UAS-B introduces a low-cost biochar production technology and trains farmers to improve soil health

Researchers from the University of Agricultural Sciences – Bangalore (UAS-B) are training 10 farmers from each in 10 districts across Karnataka to produce their own biochar using crop residues left in their fields and materials provided by the university.

Biochar is a lightweight, highly porous substance similar to charcoal that is produced by heating organic biomass (such as agricultural waste or wood) in a low-oxygen environment, a process called pyrolysis.

Krishna Murthy and his team at the Institute of Agricultural Science and Chemistry, UAS-B, used a simple and portable drum technology that does not cost much to produce biochar.

Mr. Murthy explained, “We came up with this idea keeping small and marginal farmers in mind. According to our idea, biochar can be produced using low-cost technology. We used a 200 liter portable drum with small holes drilled in it and a pipe attached to it that acts as a chimney. Farmers can dump crop residues instead of burning them in their fields.”

These plant residues can be generated from coconut shells, sunflower heads, mulberry cuttings, among others.

He added, “We have identified 10 farmers in the districts of Chitradurga, Tumakuru, Bengaluru Rural, Kolar, Chickballapur, Ramanagara, Mandya, Mysuru, Chamarajanagar and Hassan in Rashtriya Krishi Vikas Yojana (RKVY) districts funded by the Union government. We are providing them free cost of production and drums in their fields. The farmers have been identified by Krishi Vigyan Kendra established in each of these areas.”

RKVY is the flagship of a central scheme launched in 2007 to promote holistic development in agriculture and allied sectors.

Biochar production method

Farmers can use any type of crop residue left on their farms and fill the drum with it. Once the drum is filled, a fire is lit using dry grass or leaves and the lid is closed to restrict air entry. Air enters only through the holes. Due to limited oxygen, it burns and turns into biochar in two to three hours, Mr. Murthy said.

“This biochar also looks like coal, but it’s not the same. In normal coal, the carbon content is lost, while in biochar, the organic carbon content is preserved through the process of pyrolysis. Where open combustion releases almost all of the residual carbon as CO₂ within minutes, pyrolysis locks 50% to 80% of that carbon back into a recalcitrant form that resists organic carbon decomposition for decades. Intensive cultivation of crops has become exhausted over the years. We tried the same in our university and got positive results in increasing soil fertility, so we decided to introduce it to the farmers,” he said.

Benefits for farmers using biochar

He also pointed out that field trials indicate that biochar can improve crop productivity by 10% to 30% and water holding capacity by 10% to 25%, with the greatest gains on low SOC soils – precisely the most affected areas of Karnataka.

According to researchers in the Department of Science and Agricultural Chemistry, soil organic carbon (SOC) is the most reliable indicator of long-term soil health, controlling water retention, nutrient cycling and microbial activity. However, the soil organic carbon content of the Karnataka record has deteriorated sharply. The Bhoochetana initiative launched by the state government in 2009 found 52% of sampled fields to be SOC deficient, and a 2017-2024 analysis by the Department of Agriculture confirmed that more than half of the state’s farmland now falls below the critical 0.5% threshold.

Kolar district is the most severely affected, with more than 94% of its agricultural land falling into the low SOC category. The black soil tracts of North Karnataka – Belagavi, Vijayapura, Kalaburagi, Bidar, Yadgir and Bagalkot – are similarly depleted in continuous cotton and oilseed cultivation. Coastal areas maintain a relatively healthier SOC, aided by silt deposition and traditional mulching.

Dr. Murthy said the causes are interlinked mainly with disproportionate reliance on chemical fertilizers (Karnataka’s consumption exceeded 45 thousand tonnes in 2020-22), declining consumption of farmyard manure due to cost differentials (₹14,000/acre for manure vs. ₹3,000 for nitrate and nitrogen fertilizer equivalent (1.48 million in 2007 to 1.14 million in 2019), continuous mono-cropping and routine open burning of crop residues that destroy the very biomass and carbon soils need most.

Published – 21 Jul 2026 01:01 IST