Biochar Land Carbon Sequestration: a benefit or a bother?

by Clare Woo | ACICIS intern at environmental institute

If we got ourselves into this climate mess by digging up and burning coal, maybe we can fix it by creating some more coal and putting it back into the ground.

 

We face some of the greatest environmental challenges today, including sustainably feeding the world’s masses in the face of climate disruption. With estimates of the world’s population reaching 9 billion by 2050, the global demand food is projected to double¹. This is a rather wicked problem, as there are regions of the world already struggling with undernutrition, others have amassed considerable food waste and the amount of arable land in the world is finite.

A potential solution for many of these issues is a relatively new innovative product coined “Biochar”. Biochar is a natural charcoal created using a process called pyrolysis. A range of organic materials such as wood chips, agricultural by-products, human waste and food waste are burned in the presence of little or no oxygen which then turns into oil, synthetic gas (known as syngas), and a solid residue resembling charcoal².

The pyrolysis process can be tweaked, with “slow pyrolysis” (hours or days) yielding more biochar and a faster version (seconds) increasing the bio-energy production². In some systems, the syngas and oil can actually be used as a fuel to run the pyrolysis reaction self-sufficiently².

BENEFITS

Carbon sink. Creating biochar reduces CO2 in the atmosphere because the process takes the carbon-neutral process of decomposing organic matter and turns it carbon-negative: Plants absorb and store C02 as they grow but emit this back when they decay². Biochar stabilizes that carbon in a biologically unavailable form, sequestering it out of the atmosphere and into the soil for potentially hundreds or even thousands of years³.

A paper by nature communications estimated that 12 percent of global greenhouse gas emissions could be offset with biochar production⁴, making it a realistic tool to absorb net carbon from the atmosphere and possibly combat climate change. Given the drastic reduction in atmospheric CO₂ needed in such a limited time, it has been described as “the best option for atmospheric carbon sequestration”⁵. This could also be incorporated into carbon trading schemes where countries or companies will pay to produce and bury the biochar as a way of offsetting their own emissions².

Improving agriculture. Past agricultural techniques have depleted many of the world’s soils carrying capacity and productivity. Additional to providing a carbon sink on agricultural lands, biochar also has various soil remedial properties depending on the pyrolysis temperatures (between 300-700C)². The larger particle size and composition of the biochar acts like a sponge, allowing for better water absorption and reducing runoff (which helps streams, rivers and the oceans)³. This can add resilience to the soil in areas that face drought or irregular rainfall. Biochar can also act as a substrate to increase fertilizer efficiency, aid in the sorption of organic and inorganic contaminants and to buffer acidity- improving the PH and nutrient uptake for plants^3,6. It may also be used as a litter amendment or a feed additive for livestock. This can improve agricultural output, efficiency and resilience in the face of climate change.

Waste recycling. Almost all countries have valuable resources rotting in landfill that could be utilised through biochar production. Most commonly biochar uses agricultural residues such as crop-by product and animal manure as well as forestry offcuts but there is a growing movement towards utilising food waste and even human waste as well³. Interestingly, technologies are being explored in the often wasteful construction sector, which are using woodchips and other untreated wood waste to make biochar which is then used as a partial replacement of cement and/or fillers into cement-based admixtures⁷. As cement production is the world’s single biggest industrial cause of carbon pollution, responsible for 8% of global emissions⁸, this technology can further reduce emissions and raw materials consumption.

DISADVANTAGES

Biochar seems too good to be true, and that’s because it is – biochar still needs further development in order to make it more accessible, sustainable and logistically feasible². Ultimately, if the energy used to produce the biochar is made with fossil fuels and produces a large carbon footprint to transport the materials, it cancels out any net negative carbon benefits, making it carbon neutral or even carbon producing⁶. The costs of a biochar production equipment and site preparation is also quite costly, meaning the price for carbon credits need to be higher than biochar production and application costs in order to make it a profitable business model⁶. Additionally, if the carbon credits of biochar is not properly regulated, there is the possibility of people displacing agricultural land or native areas into plantations solely for the purposes of biochar production².

There is hope. Despite the many hurdles, biochar is already widely happening with more than 120 companies already producing biochar or biochar-related products in various countries². They are currently operating on a small, local farm scale using optimised methods such as root zone/ banded application, application on higher-value crops and optimising/tailoring the biochar qualities to suit the landscapes needs⁶. As a farm-scale investment, biochar can aid in integrated farm management by creating a closed loop system that promotes long-term productivity, high quality product, sustainability, climate resilience and land stewardship.

 

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References

1. Food and Agriculture Organization of the United Nations. (2009). High Level Expert Forum – Global agriculture towards 2050 [Ebook]. Retrieved 25 August 2022, from https://www.fao.org/fileadmin/templates/wsfs/docs/Issues_papers/HLEF2050_Global_Agriculture.pdf.
2. Levitan, D., 2010. Refilling the Carbon Sink: Biochar’s Potential and Pitfalls. [online] Yale Environment 360. Retrieved 25 August 2022, from https://e360.yale.edu/features/refilling_the_carbon_sink_biochars_potential_and_pitfalls
3. Land Carbon Sequestration (Biochar). Climate Foundation. (2022). Retrieved 25 August 2022, from https://www.climatefoundation.org/land-carbon-sequestration-biochar.html.
4. Woolf, D., Amonette, J., Street-Perrott, F., Lehmann, J., & Joseph, S. (2010). Sustainable biochar to mitigate global climate change. Nature Communications, 1(1). https://doi.org/10.1038/ncomms1053
5. Matovic, D. (2011). Biochar as a viable carbon sequestration option: Global and Canadian perspective. Energy, 36(4), 2011-2016. https://doi.org/10.1016/j.energy.2010.09.031
6. Buss, W. (2022). Soil Management. Lecture, ENVS2023 ANU fenner school, Centre for entrepreneurial agri-technology.
7. Sirico, A., Bernardi, P., Sciancalepore, C., Vecchi, F., Malcevschi, A., Belletti, B., & Milanese, D. (2021). Biochar from wood waste as additive for structural concrete. Construction And Building Materials, 303, 124500. https://doi.org/10.1016/j.conbuildmat.2021.124500
8. Rethinking Cement. Beyond zero emissions. (2022). Retrieved 25 August 2022, from https://bze.org.au/research_release/rethinking-cement/