Could excess pine needles help solve water pollution in India?

For a couple of decades already, India has been troubled by two particular environmental problems: the risk of fire in the pine forests cloaking the foothills of the Himalaya, and pollution by heavy metals, particularly lead, of some of the country’s water supply. A team of scientists in Delhi has now figured out how to turn one problem into a solution for the other.

The fire risk comes from the pines’ needle-like leaves. These decay only slowly once shed, and thus build upon the ground into thick, flammable layers. A single lightning bolt from a passing storm can set them off and create a serious fire.

The water pollution risk comes from lead derived from fuels, old water pipes, and paint, causing one of the most pernicious water-quality problems faced by India. Concentrations of lead above the safety limits have been reported in many of the country’s river-water-quality monitoring stations.

Thanks to Dinesh Mohan, a scientist at Nehru University in Delhi, both of the problems may soon be solved in a simple and elegant way by a simultaneous solution, namely using the needles to clean up the water.

The idea is that you could potentially use the pine needles to create biochar – a more fancy name for charcoal – which is made from wood and has been known for some time to be really good at pulling pollutants like lead out of water. And once a filter is saturated with the small particles, you can get the charcoal out of the polluted water and use other chemicals to draw the toxins out of the charcoal and then use the charcoal filter again.

Dr. Mohan already knew, from previous work, that pine-wood biochar is an effective agent for stripping lead from water. But pine wood is a valuable commodity, so he wondered if he could pull off a similar trick using another pine needles, a forest product that currently has no value and is sitting at the floor of forests and is a fire hazard.

To test the idea, Dr. Mohan and his colleagues went foraging for needles to the forest, collected a whole bunch of them, and brought them back to the laboratory. The tricky thing is that in order to create charcoal out of the needles they need not be burnt but heated up to a certain temperature instead. After heating different batches at various temperatures, the researchers found that the material charred at 550°C extracted lead most efficiently.

Whether these laboratory observations can be turned into a practical process is still something yet to be determined, but if it works, the solution would eventually kill two birds with one stone – collecting a flammable material and therefore helping to suppress fires, while simultaneously reducing lead pollution that’s going into people’s homes.

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