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Green Tech Corner

Biochar—Mitigation for Climate Change

Biochar as its name suggest is a charcoal created by carrying out pyrolysis of biomass.

When biomass undergoes natural decomposition or burned in presence of oxygen same as conventional coal it adds large amount of CO2 to the atmosphere. However Biochar is stable, fixed and recalcitrant carbon which resists degradation and can hold carbon in soil for hundreds to thousands of years. This Carbon negative technology of Biochar can help in a net withdrawal of CO2 from the atmosphere, while producing and consuming energy.

How it is made?

The basic principle in Biochar preparation is pyrolysis that is heating of biomass in absence of oxygen. Three techniques of pyrolysis are used viz. slow pyrolysis, fast pyrolysis and hydrothermal carbonization.

Process: Biomass such as woodchips, corn husk, peanut shell, chicken manure etc. is put into an octagonal shaped metal barrel. It’s then heated at 1000⁰F in absence of oxygen. After a few hours, the organic waste is transformed into charcoal like pellets

Mitigation for Climate Change:

Soil Fertilizer:

Biochar can be used as soil amendments. As per studies, after application of Biochar crop yield increases by 20-400% Following benefits and changes are observed in soil quality due to Biochar addition:
  • It enhances microbial growth and activity.
  • Biochar alters soil texture and structure of soil as well as increases water retention capacity of soil
  • It reduces nutrient leaching
  • Increases pH of acidic soils
  • Reduces need of chemical fertilizer

Waste to Energy:

It can play key role in waste management as it is recycled product of organic waste. It minimizes CO2 and methane gas emissions

After pyrolysis, Up to 50% (by weight) of the original biomass is converted in to Biochar while the remaining is converted in to by-products like syngas and bio oil. The heat generated during pyrolysis and byproducts can be sued as sources of energy and fuel.

Carbon Sequestration and Climate Change Tool:

Natural degradation of biomass takes several years along with emission of greenhouse gases. Soil amended with Biochar acts as better carbon sink. Stabilization property of Biochar reduces emission of nitrous oxide (N2O) and methane (CH4)—two potent greenhouse gases—from agricultural soils.

Fossil fuels are carbon positive hence exacerbate global warming. Conventional biomass fuels are carbon neutral; captured carbon in the biomass returns to atmosphere via photosynthesis. Carbon in Biochar can persist in soils over long time scales. If we consider recalcitrant property of Biochar and if it is used worldwide, CO2 levels could drop 8 parts per million within 50 years

Biochar in India:

Approximately 500-550 Mt of crop residues are produced per year in India. Most of wastes are either locally burned or end up in landfills where most of the time it’s again subjected to open fires about.

As per ministry of new and renewable energy, Govt. of India surplus biomass available in country is 120-150 million metric tons/annum. Alone north east region of India potentially produces 37 million tons of agricultural waste biomass. If only one percent of this is converted to Biochar, about 74 thousand tons of carbon can be sequestered annually. Out of this, if 1% of the process of producing Biochar is carried out through modern equipment, about 1300 and 900 tons of bio-oil and biogas can be produced, respectively which is equivalent to 31 terra joule of energy.

Being an agricultural country and considering above statistic; Biochar could be a good option for waste management, sustainable fuel, carbon sequestration and organic fertilizer.

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Viewer: |   Last Updated: 21-05-2018 - May