• Where Does Methane Come From? - Wastewater

Air Monitoring

Where Does Methane Come From? - Wastewater

Feb 23 2022

When most of us hear the term “methane emissions”, we likely think of dairy farms full of cows breaking wind or fossil fuel wells and refineries drilling for oil or gas. However, it should be remembered that methane is a natural gas which has many sources and even several uses. Although it’s detrimental to the environment when allowed to accumulate in large concentrations, it does have value as an energy source in its own right.

The wastewater treatment facilities which handle human faecal matter and urine are an underappreciated source of methane emissions. At the same time, they also represent an as-yet underexploited opportunity to capture methane at the source and turn it from an unwanted waste product and potential contributor to climate change into a fuel and revenue source. Here’s a closer look at exactly how that can be achieved.

How wastewater produces methane

In the developed world, most wastewater treatment plants function via an aerobic treatment system, which collects and processes all types of human waste efficiently and effectively. Although these modern systems are not responsible for significant volumes of methane emissions directly, they do entail the production of biosolids which can serve as a methane source in their own right.

However, the problem is far more pronounced in the impoverished and developing world. Here, it’s far more common for latrines, lagoons and septic systems to be relied upon for the disposal and treatment of wastewater, wherein anaerobic decomposition is utilised to break down the waste. Although effective, this process does result in significantly higher methane emissions, with an estimated 7% of all atmospheric methane derived from this source.

Benefits of methane capture

While many people only associate negative connotations with methane, it’s important to recall that it’s a valuable source of energy. As the principal component of natural gas – responsible for as much as 85% of its composition – methane can be captured and harvested as a fuel. When deployed effectively, this can help to facilitate energy independence for communities by providing them with a local power source.

Other advantages of this type of methane use include the fact that it prevents a powerful greenhouse gas from entering the atmosphere. Given that methane is up to 80 times more potent at retaining heat than carbon dioxide over a 20-year period, any method of reducing its concentrations in our environment is beneficial. It also allows for a waste by-product to be converted into a stream of revenue, as well as creating employment opportunities in the process.

How can methane be captured from wastewater?

The first step to optimising methane capture and reuse is implementing a robust monitoring system, which takes advantage of all of the latest methane monitoring techniques. In this way, site managers can keep tabs on the performance of their facility and track how much methane is produced – and how much is captured.

The exact protocol for capturing methane wastewater will depend on the system being favoured. Aerobic treatment systems can incorporate sludge digestion tools to capture the methane and process it for distillation into use as a fuel source. Meanwhile, anaerobic systems can install biogas capture systems or degassing devices at the effluent discharge to retain the methane from the wastewater and store it for future use.

This is a brief introduction into how methane is generated by wastewater systems – and how it could be captured and used in the future. For an in-depth examination of the subject, interested parties are invited to attend the upcoming Industrial Methane Measurement conference in the Netherlands on the 8th and 9th June. Details can be found at the link above.

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International Environmental Technology 32.3 - May/June 2022

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