To many people the Central Landfill in Johnston represents a pile of trash, which, of course, it is. To Ridgewood Renewable Power LLC the rubbish holds a valuable commodity – methane gas.
Construction will ramp up in earnest this year on a $120 million plant to convert the gas created by decomposing garbage to enough electricity to power about 25,000 homes. When complete, the 32-megawatt facility will become the second-largest gas-to-electric plant in the country and replace a smaller Ridgewood plant standing in the way of a planned landfill expansion.
Ridgewood Managing Director Stephen Galowitz said the company expects the new plant to open in 2012 and capture virtually 100 percent of the methane gas released by the landfill. The existing plant uses about 66 percent and the rest is flared.
“We believe in renewable energy, we think that is the way we’re going in the future,” Galowitz said “We think there are some great opportunities and this is certainly one of them. This project, it’s really going to be a showcase.”
So much so that one engineer suggested the company build an observation deck for visitors to get a good look at the operations of the plant expected to become one of the most efficient of its kind.
A network of pipes will draw methane from the landfill and send it to the plant. There, the gas will fire four combustion turbines to generate electricity. Heat released during the process will boil water flowing through nearby pipes. The steam generated will turn another turbine to produce even more electricity. And because trash shows no signs of stopping its arrival at the plant, the process will run continuously, unlike solar panels or wind turbines that generate electricity intermittently depending on weather conditions.
Ridgewood announced plans to build the plant in December 2008 under an agreement with the R.I. Resource Recovery Corporation, the quasi-state agency that oversees the state’s only dump. The corporation needed Ridgewood’s existing plant removed to create room for a bigger landfill. But the corporation would have had to pay Ridgewood millions of dollars to tear down and relocate the plant, money the organization did not have, Executive Director Michael OConnell said.
OConnell said that in the end, the corporation expects to save about $1 million annually, even factoring in the lower royalty rate. That’s because the corporation will shed $3 million to $4 million a year in maintenance costs. And while the royalty rate will be less, the new plant is expected to capture far more methane than the existing one.
“By converting 100 percent into electricity it will be really better for the environment and it will be more economical,” OConnell said.
The U.S. Environmental Protection Agency calls methane a greenhouse gas more than 20 times more effective in trapping heat in the atmosphere than carbon dioxide. Methane can remain in the atmosphere for nine to 15 years.
The new plant will use all the methane and release some carbon dioxide captured by the collection pipes, although Galowitz said scrubbers attached to smokestacks will collect some. The technology will also capture sulfur emissions, which Galowitz said engineers are trying to find a way to pump into dirt for gardeners. And plans call for the Resource Recovery Corporation to draw spent water from the plant’s cooling towers to use for dust control at the landfill. The corporation presently draws water from the municipal supply.
The plant will, however, be smaller than initially envisioned. When announced in 2008, Ridgewood anticipated building a 47.6-megawatt plant. But the amount of garage arriving at the landfill has decreased as municipalities and the state work to boost recycling efforts and the economy sputtered. In fiscal year 2007 – when Ridgewood first considered a new plant – 1.1 million tons of trash entered the landfill. For the fiscal year ending June 30, the landfill received 635,423 tons of trash, according to the Resource Recovery Corporation.
Ridgewood reacted by cutting the number of methane-fired turbines from five to four. Meanwhile the expected cost ballooned to $120 million from $80 million.
The company also sought and secured legislation to advance a process to approve a long-term power-purchase agreement between the company and National Grid. The R.I. Public Utilities Commission signed off on the contract in July 2010. Under the agreement, Ridgewood will sell electricity to National Grid for just shy of 12 cents a kilowatt-hour.
(By way of comparison electricity from traditional sources like coal sells for a few cents a kilowatt-hour. The offshore wind farm proposed by Deepwater Wind would sell electricity for 24.4 cents a kilowatt-hour in the first year of the contract.)
The approval of the Ridgewood plant did not come without opposition. The Conservation Law Foundation Rhode Island chapter told lawmakers that the bill speeding up the contract-approvals process unfairly favored one company.
Galowitz said Ridgewood needed the expedited process so it could start construction before tax incentives expire at the end of the year. The legislation that set up the process said more than $50 million in federal grants would expire if construction did not start by the end of 2010.
“We’re under tremendous time pressure,” Galowitz said. •
