The past one month has witnessed a rapid deterioration in Delhi's air quality and people who have lived in Delhi all their lives have complained that they've never been subjected to such terrible air in the city in decades.
The major reason seems to be vehicular pollution along with the burning of agricultural residues on farms in nearby states. The problem has been exacerbated by the arrival of dust- laden air from Middle East and Afghanistan which created a temperature inversion (the cold air is on the top while hot air is near the ground). This did not allow the smog and dust to disperse into higher atmosphere, thereby creating death chamber like conditions on the ground.
The dust storms and other atmospheric phenomena have existed for millions of years but the manmade practices of stubble burning and vehicular pollution are primarily responsible for Delhi's worsening air quality.
If there's adequate political and administrative will, there are various initiatives that can be undertaken to at least minimise the scourge of pollution in the city.
Power from agricultural residues
India produces anything between 600-800 million tons of agricultural residue per year. After harvesting of crops, whatever is left behind on the farm land is considered to be residue. Most farmers in India want their land to ready for the next crop and the easiest way to get rid of the leftover is to burn them. As a result, they end up polluting the environment.
In early 1990s, our NGO, Nimbkar Agricultural Research Institute (NARI), had pioneered the concept of using these residues for power generation. Our survey showed that every taluka had enough agricultural residue to meet all the electricity needs of that taluka. This work led to a national policy on taluka energy self-sufficiency in 1996 which was managed by MNRE.
Thus 600-800 million tons/year of agricultural residues can theoretically produce about 80,000 MW of electricity. Besides producing power, the selling of residues to power plants can provide extra income to the farmers. Presently farmers do not make any money from the residues. For country as a whole, this extra income for farmers can amount to about Rs. 3 lakh crores and can create substantial wealth in rural areas.
For country as a whole, this extra income for farmers can amount to about Rs. 3 lakh crores and can create substantial wealth in rural areas.
In 1995 NARI also developed the world's first loose biomass gasifier running on agricultural residue like sugarcane trash, wheat straw and those from other crops. The gas from 500 kW (thermal) gasifier was shown to be useful for producing excellent heat for community kitchens. The gasification process produces syngas (mixture of carbon monoxide and hydrogen) which could be used for producing methanol – a useful liquid fuel for transportation.
Similarly pyrolysis (one step before gasification) of agricultural residues could easily produce pyrolysis oil which is a medium calorific value (CV) fuel with CV of 17 MJ/Kg or nearly 1/3rd that of diesel. This oil can be used as a cooking fuel in suitably designed cookstoves. Thus both gasification and pyrolysis oil production can supply clean energy for cooking.
All these technologies show that agricultural residues could easily be converted into useful products (electricity and liquid fuels) and in the process reduce air pollution
No-till agriculture and perennial crops
However, to improve the quality of the soil so that agricultural productivity increases, it is necessary that most of these residues be ploughed back into the field. No-till agriculture (NTA) allows the incorporation of these residues into the soil while minimally disturbing it.
For planting crops holes are drilled into the soil in which seed can be planted and then covered up. This is done by specially designed planters. This way the soil surface remains undisturbed along with the residues from the previous crop.
NTA not only improves the soil but soil erosion is reduced drastically. Since the stubble is not burned, NTA is also one of the best mechanism to reduce air pollution.
No-till agriculture is practiced extensively in other countries with total area of about 160 million ha planted every year. Latin America, North America and Australia/New Zealand have successfully implemented this practice.
Since the stubble is not burned, NTA is also one of the best mechanism to reduce air pollution.
Around 11% of the world's total cropland is under NTA. In India, farmers have started embracing NTA over the last 6-7 years and that too is restricted mostly to about1.5 million hectares in north India. The reasons for such low level penetration of the practice are non-availability of economically priced planters, not enough publicity regarding its advantages and non-availability of low cost weedicides.
There are major industrial players producing agricultural machinery in India but somehow no-till machinery doesn't feature in their scheme of things. The government can ecourage NTA by providing economic incentives to both farmers and agricultural machinery makers.
Another method to reduce production of agricultural residues is to have perennial crops. It is like growing wheat, rice and oilseed crops on trees! Year after year the fruit (grains and oilseeds) can be harvested while the root structure (stubble) keeps on re-sprouting. This drastically reduces the energy in growing and harvesting crops and hence increases the remuneration to farmers. Extensive work is being done in U.S. on perennial crops and there are good indications that in near future, perennial wheat, sorghum and oilseed crops like sunflower, canola etc. can be developed.
In India there is a need to set up a national technology mission for perennial crops so that extensive R&D can be done on them.
One of the major causes of air pollution in cities is vehicular traffic. With increase in diesel vehicles in India this pollution has increased manifold. No matter how good the engine is, the stop-start and traffic jam conditions on Indian roads makes it run very inefficiently and hence produces increased pollution.
One of the best solutions for city air pollution is to have mobility based on electric vehicles. Electric cars and buses are becoming very common in Western countries. In fact, all major car companies of the world have electric cars in pipeline.
Tremendous achievements in battery technologies, motors and controllers have made electric vehicles comparable in range and power to fossil fueled vehicles. In India we need to introduce electric vehicles, specially electric motor cycles in a big way.
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