15 July 2013

Natural waste solution for reclaiming contaminated land

Charcoal
A special charcoal – biochar – made from abundant materials such as wood chips, animal manure, agricultural and other natural waste could hold the key to re-claiming thousands of square kilometres of polluted ‘brownfield’ land across the world.

In China, USA and UK alone it is estimated that brownfield sites – abandoned industrial and commercial land – covers an area in excess of 120,000 square kilometres equivalent to countries the size of England and North Korea, and the state of Mississippi, US.

Much of this land is contaminated, hazardous and costly to reclaim despite increasing pressures on valuable agricultural land, especially in developing countries.

One solution attracting the interest of scientists, chemical engineers and environmentalists is biochar, a charcoal made from natural waste known as biomass. Charcoal has long been known for improving soil fertility and structure. New research is now revealing its potential to control contaminants such as organic pollutants and heavy metals including Lead, Copper, Cadmium and Zinc.

Adding biochar has the ability to lock in chemicals such as Arsenic for slow release into the soil. A study1 comparing soil treated with biochar using waste rice straw was able to reduce the movement of heavy metals in soil by up to two-thirds.

Food chain safety can also be improved. Another study1 found that biochar, made from green waste compost, could significantly reduce the take-up of heavy metals in ryegrass, which is widely used in pastures for grazing animals.

David Brown, chief executive of the Institution of Chemical Engineers (IChemE), said: “Chemical engineers and other fields of study are looking very closely at the potential of biochar.

“It clearly presents an important opportunity to reduce the impact of harmful pollutants in the environment and bring back into use huge areas of unproductive land with global population expected to grow by nearly a third to nine billion by 2050.

“Some countries like the US and UK have made good attempts at quantifying abandoned or contaminated land.

“In England alone, it is estimated that an area equivalent to the West Midlands conurbation – around 66,000 hectares - is designated as abandoned or derelict brownfield land.

“The picture is less clear in other countries especially in fast developing and growing nations. The problem will need to be addressed sooner or later, and biochar could be the solution in many parts of the world”, concluded Brown.

‘Innovating to ease the strain of changing land use’ is just one of the issues identified in IChemE’s latest technical strategy, Chemical Engineering Matters. Major themes identified in the strategy include food, water, energy and health.

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IChemE is a registered charity in England & Wales (214379), and a charity registered in Scotland (SC 039661).