UNH takes lead in using methane from landfills for alternative energy
In the old days of town dumps, officials would occasionally ignite their municipal trash to shrink the pile and scare the rats; heaven help those who were standing downwind.
Ignition is still part of life at dumps. Now, however, it isn’t garbage that gets burned, but methane produced by bacteria deep within the trash pile.
And far from avoiding the result, people pay for it.
“This is really a fuel substitution project,” Paul Chamberlin, assistant vice president of the University of New Hampshire’s Energy and Campus Development department, said as he considered the huge amount of methane that the university is about to start buying from the massive Turnkey Landfill in Rochester.
“We were going to do this with natural gas. . . . Instead, we’ll use (landfill gas).”
This EcoLine project, which is costing $45 million, will eventually produce around 80 percent of the electricity and heat consumed by the school’s main campus at Durham.
It will also put UNH on the leading edge of an unglamorous but growing corner of alternative energy: using the gaseous byproduct of landfills to substitute for coal, oil or natural gas.
Waste Management, the giant multinational firm that owns the 150-acre Rochester landfill, “has more than 100 power plants around the country,” Alan Davis, senior district manager for the company, said during a recent tour of the site.
“We have two (turbines) here, producing the equivalent of (heating) 9,000 homes.”
Waste Management isn’t alone. At the end of 2006, according to the federal Energy Information Administration, there were 221 plants around the country that burned landfill gas to make electricity, including four Waste Management sites in New Hampshire.
Between them, these plants consumed an estimated 174 trillion BTUs worth of gas, producing about as much electricity as two Seabrook nuclear plants. Their production has risen by more than 20 percent since 2003, and it’s more than twice the figure produced by solar-power plants.
The UNH project will increase the number because right now, Waste Management is only using about half the methane produced at Rochester to power its two electric turbines. This project means they can get more income by selling gas that it currently burns away uselessly, although not without complications.
Those complications range from wet weather, which reduces the amount of methane produced by bacteria, to regulations with the regional electric grid that reduces UNH’s flexibility for using excess power, to the chemical mess made by decomposing cosmetics (yes, cosmetics).
“The toughest times are ahead,” said Davis, a civil engineer who has spent his working life in waste management. “I thought the two years of contract negotiations were tough.”
UNH didn’t set out more than four years ago to become the first university in the country to depend on landfill gas for most of its power. As Chamberlin explains it, they just needed to replace the aging boiler that produced steam heat for the campus.
The university had already taken big steps to be more ecologically conscious with its energy production. It switched from thick, heavy No. 6 oil to natural gas a decade ago, and in 2006, opened a $28 million cogeneration power plant.
Cogeneration facilities grab waste heat that’s usually lost during the production of electricity and use it to heat buildings. This is a booming area in energy efficiency because it’s a relatively simple technology with big results: UNH estimates that cogeneration cut the campus’ greenhouse-gas emissions by a whopping 21 percent.
As this was going on, another idea was floated: powering the plant with landfill gas from Turnkey, which is about 12 miles from Durham.
“It just came up during a conversation,” Chamberlin said. “It took four years to make it happen.”
In theory, the transition is simple because landfill gas is roughly one-half natural gas – or methane, chemical symbol CH4 – although amounts vary depending on what’s rotting in the landfill. Just get rid of the rest – the bulk of which is carbon dioxide – and you have free fuel.
Getting rid of the rest is hard, however. Part of the reason the EcoLine is so expensive is that UNH had to build an industrial chemical complex next to the landfill’s 100-foot mountain. This processing plant separates the good from the bad with techniques that include activated charcoal; compression, refrigeration and heating; and even a sieve with holes so tiny that some molecules fit through and others don’t.
One big problem, Chamberlin and Davis said, is a family of silica-based compounds known as siloxanes. These are produced by the decomposition of various materials, most notably cosmetics, and they have a nasty habit of building up on the fast-spinning blades of turbines, throwing them off balance and causing huge damage.
There’s also all the leftover CO2, which will be released into the air. A project this ecologically friendly would like to do something useful with that notable greenhouse gas – for example, build real greenhouses and use it to goose vegetable production.
But first, EcoLine has to get operating.
EcoLine should begin producing landfill gas power within a month or two, and be in complete operation by the fall. It’s a slow process because of technical issues – but perhaps the biggest issue for a project of this magnitude is financial.
“This is a huge commitment for the university,” Chamberlin noted.
The Energy and Campus Development department operates as a “quasi-utility” within the UNH system, as Chamberlin describes it. The university says it’s paying for the project through borrowing, without using state money or tuition fees, because the cost over 20 years – the minimum length of time that the Rochester landfill is permitted to operate – would be lower than sticking with the usual route.
That projection, however, is based on savings compared to the expense of using traditional fuels. The price of natural gas, like the price of oil, soared and then collapsed as the recession hit, falling from a high $20 per million BTU in September to as low as $5 in December.
Like many alternative energy projects, EcoLine is much harder to justify when traditional fuel is cheap.
“When it was $15, I was a hero. At $5 – not so much,” Chamberlin said wryly.
The long-term expectation, however, is that natural gas prices will rise again. From UNH’s point of view, the higher, the better.
“The economics aren’t quite as good today, but for the life of the project, it’s still good,” Chamberlin said.
He won’t discuss details of the contract with Waste Management, but says UNH will pay a “good price” that’s tied to the natural gas index.
Another factor is state and regional attempts to provide monetary incentives for cutting energy use and greenhouse-gas emissions.
“Without the subsidies, you would never do it,” Davis said. “We can’t compete with the cost of coal.”
For example, EcoLine is eligible for Renewable Energy Certificates, which are tradable certificates for alternative-energy projects that can be sold and create an income source. The Regional Greenhouse Gas Initiative, a 10-state project that caps the amount of carbon emissions by power producers, will also provide a financial benefit.
“Something like this takes a lot of work from a lot of smart people – technicians, scientists, engineers – and finance people,” Chamberlin said. “It can’t happen without all of them.”
Considering that it will be used by an institution whose job is to produce smart people, that seems reasonable.
Methane is naturally produced by anaerobic bacteria – microbes that don’t need oxygen – while they decompose organic material, either in landfills or in places such as bogs, where it becomes “swamp gas.”
In general, about four to eight months after trash is covered – at a giant site such as Turnkey Landfill in Rochester, trucks and tractors place layers of dirt over the trash every day – the oxygen gets used up and methane production begins.
As a result, the amount of methane produced at a landfill depends both on the amount of bacterial action and the amount of organic material.
Ironically, this means that some environmentally friendly moves can lower production of this environmentally friendly fuel.
The first of these are recycling and composting, which keep organic material such as yard waste out of landfills – thus reducing the food for bacteria.
The second is the need to keep pollutants from oozing out of trash into groundwater, largely by keeping landfills as dry as possible. Huge landfills now sit atop thick layers of impermeable clay and are covered with sloping soil to encourage snow and rain to run off rather than seep through.
Bacteria need water to thrive, however. So in general, the drier the landfill, the less methane it produces.
As an example, Waste Management wants to add water to a closed landfill within its massive Turnkey operation so that methane could be produced from the trash within. Environmental laws won’t allow this, however, for fear of groundwater pollution.
As a final complication, too much water is also bad for methane production at landfills because it can block the hundreds of little wells that draw the gas out of the trash. Turnkey faced that problem over the last two years, which have been unusually wet.
– DAVID BROOKS