Aug 8, 2025
15
mins read
Biochar, often called bio charcoal, is a carbon-rich organic material created by heating organic waste (crop residues, wood, manure) in low-oxygen conditions (pyrolysis). This physical and chemical properties of stable charcoal like product - bio char, enhances soil fertility and water retention while locking away carbon dioxide for decades to centuries. Applied to agricultural soils, biochar improves soil structure, nutrient-holding capacity (CEC), and microbial activity, leading to higher crop yields. At the same time, it sequesters carbon, reducing greenhouse gases (CO₂, N₂O, CH₄) in the atmosphere. International bodies like the International Biochar Initiative promote biochar as a win–win solution for waste management, soil health and climate change mitigation.
The Indian carbon market set to be launched in 2026, CO2 removal technologies such as biochar are expected to play a crucial role.
Climate Context: With rising global warming and sustainable agriculture goals, biochar – a carbon-rich charcoal made from biomass – is highlighted as a tool to capture CO₂ and improve degraded soils.
Table of content
Biochar Definition & Origin: Biochar is a carbon-rich, porous charcoal organic material produced by thermochemically converting biomass (agricultural/forestry waste) in the absence of oxygen. It’s essentially charcoal made for soil enrichment.
Production Process: Heating plant biomass (crop stalks, wood chips) at 400–700°C in a sealed kiln (pyrolysis) yields biochar, syngas and bio-oil. The low-oxygen environment prevents complete combustion, preserving carbon in a stable form.
Long-term Carbon Sink: Biochar’s aromatic carbon structure is extremely stable; it resists decomposition, holding carbon dioxide in soils for hundreds to thousands of years. This makes it a long-term carbon sink and a tool for carbon sequestration.
Historical Note: Ancient Amazonians created fertile “Terra Preta” soils by adding charcoal-rich waste. Modern biochar mimics this by enriching soil organic matter and recreating those carbon-rich soils.
IBI Promotion: The International Biochar Initiative (IBI) actively promotes biochar use for climate and soil health, linking waste management with greenhouse gas reduction and sustainable agriculture.
Pyrolysis: The most common method. Biomass is heated in a low-oxygen reactor. Slow pyrolysis (low heat rate, hours to days) maximizes solid char yield and carbon content, producing a high-quality biochar. Fast pyrolysis (quick heat, seconds) yields more bio-oil and syngas, less char.
Key Factors: Pyrolysis temperature and heating rate influence biochar properties. Higher temperatures generally increase carbon content and surface area but reduce yield. Controlling these parameters tailors the biochar (e.g., porosity, pH, nutrient content).
Hydrothermal Carbonization: Converts wet biomass (e.g. food or sewage sludge) into biochar by heating it in water under pressure. This produces a hydrochar (biochar-like solid) without needing dry feedstock, useful for wet waste streams.
Gas and Liquid Co-Products: Pyrolysis also produces syngas (used to heat the process) and bio-oil (potential fuel). Efficient systems use these co-products to power the reactor, improving energy balance and making biochar production more sustainable.
Examples: Farm-scale pyrolysis kilns and industrial reactors exist. Mobile pyrolyzers are being piloted to convert agricultural residues on-site, reducing transport costs of biomass and enabling rural biochar production.
pH and Liming: Many biochars are alkaline (high pH) because minerals remain when organic acid volatiles are driven off. This can neutralize acidic soils, but overapplication can raise pH too much.
Surface Area & Porosity: Biochar’s porous structure and large surface area allow it to adsorb water, nutrients, and organic compounds. This improves soil water retention and provides habitat for soil microbes.
Nutrient Content: Depending on feedstock, biochar may contain nutrients (K, P, Ca, Mg). Wood-based biochars are mostly carbon with fewer nutrients, while crop-residue biochars retain more ash and minerals.
Stability: Biochar is a stable form of carbon (recalcitrant organic matter). Its resistance to microbial decay is what makes it effective for long-term carbon dioxide storage.
Pollutant Adsorption: The same adsorption properties help biochar capture contaminants (heavy metals, pesticides) from soil or water, aiding phytoremediation or wastewater treatment when applied as a filter.
Carbon Sequestration: By converting biomass carbon into stable soil carbon, biochar removes CO₂ from the atmosphere. Applied to fields, it effectively turns agricultural soils into carbon sinks.
Greenhouse Gas Reduction: Biochar-amended soils often emit less N₂O (a potent greenhouse gas) and sometimes less CH₄. This is because biochar improves nitrogen retention and soil aeration.
Fossil Fuel Offset: Biomass used for biochar production diverts waste from burning (which emits CO₂) and instead stores that carbon. Also, energy co-products (bio-oil, syngas) can substitute fossil fuels.
