Humble, but useful

The humble peanut - loved and reviled depending on your perspective - has new tricks to offer. Once a peanut is shelled to allow the inside to be used, the husk becomes garbage. In fact, all those peanut shells add up to one of the biggest waste products of the food industry. So, wouldn’t it be great to turn that garbage to some use?

A new study uses peanut husks to filter waste water. Copper is a metallic element that occurs naturally in the environment. It is a micronutrient found in most organisms, including plants and animals. At trace levels, it is a crucial part of enzymatic and other physiological functions. Insufficient copper is linked to human health problems. However, at higher concentrations, it becomes toxic.

Copper is a component of industrial waste discharged from pulp and paper mills, fertilizer plants, and metal-plating companies, among other manufacturing sectors. Copper is also used in some agricultural treatments for plant mildew. Vehicle brakes and other operations are another major contributor of copper. The multiple avenues for copper discharge include mining, farming, industry and waste water; natural sources may be volcanic eruption, dust, vegetation, and fire. Once into aquatic systems, copper ions act as a heavy metal pollutant.

Copper usually bonds to organic particles, as well as sand and clay. Its toxicity is reduced once it has attached to some other material. As a result of copper’s tendency to form complexes, water treatment includes a range of possibilities for removing these ions. Processes include carbon filtration, electrolysis, ion exchange, and precipitation.

Turkish researchers have found that peanut husks are able to absorb copper ions out of waste water. This interaction is most efficient with longer processing times, removing up to 95% of the copper. The same research team also looked at pine sawdust as a possible absorbent, but it only removed 44% of the copper ions. Other organic compounds may also have potential for copper removal, but the virtue of peanut husks is the combination of using garbage to reduce another form of waste.

Water treatment is not the only reuse project suggested for peanut shells. They are already used in cattle feed, to make activated carbon, and in a variety of products from glue and paper to linoleum. Along with polyethylene plastic, discarded husks may be part of a new construction material to replace common concrete . These possibilities give a new edge to the ‘reduce-reuse-recycle’ mantra.


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