon dioxide removal: quantifying the global impact of biochar

Literature Review Series

Authored by Wil Burns, Co-Director, Institute for Carbon Removal Law & Policy, American University

To date, the vast majority of purchases of durable carbon dioxide removal have been for biochar, a process that can transform biogenic carbon dioxide into a far more stable form via the process of pyrolysis. Pyrolysis is a thermal process that, in the absence of oxygen, can deconstruct bio-polymers into, among other things, biochar, a charcoal-like substance that can securely store carbon for hundreds to thousands of years when applied to soil. Conversion of biomass to biochar can sequester 50% of initial carbon, compared to 3% associated with burning, or less than 10-20% after 5-10 years from biological decomposition.

Image Credit: Lefebvre, et al. The above image is a graphical abstract.

A number of studies in recent years have suggested that biochar potential could be much greater in the future, perhaps in the range of 3.5 GtCO2/yr., or up to 350 Gt during this century. However, to date, studies have focused on global or regional aggregate estimates. In a recently published study, researchers led by David Lefebvre of the University of British Columbia sought to extend these analyses by assessing the potential of biochar sequestration in each of 155 countries. The study restricts itself to the assessment of sequestration potential associated with biomass residue feedstocks in the contexts of agriculture, forestry wood residues, animal manure, and wastewater biosolids. The study also presumes that 30% of residues are left in the fields in the interest of maintaining long-term soil health.

Among the conclusions of the study are the following:

  • Four countries, all characterized by large populations, land areas, and agricultural sectors have the greatest potential, including:
    • China: 468 Mt CO2e/yr.
    • United States: 398 Mt CO2e/yr.
    • Brazil: 303 Mt CO2e/yr.
    • India: 225 Mt CO2e/yr.
  • North America and South America are characterized by a large number of countries with biochar sequestration potential of 25 Mt CO2e/yr., with bands of relatively low potential across North Africa into the Middle East, with low potential in portions of Europe and southern Africa.
  • 28 countries have the potential to sequester more than 10% of their CO2 emissions with biochar, with the largest number in Europe
  • The “conservative approach” of the study (including assessment of only recalcitrant carbon with permanence factors based on national averages) yielded an estimated carbon dioxide removal potential of 6.23% of total greenhouse gas emissions of the 155 countries in the study.

Notably, the researchers observed that its estimates didn’t take into account a number of potentially compelling co-benefits, such as potentially reducing emissions of methane and nitrous oxide, enhancement of crop yields and displacement of fossil fuels. Any effort to assess the potential costs and benefits of biochar deployment in individual countries, as well as globally, will require a more granular assessment of these factors, suggesting one potential research tributary flowing from this study.

Overall, this study could prove extremely helpful in helping to operationalize biochar programs nationally, and regionally, moving forward. It suggests that biochar could play an important role in the carbon dioxide removal portfolio of many countries.

ICR Fact Sheets Provide a Comprehensive Overview of All Things Carbon Removal

Although the emerging field of carbon removal has great potential to help curb climate change when coupled with more traditional methods of mitigation, it is riddled with uncertainty. There are many risk factors and many components within each individual method that are still poorly misunderstood. The Institute for Carbon Removal Law and Policy is dedicated to creating a set of comprehensive tools that can aid in providing clarity on carbon removal practices and technologies on many different levels.

Among these valuable resources are a comprehensive set of Fact Sheets that provide overviews on each of the individual topics regarding carbon removal, the production of which was provided for by a grant from The New York Community Trust. These fact sheets are broken down into two categories, topics in carbon removal and approaches to carbon removal. 

The topics in carbon removal fact sheets provide an overview and background on:

What is carbon removal?

Nature-based solutions to climate change and 

Carbon capture & use and carbon removal

The approaches to carbon removal fact sheets break down the ten different topics, providing a deeper context to the potential methods behind carbon removal. Each of these provides not only an overview but weigh in on the co-benefits & concerns, potential scales and costs, technological readiness, governance consideration, and provide sources for further readings. These methods include:

Agroforestry: Incorporates trees with other agricultural land use which not only removes carbon dioxide but also provides benefits to farmers and their communities.

Bioenergy with carbon capture and storage: A technique dependent on two technologies. Biomass that is converted into heat, electricity, liquid gas, or fuels make up the bioenergy component. The carbon emissions generated from this bioenergy conversion are then captured and stored in geological formations or long-lasting products, this being the second component of this method.

