Solution to stubble and straw burning

The only way to avoid burning straw and stubble is to find another use for the crop residue. Fortunately, there is a way. This is to not burn the straw and stubble but gasify it in a two-stage process that yields a fuel gas that can meet cooking, heating and power generation needs in the village in the first stage, and any type of transport fuel – diesel, aviation turbine fuel, methanol or CNG – in the second.

Gasification is the incomplete burning of biomass or coal in a limited supply of air or oxygen. While full combustion yields only large amounts of carbon dioxide, gasification yields a substantial amount of hydrogen, carbon monoxide and methane.

Two other chemical processes, called the Fischer-Tropsch synthesis and the water-gas shift reaction, which have been in use for more than a hundred years in the petro-chemicals industry, can convert this mixture into any type of transport fuel one desires, from CNG to diesel, methanol and aviation jet fuel. They can also produce dimethyl ether, which is a heavy condensate gas that can effortlessly replace LPG as a cooking gas.

The technology chain described above has been perfected to the point where it is now possible to convert any form of biomass – from urban solid waste to crop residues – into transport fuels. In 2011, British Airways signed an 11 year purchase agreement with a US-based company, Solena fuels, to set up a plant outside London that would convert 575,000 tonnes of London’s municipal solid waste into aviation turbine fuel every year.

Three other airlines signed memoranda of agreement with the company to do the same. But those, and several other projects that were in the pipeline in Europe, went into cold storage in 2014 when oil prices crashed for the third time since 1985, making future fuel prices uncertain. However, earlier this year, a Texas-based company S.G Preston signed an agreement to provide Quantas with 800 million gallons of Aviation turbine fuel a year, obtained from biomass.

Benefits beyond combatting pollution

In India, the large-scale induction of this technology can not only end the annual invasion of smog, but greatly increase farm incomes and save the country valuable foreign exchange. It can therefore solve a multiplicity of problems: give urban solid waste a value and get it off the streets; stop the burning of straw and stubble; and give the farmers a valuable ‘lean’ gas to use for cooking and generating electricity locally and provide them with biochar, a solid, carbon-rich residue that they can briquette and sell to large scale modern bio-fuel plants of the kind that are being planned for Europe and the US.

Biochar is 70-80% pure carbon, and contains no sulphur, so it is similar to superior varieties of imported coal, and will fetch a similar price. At present, India is importing coking coal for blast furnaces at Rs 22,300 per tonne, if farmers can get half that price for their biochar from bio-fuels plants, they will add Rs 20,000 to the Rs 70,000 that they gross from every hectare of land under paddy.

Finally, it will save foreign exchange. Punjab, Haryana and western UP produce close 45 million tonnes of rice straw and stubble. This is sufficient to produce between 15 and 20 million tonnes of transport fuels. The reduced dependence upon oil imports will convert India’s 1.5% balance of payments deficit into a comfortable surplus.

These are not over-the-horizon technologies of the kind that are continuously being proposed by high-tech global corporates abroad to their own and developing country governments, but tried and tested ones, with some of which Indian industry is already familiar, that need only a stable transport fuel pricing environment to take off. India could, for just this once, be a pioneer in providing an enabling price and marketing environment instead of the eternal laggard that it is today. more