Complementary Strategy: Climate experts recommend biochar as part of a portfolio of carbon-negative technologies (alongside afforestation, BECCS). It’s relatively quick to deploy using existing waste streams and can be scaled with agricultural practices.
Policy Integration: Recognized by climate initiatives, biochar qualifies for carbon credits in some frameworks. Promoting biochar aligns with NDC goals of reducing emissions and enhancing soil carbon stocks.
Biochar in Agriculture:
Soil Amendment: Mixed into farmland soils, biochar improves soil structure (aggregation), increases water retention, and enhances its fertility. Farmers have reported higher yields in maize, rice, wheat and vegetables after biochar application.
Nutrient Management: Biochar reduces nutrient leaching. For example, it can adsorb fertilizers, releasing them slowly and making them available to plants over a longer period. This can lower dependence on synthetic fertilizers and pesticides, supporting sustainable agriculture.
Crop Examples: Studies show yield increases in staples (corn, soybeans, wheat) with biochar in poor soils. In acidic soils, alkaline biochar can also raise pH, benefiting crops that dislike acidity.
Soil Amendment Benefits: Improved aeration and water holding capacity help plants during droughts. Biochar-amended soils also resist erosion better due to stronger structure.
Biochar in Forestry:
Forest Soils: Applying biochar in reforestation or afforestation projects promotes tree growth. It enhances nutrient availability and moisture retention for young saplings.
Wildfire Waste: Charred wood from controlled burns or wildfire salvage can be turned into biochar and returned to forest soils, recycling nutrients and sequestering carbon.
Pest & Disease: Healthier soils make forests more resilient to pests and drought. Biochar use in managed forests is being explored to improve forest ecosystem services.
Biochar in Industry & Construction:
Building Materials: Biochar can be mixed into bricks, concrete, or blocks. It reduces the carbon footprint of construction materials (by replacing cement/aggregates) and permanently stores carbon in buildings.
Carbon Capture: Modified biochar is being tested in filters to adsorb CO₂ from flue gases (though currently less efficient than conventional CCS, it is low-cost and adds to carbon storage).
Energy Storage: Activated biochar (activated carbon) is used in supercapacitors or batteries. While not carbon-negative itself, it’s an industrial use of biomass charcoal.
Biochar for Wastewater Treatment:
Pollutant Removal: Biochar can remove nutrients (nitrogen, phosphorus), heavy metals, and organics from wastewater or run-off. For example, adding biochar to ponds or septic systems can reduce water pollution.
Sludge Composting: Mixing sewage sludge or manure with biochar before composting reduces odors and pathogens, and yields a more nutrient-rich compost.
Biochar in Urban Agriculture & Green Spaces:
Rooftop and Urban Farms: Biochar is used in urban garden soils and planters to improve growth in limited spaces. Its light weight and water-holding ability make it ideal for rooftop gardens and park landscaping.
Green Infrastructure: In bioswales and rain gardens, biochar filters stormwater, trapping pollutants and recharging groundwater. This provides ecosystem services by cleaning urban runoff.
Biochar for Ecosystem Services:
Biodiversity: By creating healthier soils, biochar promotes beneficial soil organisms (earthworms, microbes).
Carbon Sink Restoration: Enriching degraded lands with biochar can help restore soil fertility and function, similar to the Amazon’s terra preta soils that sustained communities for millennia.
India generates over 600 million tonnes of agricultural waste and 60 million tonnes of municipal waste each year, much of which is burned or dumped, contributing to pollution.
By converting just 30–50% of this waste into biochar, India could:
Produce 15–26 million tonnes of biochar
Remove 0.1 gigatonnes of Carbon Dioxide (CO₂) equivalent emissions annually
Biochar production also provides with the following:
Syngas (20–30 million tonnes) which can generate 8–13 TWh of electricity, replacing about 0.5–0.7 million tonnes of coal
Bio-oil (24–40 million tonnes) which can offset 12–19 million tonnes of diesel/kerosene, reducing oil imports and fossil fuel emissions by more than 2%
Enhancing Natural Carbon Sinks
Forests and soils act as natural carbon sinks, absorbing atmospheric CO₂.
Biochar application enhances soil carbon storage, making the sink more effective and long-lasting.
Unlike vegetation, which can burn or decompose, biochar remains stable for centuries, locking carbon dioxide in the soil reducing greenhouse gas emissions.
Biochar's Climate Mitigation Potential
If scaled globally, biochar could offset 2–6% of annual CO₂ emissions, according to current estimates.
