Dealing with crop residue burning

Severe pollution in Delhi and other parts of north-west India during October and November has become a regular phenomenon for some years now. Though several factors contribute to this crisis, the burning of residues of paddy crop in the neighbouring states is held responsible for driving pollution to such dangerously high levels. In order to find a durable solution for this recurring problem it is important to look at the genesis of paddy stubble burning and explore options to turn farmers away from such unhealthy practices.

Traditionally, crop residue (stalks, straw and stubble) was used as fodder for livestock or as a fuel. A small amount was converted into compost. Over time, the supply of crop residue has far exceeded the demand mainly because of its substitution by other sources. Green fodder is replacing dry fodder and the use of crop residue as fuel is replaced by LPG and other sources with high calorific value and less smoke. Because of the fall in demand and the increase in supply, the market for the residue of most crops has collapsed. The residue of paddy in north-west India has an added problem. Dry straw of non-basmati paddy is poor quality fodder compared with wheat straw. Farmers are left with no choice but to either incorporate it in the soil or destroy it by burning. Consequently, crop residue burning has become widespread and practiced throughout the country. It is felt more seriously in Delhi and the surrounding areas where its concentration is very high and where air quality is already poor.  

It is common to find farmers in Haryana and Punjab even burning the residue of wheat in their fields, harvested with combine harvester in the months of April and May. However, the damage from the burning of wheat straw is not felt much because of its low incidence and because of the hot weather and windy conditions prevailing during that time that helps dissipates smoke quickly. But putting one acre of wheat straw on fire is no less damaging for the atmosphere than burning one acre of paddy. It is sad that the growing tendency towards crop residue burning has not been taken seriously. It is going to assume catastrophic proportions throughout the country in the coming years if effective measures are not taken soon.

Turn to paddy. Till a few years back most of the crop was harvested manually and a small area was harvested using combine harvester. In manual harvesting, the paddy plant is cut at 6-10 cm above the ground. This leaves a very small stubble after harvest, which is easily incorporated into the soil through ploughing by disc-plough or by using the rotavator. Paddy crop was then manually thrashed and straws were kept in one corner of the field where they decomposed over time and then got mixed up with the soil.

Most farmers settle for the easy and almost zero-cost option — of putting the straw on fire to reduce it to ashes. This takes little time, involves no cost for the farmer but is environmentally hazardous
At present, due to a shortage of manual labour and for quick completion of harvest operations, about 94 per cent of the area in Punjab is harvested through combine harvester. This machine picks about 20 cm from the top of the plant consisting of the pinnacle and spikes and leaves the rest of the plant (straw and stubble) as it is. The straw left in the field comes in the way of field preparation for the next crop. Wheat is sown after a short span of four to six weeks after the harvest of paddy, but late sowing varieties can be sown till the fourth week of December but the yield is lower. This raises a serious problem — that of clearing the field of straw and stubble and preparing fine soil for the next crop within a tight schedule. Most farmers settle for the easy and almost zero-cost option — of putting the straw on fire to reduce it to ashes. This takes little time, involves no cost for the farmer but is environmentally hazardous.

The problem is much more severe in Punjab where 75 per cent of the net sown area in kharif is under paddy and about 78 per cent of paddy biomass is disposed through burning. This amounts to burning about 20 million tonne of biomass which has high moisture and low combustibility.

Some farmers, who realise the harm to ecology and environment and to human health, go for incorporating crop residue into the soil. This requires chopping and shredding of the crop residue into small pieces and ploughing them back into the soil. This practice improves soil fertility, but as crop residue gets decomposed, it releases methane into the environment, though at a very slow rate. This method involves some cost as the farmer has to use some sort of a straw management system to plough small pieces of straw back into the soil. Machines like straw choppers, straw shredders, mulchers, new seeder and happy seeder are available, which help incorporate crop residue into the field. This process involves an investment — of about Rs 3,000 per acre as machinery charges. A sizeable part of this cost is supposed to be included in the cost of cultivation of the next crop, as preparatory tillage, and thus factored into the MSP of the next crop.

The central government has given huge subsidies for machinery to be used for straw management and or the incorporation of straw back into the soil. However, its adoption has remained slow because of the cost involved, the restriction of subsidy to selected manufacturers, and the lazy option available for destroying the biomass through fire.

There is a pressing need to find a long-term solution to paddy straw burning in north west India as well as to address the potential problem of crop residue burning in other parts of the country. There are three options to check paddy straw burning and all three must be used. The best option seems to be the production of bio-CNG from crop residue. The process involves anaerobic digestion in completely sealed digesters where only biogas is taken away from crop biomass, involving almost zero emission. The rest of the biomass is turned into manure suitable for use in soils. Discussion with experts working in the field reveals that the use of rice straw for CNG is economical and financially viable. This process is also environment friendly as it does not result in the slow release of GHG from decomposition of biomass incorporated into soil using any of the straw management systems or with the happy seeder. Such investments should be considered eligible for loans at concessional rates of interest as green projects.

The Ministry of Petroleum and Natural Gas and the government of Punjab had announced plans for setting up bio-CNG plants but they have not seen much progress except for the setting up of two plants -- one coming up in Sangrur district of Punjab with German investment and another coming up in Karnal in Haryana. The centre and the states should facilitate setting up bio-CNG plants and provide quick credit at concessional rates to the parties interested in setting up the Bio CNG plants.  

The second option is briquetting of loose biomass into compact, high density, easy to transport material that can be used for energy generation in place of coal in thermal plants or as a fuel in industry. Both the bio- CNG and briquetting options can work well in areas with intensive cultivation of paddy that generate large biomass from small, contiguous areas.

The third option is to decompose biomass in a short period and plough it back into the soil. Scientists in ICAR, Indian Agricultural Research Institute, New Delhi, have developed a microbial formulation (consortia of 4 fungi) which decomposes paddy biomass in 20-25 days. They are now working on standardising the technology for mass application in the fields. Hopefully, this technology will be ready for adoption in farms in a year or so.

These options can convert waste into wealth and can effectively check the serious problem of rampant burning of paddy biomass and the prospect of crop biomass burning spreading through the country.

During the last three decades our crop patterns have been seriously distorted through an output price policy and the input subsidies. Today we are producing 10 per cent more rice than there is demand. The reason is policy bias towards rice. This is destroying groundwater, damaging environment, and putting severe burden on fiscal resources. We must reform our policies to incentivise a shift away from paddy particularly in Punjab and Haryana. Stopping free power for irrigation and the transfer of the same subsidy to farmers in other forms alone will make a significant difference and dilute the concentration of paddy and the problems associated with it.

The author is member, NITI Aayog. Views are personal

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