Biochar: A carbon sequestration tool for rural communities?

Biochar has been identified by The Intergovernmental Panel on Climate Change (IPCC) (AR 6, WGIII, SPM, footnote 70)[1] as one of the solutions to fight climate change thanks to its long-term carbon sequestration potential and its multiple co-benefits.

What is biochar?

Biochar production is a technique through which carbon from certain biomasses is transformed into stable carbon that can be captured in the soil. In addition to this long-term carbon sequestration role, biochar is also beneficial to soil performance as it improves the retention and diffusion of water and nutrients.

Biochar is a highly resistant soil amendment produced by burning or gasifying biomass. After waste (manure, agricultural or forestry residues) has been processed in high-temperature furnaces in an oxygen-limited environment, it is converted into a solid, porous, carbon-rich and stable material. This stability can vary from a few decades to several centuries[2]^,[3].

When added to soil, biochar has the ability to store carbon, and to retain nutrients and water due to its porous physical structure[4]. It helps restore soil fertility and reduces water runoff.

Biochar has been found in the “terra preta” (‘black soil’ in Portuguese), parcels of highly fertile land within the Amazon. Exploration of terra preta soils has revealed that more than 2,000 years ago, Amazonian Indians used to bury stable carbon in the soil. A mixture of broken pottery and other various organic materials has maintained the high fertility potential of these plots to this day[5]. Replicating this technique could improve degraded soil and climate conditions of some rural communities in developing countries.

Verified Carbon Standard (VCS)[6], an international certification body for carbon finance, recently published a certification methodology that provides a framework for carbon accounting and eligibility rules for biochar projects. Since the beginning of the development of this methodology, EcoAct has implemented a full-scale pilot project aligned to the conditions defined by VCS. This project aims to support rural communities in East Africa.

 

Innovation driven momentum for biochar development

On 12^th August 2022, VCS validated a  methodology recognising the sequestration properties of biochar. Like EcoAct, many organisations had already set up experimental projects while waiting to be allowed to apply this methodology. The launch version of the certification process was adjusted following various consultations and public comments.

The validation is based on numerous scientific studies as well as on reports published by the IPCC which confirm the huge potential of biochar for carbon sequestration. For the IPCC, biochar is a high impact solution to the climate emergency.

EcoAct is fully committed to this phase of experimentation and is exploring the adjustments and innovations needed to make this methodology specifically applicable to rural communities in developing countries.

Rural communities as primary suppliers of raw materials for biochar production

The biomass eligible for biochar production in rural areas is mainly agricultural and forestry waste, which is usually burnt in open air or left unused as there is no other way to exploit it. The choice of materials for biochar production is usually either combustion (other than for energy production) or slow decomposition. The transformation of biomass by pyrolysis under ideal conditions emits little GHG emissions compared to it being burnt or left unused.

 

Through their agricultural production activities, rural communities are likely to generate agricultural and forestry waste or material in large quantities, such as rice husks, hulls, or fruit pulp. These communities or groups of farmers are used to managing large flows of waste and optimising their volumes. The challenge is therefore to recover large quantities of these wastes while limiting GHG emissions and increasing their share of renewable carbon.

EcoAct has partnered with Akili Holdings Ltd in Kenya on a new biochar project. It has selected materials that meet the criteria of the VCS methodology, as well as the availability of agricultural raw materials for Kenyan farmers (Image 1 and 2).

 

Seeking the right pyrolysis technology for rural communities

The VCS methodology recognises two types of pyrolysis, ‘high technology’ and ‘low technology’. The difference between the two is that the “high technology” type has better control over the heat, the capture of emitted gases and the measurement of the temperature. This better control generally enables improved value of pyrolysis co-products and better efficiency in the reduction of GHG emissions. In the absence of continuous measurements and heat recovery, low technology achieves comparable results in terms of stable carbon production. Therefore, the first challenge for low technology is to limit the gases emitted during pyrolysis.

Close attention must also be paid to which type of technology can exploit natural convection processes to create a combustion zone above the pyrolysis zone to limit methane and soot emissions, without which the environmental benefit of biochar would be compromised. The second challenge is to make this “low technology” accessible in terms of cost and operability to these same rural communities in areas with deteriorated land.

To address this, EcoAct experts are working with our partner Akili on the local design of low technology stoves to find the most suitable technology for the area concerned and to verify its operability.

EcoAct is currently working with Akili to conduct an experiment to meet the dual challenge of producing biochar on a significant scale for carbon sequestration and for the benefit of rural communities. To ensure the quality of the biochar produced, a partnership has been established with the local Kenyatta University which will be responsible for a series of laboratory analyses. As part of the experiment, various tests will be conducted with rural communities to identify the best ratio of biochar supplemented with compost to apply to soils for short-term (e.g., cabbage, tomatoes) and long-term (e.g., coffee) crops.

 

 

 

 

 

 

 

 

Notes

[1] https://www.ipcc.ch/report/ar6/wg3/downloads/report/IPCC_AR6_WGIII_SPM.pdf

[2]Christophe Naisse. Potentiel de séquestration de carbone des biochars et hydrochars, et impact après plusieurs siècles sur le fonctionnement du sol. Sciences de la Terre. Université Pierre et Marie Curie – Paris VI, 2014. ⟨NNT : 2014PA066518⟩. ⟨tel-01130038⟩

[3] Fang, Y., B. Singh, B.P. Singh, and E. Krull, 2014: Biochar carbon stability in four contrasting soils. European Journal of Soil Science, 65(1), 60–71, doi:10.1111/ejss.12094

[4] Brown, R. (2009) Biochar production technology. In: Biochar for environmental management: Science and technology. (Lehmann, J. and Joseph, S.). Earthscan, London, pp 127-146. https://doi.org/10.4324/9780203762264

[5] Bruno Glaser, Jago Jonathan Birk, State of the scientific knowledge on properties and genesis of Anthropogenic Dark Earths in Central Amazonia (terra preta de Índio), Geochimica et Cosmochimica Acta, Volume 82, 2012, Pages 39-51, ISSN 0016-7037, https://doi.org/10.1016/j.gca.2010.11.029. (https://www.sciencedirect.com/science/article/pii/S001670371100144X)

[6] https://verra.org/methodology/methodology-for-biochar-utilization-in-soil-and-non-soil-applications/