Given the right circumstances, organic material will break down and release odour as it decays. Those ‘right’ circumstances are easily found, to the misfortune of those working with and living near the thousands of facilities world-wide where municipal waste is disposed of by landfilling.
In the USA, just over 50% of all municipal waste is disposed of by landfill. In Europe the proportion is 25%, although it is highly variable between member states. There is a general trend in most countries towards reducing the proportion of waste disposed of by landfill, with efforts to recycle, incinerate, compost or otherwise treat various waste streams, depending on local regulations and environmental conditions.
At first glance a view of the historical trends would suggest a dramatic decline in landfilling – in many countries the numbers of active landfill operations have fallen dramatically over the past few decades – for example in the US from nearly 8,000 in the mid 1980s to less than 2,000 today. However, this is offset by increased landfill size, and by overall growth in waste generation on that timescale.
Modern landfills are more than just ‘dumps’. They are engineered and operated to achieve efficiencies and various environmental performance objectives. Often taking advantage of old quarry or mine sites, landfills have become larger to help achieve required efficiencies. Waste is contained within lined cells, each being filled in layers and then sealed before moving onto the next one. Depending on the site, each cell might receive waste for one to a few years before being capped.
A feature of modern landfills is that there are a few different ways that odours are generated and can be noticed off site. Let’s take a quick look.
What part of the process creates odours in landfills?
Typically, trucks deliver waste to an active face, where the control principle is to bury the waste with a thin cover of soil as soon as possible. Managing the extent of the exposed active face, is a critical part of managing odour emissions.
Municipal waste includes putrescible materials: i.e., organic materials like food waste that can create offensive odours as bacteria break them down. As waste comes onto site, it has already had an opportunity to ‘cook’. It may have been held in warm temperatures for up to a week, allowing bacterial decay processes to get a foothold, with a consequent off-gassing of a rich cocktail of volatile compounds that we detect as a bad, rotten smell. In hot weather, we can expect more odour than in cold weather, as bacteria like warmth.
As waste is placed at an active face, odours are released and at the boundary of many sites this can be a readily detectable signal of the operation. Unsurprisingly, it can tend to smell like a loaded garbage bin (trash can). A normal feature of this smell is that it is not ‘swampy’ or sulphurous – it has been generated in the presence of some oxygen which supports certain groups of bacteria. What we smell is largely the by-product of this type of bacterial metabolism.
Once waste is buried, and particularly after a landfill cell is filled and capped, the waste is no longer in contact with atmospheric oxygen. Under these conditions, different (methanogenic) bacteria operate and continue to break down the waste, including materials that are not so readily broken down, like paper. This process can take decades and is marked by the generation of methane, which is odourless, plus a host of odorous compounds that include reduced sulphur compounds like hydrogen sulphide (H2S). This mixture is landfill gas (LFG), which can smell swampy, and will leak out of any cracks in the cell, as it continues to generate long-term.
Uncontrolled release of LFG is not good for several reasons: it creates an offensive smell, can create a safety hazard, and is poor practice in terms of energy and greenhouse gas emissions management. Hence, modern landfill operators have become more attentive to the design and management of LFG collection systems, which include piping to a hub and combustion of collected LFG for energy production.
A diagram showing how a methane collection system at a landfill can be used to produce energy. Courtesy of US EPA.
Maintaining landfill integrity by monitoring odours
Monitoring and maintaining the integrity of this system is essential to both optimise the energy and greenhouse gains, and to minimise odorous LFG emissions.
Moisture that infiltrates through the waste in a cell is a source of odour and contamination, and so this leachate is managed by collection in sumps and suitable treatment or disposal.
A landfill operation is not always straightforward. For example, constructing and managing cells can require that old waste is sometimes disturbed and opened to the air, releasing offensive odour temporarily. Perhaps this can be planned to coincide with favourable winds and avoid the wrath of neighbours.
Finally, with increased focus on waste separation and composting of organic waste, some landfills have related or independent composting facilities nearby. These are themselves capable of being potent odour sources. It was found that a composting facility in Australia caused most of the many complaints in a suburb, but the adjacent landfill received the blame.
With several distinct aspects of a landfill’s operation running in parallel, and with each of them carrying some odour risk, it can be difficult to know if a complaint is valid, and if so, what exactly caused it.
Communities are increasingly impatient about slow and indecisive responses to odour complaints, so it is more important than ever that operators can minimise uncertainty, and reduce the time between a problem occurring and a solution being actioned. Envirosuite provides tools that can arm landfill operators for faster, more effective action, and be better neighbours.
Odour allegations against landfills
Waste management operations are essential for life in today’s growing cities. Operators provide a vital service to the communities around them. Nevertheless, maintaining "good neighbor" status is difficult when nearby residents are affected by nuisances like odor, noise and dust from waste management operations.
Odour is still a challenge for operators today despite a wide range of abatement options. It’s critical to know the precise time to engage odor control measures or how external factors like the weather might determine future impact. Lack of knowledge of these areas can lead to impacts on nearby communities which creates costly investigations and disruptions from lawsuits and fines. This results in poor publicity for site operations in the media and a damaged reputation.
Click here to find out how real-time environmental intelligence can help your site avoid problems, reduce costs, and maintain a good reputation in the communities you serve.