Biochar

Biochar is a type of charcoal made by thermal decomposition of biomass, but without the use of oxygen. It is used as a soil conditioner for both carbon sequestration and soil health benefits. Biochar can be a simple yet powerful tool to combat climate change.

Research is being carried out on how biochar can be used to mitigate the effects of climate change.

Details of biochar will be useful in the Environment and Ecology segment of the IAS Exam.

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Overview of Biochar

• The word ‘biochar’ is derived from the Greek word ‘bios’ meaning life and ‘char’ short for charcoal. It is basically charcoal, but used in certain applications.
• Biochar is a charcoal-like material that is produced from plant materials such as grass, agricultural and forest residues that are decomposed at high temperatures, often during renewable energy production.
• During the process, the physical and chemical properties of the plant material change into a highly porous, stable, carbon-rich material known as biochar.
• Biochar is a high-carbon, fine-grained residue produced through direct thermal decomposition of biomass without oxygen being used in the process.
• It produces a mixture of solids, liquid and gas products. The yields gained depend on conditions such as temperature and heating rate. These parameters can be used to produce energy as well.
• The ideal temperature of biochar creation is at 400 – 500 °C, while temperature above 700 °C favours the yield of liquid and gas fuel components.

For more UPSC notes on Environment and Ecology, visit the linked article.

Uses of Biochar

The following are the uses for Biochar:

1. Carbon Sink:  When biomass is burnt or naturally decomposed, large amounts of carbon dioxide and methane is released into the Earth’s atmosphere. Biochar also similarly releases the same elements into the atmosphere, but the carbon content is stable by comparison. As such, biochar provides for suitable storage of carbon in the ground, potentially reducing atmospheric greenhouse gases (GHG) while at the same time increasing soil fertility and improved agricultural productivity.
2. Soil Amendment: The porous nature of biochar is ideal for soil enrichment, as it retains both water and water-soluble nutrients. Biochar is recognized for its offering of a number of soil health benefits. Thus, biochar is capable of improving quality of water, reduce nutrient depletion, reduce soil acidity and reduce irrigation and fertilizer requirements
3. Water Retention: Biochar is hygroscopic, as in able to absorb and hold water from the surrounding environment. This makes it ideal as a soil material where water shortages are common. Nutrients crucial for a plants benefits such as phosphate and nitrogen are retained, making the plants healthy and requiring far less fertilizer.
4. Biochar has the potential to be used as a soil conditioner and as a container substrate amendment in agriculture and horticulture, and it may improve several soil and substrate physical, chemical and biological properties.

Characteristics of Biochar

• From a physical point of view, biochar has a low bulk density due to its porous structure, leading to a high specific surface area and a high water holding capacity.
• From a chemical point of view, the most striking feature of biochar is its poly condensed aromatic structure caused by dehydration during thermochemical conversion, leading to its black colour.
• In addition, basic ash compartments lead to a high pH value.
• Biochar is the pyrolysis product which contains all non-combustible constituents of the feedstock (ash), and therefore is always present as a product of pyrolysis and gasification, regardless of process temperature and feedstock.

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