Landfill mining

These days, we in the developing world are encouraged to compost our garden and kitchen waste at home or dispose of it in our “green” bin for kerbside collection and processing. However, not everyone has a compost bin and not all of us are willing or able to separate waste into compostable materials and non-compostables. In the developing world, the problems are very different. Open dumps are prevalent and have a poor environmental record, according environmental engineer Kurian Joseph and colleagues at Anna University, in Chennai, India.

His team has considered the possibility of landfill mining as a viable means of rehabilitating open dumps. An earlier analysis of decomposed waste from the Deonar dumpsite, in Mumbai, India, revealed that almost a third of the mass is organic matter, while moisture accounts for 14 percent of the sieved material and inert matter the same. Soft plastics, textiles, glass, ceramics, metals, rubber, leather, and other substance account for the remainder of the sieved mass.

“Landfill mining can recover recyclable materials, landfill space and compost,” explains Joseph. He suggests that mining of compost from open stabilised dumpsites and the application of the bioreactor landfill concept across the developing world could make dumps much more sustainable and reduce their environmental impact. The current study as part of the “Asian Regional Research Programme on Sustainable Landfill Management in Asia” funded by the Swedish International Development cooperation Agency (Sida) indicates that up to half of material dumped at such sites could be recovered and re-used as compost for non-edible plants or as daily cover material for landfills.

Over the last two decades, experimental testing and field pilot studies have been conducted to develop and improve landfill techniques and designs with the aim of reducing their negative impact on the environment. The researchers suggest that by encouraging microbial degradation of solid waste in landfill bioreactors it should be possible to improve the overall efficiency of the landfill mining process. This, they explain, needs to be demonstrated at the pilot scale to complement the ongoing research in this area.

“Landfill may no longer be viewed as a final disposal system,” adds Joseph, “rather it should be viewed as a method for large-scale processing of waste that combines recovery and recycling processes.”