Biochar

Biochar is a charchoal product added to the soil to increase fertility and lock carbon into the soil. It could help tackle climate change. It is a sustainable production and utilization system that removes carbon from the atmosphere and enhance the earth’s soils.

Why should I be aware of this?

• Biochar is a solution that can provide us with a valuable tool for fighting climate change, world hunger, poverty, and energy shortages all at the same time. Being mostly inert, biochar is known to stay in the soil for thousands of years.
• Biochar is used to:

• improve the Earth’s soils;
• help mitigate the anthropogenic greenhouse effect by reducing greenhouse gas emissions and sequestering atmospheric carbon in a stable soil carbon pool; and
• improve water quality by retaining agrochemicals.

All about biochar

Biochar uses simple equipment to convert crops into a granular form of charcoal through “pyrolysis” – partial combustion in a low-oxygen environment. The pyrolysis process generates useful energy as other chemical elements are driven off, leaving behind fairly pure carbon in the form of charcoal, which is then mixed into soil. Because biochar resists degradation, it can sequester carbon in soils for hundreds or even thousands of years.

The production of biochar via pyrolysis also yields bio-energy in the form of synthesis gas (or ‘syngas’). Syn-gas consists of a variety of gases which in turn can be used to produce heat and power.

Ancient tradition in South America

This is an ancient tradition in South America to add powdered charcoal to soil. Biochar was traditionally added to soil to improve soil quality and increase crop yields. Now this is being looked at for an additional benefit of improving air quality by carbon sequestration.

There is no risk of it being blown down in a hurricane, or cut down, or otherwise placed in a process for a more rapid return of carbon dioxide to the atmosphere.

Agricultural benefits

Biochar has the following 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.
• It retains moisture, helping plants through periods of drought more easily.
• It replenishes exhausted or marginal soils with organic carbon and fosters the growth of soil microbes essential for nutrient absorption, particularly mycorrhizal fungi.

All biochars are not same

All biochars, however, is not the same. The key chemical and physical properties of biochar are greatly affected by the type of material being used and the conditions of the pyrolysis process (i.e. temperature and time). Biochar made from manure will have a higher nutrient content than biochar made from wood cuttings, which in turn has greater aromaticity, making it more stable over a longer period of time.

Biochar that is produced at 700°C will have a much greater adsorptive capacity and higher degree of micro-porosity compared with biochar produced at 400°C8. Essentially, a higher temperature biochar will have a greater potential for adsorption of toxic substances and rehabilitation of contaminated environments.

90 degrees

When biochar is created from biomass, approximately 50% of the carbon that the plants absorbed as CO2 from the atmosphere is “fixed” in the charcoal. As a material, the carbon in charcoal is largely inert, showing a relative lack of reactivity both chemically and biologically, and so it is strongly resistant to decomposition. Research scientists have found charcoal particles as old as 400 million years in sediment layers from wildfires that occurred when plant life first began on earth.

References:

• International Biochar Initiative
• Biochar Offers Answer for Healthy Soil and Carbon Sequestration
• Biochar Fact-sheet