About biochar

What is biochar?

Biochar can be made from a wide range of organic matter, as long as it is renewable. At NetZero, we only use agricultural residues as a feedstock. For example: coffee or cocoa husks and shells; sugarcane bagasse; coconut shells and fibers; peanut or cashew shells; palm empty bunches.

This feedstock is turned into biochar through pyrolysis, a thermochemical reaction where intense heating in the absence of oxygen breaks down complex molecular chains and rearranges molecular bonds to form a solid, very stable product – biochar.

Although biochar can be used for many purposes, we focus on its agricultural use, which requires to mix it with topsoil.

The production process of biochar generates significant amounts of renewable energy in the form of gases and heat. At NetZero, we recover this energy to reuse part of it for our own needs and supply local partners with the remaining part, whether as electricity or heat.

Some biochar in a hand.

Biochar for climate

The global sustainable potential for negative emissions through biochar is between 1 and 2 GtCO2 per year.

Biochar's main chemical component is carbon. This carbon was originally captured by plants in the atmosphere through photosythesis, and is then extracted and stabilised during the pyrolysis process. When put in the soil, this carbon remains there for at least hundreds of years. Thus, biochar is a long-term carbon removal solution.

According to the IPCC, when deployed at a global scale and taking into account sustainability constraints, biochar can remove every year up to 2 billion tonnes of CO2 from the atmosphere.

Biochar for agriculture

Biochar is used in agriculture as a soil amendement, to be mixed with topsoil at plant root level. It is applied only once and provides very long-lasting agronomic benefits.

The physicochemical properties of biochar allow to improve soil's quality: its high porosity improves the water-holding capacity of soils; its negatively charged surface allows for better nutrient retention; and its high carbon content helps rebalance acidic soils. The result is a durably improved crop productivity and the possibility to switch to 100% organic farming.

Biochar in agriculture is most effective on tropical crops. Jeffery et al. (2017) has shown a global average production increase of +25% in the tropics at a median biochar application rate of 1.5 kg/m2.

At NetZero, we provide agricultural training and support to farmers to use the biochar.

Agronomic trial on maize, showing a clear difference with and without biochar.
From left to right, maize with: biochar+fertiliser, biochar only, fertiliser only, control (NetZero Cameroon, 2022)