By David M. Fitzpatrick
Special Sections Writer
Ever wonder what happened to that half-eaten burger you threw in the garbage 20 years ago?
Probably not. But if you’re in this part of Maine, anything you threw away since 1975 likely ended up in a landfill like Casella Waste Systems’ Pine Tree Landfill in Hampden. What you might not know is that, as it decomposes, anything organic generates greenhouse gases.
“We’ve known for a long time that landfills that contain organic matter, which is pretty much most of them, generate methane,” said Don Meagher, Casella’s manager of planning and development. In fact, about 54 percent of landfill gases is methane, and 42 percent is carbon dioxide. Now consider all the scary things you’ve heard about carbon dioxide contributing to the greenhouse effect: Methane is far worse.
To put it in perspective, carbon dioxide has a Global Warming Potential of 1. Over a 20-year period, methane has a GWP of 72 (21 over a 100-year period). That’s a lot more greenhouse power. But burning methane in the presence of oxygen produces one molecule of carbon dioxide and two molecules of water — greatly decreasing the GWP.
The problem is compounded by the fact that not too many decades ago, just about every municipality had its own landfill, and today they’re all venting methane into the atmosphere. But how much methane?
Pulling Gas from Garbage
To handle the methane output in Hampden, in 2002 Casella installed a gas reclamation system. First, Casella drilled multiple wells, about 100 feet apart, all the way to the bottom of the landfill. Consider that that Hampden site began as a pit in 1975; 33 years later, its highest point is 200 feet above-grade. Those are some deep wells.
Casella then sunk perforated pipes into the wells and graveled them, installed vacuums atop each well head, and connected them all to a central point with solid pipes sunk just beneath the surface. If you’ve ever driven by the landfill on I-95 at night, you’ve seen the results in the form of a giant flame next to the landfill. That’s the methane burning off. In addition to the greenhouse gas reduction, burning the gas also eliminates hydrogen sulfide, the odor-causing component of landfill gas.
“To my knowledge, there are only four landfills in Maine that are doing this — that’s us in Hampden and Old Town, Waste Management in Norridgewock, and the City of Bath Landfill,” said Meagher. “Now, that flaring in and of itself has a substantial environmental benefit, since methane is many times the greenhouse equivalent of carbon dioxide, which we hear so much about.”
Landfill Gas to Energy
In January, Casella began a new phase: landfill gas to energy. Methane is used as a fuel to run engines that generate electricity. Rising fuel costs, tax breaks, and federal renewable-energy credits have recently made this economically feasible; now that it’s operating, the results are significant. The plant was built by the Cianbro Corporation and is being operated by Bluewater Energy Solutions.
Under normal operations, Casella pulls about 1,500 cubic feet of landfill gas out of the landfill every minute, 24 hours a day. More than half of that is methane which, when burned, produces enough electricity to power about 3,000 homes — just over 3 megawatts every of power. The greenhouse-gas reduction is equivalent to taking 25,000 cars off the road and eliminating 130,000 metric tons of carbon dioxide per year.
The gas levels do fluctuate, so when the amount of methane extracted exceeds the engines’ processing ability, it’s vented and burned on the flare. End result: Methane emissions from the landfill is reduced to almost zero.
Just imagine if this process were applied to the 350 closed municipal landfills in Maine. Just collecting and burning the methane would be great; consider how much electricity could be generated as well. Unfortunately, that’s cost-prohibitive; even after the extensive design and construction, there’s labor involved in running the facility.
Because Pine Tree is an old landfill, its methane generation is actually on the decline. “That being said, even though this landfill is going to close at the end of 2009, we will continue to produce enough gas to generate electricity for another 20 years,” said Meagher.
Casella also manages the Juniper Ridge Landfill in Old Town, and will likely install an LFGTE plant there as well. That landfill is currently generating as much gas as the one in Hampden, but the amount of landfill gas will increase over time. At its peak, it could generate about 12 megawatts — four times that of Pine Tree.
“It has the potential for generating electricity out to the year 2065, and that’s a conservative estimate,” Meagher said. “So more power will be generated over a longer period of time, because we’re harvesting the gas at the beginning of the landfill’s life.”
Casella manages other landfills in Maine, New Hampshire, Vermont, New York, and Massachusetts. This is the first LFGTE plant it owns directly, but manages other landfills that supply methane to other gas-to-energy projects.
“There are a number of projects that we have in the discussion stage,” Meagher said. “It is a growing trend in the solid-waste business, there’s no question about it.”
The installation of the engines and electrical-generation equipment was planned for a year and implemented in 10 months. Getting up and running has been a learning experience, but just over two months later, Casella has worked out most of the kinks. Challenges aside, Casella is managing an enormously successful project.
While methane reclamation is sweeping the nation, “This happens to be the first such project in Maine,” Meagher said, “and we’re kind of proud of that.”