What is Biochar?
Biochar is defined simply as charcoal that is used for agricultural purposes. It it created using a pyrolysis process, heating biomass in a low oxygen environment. Once the pyrolysis reaction has begun, it is self-sustaining, requiring no outside energy input. Byproducts of the process include syngas (H2 + CO), minor quantities of methane (CH4), tars, organic acids and excess heat.
Once it is produced, biochar is spread on agricultural fields and incorporated into the top layer of soil.
Biochar has many agricultural benefits. It increases crop yields, sometimes substantially if the soil is in poor condition. It helps to prevent fertilizer runoff and leeching, allowing the use of less fertilizers and diminishing agricultural pollution to the surrounding environment. And it retains moisture, helping plants through periods of drought more easily. Most importantly, it replenishes exhausted or marginal soils with organic carbon and fosters the growth of soil microbes essential for nutrient absorption, particularly mycorrhizal fungi.
Studies have indicated that the carbon in biochar remains stable for millenia, providing a simple, sustainable means to sequester historic carbon emissions that is technologically feasible in developed or developing countries alike. The syngas and excess heat can be used directly or employed to produce a variety of biofuels.
This 2,000 year-old practice converts agricultural waste into a soil enhancer that can hold carbon, boost food security 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 Help 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.