Aerobic Landfills: An anachronism flying in the face of EU landfill principles, or a worthwhile subject for UK research?
Steve Last’s view on the Landfill Workshop session held in June last year, during the CIWM Annual Conference & Exhibition (15th – 17th June 2004, Torbay, Cornwall, UK).
While the Landfill Workshop also included excellent papers by, for example, Dr Jan Gronow who discussed the sustainability of landfill and the implications of recent legislation on landfills, the main topic was that of aerobic landfills.
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Information: For those new to this subject, all modern landfills are anaerobic (ie lack oxygen). To create and maintain aerobic conditions in municipal waste requires forced ventilation, and for large landfills would need a lot of air to be pumped into the waste continuously. Air must be introduced in order to replenish the oxygen consumed by decomposition of the organic content.
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Those who advocate aerobic landfilling do so to minimise the impact of landfills not by reducing the proportion of organic matter in the waste, which is the intent of the current EU Regulations, but by maintaining aerobic conditions, to accelerate decomposition.
Aerobic conditions allow “composting” (biological decomposition) to take place much more rapidly than occurs in anaerobic waste. Aerobic conditions allow decomposition within timescales of 1 to 5 years, and the leachate generated will be orders of magnitude less contaminated than in the equivalent anaerobic landfill. Another considerable benefit is that in aerobic landfilling, the generation of landfill gas (methanogenesis) can be almost entirely avoided.
Even if an anaerobic landfill has an energy from waste plant installed to burn the methane, something like 50% will still be lost to the atmosphere. As methane is much a more damaging global warming gas than the carbon dioxide produced by aerobic landfills, its avoidance has to be good news for the planet.
In fact, although hard figures are hard to come by, aerobic landfills are said to be more environmentally benign in 5 years, than their anaerobic equivalents after 100 years.
Aerobic decomposition was the by-default method of decomposition for all those relatively shallow and un-restored open-tips filled before the 1970s. During the !970s in the UK, landfill practices were changed by more stringent environmental regulations, and landfills became much fewer in number and larger. The the “old tips” were closed, and replaced by landfills large enough to exclude oxygen and to become methanogenic (methane producing).
Data was provided which showed that after the initial decomposition phase quite rapid reductions in environmental impact risk can being achieved in such aerobic sites, both in pilot scale (as reported by the UK’s Prof Adam Read), and at full scale (USA - W Gregory Vogt).
Concerns were voiced by Dr Jan Gronow, regarding the potential for landfill fires to be induced by ventilation), and technical difficulties were cited in providing infrastructure which would effectively distribute air throughout the waste mass.
Some thought UK experience of fires arising just from the presence of excess air, causing spontaneous ignition of waste, showed that these would be frequently induced by the negative landfill suction pressures induced by high gas pumping rates. So for them, the concept of the aerobic landfill would self-evidently also suggest a significant fire problem . However, W Gregory Vogt reported that fires have not been found to be a significant factor at the many aerobic landfills already operating in the US.
One delegate proposed a technique for final aerobic stabilisation of end-of-life landfills. However, a consensus was evident in the audience that avoidance of the perils of entombment, as embodied by EU Directive compliance requirements for non-hazardous waste, would be sufficient to justify the UK’s involvement in pilot scale studies. These need to be of similar scale to the ill fated “Landfill 2000” experimental cells funded by the DoE during the late 1990s.
Unfortunately, given the current commitment Europe-wide to organic waste pre-treatment and the almost “politically incorrect” implications of aerobic landfilling, it would be a brave step by any landfill operator to seek a permit (even for research purposes) in the current context of the waste regulations - and a courageous step by any EA officer to back it).
Such thoughts do nevertheless, highlight the fact that while much of the world aspires to follow the European lead in landfill “entombment” policy, to others aerobic landfills are far from being an anachronism. As W Gregory Vogt explained, a significant section of the USA’s landfilling community, and the Japanese as a nation, remain unconvinced, and retain their dedication to aerobic landfilling principles.
While the tide of European styled regulation flows unabated, lets not forget the aerobic alternative.
More about this subject: A perspective on the discussion of Aerobic Landfills at the International Landfill Symposium 2003, Cagliari, Sardinia
Footnote: Enviros Consulting and Biogas Limited are currently applying for funding, for a UK end-of-landfill-life aerobic landfill completion phase experiment.
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