LANDFILL

Landfill, like incineration for disposal, languishes at the bottom of the waste hierarchy due to its environmental impacts, especially on groundwater. The primary reason for the impacts of landfill containing municipal solid waste is the organic fraction of waste rotting and generating gases and a reducing environment within the landfill. The primary gas emission is methane from decomposing organic matter, a potent climate change pollutant. There are also dozens of secondary toxic gas emissions related to the breakdown of waste chemicals and products within the landfill. The leachate (liquids) in a reducing, anaerobic landfill environment tends to be acidic, and accelerate the leaching of toxic metals from waste materials. When the landfill liner eventually leaks, contaminated leachate enters and pollutes the groundwater beneath the landfill.

Landfills are usually only fully capped at the end of their space capacity, and then methane extraction systems can be employed to draw off methane and convert to energy or simply flare it. Some landfills can install methane extractors earlier in a staged manner to try and capture methane earlier in the life of the landfill. The expected methane generating life of a landfill is up to 50 years from decommissioning. There are not many reasons to recommend sanitary MSW landfills from an environmental perspective.

However, when comparing mono landfilling of plastic under controlled conditions, many of the problems of MSW landfill do not apply. If only plastic is interred in the absence of organic matter within a specifically designed dry landfill dedicated to plastic, the problems of methane generation and leachate are greatly reduced. While plastic can generate methane and ethylene , it is mostly when subject to ambient solar radiation. When buried, this is greatly diminished.

Rain can also penetrate such a landfill unless is it capped and shielded in such a way to prevent precipitation entering the landfill and leaching toxic chemicals from the plastics.

WHY WOULD YOU LANDFILL PLASTIC WASTE?

Under normal circumstances and in mixed waste landfills, you would take all steps to avoid it. However, in certain circumstances it may be more environmentally sound to ‘store’ plastic waste in compressed bales underground (sorted by polymer preferably), as a transitional measure. The same may be argued for storing plastic above ground, but the potential for fires and the loss of valuable surface land may preclude this option. Dedicated, dry storage of plastic in landfill separate from any organic or other forms of waste may be necessary while the techniques for safe recycling of the plastics mature and become economically viable. ‘Banking’ plastic waste and its intrinsic value could assist remote communities, low-income countries, and isolated island nations to manage plastic waste without burning it, leaking it in an uncontrolled manner to the environment, or suffering exposure to the impacts of incineration.

Dedicated landfill storage of plastic wastes may be necessary in certain circumstances to allow technologies and regulation to ‘catch up’ with the waste problem, and permit decentralized, environmentally sound processing techniques to be established. At such a point the plastic waste can be unearthed and processed according to ESM, or exported to wealthy countries that have the processing capability.

In no way can this be considered a ‘solution’ to the plastic pollution issue - it is more a strategy borne out of necessity. The only long-term solution is to minimize the production of plastic.