Waste potential

Most people in the UK would not choose to live near a landfill site. Odour, truck noise and vermin are all reasons for the public to understandably declare “not in my back yard”.

Yet, despite the government’s best recycling efforts and intentions, the UK is still finding it hard to kick the landfill habit. According to 2009 study published by the Local Government Association (LGA), the UK landfilled 19.9m tonnes of municipal waste in 2007, the highest figure of any EU member state. By comparison, Germany, which has the highest population in Europe, dumped a mere 464,340 tonnes.

As things stand, the UK is unlikely to meet its EU Landfill Directive targets for 2010 of reducing landfill waste to 75 percent of 1995 levels. By 2013 this target will rise to 50 percent and 2020, 35 percent. The failure to meet these targets would result in an initial fine of £180m, potentially rising to £500m if the second and third targets are missed.

With the UK sending over 85 percent of its waste to landfill and the government trumpeting a housing target of three million new homes by 2020, more and more of us are likely to find ourselves living and working close to – even on – our waste’s final resting place.

“Most people do not want to live near landfill sites because there is a perception that there will be visual impacts, as well as impacts associated with noise and odour,” explains Rob Arthur, managing director of RSK Argus, which is a part of RSK Group, one of Europe’s leading multi-disciplinary environmental consultancies.

“In actual fact, these impacts tend to be relatively well-managed and are easy to mitigate against. It is unlikely that a landfill that deals with standard waste will be the cause of an odour, as since the Control of Pollution Act 1974 was put into place, there has been a strict set of environmental standards that operators are obliged to meet,” he adds.

“This legislation has been updated several times and has more recently been incorporated into the Environmental Permitting Programme 2007.”

“However, public perception hasn’t changed. We worked on a site recently and there was a terrible smell coming over a nearby village, which caused people to blame the landfill. Our odour monitors have ‘calibrated noses’, which essentially means that they are rigorously tested to see if their sense of smell is suitably sensitive for monitoring. Some candidates fail because they are not sensitive enough and some because they are too sensitive.”

“We sent in a large team of odour monitors and in the end, we identified that the smell was probably coming from bilge water release at a nearby harbour.”

After seeing a troupe of RSK Argus field scientists walking around the village in high-visibility jackets, the local residents’ fears were soon alleviated.

While a landfill may not look or smell very nice, the real danger is usually out of sight. The decomposition process produces gases such as carbon dioxide, methane, ammonia and hydrogen sulphide, which can build up underground or migrate to the surface and escape into the atmosphere.

“There are several dangers facing buildings located near landfills,” explains Mr Arthur. “Firstly, there is a chance that the gas could escape into buildings and there would be a risk of asphyxiation or explosion. Decomposition of organic materials in landfill creates heat. In a properly maintained site, oxygen is excluded from the waste, so anaerobic digestion produces methane. If the landfill cap degrades or if too much suction is applied to the site, oxygen can be drawn in, resulting in a fire deep underground.”

“You only need to have five percent methane in air before it becomes an explosive mix and the presence of any oxygen then allows the fire burn.” An underground fire can take weeks or even months to extinguish and become a nightmare in terms of development.

“There are a number of safety measures that developers can take advantage of, such as installing a sub-floor void and installing gas resistant membranes between buildings,” says Mr Arthur. “But beyond the planning and construction phases, close monitoring of landfills is the best way to help avoid danger to nearby housing.”

Landfill monitoring uses a range of high-tech devices to record changes in the concentrations, movement and component chemicals of landfill gases and groundwater. Leachate is a poisonous liquid caused by precipitation leaking through the structure and collecting on the bottom of the landfill. Before 1975, there was no obligation to line landfill sites and the leachate was allowed to leak into the surrounding strata, potentially causing large-scale environmental damage and even poison underground aquifers.

Boreholes surround landfills, both lined and unlined: some to monitor gas escaping from the site and others to compare the quality of the groundwater both before and after it passes below the site. This makes sure that whatever environmental protection schemes are in place are working effectively.

“The Environment Agency firmly regulates what is acceptable in a landfill’s behaviour,” states Mr Arthur. “To facilitate this, we have a sophisticated field team, with encrypted data loggers to provide same-day turnaround on monitoring data and strong leverage on the information that is collected. This enables us to provide reports that allow operators to make fast and informed actions. Our clients set control and action triggers that we use to alert them to any problems that may be developing and give them plenty of time to resolve issues before they become problems.”

It can be perfectly safe to live within the vicinity of a landfill, as long as operators employ a reliable, prompt and accurate monitoring service. As the population grows along with its waste production, it seems that we are going to have to change the way we view our waste.

In the not-too-distant future, it may even be commonplace to laud the landfill for its environmental benefits. “Waste-to-energy schemes on landfill sites have proven to be of tremendous value in tackling the UK’s current energy difficulties,” confirms Mr Arthur. “The basic premise is that you draw off flammable gas from the landfill site. The gas is then used to power a generator which produces electricity that is fed back into the grid.”

However, gas extraction is a tricky process to manage. Suction is applied to the site in an effort to draw off gas; if not carefully monitored it can result in a vacuum that pulls air into the site. This can cause an underground fire, which is not only notoriously difficult to put out, but also consumes both the flammable gas and the gas-producing waste that were producing the energy.

Companies like RSK Argus monitor the concentrations of gas and provide waste-to-energy operators with detailed feedback that helps them to avoid any incidents. “We monitor gas around the perimeter of a landfill as an environmental precaution,” says Arthur. “We also monitor how much gas is being drawn off and the quality of that gas. One landfill site can produce up to 20MW – the same amount of electricity as a small power station, so it is environmentally very attractive and profitable.”

As for local residents’ peace of mind, Arthur confidently believes that today’s procedural and technological wherewithal is capable of detecting and mitigating any potential concerns before they become a danger.

“The technology surrounding landfill management is already extremely advanced and has come a long way since my company was first established in 1992,” he concludes. “Because of this I think that it can be safe for housing estates to be positioned near landfill sites, as long as developers consult with the Environment Agency early on and employ the help of monitoring experts.”