Carbon is essential to life. But by burning hydrocarbons, logging forests, and eroding soils, the planet’s natural carbon cycle becomes dangerously disrupted. The carbon trapped in oil, trees, and soil organic matter transforms into atmospheric carbon dioxide (CO2), the greenhouse gas putting the planet on a path toward catastrophic climate change.
Reducing these emissions is critical, but not enough on its own. We have to re-engineer the carbon cycle, storing and sequestering it to keep it out of the atmosphere. Carbon farming, or the sequestration of carbon in agricultural soils, is one of the most promising ways to do this.
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What is Carbon Farming?
The European Commission, in its Sustainable Carbon Cycles plan, defines carbon farming as:
“A green business model that rewards land managers for taking up improved land management practices, resulting in the increase of carbon sequestration in living biomass, dead organic matter and soils by enhancing carbon capture and/or reducing the release of carbon into the atmosphere, in respect of ecological principles favorable to biodiversity and the natural capital overall.”
Soil is, by far, the largest terrestrial carbon store. In fact, agriculture is perhaps the only industry with the potential to transform from a net-emitter to a net-sequesterer of CO2. Changing how we farm and manage our soils is one of the most exciting climate solutions we have. If implemented correctly, carbon farming practices that maximize the carbon-storing capacity of agricultural soils can also provide a host of co-benefits—from reducing our reliance on synthetic fertilizers to preserving the biodiversity of our agricultural land and managed landscapes.
Ultimately, like so many agricultural climate solutions, successful carbon farming all begins with what happens in the soil microbiome.
Carbon Sequestration and the Soil Microbiome
Carbon sequestration begins with the interaction of plants and microorganisms in the soil. Plants capture carbon dioxide from the atmosphere through photosynthesis, and some of this carbon is released to the rhizosphere via root exudation, sloughed root cap cells, and mycorrhizal fungi. But much of that captured CO2 is utilized by plants to grow. In conventional agricultural systems, that carbon is often released back into the atmosphere when plants die. But carbon farming practices can redirect that carbon deep into the soil, where it can be stored for decades, or even centuries.
A healthy soil microbiome is crucial for carbon sequestration as microbes play a significant role in organic matter decomposition. Healthy and diverse microbial ecosystems can effectively break down complex organic matter such as lignins, cellulose, and hemicellulose into soil organic carbon (SOC). Increasing SOC not only sequesters more carbon, but it also aids overall crop productivity by improving soil nutrient retention, aeration, and water-holding capacity, and by providing an important substrate in which soil microbes tend to thrive.
Carbon Credits and Carbon Farming Controversies
Carbon farming practices are rapidly being incentivized through carbon credit programs. In these programs, polluters pay to offset their emissions by purchasing carbon credits, compensating farmers that adopt carbon farming practices.
These programs have generated a fair amount of well-deserved controversy. Critics argue that carbon credits are simply a way for corporations to continue polluting without making any meaningful changes. Soil carbon can also be extremely difficult to quantify on the farm scale over short time periods, which has resulted in some carbon credit programs exaggerating how much carbon is really being sequestered.
However, despite issues in the implementation of large-scale carbon farming programs, the potential environmental benefits are clear. Carbon farming practices not only help sequester carbon, they can also help growers improve soil health, crop productivity, agricultural biodiversity, and drought resilience.
Tips for Successful Carbon Farming and Sequestration
Carbon farming practices all relate back to the biochemical functioning of the soil microbiome. A diverse microbiome converts organic matter into stable forms of soil organic carbon. These soil microbes play a fundamental role in determining how carbon is stored, and for how long.
Healthy, diverse carbon-sequestering soils can be encouraged by maximizing carbon inputs and minimizing carbon outputs. Carbon-rich inputs, like compost, manure, and biochar, can enhance microbial activity and transfer more of that carbon belowground. No or low-till practices, fertilizer management, cover cropping, and regular crop rotations minimize carbon outputs by reducing soil disturbances and increasing microbial biomass. This allows organic matter to be converted into stable forms of soil organic carbon, rather than being transformed back into atmospheric CO2.
Microbial Inoculants for Carbon Farming
The soil microbiome can perhaps be most directly manipulated through the addition of microbial inoculants. Microbial inoculants usually contain a consortium of plant growth-promoting bacteria (PGPR), species that are known to improve plant development and yields. The benefits of microbial inoculants center on boosting yields by improving nutrient use efficiency, root development, and plant stress tolerance, but they can also help build soils that effectively sequester carbon.
The soil microbiome is wildly complex, and there is much we still don’t know regarding the potential of microbial inoculants to influence carbon sequestration directly. Eventually, it may be possible to design targeted microbial inoculants containing a consortium of microbial species that both encourage plant growth and drive carbon decomposition into highly stable forms.
However, we already know that inoculants like Impello’s Continuμm™ can aid in carbon sequestration in more indirect ways, primarily by increasing microbial biomass formation in the soil. By encouraging greater plant development, root biomass, and root exudation, Continuμm™ also encourages the conditions that lead to carbon mineralization and soil organic matter formation.
This is, of course, on top of the other environmental benefits provided by microbial inoculants, like reducing the demand for fertilizers, pesticides, and freshwater. If anything, the breadth of environmental benefits demonstrates how vital soil health is—not just for agriculture, but for the entire planet.
Without healthy soil, we have nothing. How we farm must strive to reflect that reality.
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Publications Office of the European Union. (2022). Technical guidance handbook : setting up and implementing result-based carbon farming mechanisms in the EU : executive summary. Publications Office of the EU. https://op.europa.eu/en/publication-detail/-/publication/b7b20495-a73e-11eb-9585-01aa75ed71a1/language-en
Rao, D. L. N., Aparna, K., & Mohanty, S. R. (2019). Microbiology and biochemistry of soil organic matter, carbon sequestration and soil health. Indian Journal of Fertilisers, 15(2), 124-138.https://www.researchgate.net/publication/332038028_Microbiology_and_Biochemistry_of_Soil_Organic_Matter_Carbon_Sequestration_and_Soil_Health
Sharma, M., Kaushal, R., Kaushik, P., & Ramakrishna, S. (2021). Carbon Farming: Prospects and Challenges. Sustainability, 13(19), 11122. https://doi.org/10.3390/su131911122
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