Biochar, a scalable carbon sink and a high-value material

Biochar is the result of a pyrolysis process, which consists in heating biomass in an oxygen-free environment at 550-600°C. In addition to producing a solid component (biochar), pyrolysis produces a gaseous by-product called ‘syngas’, which is a convenient source of renewable energy. Part of this energy is used to supply the upfront biomass dryer and the pyrolysis equipment, ensuring energy self-sufficiency of the process. The excess of syngas is used by local industries and by public authorities (for heating networks, swimming pools, hospitals for example), or for upgraded energy such as power and or bio-oil.

Biochar is a solid component produced from residual and waste biomass, such as agricultural biomass (crop residues and unused by-products), wood and forestry residues, and a wide spectrum of solid organic waste from food processing or secondary uses of biomass (such as rice husk, sugar cane bagasse, nutshells, fruit stones, coffee chaff and dregs…). In a nutshell, it can be assumed that any biomass waste having no commercial/technical interest to be digested or composted may be a suitable feedstock for biochar production.

Biochar is preferably produced by using local biomass sourcing and short transportation distances.

Biochar production facilities can easily be implanted near wood sawmills or agri-food plants for example, directly using wood and agri residues to produce biochar in a very short processing chain.

Yes, it is. Biochar is a persistent material which allows to durably store carbon. Throughout their lifetime and in order to grow, plants extract efficiently and usefully CO₂ from the atmosphere through photosynthesis. When this biomass naturally decays or is burned, carbon is rejected to the atmosphere in the form of climate-damaging gases, such as carbon dioxide (CO₂) and methane (CH₄). Usefully coupled with the natural carbon cycle, pyrolysis conversion (the process of transforming this biomass into biochar) allows to durably convert higher amounts of carbon into a stable form, which would have otherwise been rejected to the atmosphere.

Depending on the Life Cycle Analysis of each plant and the input biomass composition, one ton of biochar can durably remove between 2.5 and 3 net tonnes of carbon dioxide equivalent from the atmosphere. Because biochar is highly resistant to chemical and geological degradation, the carbon storage effects of biochar are lasting irreversibly and surely for hundreds of years, which is significantly more than other carbon removal processes and applications.

No, the biochar is not at all burnt wood.

The organic matter, whether it is wood or agricultural products, contains 50% of carbon (on dry matter) that has previously been absorbed by plants through photosynthesis.

During the combustion of organic matter, carbon is rejected in the atmosphere in the form of climate-damaging gases, such as carbon dioxide (CO₂).

On the contrary, the pyrolysis of organic matter concentrates the carbon inside a solid fraction, which is called biochar. In this solid fraction, the carbon is organized in very stable molecular forms, called inertinite and semi-inertinite, which will last for centuries when properly used.

No, biochar is not ash. Ash is the solid remnants of fire and contains minerals and metals.
Biochar is made of 80-90% of carbon and 10-20% of minerals, volatiles, metals, etc.

Depending on the production parameters, the biochar has a wide range of properties and can be used for diverse applications, enabling to conserve the carbon once it has been stabilized through pyrolysis. Moreover, biochar helps improve the quality and performance of widely used products and applications, making them more climate efficient in terms of GHG balance, value creative and resilient.

For a few decades, biochar has been particularly recommended for soil application where it ensures long-term carbon sequestration compared to all other organic carbon compounds which will gradually decay. It also contributes to soil health. So far, it has been mainly used in agricultural fields, where the addition of biochar helps improve water retention, microbiotic diversity and nutrient availability, lighten the soil, and, in combination with fertilisers, increase crop yield and natural plant resistance. Biochar can also be used as an additive to compost or liquid manure, improving compost quality and reducing nitrogen losses. By regenerating soils and supporting plant growth and resistance, biochar accelerates the carbon absorption of any cultivated lands in rural and urban areas, creating a true virtuous circle.

In addition, biochar has proven its qualities in other sectors. It can be used as a feed additive for ruminants, improving animal health and reducing enteric methane emission, or in urban and industrial areas to rehabilitate degraded and contaminated soils and improve the replantation of urban trees. It can generate avoided emissions by substituting impactful and/or non-sustaining materials (e.g. peat replacement by biochar) and it can also improve the direct carbon footprint (scopes 1 & 2) and sometimes specific properties of construction materials such as concrete, asphalt or gypsum. Finally, it can also be useful in water treatment to reduce pollution of ground and surface water.

The pyrolysis of organic matter organizes the carbon in very stable molecular forms, called inertinite and semi-inertinite. These molecules are part of the natural organic carbon cycle and thus do exist in the soil and sub soil. These carbon fractions are well-known to the scientific community.

Recent research has shown that the inertinite content of biochars can overpass 95% (dry ash-free basis) which indicates superior carbon permanence and resistance to microbial degradation. When used in a conservative way, for instance in a soil or in building materials, these biochars last for centuries, even millennia.

Biochar and compost do not have the same properties in a soil. Using both products is useful to enhance soil health and crop yields.

In a nutshell, the compost provides soils with nutrients and degradable carbon, whereas the sponge properties of the biochar help retain water and nutrients, as well as developing the microbiotic life of the soil. Using a mix of compost and biochar offers a highly relevant and sustainable solution to improve soils.

In addition, the production of compost naturally rejects to the atmosphere climate-damaging gases. Using biochar in the composting process helps reduce the GHG emissions.

Biochar and charcoal are two different products with different properties. Charcoal is obtained when organic matter is heated in an oxygen free environment at 300-350°C, through a conversion process called torrefaction, whereas the biochar production requires a pyrolysis process.

Charcoal is not a carbon-sink and then is not used to tackle climate change because the carbon contained in the product is not stable enough to resist to chemical and geological degradation. Charcoal is mainly used as a fuel.

When produced and used correctly, the biochar is safe.

Because of its recognised benefits, technology providers have been significantly investing in biochar technology in the past years. Currently, the biochar production technology, called pyrolysis, is considered as mature.

Biochar production technology is certified under the European Biochar Certificate (EBC), a precise and transparent indicator which takes into account the whole production lifecycle of biochar.

In the climate change field, biochar is considered as a "negative-emissions technology" (NET) that can complement the necessary emissions’ reduction efforts by creating carbon sinks, a status that was officially recognised by the Intergovernmental Panel on Climate Change (IPCC) in 2018.

While CO₂ emissions from fuel combustion have been declining in Europe through a combination of efforts, some sectors, or countries, in addition to drastically reducing their emissions, will have no other option than to use emission mitigation technologies to meet the targets and achieve climate neutrality by 2050.

It is worth remembering that, to fight against climate change, carbon sequestration must never be an excuse to delay reducing emissions. Carbon removals must be additive to the necessary decarbonization efforts.