What Is Biochar?

Biochar is a solid material obtained from the carbonisation of biomass. Biochar may be added to soils with the intention to improve soil functions and to reduce emissions from biomass that would otherwise naturally degrade to greenhouse gases. Biochar also has appreciable carbon sequestration value. These properties are measurable and verifiable in a characterisation scheme, or in a carbon emission offset protocol.

This 2,000 year-old practice converts agricultural waste into a soil enhancer that can hold carbon, boost food security, and increase soil biodiversity, and discourage deforestation. The process creates a fine-grained, highly porous charcoal that helps soils retain nutrients and water.
Biochar is found in soils around the world as a result of vegetation fires and historic soil management practices. Intensive study of biochar-rich dark earths in the Amazon (terra preta), has led to a wider appreciation of biochar’s unique properties as a soil enhancer.
Biochar can be an important tool to increase food security and cropland diversity in areas with severely depleted soils, scarce organic resources, and inadequate water and chemical fertilizer supplies.
Biochar also improves water quality and quantity by increasing soil retention of nutrients and agrochemicals for plant and crop utilization. More nutrients stay in the soil instead of leaching into groundwater and causing pollution.

Biochar is a Powerfully Simple Tool to Combat Climate Change

The carbon in biochar resists degradation and can hold carbon in soils for hundreds to thousands of years. Biochar is produced through pyrolysis or gasification — processes that heat biomass in the absence (or under reduction) of oxygen.
In addition to creating a soil enhancer, sustainable biochar practices can produce oil and gas byproducts that can be used as fuel, providing clean, renewable energy. When the biochar is buried in the ground as a soil enhancer, the system can become "carbon negative."
Biochar and bioenergy co-production can help combat global climate change by displacing fossil fuel use and by sequestering carbon in stable soil carbon pools. It may also reduce emissions of nitrous oxide.
We can use this simple, yet powerful, technology to store 2.2 gigatons of carbon annually by 2050. It’s one of the few technologies that is relatively inexpensive, widely applicable, and quickly scalable. We really can’t afford not to pursue it.

How Can Biochar Be Carbon-Negative?

Fossil fuels are carbon-positive -- they add more carbon to the air. 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. The result is a net reduction of carbon dioxide in the atmosphere, as illustrated below.

Biochar can hold carbon in the soil for hundreds and even thousands of years. Biochar also improves soil fertility, stimulating plant growth, which then consumes more CO₂ in a feedback effect. And the energy generated as part of biochar production can displace carbonpositive energy from fossil fuels. Additional effects from adding biochar to soil can further reduce greenhouse gas emissions and enhance carbon storage in soil. These include:

• Biochar reduces the need for fertilizer, resulting in reduced emissions from fertilizer production.
• Biochar increases soil microbial life, resulting in more carbon storage in soil.
• Because biochar retains nitrogen, emissions of nitrous oxide (a potent greenhouse gas) may be reduced.
• Turning agricultural waste into biochar reduces methane (another potent greenhouse gas) generated by the natural decomposition of the waste.

How Much Carbon Can Biochar Remove from the Atmosphere?

IBI has developed a simple model to predict the carbon removing power of sustainable biochar systems. The figures here show the results of this preliminary model. We expect these answers will change as more is learned about the impacts of biochar, but the model gives a sense of what is possible.
The top figure on the right shows several scenarios that assume biochar production from waste biomass only, which is a small fraction of Earth's annual net primary production (NPP). Counting only the impacts of biochar burial in soil, and without considering the displacement of energy from fossil fuels, we can conservatively offset one quarter of a gigaton of carbon annually by 2030.
Optimistically, we could achieve one gigaton of offsets annually before 2050.
In the "Optimistic Plus" scenario, we account for reductions in nitrous oxide emissions and for the feedback effect of increased biochar production that may arise from increased plant growth in soils enhanced with biochar.
The second figure highlights additional carbon offsets possible if energy from biochar production displaces fossil fuel energy, and if CCS (carbon capture and storage) is used.