Biochar-stabilized soils improve water retention and fertility, building resilience to climate stresses like droughts or floods.
It aligns with India’s NDC goals, complementing other nature-based climate solutions like afforestation and renewable energy.
Supporting Sustainable Development Goals (SDGs)
Healthy soils from biochar support:
SDG 2 (Zero Hunger) through improved crop yields
SDG 6 (Clean Water) by reducing runoff and contamination
SDG 13 (Climate Action) via long-term carbon sequestration
Biochar and Soil Ecosystem Services
Soil is the foundation of ecosystem productivity. Degraded soils reduce food security and carbon sequestration.
Biochar:
Adds stable organic carbon, improving soil aggregation and structure
Enhances microbial activity, aiding nutrient cycling and plant growth
Adsorbs pollutants like heavy metals, aiding soil remediation
Reduces erosion and improves water infiltration
Synergizes with compost and organic manures to promote sustainable farming systems and build long-term soil fertility.
Cost & Infrastructure: Building pyrolysis plants or kilns requires investment. Many farmers lack access to affordable biochar production, making large-scale deployment a challenge.
Feedstock Supply: Sustainable biochar needs waste biomass. Competing demands for crop residues (fodder, fodder, mulching) or deforestation concerns can limit raw materials.
Quality Control: There’s no universal biochar standard. Different feedstocks and conditions yield biochars with variable properties. Without regulation, poor-quality biochar could harm soils (e.g., unbalanced pH or toxic PAHs if not properly produced).
Soil pH and Nutrient Effects: Highly alkaline biochar may not suit all crops. Also, fresh biochar can adsorb nitrogen, temporarily making it less available to plants (“nitrogen drawdown”). Proper composting or nutrient charging of biochar before use is advised.
Over-application Risks: Excess biochar can disrupt soil microbial balance or phosphorus availability. It must be applied at agronomically appropriate rates (typically a few tons per hectare, not tens).
Research Gaps: Long-term field studies are still limited. We need more data on effects in diverse climates/soils to guide practices.
Policy & Awareness: Without subsidies or incentives (e.g., carbon credits), farmers may be reluctant. Awareness of biochar benefits is still low in many regions.
Research & Development: Invest in R&D for low-cost pyrolysis (e.g., solar-powered kilns, biochar from municipal waste) and for tailoring biochars to specific soils/crops.
Standards & Certification: Develop quality standards (carbon dioxide content, stability) so users know what they’re getting. Certification can build trust and markets.
Financial Incentives: Encourage biochar through carbon markets or subsidies. For example, farmers could get carbon credits for sequestration, or biochar production could be part of rural energy schemes.
Integrate with Sustainable Ag: Promote biochar use in organic farming and conservation agriculture. Combine it with cover crops, compost, and agroforestry for maximum soil and climate benefit.
Education & Training: Train extension workers and farmers about how to produce/apply biochar. Demonstration projects can show results on the ground.
Policy Inclusion: Include biochar in national climate action plans (NAPCC), waste management policy, and agricultural extension materials. It can tie into clean energy (syngas/bio-oil use) and afforestation programs.
International Collaboration: Work with global bodies (IBI, UNDP) to share best practices, mobilize funding and technology transfer for biochar projects, especially in developing countries.
Q. What is biochar made from?
A. Biomass waste (crop residues, wood, manure) heated without oxygen (pyrolysis) to produce carbon-rich char.
Q.What is bio charcoal and how is it different from normal charcoal?
A.Bio charcoal (biochar) is used for soil improvement, unlike traditional charcoal, which is mainly used as fuel.
Q. What are Terra Preta soils?
A. Ancient Amazonian “black earths” enriched with charcoal (biochar) and organic waste, are famous for their high fertility.
Q. Does biochar help with greenhouse gases?
A. Yes. Biochar in soil sequesters CO₂ and can reduce N₂O/CH₄ emissions from soils, cutting overall greenhouse gases.
Q. Can biochar improve water retention?
A. Yes. Its porous structure and high surface area allow biochar-amended soil to hold more water, aiding plants during droughts.
Biochar offers a practical approach to mitigate climate change and restore soil health simultaneously. By converting biomass waste into a stable carbon-rich soil amendment, it captures carbon dioxide and enriches the land. This synergy supports multiple Sustainable Development Goals – from climate action to zero hunger and healthy ecosystems. Moving forward, scaling up biochar requires research, standards, and policy support. For more insights on biochar’s role in sustainable agriculture and climate, and related UPSC-focused environment topics, see the Padhai blogs resource. Embracing biochar as part of integrated climate-smart farming can help achieve long-term carbon reduction and fertile soils.
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