They may taste great on a pizza, but could onions and garlic be used to help clean up hazardous heavy metals?
Onion and garlic waste could be used to mop up hazardous heavy metals in contaminated materials, according new research published in the International Journal of Environment and Pollution.
Phytoremediation – taken from the greek word phyto for plant, and the Latin word remedium, meaning “restoring balance” – describes the treatment of environmental pollution through the use of plants that contain, degrade, or eliminate the contaminant material.
A team of researchers from the University of Delhi is developing a filter made of garlic and onion, to clean up arsenic, cadmium, iron, lead, mercury, and tin. The process could be used to treat industrial effluent at factories, and it could also join the growing bio remediation toolkit for cleaning up polluted sites.
Researchers are already beginning to look into food-related substances like lactate, bananas and vitamin B12 as a sustainable means of neutralizing toxic substances in soil, also known as “green remediation.”
Green remediation presents a marked improvement over conventional “remediation,” which used to involve either capping a site and letting the contaminants fester under the cap, or digging out tons of contaminated soil and trucking it to a landfill where it would also fester.
The Delhi University process is of particular interest because it involves a double dose of re-use.
The filter itself consists of waste biomass — namely, the leftovers from processing garlic and onions at food canneries. The biomass absorbs as much contaminants as it can handle, and then nitric acid is applied to separate the metals into another vessel. The filter can then be reused all over again.
The process depends on achieving an efficient pH of 5, and so far the researchers have found that this can be achieved under a relatively low temperature of 122 degrees Fahrenheit.
Using food production waste to make a reusable filter is good enough. To ice the cake, once the filter has outlived its usefulness as a contaminant-trapper, it can be slipped into the food waste stream as feedstock for biofuel refineries.
Commercial scale food waste biofuel is still in the development phase, but a pilot food waste biorefinery in Germany looks promising. So, let’s call this a sustainability threefer.
The Delhi team isn’t alone in its quest to turn a vampire remedy into a bioremediation tool. In Bulgaria, a team of researchers is experimenting with on-site plantings of garlic and grasses to absorb contaminants.
The use of plantings in green remediation is a whole ‘nother ball of wax, since it can involve perennial grasses, shrubs and fast-growing trees like poplar, all of which can double as biofuel crops.