Scientists in Pakistan overcome issues of walnut shell waste

Scientists at Pakistan's Indian Institute of Science, Education and Research have discovered that chemically treated and burned walnut shells can provide high-quality carbon for use in the anode of sodium-ion batteries. If the method can be scaled and commercialised, it could not only provide a source of carbon for Na-ion batteries, which are cheaper than their lithium-ion equivalents, but also provide an income for local farmers. Kashmir currently cultivates 63,000 hectares of walnuts, producing 15,000 tonnes of shell waste.

A team of scientists from IISER processed walnut shells to obtain high-quality carbon that can be used in batteries.

If you think that walnuts only help in improving brain functioning, think again!

A team of scientists from the Indian Institute of Science, Education and Research (IISER) , led by Satishchandra Ogale, may soon have a solution for Kashmir’s greatest organic waste problem — the nutshells of walnuts.

One of the researchers, Wahid Malik, came up with a unique idea of using walnut covering, during one of his visits to his hometown in Kashmir, about nine months ago.

These researchers processed the nutshell, an abundantly grown dryfruit found in Kashmir, to obtain high-quality carbon, meant to be used in the anode part of the sodium-ion battery. These batteries are basically similar to the commonly used Li-ion batteries, but are expected to be much cheaper due to the few thousand-fold higher abundance of sodium over lithium in nature. Battery systems are central to all renewable energy resource management and usage, including grid-based set ups, electric vehicles, and biomedical or handheld devices.

When asked about this novel idea, Malik stated, “It is one of the greatest issues for farmers back home, to deal with the hard and nutty shell of dry fruits, especially that of walnut. That is when, while thinking of his proposal for CSIR-800 mission as a doctoral student, it was ideated and worked upon.”

According to the study team, 63,000 hectares of land is under cultivation of walnuts in Kashmir. Of the total 36,000 tonnes of organic waste generated from the farm produce, 15,000 tonnes is contributed by walnut shells alone.

The crushed shells are first cleansed using acids and then subjected to pyrolysis process, where it is heated at temperatures as high as 1,000 degrees Celsius for about 4 to 5 hours. Later, the carbon chunks are extracted within the specially created inert atmosphere, before it is powered or converted into a paste form, the researchers explained. One of advantages of using this nutshell, according to Ogale, is its natural composition. He said, “The foliage of the shell perfectly suits the requirements once it is treated chemically, giving an edge over other natural resource substances.”

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“These Na-ion batteries are expected to be at least five-times cheaper than the lithium batteries and can make the overall setups affordable,” Malik claimed.

If this is technique becomes commercially viable, farmers in the valley can have an additional source of income, added Malik. Currently, the leftover organic waste is used in making packaging products. “But, that too is limited to just 5 – 10 per cent of the waste, while the rest lay unattended causing serious concerns to the cultivators, who otherwise burn it further resulting to air pollution,” he added.

At the lab testing stage, the scientists were able to extract about 300 – 400 mg of battery grade carbon from one gram of power obtained from the shell.