Biochar is a kind of charcoal produced by burning biomass (organic material) in a low-oxygen environment. This process, known as pyrolysis, converts the carbon in the biomass to a form that resists decay. When the charcoal is buried or added to soils, most of the carbon can remain in the charcoal or soil for decades to centuries, given the right conditions.
The process of growing plants or collecting waste biomass, converting that biomass to biochar, and adding the biochar to soils removes carbon dioxide (CO2) from the atmosphere: as plants grow, they remove CO2 from the atmosphere and use it to make more biomass; the carbon in that biomass gets converted to a stable form in biochar; and burying the biochar can keep the carbon out of the atmosphere for long periods of time. This makes producing and burying biochar a form of carbon removal.
Co-Benefits and Concerns:
- Improved soil quality: biochar can help restore degraded soils, improving agricultural productivity and helping soils retain water.
- Energy production: burning biomass to produce biochar produces energy, which can be used for heat or electricity.
- Reversibility: the carbon captured via biochar can be released if the soils are disturbed.
- Difficulty of measurement: monitoring and verifying the permanence of carbon removal via biochar could be difficult.
The term biochar is relatively new and may be unfamiliar to many, but the fundamentals of augmenting earth with fine-grained charcoal created by pyrolysis (heating carbon-rich organic matter in low oxygen conditions) have boosted the fertility of soil for thousands of years.
Perhaps the most striking example of biochar in action is the rich soil known as “terra preta” (black earth) in the Amazon basin, where over a thousand years ago natives burned jungle plants and branches in slow smoldering piles and combined the charcoaled remains with manure to enrich nutrient-deficient clay soil. Unlike compost, biochar does not decompose and its benefits can last hundreds of years. Indeed, the terra preta remains fertile to this day.
When organic matter like wood, leaves, manure or gasses burns in limited oxygen environments, the water, chemicals and gasses within are released, but the carbon structures are left behind, resulting in microscopic pockets where moisture and bacteria are captured. Thriving bacterial growth in these microscopic chambers are building blocks for developing nutrient-rich soil.
The Value of Organic Waste
One of the most interesting things about biochar is that it can turn what a lot of people think is useless into something valuable. Sustainability experts call this valorization.
Valorization might sound like an overly technical word, but what it describes is actually fairly simple: returning value to wasted materials. That value might be as an industrial additive, a new product, or even as a form of clean energy. The concept of valorization redefines the very idea of waste, applying instead a more dynamic understanding of how material changes over the course of its life cycle as a product. Using different methodologies and technologies, the properties and qualities of wasted biomass can be exploited to keep materials in circulation, rather than going into a landfill or a conventional treatment facility, both of which levy a heavy toll on our resources and ecosystems. Waste valorization is an application of the principles that underpin the concept of the circular economy
The Role of Biochar in Sequestering Carbon and Mitigating Climate Change
Biochar production is a carbon-negative process, which means that it actually reduces CO2 in the atmosphere. In the process of making biochar, the unstable carbon in decaying plant material is converted into a stable form of carbon that is then stored in the biochar. When biochar is applied to the soil, it stores the carbon in a secure place for potentially hundreds or thousands of years. To put it simply, the feedstocks that were used for making biochar would release higher amounts of carbon dioxide to the atmosphere if they were left to decompose naturally. By heating the feedstocks and transforming their carbon content into a stable structure that doesn’t react to oxygen, biochar technology ultimately reduces carbon dioxide in the atmosphere.
Biochar also contributes to the mitigation of climate change by enriching the soils and reducing the need for chemical fertilizers, which in turn lowers greenhouse gas emissions. The improved soil fertility also stimulates the growth of plants, which consume carbon dioxide. The many benefits of biochar for both climate and agricultural systems make it a promising tool for regenerative agriculture.