Air Pollution | The burning issue of crop residue

The sharp drop in air quality in the Delhi-National Capital Region (NCR) has once again triggered the debate on air pollution. The burning of paddy residue is a significant contributor to the sharp spike in winter air pollution and continues to receive significant attention.

It is important to start the discussion with an acknowledgment of the state and central governments’ ongoing efforts to curb crop burning, and to recognise their impact. These efforts range from imposing a ban on stubble burning, providing subsidies to promote in-situ management (using technologies such as the Happy Seeder), and the use of paddy straw residue in ex-situ applications such as in existing thermal plants and biomass-based power plants.

Active monitoring and real time data on crop residue burning incidents over the past few years indicate that these initiatives do seem to be working. Satellite surveillance by IARI and NASA in 2019 reported a 50 percent reduction in these incidents in Punjab, Haryana, and Uttar Pradesh from 2016 to 2019. The IARI’s real-time monitoring indicates that the numbers of such incidents continue to fall in 2020, at least in Haryana and UP. However, as the recent surge in cumulative crop burning events in Punjab shows, challenges remain.

The complexity of managing paddy residue encompasses its collection, processing, storage, and transportation to the point of ultimate utilisation. The dispersed and voluminous nature of this resource means that transportation costs can become prohibitively high if processing and utilisation involves covering long distances. The paucity of time before planting the Rabi crop also means that there is a very short window available for residue collection, further adding to logistics costs and operational challenges.

A possible solution to this annual problem can be through creation of monetary value for straw. The ability to realise gains from products which would otherwise go up in smoke would incentivise farmers to put in the additional cost and effort required to remove paddy residue through specialised machines (such as balers), and selling it ahead instead of burning it. Creating a market for products from this straw would also incentivise local entrepreneurs to step in.

However, no single solution is likely to provide a complete answer.

For example, the NTPC’s usage of pellets made from crop waste as a partial replacement for coal in its thermal power plants has justifiably generated a lot of enthusiasm. However, the widespread distribution of thermal power plants across the country may pose a challenge. If the power plants closer to the sites of paddy cultivation cannot absorb all the biomass pellets generated, the pellets would need to be transported over longer distances, adding significantly to overall costs.

The first part of the answer, then, lies in developing markets for multiple, alternative uses of paddy straw, which would help sustainably absorb larger proportions of crop waste. Support for a diverse range of solutions would also help regions adopt options better suited to them.

Brick kilns, for example, could be another potential source for demand for straw pellets. Typically small and scattered, brick kilns are mostly in the same areas as paddy fields. Already cheaper than coal or firewood, increased ease of access and availability could spur the adoption of biomass pellets. Paper, board, disposable packaging, and tableware manufacturers could also absorb paddy straw, creating additional demand.

However, developing a market for the residue would help solve only part of the problem. It would not provide a holistic solution to the problems caused by excessive paddy cultivation. Excessive dependence on the highly water intensive crop has had a ruinous impact on the water table.

In Punjab, for example, the water table is over-exploited in over 80 percent of the land area. However, the lack of reliable power and decentralised cold storage has been a substantial barrier for farmers to break out of the rice-wheat production cycle and growing high-value but perishable crops such as fruits and vegetables.

Using paddy straw pellets to power local biomass gasification plants could be one way of supporting the transition. For example, a 250 kWe capacity biomass gasifier plant, which can utilise about 2,000 tonnes of paddy straw annually, can support a 50-tonnage refrigeration facility, besides producing electricity. The unburnt residue generated from gasification can also be used in form of bio-char and ash, acting as soil conditioner and helping maintain micro-nutrients in it.

Facilitating greater food processing and cooling infrastructure at the village level would help farmers shift to other crops. This would further reduce the demand intensity of crop waste processing machines in the short term and improve both soil health and the water table in the long term.

 Sunil Dhingra is a Senior Fellow, and TCA Avni is a research associate, at The Energy and Resources Institute, New Delhi. Views are personal.