For a long time, indigenous peoples throughout the world have applied a simple technique to improve soil quality and increase productivity.
Today, scientists are rediscovering the value of adding carbonized biomass (biochar) to soils. The process (pyrolysis) involves heating the organic matter without oxygen (no direct CO2 release into the atmosphere), the result being a carbon-rich product that has been called biochar when it is intended to be incorporated into soils.
In the form of fine particles (less than 2 mm) and combined with organic fertilizers (compost), biochar can be introduced in a wide variety of soils and environments.
The long-term maintenance of the fertility of formerly biochar soils, compared with a growing number of trials in many countries, shows that the introduction of biochar can double productivity and create long-lasting fertility.
Biochar, applied in the surface layer of the soil, is not itself consumed by plants. It provides a habitat, such as a sponge, for microorganisms in the soil whose fertility is then restored durably.
Studies show that biochar stimulates soil metabolism, the immune defenses of the plant, which defends against diseases without the aid of fungicides.
When the soil dries on the surface, biochar acts as a moisture retainer and saves up to 80% water. The more acidic the soil is, the more effective it is.
Obtentaining a biochar
Biochar is obtained by pyrolysis of plant biomass of various origins, generally agricultural or forestry residues (grey or yellow straw, cereals, branches, cutting wood, bark, carpenter residues, sawdust ...).
It looks like small, black, light, and extremely porous fragments.
The result of the pyrolysis process produces a combustible gas, a liquid that can be used as a biofuel, and a solid residue with a high carbon content: biochar.
The ideal carbonization temperature is around 500-550 ° C.
Hydro-Biochar is a 100% biosourced hydro-retainer biochar, designed to offer an innovative and sustainable alternative to increase the water retention capacity of soils and substrates, thus contributing to an increase in the amount of water available to the plant while preserving the environment and contributing to the reduction of greenhouse gases.
These images are examples of biochars that have been produced from rubber in a small-scale gasifier, used to generate electricity in remote rural areas of north-western Cambodia.
Biochar is rich in carbon molecules that are resistant to mineralization by microorganisms, and is therefore a potentially important means of long-term storage of carbon in soils, helping to limit CO2 concentrations in the atmosphere.
The images represent surfaces of approximately 700 μm and 50 μm wide, respectively.
With the kind permission of Dr. Simon Shackley's sample,
School of Geosciences at the University of Edinburgh and Erik Middelink.
Benefits and applications
It has been scientifically possible to evaluate:
The Increase in water holding capacity in soils
The increase of organic matter in the soil
The stimulation of soil biology (+ 40% mycorrhizal fungi)
The improvement of nutrient retention (+ 50% cation exchange)
Increasing the pH of acid soils (1 point more)
The impact of biochar is greater in degraded or depleted soils than in those already containing much organic matter. Biochar is therefore particularly suitable for poor and / or drought damaged soils. Its use can play a major role in improving soil quality.
Today's research focuses on the mechanisms by which biochar modifies soil properties and optimal conditions for its production and use.
Reduced stress due to lack of water
Decrease in watering frequencies 30 to 50%
Increased crop yield
Increased fertilizer retention
Increased water retention in soil
Ventilation of soils
Qualitative structure of the support (color, density)
Arboriculture, horticulture, nurseries
Green spaces, sports fields, golf
Fight against climate change
Growing plants absorb CO2, producing biomass that contains carbon.
Rather than allowing unused plants to decompose by emitting CO2, pyrolysis transforms about half of the carbon into a stable, inactive form.
Photosynthesis absorbs CO2 from the atmosphere, biochar stores carbon in a solid and beneficial form.
Biochar also reduces emissions of other greenhouse gases, including methane and nitrous oxide. A recent study estimates that 12% of greenhouse gas emissions from human activity could be offset by the use of biochar.
Biomass sources to produce biochar
Biomass sources for the production of biochar should be selected after a life cycle analysis.
So as not to repeat the same errors caused by the expansion of biofuels, only biomass resources that can be obtained in a sustainable way, ie without compromising food security, biodiversity or soil, can be used to produce biochar.
This takes into account the importance of leaving crop residues so as to enrich the soil with organic matter and nutrients