What is Biochar?
Biochar is charcoal that is made for use in soil. Biochar is made from biomass (like wood or straw) by applying heat in the absence of oxygen. Heat bakes the biomass, releasing flammable gases and leaving behind a solid carbon structure – charcoal.
Charcoal is beneficial as a soil amendment. It absorbs and holds water, air and nutrients, making them available to plants. Charcoal works best in soil if it is composted with other organic matter first. Composting makes it more compatible with soil. When we add charcoal to soil it becomes biochar.
The history of Biochar
In the Amazon rainforest, people added biochar to soils over thousands of years to help grow food crops in the poor tropical soils. Tropical soils can grow giant rain forests, but when the forest cover is removed, rain washes the soil away. Biochar helped people stabilize the soil for agriculture. A lot of the biochar is still there, thousands of years later. Even today, farmers value these old, black Terra Preta soils for their increased productivity compared to the nearby red soils.
Before the development of modern agricultural technology, farmers in Japan, China, Europe and many other countries, including the United States, used biochar. Farmers wrote about the benefits of charcoal in the first scientific agriculture journals that were published back in the 1800s
Advantages of Biochar
- Adding biochar to the soil increases the water and air holding capacity of the soil.
- It promotes the proliferation of mycorrhizal fungi and other beneficial soil microbes.
- Biochar improves the cation exchange capacity of the soil and prevents nutrients from being washed away.
- When biochar is incorporated into the soil, there is approximately 50% to 80% reduction in nitrous oxide emissions, as well as a reduced runoff of phosphorus into surface waters and a reduced leaching of nitrogen into groundwater.
- Biochar reduces the amount of methane released from the soil.
- Biochar adsorbs dissolved organic matter and prevents their rapid consumption by soil microbes. This adds even more carbon to the soil. This eventually becomes stable humic matter, the most beneficial form of carbon needed for plant growth.
- As a soil amendment, biochar significantly increases the efficiency of, and reduces the need for, traditional chemical fertilizers, while greatly enhancing crop yields.
Biochar is a climate solution
Because plants pull carbon dioxide out of the air when they grow, if you convert part of a plant’s carbon to biochar and put it in the soil, you are reducing the amount of carbon dioxide in the atmosphere. This is called Biochar Carbon Capture. But be careful, your biomass must be sustainably grown and harvested and your biochar production process must be clean, or you might make more carbon dioxide than you bury as biochar.
The process of making biochar releases energy. It is a form of burning or thermal conversion without oxygen that is called pyrolysis. If you can use that energy to substitute for energy from fossil fuels, that is another way that biochar can reduce carbon in the atmosphere. You can use your biochar stove to cook dinner instead of using a gas or electric stove.
Char Briq Solutions based in Nairobi, Kenya suggests if we do it right, biochar can help reduce climate change by substituting renewable biomass energy (with biochar carbon capture) for some of the fossil fuel energy we consume. Biochar could be harmful if it is made from unsustainable feedstocks like large trees. Biochar should be made from residues and waste products or quick growing fuel crops that are grown sustainably on formerly degraded land. The goal must be to increase the carbon content of soils and vegetative cover wherever possible. Agricultural practices that deplete carbon in order to grow biofuels would defeat the purpose.