Pollution from landfill

Does landfill waste pose a threat to the environment?

Waste management places considerable strain on the environment. Waste disposal sites, whether active or closed, can result in serious pollution of groundwater due to leachate. A recent survey by the Environment Agency of groundwater pollution in England and Wales, revealed that the main sources of pollution (in order) are:

Landfill leachates rank alongside heavy metals and organic compounds as the most frequently recorded pollutants. Locally, in the Great Stour catchment, 26 sites of waste disposal have been identified by the Environment Agency as potential groundwater contaminants. Brett Waste Management Ltd. (Shelford Quarry, Broad Oak Road) is one of them. At present, however, there is no contamination of the river via groundwater leakage of leachate from any of these sites; all landfills are under licence, and are monitored closely. There are alternative ways of disposing of our domestic, commercial and industrial solid waste, but for the moment, landfill remains the cheapest disposal option.

What is the potential pollution from landfill waste disposal?

Solid household waste is recognised as a major threat to the environment, with high pollution potential. The average household in Britain generates 600 kg of waste per year (11.5 kg per week); the total waste generated nationally is 380 million tonnes per year! Each household produces on average each week:

In mixed (unseparated) compostable waste, including kitchen and garden refuse, there is also a diverse range of other materials, some of which are potentially hazardous. These hazardous substances include: decorating products (paints, stains, varnish, paint thinners), garden products (pesticides, fungicides, herbicides), vehicle products (engine oil, brake fluid, antifreeze, car batteries), household cleaners (bleach, disinfectant, air fresheners), toiletries (cosmetics, old medicines) and other miscellaneous items. Batteries from watches, radios, mobile phones, etc. may contain heavy metals like mercury, nickel, cadmium.

When such household waste in landfill sites is acted on by rainwater, the organic and inorganic constituents are dissolved, and a highly toxic leachate results, collecting at the base of the landfill. This is normally high in heavy metals, ammonia, toxic organic compounds and pathogens. It also has a high BOD, and if it escapes into the groundwater serious contamination results. Meanwhile, at the top of the landfill, gas is produced by the fermentation of organic material. Approximately equal quantities of carbon dioxide (CO 2 ) and methane (CH 4 ) are released. Both are greenhouse gases, but methane is 26 times more effective than carbon dioxide in this respect. In addition to leachate and biogas problems, landfill sites are very unpopular with local residents: traffic, smell, noise, vermin, seagulls, blown litter, and disease can all spoil the neighbourhood and lower property prices.

What preventative measures are being taken to limit pollution from Landfill waste?

In the past it was considered acceptable to allow leachate to seep away slowly and be dispersed through the ground. This old dilute-and-disperse method of waste disposal is now no longer acceptable. New methods are based on the idea of containment. Landfills are lined with clay and flexible synthetic membranes intended to prevent leachate escaping and contaminating the groundwater. Leachate is drained through a horizontal array of perforated pipes to be collected by a sump for treatment. Methane (biogas) is also collected at the top, and is either vented to the air or tapped off and re-cycled for industrial or heating use. Landfill is a long process. Compaction of waste means that material might only reach a final stable state after about 30 years. Landfill operators are required to have a licence, and to comply with strict waste management regulations. Landfill sites must be designed and constructed to high standards to ensure safe containment and long-term protection.

"Prevention is better than cure" Do you agree?

Another approach to landfill pollution prevention is to minimise domestic waste in the first place. Separation of waste products, composting of organic remains, recycling schemes, and awareness-raising campaigns can all be used by local authorities in the task of domestic waste reduction.

In the Great Stour catchment, 26 sites of waste disposal have been identified by the Environment Agency as potential groundwater contaminants. At present, fortunately, there is no contamination of the river via groundwater leakage of leachate from these sites; they are all are under strict licence, and closely monitored. Landfill remains the most important option locally, the main advantage being the relatively low costs involved. But land shortage, especially in the south-east of England could mean that we will run out of landfill sites within 10 years. Kent County Council has a target that "by 2006, landfill with unprocessed wastes will become the exception in Kent". The county has the vision of "ultimately aspiring to zero waste".

Is there a threat from old landfill sites (brownfield sites)?

Land is said to be contaminated when substances are present at concentrations that could be harmful to human life, wildlife or the environment as a whole.

To pose a risk of contamination there must be:

The precise scale and nature of contaminated land in urban areas is often unknown, because there may be few written records of old landfill and other disused 'brownfield' industrial sites; local authorities and the Environment Agency will try to compile registers of these as accurately as is possible. Brownfield industrial sites in the Canterbury area, including old waste disposal landfill, provide good opportunities for redevelopment on the outskirts of the city. The Sturry Road park-and-ride car park is a good example. Many of these local sites are close to the River Great Stour, including:

Slow degradation of compostable materials beneath the Sturry Road park-and-ride site is currently releasing ammonia leachate from below. Degradation of old landfill material is a slow process; disposed solids in old waste tips might only reach a final, stable unpolluting state after about 30 years. Meanwhile, discharge of leachate has to be collected in a sump, treated and released slowly into the river under consented agreement with the Environment Agency. Other examples of local brownfield redevelopments (e.g. Safeways, Wincheap) have revealed the presence of contaminated soil, which needs to be carefully removed to avoid pollution of watercourses during the construction phase.