Biochar could help reduce pollution

Biochar, the other so far neglected product of rice-straw gasification, holds the key not only to reducing air pollution but also to rejuvenating agriculture and boosting rural employment.

While the carbon content of fresh rice straw is a shade below half, it rises to 70-80% in biochar It contains no sulphur or phosphorus and can thus be briquetted and sold as a substitute for metallurgical, i.e coking, coal to steel plants. Coking coal is important to reduce iron ore into pig iron in blast furnaces. It has no substitutes and the world is running out of it. India uses about 90 million tonnes a year, of which half is imported for over $4 billion a year. Most of the remainder is obtained by washing thermal grade coal to remove sulphur, phosphorus and other inorganic materials to raise its carbon content.

The ability of biochar to replace coking coal was described in detail at a BioCleanTechForum conference held earlier this month in Ottawa.

But biochar can yield a second, more valuable product. If it is pelletised and gasified a second time in high temperature, oxygen-blown gasifiers, it yields a mixture of carbon monoxide and hydrogen called synthesis gas. Since the Second World War, synthesis gas has been used to synthesise transport fuels.

For example, a plant in Wuhan, China, has been using plasma gasification to produce aviation transport fuel from 40,000 tonnes of urban solid waste and agricultural residues a year for the last five years. A similar but larger plant to convert 200,000 tonnes of raw urban waste into 42 million litres of aviation turbine fuel is under construction outside Reno, Nevada. This plant will start production in 2020. So by the time the technology comes to India, it will have been fully proven for urban solid waste.

However, biochar is easier and cheaper to gasify than municipal solid waste because it has uniform composition, a stable moisture content and contains far more carbon. So there should be few, if any, teething troubles to install the technology in Punjab.

Implications for Punjab and India

This technology could have a stunning impact on the futures of Punjab and India both.

Punjab has 12,541 villages, of which more than 12,000 grow both wheat and rice. Of late, the state has been producing up to 18 million tonnes of rice and close to 20 million tonnes of wheat a year. With this has come ~23 million tonnes of paddy straw and 25 million tonnes of wheat straw. Paddy straw has limited use in Punjab but wheat straw used to be fed to cattle as an inferior variety of fodder in the pre-Green Revolution era. Punjab has since graduated from ploughs and bullock carts to tractors and combined harvesters. So this straw is also available for gasification now. The two crops together can keep a 10-tonne-a-day gasifier and an accompanying briquetting plant working in every village for 300+ days a year.

One can conservatively estimate they will generate 250,000 direct jobs and perhaps half as many indirect jobs in aggregation, collection transportation and allied services, in the state. But that would only be the beginning. If only three-quarters of the straw generated in the state was gasified, it could yield up to 10 million tonnes of biochar briquettes.

In November 2017, coking coal sold for Rs 23,000 per tonne in India. Last week, its price was Rs 27,000. Were the farmers to get only Rs 10,000 per tonne out of this for the sale of biochar briquettes at their doorstep, it would add Rs 10,000 crore to rural incomes in Punjab. When this is spent, it will – conservatively, again – create close to another million jobs in construction, trade, transport, hotels, restaurants, travel and financial services.

India produces 178 million tonnes of surplus crop residues every year. Three quarters of this would generate close to 60 million tonnes of biochar for use as coking coal, and save India $5-6 billion in foreign exchange.

But if the same biochar is turned into synthesis gas, it can be catalytically converted into 51.35 billion litres of gasoline, diesel and aviation turbine fuels. This is over a fifth of the transport fuel that India consumes. Therefore, it could save close to $50 billion India spends every year on importing oil, and free the country from the foreign exchange constraint on its economic growth.

Best of all, we will still have only scratched the surface of the potential for agricultural and rural growth locked in this technology even after doing this. Just over the horizon is the sugarcane industry. It can producing another 250 billion litres of diesel, methanol gasoline and/or aviation turbine fuel from the 400+ million tonnes of sugarcane crop wastes, bagasse and press mud that it generates every year. This could suffice to turn India into a net-exporter of carbon-neutral transport fuels.

If Punjab, which produces a sixth of the country’s wheat and rice, can create 1.5 million additional jobs at a minimum in its villages, think of what the rest of India can add with rice, paddy, coarse cereals, maize and sugarcane waste. more