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Scientists have found a potent method to convert rice straw biomass into bio-coal

Updated: Feb 13, 2020

Farmers from paddy growing states like Haryana, Punjab, Uttar Pradesh, Uttarakhand are burning rice straw in the fields. This is the cheaper way for them to make the field ready for the next crop. Rice straw burning in agricultural land has arisen as a new problem that imposes a highly negative impact on the environment and people’s health as well. Scientists from the Council of Scientific and Industrial Research-National Physical Laboratory (NPL), Delhi, have converted rice straw to a useful product, i.e., bio-coal, to solve the problems arising due to its burning. It is reported that “Among the different countries, Asian countries

It is reported that “Among the different countries, Asian countries produce 667 million tonnes of rice straw and India alone produces ~ 140 million tonnes annually”. In India, some of the rice straw is used as animal feed, fuel, packing material, and roofing- material while the remaining is disposed of by burning in the fields to make fields ready for sowing the next crop. Burning rice straw is an easy and cheaper way for its disposal. Ash produced from its burning is used by farmers as soil fertilizers.

Researchers say that “Ash has a low concentration of nitrogen and phosphorus along with the occasional presence of some heavy metals which harm the soil and therefore reduces crop productivity.” Burning of rice straw also produces significant visible smoke covering a larger area and hence affecting major populace with health risks like asthma, bronchitis, lung disease.

To overcome these problems and to make rice straw as an acceptable alternate energy source, scientists have converted its biomass to bio-coal using the torrefaction process. Torrefaction is a thermal process (temperature ranges from 2000°C to 3500°C) that converts biomass into a coal-like material known as bio-coal by changing the physical and chemical structure of rice straw. The biomass of rice straw is mainly composed of cellulose, hemicellulose, and lignin. These organic molecules stored their solar energy in chemical bonds of carbon, hydrogen, and oxygen. When these bonds are broken, energy is released. This is recognized as a renewable source for energy production. This torrefaction process has more advantages over other processes in terms of cost-effectiveness, high gross calorific value, and additional shelf-life of biomass.

This study reports that “In India, the majority of the thermal power plants utilize coal as a fuel for power generation. In 2017-18, 200 GW power was generated by using coal, which is around 57% of the total power generated by thermal power plants.” The co-firing of coal in thermal power plants may reduce the depletion of fossil fuels, environmental pollution, and hence people-health issues too. If farmers would get a monetary incentive for this crop stubble, the rice straw burning can be stopped in crop fields and hence can be a source for alternate energy. This study is reported in “Current Science, March 2019.”

-Written by Pragya Mishra

Pune, Dec 2019

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