Remedy in works for straw burning issue

Bengaluru : A joint effort is under way by Indian and US scientists to end the harmful practice of rice and wheat straw burning in Punjab and convert the crop residue into a product of value to benefit the farmers.

Ever since machines replaced manual harvesting in the late 1980s, rice farmers in Punjab and Haryana have been burning the left-over stalks to quickly ready the fields for the next planting.

About 35 million tonnes of rice straw are burned in Punjab and Haryana each season, with Punjab contributing 55 per cent. This extensive crop residue burning – lasting for more than three weeks every year during October and November – has been contributing to atmospheric pollution over the entire Indo-Gangetic plains with implications for global warming and the health of people in the adjacent National Capital Region.

Punjab's farmers, already burdened with burgeoning debts, are now threatened with fines and possibly prison sentences for rice straw burning.
The Indo-US team expects to simultaneously address the farmers' agony and environmentalists' concern by introducing a century-old thermo-chemical process called "torrefaction." This is a low-cost process that turns organic waste into "biochar," a kind of charcoal from biomass. The process requires no external energy and consumes all the smoke-causing emissions from the agricultural residue.

MIT scientists Ahmed Ghoniem, Alexander Slocum, and Kevin Kung have successfully built and validated a laboratory-scale torrefaction reactor and are currently working on scaling it up to a pre-commercial prototype capable of processing 20 kg of biowaste per hour.

Once the prototype is validated at MIT, it will be tested in India using locally available feedstock such as rice straw, Chandra Prakash, a biotechnologist and one of the Indian promoters of this project, told this correspondent in an email.

The joint project, which is supported by the Tata Trusts and the MIT Tata Center for Technology and Design, seeks to specifically design the technology to be deployable in the Indian context.

"This technology therefore has the potential to reduce the contribution of rice straw burning to smog formation in cities, at the same time turning the agricultural waste valuable as a solid fuel (as a charcoal or coal substitute) that can increase farmers' income," Prakash said, adding that the technology would eventually be deployed in Haryana too and would also be employed to check the scourge of farmers in the two states burning the residue of the wheat crop.

Existing technologies to convert agricultural residue into useful products through incinerators, gasifiers, and anaerobic digesters are big-sized, centralised and complex to operate. The MIT prototype, being portable, can be effectively deployed in rural areas where a centralised processing unit is difficult and capital-intensive.

"A mobile torrefaction reactor, similar to a harvester combine, can go from farm to farm rather than farmers carrying their straw to a centralised location," Prakash said.

If all goes as planned, adoption of MIT's innovation in torrefaction to prevent paddy straw residue burning in Punjab will become a reality "hopefully by the next crop season", Prakash said. For the reccord, the Haryana government announced on Thursday it will spend Rs 12 crore for the management of the paddy and wheat crop residue in the state to prevent farmers from burning the stubble.