Biochar: A type of charcoal that is produced by burning organic material in a low oxygen environment, converting the carbon within to a form that resists decay. It is then buried or added to soils where that carbon can remain harbored for decades to centuries.

Blue Carbon: Refers to the carbon that is sequestered in peatlands and coastal wetlands such as mangroves, tidal marshes and seagrass among others, many of which have been destroyed in recent decades. 

Direct Air Capture: An approach that employs mechanical systems that capture carbon directly and compress it to be injected into geological storage, or used to make long-lasting products.

Enhanced Mineralization: Also known as enhanced or accelerated weathering. Accelerates the natural processes in which various minerals absorb carbon dioxide from the atmosphere. One implementation involves grinding basalt into powder and spreading it over soils, causing a reaction with CO2 in the air, forming stable carbonate materials.

Forestation: This includes forest restoration, reforestation and afforestation. Forests remove carbon dioxide and through the trees within, and have the potential to store that carbon for long periods of time.

Mass Timber: A method that involves utilizing specialized wood products to construct buildings, therefore replacing emission-intensive material such as concrete and steel. Further, this wood stores carbon that was captured from the atmosphere through photosynthesis. 

Ocean Alkalization: A process involving adding alkaline substances, such as olivine or lime, to the seawater to enhance the ocean’s natural carbon sink.

Soil Carbon Sequestration: Also referred to as “carbon farming” or “regenerative agriculture.” This process involves managing land in ways that promote carbon absorption and sequestration within soils, especially prominent among farmland.

By reviewing each of these succinctly written fact sheets, it is possible for one to gain a solid understanding of what is happening in the world of carbon removal; the good, the bad, and the misunderstood. 


Biochar could exacerbate existing inequalities

Author: Wil Burns

Biochar is charcoal produced through the thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. The process has been touted by some proponents as a potentially important component of climate policymaking over the course of this century. Because biochar can sequester carbon in soil for hundreds to thousands of years, supporters argue that it constitutes a “carbon negative” process:

“Ordinary biomass fuels are carbon neutral — the carbon captured in the biomass by photosynthesis would have eventually returned to the atmosphere through natural processes — burning plants for energy just speeds it up. Sustainable biochar systems can be carbon negative because they hold a substantial portion of the carbon in soil.” (International Biochar Initiative)


(image courtesy International Biochar Initiative)

Biochar has been fulsomely characterized by climate activist Bill McKibben as “the key to the New Carbon Economy,” and received prominent coverage in the Working Group III report of the IPCC’s Fifth Assessment Report as one of the technologies that could effectuate negative emissions scenarios that might be critical to avoiding the passing of critical temperature thresholds. However, an article by Melissa Leach, James Fairhead and James Fraser in 2012 in the Journal of Peasant Studies (free subscription required) sounds a cautionary note in terms of potential implications of a full-scale commitment to biochar for farmers, with a focus on Africa.

Among the conclusions of the article:

    1. Analyses that contemplate large drawdowns of carbon from biochar (e.g. one study projecting a potential sink of 5.5-9.5 GtC/year by 2100) “suppose an enormous growth in the resources and land areas devoted to the production of biochar feedstocks . . .” Some advocates have proposed dedicating somewhere between 200 million-1 billion hectares of forests, savannah and croplands to biochar projects. Such opponents have invoked the specter of large-scale “land grabbing” that they contend could threaten agricultural, pastoralist, collecting and other livelihoods;
    2. Foreign deals for biochar feedstock land could ultimately result in competition between biofuels and biochar projects;
    3. While some have argued that small farmers in developing countries could develop a substantial new income stream from sequestering carbon in biochar systems, many proponents of biochar as a climate solution are advocating development of new technologies to produce “clean char” that are different than indigenous practices in this context. Moreover, in contrast to REDD+, very little attention has been devoted to ascertaining how farmers could financially benefit from biochar projects;
    4. “The logic of the market” is likely to gravitate against small-scale projects that conducive to local priorities and livelihoods;” the need for verification and standardization protocols are likely to lead to large-scale industrialized biochar projects.

In contrast to the rather dry rendition of the potential socio-economic threats posed by biochar projects in the IPCC’s Fifth Assessment Report, this article is a stark reminder of how such projects pose the threat of exacerbation of existing inequalities associated with climate change. Moreover, while some proponents of carbon dioxide removal (CDR) climate geoengineering approaches argue that they are more benign than solar radiation management (SRM) approaches because they allegedly don’t threaten trans-boundary impacts, this article is a palpable reminder that this is not necessarily the case.

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