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Biochar: Valuable Soil Amendment

This 2,000 year-old practice converts agricultural waste into a soil enhancer that can hold carbon, boost food security, and increase soil biodiversity, and discourage deforestation. The process creates a fine-grained, highly porous charcoal that helps soils retain nutrients and water.

Biochar is found in soils around the world as a result of vegetation fires and historic soil management practices. Intensive study of biochar-rich dark earths in the Amazon (terra preta), has led to a wider appreciation of biochar’s unique properties as a soil enhancer.

What is Biochar?

Biochar is made from biomass via pyrolysis. Biochar is the carbon-rich product when biomass, such as wood, manure or leaves, is heated in a closed container with little or no available air. In other words, biochar is produced by so-called thermal decomposition of organic material with limited supply of oxygen, and at relatively low temperatures (around 550oC). This process often mirrors the production of charcol.

However, biochar can be distinguished from charcoal and similar materials in that it is produced with the intent it be applied to soil as a means of improving soil productivity, carbon (C) storage and possibly filtration of percolating soil water (to try and cut pollution of surface and groundwater bodies). The production process and the intended use, forms the basis for distinguishing biochar. Biochar is the appropriate term where charred organic matter is applied to soil in a deliberate manner, with the intent to improve soil properties. This distinguishes biochar from charcoal that is used as fuel for heat, as a filter, as a reductant in iron making or as a colouring agent in industry or art . Biochar is very variable in quality, depending on raw material, pyrolysis conditions, whether it is enriched with other compounds and how finely it is ground.

Physico chemical properties of Biochar:

Biochar Powerful Tool to Combat Climate Change:

The carbon in biochar resists degradation and can hold carbon in soils for hundreds to thousands of years. Biochar is produced through pyrolysis or gasification — processes that heat biomass in the absence (or under reduction) of oxygen.

In addition to creating a soil enhancer, sustainable biochar practices can produce oil and gas byproducts that can be used as fuel, providing clean, renewable energy. When the biochar is buried in the ground as a soil enhancer, the system can become “carbon negative.”

Biochar and bioenergy co-production can help combat global climate change by displacing fossil fuel use and by sequestering carbon instable soil carbon pools. It may also reduce emissions of nitrous oxide.

We can use this simple and powerful, technology to reduce carbon emissions.

Benefits of biochar amendments on soil

Benefits of biochar:

  • Store recalcitrant form of carbon in soil.

  • Enhance plant growth. Raise and sustain crop yields. Help improve good and problematic nutrient-poor soils, including acidic tropical humid and drier environment soils.

  • Help compensate for greenhouse gas emissions associated with agricultural development.

  • Biochar may improve soil moisture retention, increasing agricultural resilience and provides support to intensive sustainable agriculture which could help to cut pressure for new forest clearances and enhances biodiversity conservation benefits.

  • Enable production of useful materials from uncropped land making use of unused wastes with increased adaptability to environmental change by making production more resilient.

  • Reduce the need for fertiliser/manure/compost. Reduce costs of sewage and animal waste treatment and cut emissions that they would otherwise cause if held in lagoons or heaps.

  • Offer a more environmentally-friendly way of processing plastics and refuse if biochar is too contaminated for agricultural use for growing non-food crops or send to landfill to sequester carbon.

  • Nutrient affinity i.e. retention of plant nutrients, notably retention of N on permeable soils under rainy conditions is found higher with biochar application. Biochar may play role in bioremediation by binding agrochemicals and help reduce phosphate and nitrate and agrochemicals pollution of streams and groundwater. Thus helping resolve major problems hindering sustained and improved agriculture. Reduce plant uptake of pesticides from contaminated soils

  • Reduce soil acidity/raise pH. Reduce aluminium toxicity and increases cation exchange capacity .

Effect of biochar on different soil properties

soil properties

Findings

Cation exchange capacity

50% increase

Fertilizer use efficiency

10-30 % increase

Liming agent

1 unit pH increase

Crop productivity

20-120% increase

Biological nitrogen fixation

50-72% increase

Soil moisture retention

Up to 18 % increase

Mycorrhizal fungi

40 % increase

Bulk density

Soil dependent

Methane emission

100% decrease

Nitrous oxide emissions

50 % decrease

 

  • By improving moisture retention biochar may reduce the demand for irrigation and make cropping more secure.

  • Support biofuel production and reduce its carbon footprint and even enable it to move toward being carbon neutral.

  • Increase soil microbial biomass and support other beneficial organism like earthworms.Support nitrogen fixation. Increase arbuscular mycorrhizal fungi in soil.

  • Opportunities for poor to benefit from carbon offset market and also reduce dependency of farmers on input suppliers.

  • Periurban/urban agriculture: biochar may be a useful input to counter harmful compounds like heavy metals, dioxins, PAHs (polycyclic aromatic hydrocarbons) present in sewage or refuse inputs.

Limitation:

Biochar has an inhibitory effect on soil aging and intermittent addition of fresh biomass might be required for optimal nutrient cycling and soil-water environment in a soil.

Authors:

Priyanka Rani, Sumit Rai 

Address Banaras Hindu university Varanasi , Veer kunwar Singh college of agriculture, Dumraon
G.B.Pant national institute of Himalayan environment and sustainable development.

Corresponding author: sumitssac101@gmail.com


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