14-04-2025
Iowa landfills capture methane and convert it to usable natural gas
The Loess Hills Regional Sanitary Landfill is one of a handful of landfills in Iowa that converts landfill gas into renewable natural gas. (Photo courtesy of Bret Stephens/Loess Hills Landfill)
When household waste decomposes at a landfill, it produces methane, a greenhouse gas that traps significantly more heat in the atmosphere than carbon dioxide.
The U.S. Environmental Protection Agency requires that large landfills monitor and capture the gas, but some landfills in Iowa are going a step further and 'upgrading' the landfill gas into renewable natural gas.
John Foster, the board president of the Iowa Society of Solid Waste Operations, said this process can make economic sense for a landfill and provide an environmental impact during a time when 'there's an energy crisis around the corner.'
Landfills that upgrade their gas end up shifting their wells into what Foster called a 'production' model that captures far more methane and carbon dioxide than what is required for compliance with the Clean Air Act.
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According to EPA, landfills account for 17% of overall U.S. methane emissions and the agency holds that renewable natural gas and other gas upgrading processes help to reduce the amount of methane emitted.
Only a handful of landfills in Iowa are converting their landfill gas, so some advocates hope to involve smaller facilities by making the process more accessible.
When combusted, methane is converted to carbon dioxide, which while still a greenhouse gas, has a much lower global warming potential than methane.
Sending captured landfill gas up through a flare reduces the emissions of a landfill, by converting that methane to carbon dioxide. But Foster said there is also a potential for energy capture that the industry became interested in.
He said 20 years ago, the focus was on direct uses of this energy, like using the flare to heat water needed for part of the landfill processes, or using it to power equipment at the facility.
Then the industry began to realize that energy could replace some fossil fuels and offset some of the environmental cost of burning coal. Foster said some facilities installed generator sets that essentially converted landfill gas into electricity for use either in the plant or to connect and sell into a power grid.
But, Foster said, as the renewable energy sector continues to focus more on wind and solar, the purchasing price for electricity 'doesn't justify' the cost of maintaining, and installing those generators.
Updates to the EPA's Renewable Fuel Standard program created a structure to sell renewable fuel credits, as it does for other biofuels, for landfill gas converted into renewable natural gas. The program presented an economic incentive for landfills to pursue the costly process of upgrading gas in this way.
Foster is also the administrator of the Black Hawk County Solid Waste Management Commission, a landfill in Waterloo that is converting its landfill gas into renewable vehicle fuel.
'We're taking gas that's just naturally going to be emitted into the atmosphere from our activity … but instead of just letting it go into the environment as carbon dioxide, we're actually offsetting diesel fuel by putting it into a vehicle,' Foster said.
The renewable natural gas, or RNG, facility in Black Hawk County started operating during the summer of 2024. Foster said part of the process involved switching the landfill capture system from 'compliance' to 'production' to pull as much gas from the landfill wells as possible.
This process reduces the amount of methane emitted into the atmosphere from the facility by an estimated 5,000 tons annually.
The Loess Hills Regional Sanitary Landfill in western Iowa is similarly operating with a production capture system.
The facility installed an automation system that maximizes the amount of landfill gas, or LFG, captured from landfill wells. The gas is then pumped to the Loess Hills Landfill RNG Facility, where the gas is cleaned and injected into a pipeline as natural gas.
On average, the automated monitoring on the wells, from the company LoCI Controls, increases the amount of methane captured by 15-20%.
Andrew Quigley, the director of environmental attributes for LoCI, said the technology increases LFG capture by monitoring the gas temperature, flow and composition every couple of hours.
Traditionally, these same metrics would be taken manually, once a month and the valves adjusted to meet the measurements. But, Quigley said landfills are 'dynamic' and the gas composition 'changes constantly' because of temperature and atmospheric pressure fluctuations.
'Between these once a month measurements, you can have a ton of variation on what's going on with the gas generation and what gas collection systems should be doing to better effectively capture that gas,' Quigley said.
The automated system analyses the readings it takes throughout the day and tunes the system to 'most effectively' capture the landfill gas, and provide consistency in the gas that is sent to the RNG facility.
According to LoCI's data, the Loess Hills facility processes 1,500 standard cubic feet of landfill gas per minute to upgrade to RNG. The facility hopes to increase that amount to 4,000 standard cubic feet per minute within 15 years, as the amount of waste grows at the facility, which would convert to renewable natural gas equivalent to the energy needed to power nearly 14,000 homes in Iowa per year.
Bret Stephens, the plant manager at the Loess Hills Landfill RNG Facility, said the automation system gives 'real time data' on the wells, which helps not only to pull more landfill gas, but also to identify oxygen leaks in a well which saves time and manpower.
'What those units can do with their automated tuning in minutes or hours, it would take us all day to do manually,' Stephens said. 'If the barometric pressure changes again, we'd be out there readjusting all the wells, and so we'd be constantly chasing our tails.'
Stephens said the landfill is also able to capitalize on some early action carbon credits, by operating the LoCI systems on waste piles that have been in place less than five years.
Like the Black Hawk facility, RNG upgraded at the Loess Hills facility is injected into a pipeline and used as renewable vehicle fuel.
Foster said the next step is to get these practices onto smaller landfills, many of which don't currently have the tonnage requirements set by EPA that require landfill gas capturing.
Some landfills are preemptively building out capture systems and engineering their outfits with methane capture in mind. He said the infrastructure costs of building something like an RNG facility, which was a $40 million investment at Loess Hills for example, continues to be a barrier, though he has seen the cost drop some in recent years as it becomes more widespread.
A landfill in Dubuque also cleans landfill methane and converts it to natural gas. According to the EPA database, the Loess Hills site has the highest rate of gas flow out of the three RNG facilities in the state.
EPA also shows that RNG facilities, both in landfills and those on agricultural operations that capture and clean methane from manure are growing in popularity. In the past 10 years, the number of landfill RNG facilities in the country has more than doubled, with more than 100 facilities in 2023.
Gov. Kim Reynolds introduced a bill that would create regulations for anaerobic digesters as part of her plan to expand energy programs in Iowa.
Foster said energy derived from anaerobic digestion is 'really the next step,' though he said the digesters can be applied to many types of organic waste, like food waste for example, and not just from digesting manure on agricultural operations.
The energy bills are advancing through both the Iowa House and Senate.
Foster said public-private partnerships can also be a way forward for landfills wanting to implement methane upgrading technologies.
The Black Hawk County Landfill's operation is a partnership with Pine Creek RNG, a private company that invested in both the gas capture system at the landfill and the gas upgrading facility.
'A landfill is not just this pile of trash,' Foster said. 'Once you start realizing that there can be value to it — if somebody can see that value, they're going to invest in it.'
Foster said he envisions the Black Hawk County facility to eventually work in a 'hub and spoke' model and partner with area landfills. This would allow the landfills to transport their captured gas to the Pine Creek RNG facility to be 'cleaned' and put on the pipeline, without the smaller landfills bearing the capital investment of building the facility.
Foster said he believes the RNG market will persist, despite changes to energy policy from the current administration. To him, President Donald Trump's 'drill baby drill' policy is less about fossil fuels and more about prioritizing domestic energy over imported fuel.
'Renewable energy, it fills in that gap,' Foster said.
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