Flyash Pesticide

Flyash, the notorious waste product of coal-based thermal power plants, known for its ill effects on agricultural land, may now come as an aid for the farming community.

Scientists of Annamalai University, Tamil Nadu, have developed flyash-based herbal pesticide with turmeric, neem, eucalyptus, pepper and chilli dust and found them effective against several pests of rice and vegetables.

"We have found that flyash-from both coal and lignite-acts as a good carrier for herbal pesticides. We combined it with turmeric, neem seed kernel, eucalyptus, tulsi, chilli and seeds of pepper to make eight flyash-based pesticides," said P Narayanaswamy, one of the researchers.

The pesticides showed efficacy in thwarting various groups of pests infesting rice and vegetables. Among all the pesticides, the ones made with 10 per cent turmeric dust and 10 per cent of neem seed kernel dust were found to be most effective on pests such as Epilachna beetles attacking brinjal and a species of spodoptera affecting okra, said their paper published in Current Science (March 25, 2007).

Clarifying that heavy metal in flyash was not harmful, Narayanaswamy said a research by Flyash Mission of tifac had shown that grains, seeds and vegetables harvested from crop applied with tonnes of flyash were found to contain negligible amount of heavy metals.

"The pesticides were analysed at the National Institute of Nutrition, Hyderabad, and they found no harmful effects in animals or humans," he said.

The recommended level of harmless use of flyash pesticides is 40kg/hectare. The pesticides should be applied through dust, spray and manual spread.

Scientists at Bhabha Atomic Research Centre, Mumbai say most Indian coals have very low levels of radioactivity, well below the hazardous limit. Hence, radioactivity of flyash may not be a limiting factor for its application in agriculture. Central Fuel Research Institute, Dhanbad, observes that there is no significant uptake of radioactive elements by plants. Also, there is negligible cumulative build up of these contaminants in soil when flyash is used in agriculture.

India generates around 112 million tonnes of bituminous wastes from coal and lignite based thermal power plants annually. This waste is normally diverted to the manufacture of bricks and as fillers for roads. Its use in making herbal pesticides shows a new direction. But the long proclaimed ill effects of flyash should be thoroughly examined before putting it to large-scale use.

Source: Down to Earth, September 2007