Dr. Ben Dearman is first and foremost an environmental pragmatist. He knows that sustainability is key for the waste and resource recovery industry moving forward. His company, Ennovo, is at the forefront of making sure landfills are managed properly with the least impact on the environment.
For seven years, Dearman and his team have knuckled down to find solutions that meet industry and community standards when it comes to landfill management. With a PhD in anaerobic digestion and a thesis titled Anaerobic Digestion of Source-Separated Food Waste Followed by Composting, you could argue he is in the driving seat when it comes to understanding how waste works in landfills.
Dearman believes a lot of landfill gas capture enterprises are driven by the amount of power and carbon credits they can generate when capturing the gas and utilising it to create power or flare. He said that while this is an important part of the process, he sees it as a by-product of what Ennovo is doing, not the principal reason. There are also other issues, such as managing landfill gas emissions and leachate.
“We’re driven by ensuring a very high standard of environmental management is maintained,” he said. “Doing this for the greater good and the environment is important because methane is a very potent greenhouse gas. We are also aware of the role leachate has in the process and how important leachate management is, because not managing it properly can have dire impacts on both groundwater and surface water.”
Dearman said that leachate is pumped out of the landfill, where it either evaporates or is sent to a treatment plant. Once treated, it can be disposed of properly.
One of the main services offered by Ennovo is managing the pumping system. It also offers a cost-effective leachate telemetry system that allows landfill operators to know where the leachate levels are in the landfill and whether the pumps are working properly.
“The telemetry system measures the leachate levels in a landfill,” he said. “There’re strict regulations about how deep that needs to be. Normally it’s only 300mm deep. It has to be in compliance constantly. That’s the beauty of the telemetry system – it’s telling you that the depth of the leachate in real time, so you’re constantly getting real time data.”
Once a landfill is no longer taking in feedstock, it is capped, and the amount of leachate will abate. Dearman said that in theory, once that happens, the infiltration of the stormwater – which causes the leachate – shouldn’t exceed the evaporation that occurs in that landfill cap.
“To cap it, you can put geotextile membrane over the landfill, and then you can put some soil on top and plant plants,” he said. “Alternatively, it can be a much thicker soil layer, which is called a PhytoCap. They’re quite good to use in southern parts of Australia, but not so good in the tropics because of the amount of rain that occurs.”
Dangers of Landfills
Landfill owners have an obligation to manage their landfills, even legacy ones that have been closed for some time. There is even an argument that the legacy landfills from yesteryear need more attention because they were not subject to the stringent rules that now apply.
Read more: ACT expanding its landfill gas capture capabilities
“Any owner of a landfill has an environmental duty to manage the environmental impacts,” said Dearman. “There’re legal obligations to manage human health around these sites. In the case of landfill gas, the consequences of it going wrong are quite severe if the gas builds up and enters buildings, and nothing is done about it. People can die. The management of it is
incredibly important.”
Dearman said considerations just don’t include fugitive emissions that come out of the cap and have an impact on greenhouse gases – it’s also that lateral migration of the gas; i.e that which goes through the side of the landfill. In worst-case scenarios, this can include gases travelling up into buildings, creating an explosive atmosphere.
And what landfill owners and the general public have to be aware of, said Dearman, is that there are literally thousands of these legacy landfills around Australia. A lot are low risk and will not cause issues, but there are some that need to be managed carefully. Also, a lot of these old landfills, especially those in major cities and regional towns, are covered over with soil and turned into parks or recreational facilities like sports fields and club rooms.
“You’d be surprised at how many sites we’re going around that have sporting club buildings, and we look to detect methane in them,” he said. “And quite often we get a hit.”
Solutions
Dearman said there are several ways landfills can be managed successfully without causing a lot of disruption, while making for a much safer environment. Ennovo’s solutions are varied and include innovative pinwell systems, which are small extraction wells, but capable of mitigating the lateral migration of gas. They pair it up with a Lo-Cal flare to effectively manage the low-quality gas.
“That flare has the ability to combust the landfill gas with a very low concentration of methane,” he said. “This means that it can operate over a long period of time. What the flare is doing is creating a vacuum and always sucking the gases out.”
Ennovo also installs interception trenches and biofilters around the perimeter of landfills so that, as lateral migration occurs, it can intercept any gas. The company also owns the Gasflux continuous gas analyser technology,
which is used on perimeter monitoring wells that surrounds a landfill. This technology detects both gas composition and borehole flow.
“This means if there’s a positive pressure from the gases coming out of the landfill, we quantify that, and that goes into our landfill gas risk assessment plan,” Dearman said. “This is a well-recognised process for quantifying that risk.”
Legacy
Dearman said a rule of thumb is that once a landfill stops taking waste, it needs to be managed for about 30 years, which happens in stages. He said flaring the gas might be carried out for up to 15 years. Then it’s best to move to a passive system such as cut-off trenches or monitoring. That might happen for the last 10 years, depending on how much gas is being produced.
He said that although a lot of Ennovo’s clients, including councils and large waste management companies, are up to date on leachate and landfill gas requirements when managing a site, there is expertise lacking in some areas.
“That’s why we’ve been able to do quite well because we do know how to marry those technical consulting abilities with really good design and construction capabilities,” he said.
Dearman said one of the key features of Ennovo is that the company is not only a consultancy, but it is also a supplier and designer of landfill gas management systems.
“When we talk about a particular design, we know if you can physically construct it, build it and operate it,” he said. “We’re not just behind the desk, white collar consultants. We do the full range. We employ people, from excavator operators to people with PhDs writing reports and interrogating data.”
Dearman said that Ennovo is a technology-driven company, and he loves the whole cradle-to-the-grave approach to a project.
“The technology in this space is phenomenal in terms of the speed at which it is developing, and it’s mainly around the detection of methane from landfills,” he said. “A lot of it is coming out of the oil and gas industry, where the ability of drones, fixed-wing aircraft, and satellites can pinpoint sources of methane and also quantify methane being released from point sources – whether it’s an oil and gas field or now landfill. The onus is really on operators to make sure they’re mitigating those emissions that have significant greenhouse gas impacts. That’s where we fit into being able to provide cost-effective solutions for our clients and for the broader benefit, too.”