Taking Out the Trash

Covanta Energy operates more than 40 waste-to-energy facilities across the globe. These plants collectively convert 19 million tons-or more than 5 percent-of the nation's waste into renewable energy each year.
By Anna Austin
The number of power companies striving to implement waste-to-energy initiatives is rapidly increasing. Whether it involves introducing a new technology or well-established power utilities converting fossil fuel operations to biomass power, securing a plentiful, steady and convenient feedstock supply is essential to making any energy-from-waste venture economically viable-and it shouldn't be too difficult for plants that use municipal solid waste (MSW) to achieve.

Americans are producing more and more trash. According to the U.S. Energy Information Administration, in 1960, the average American threw away 2.7 pounds of trash per day. Today the average American throws away approximately 4.5 pounds per day, or more than 1,600 pounds per year.

As the annual amount of MSW generated continues to increase, the ways and means of disposing of it must expand and evolve, and Covanta Energy Corp. is one power provider that has rapidly expanded along with the increase. The company serves the disposal needs of more than 12 million people in communities across the U.S., which, according to Paul Stauder, Covanta Energy senior vice president of domestic business management, equates to processing more than 5 percent of the MSW generated annually within the country.

Hours before talking to Biomass Magazine, Stauder says the company closed on a deal resulting in its operations acquisition of six waste-to-energy plants previously owned by Veolia Environmental Services. Covanta Energy will likely acquire one more facility by the end of this year.

At 44 facilities, the company now operates the majority of the waste-to-energy plants in the U.S., and has divisions in Europe and Asia.

Gold River Project

Covanta Energy is active in projects beyond its recent acquisitions. In particular, the reconstruction of a brownfield site at Gold River, Vancouver Island, British Columbia. At the site of a former pulp and paper mill, which closed more than a decade ago, the company has the potential to provide considerable economic development opportunities in a community that currently has an unemployment rate of more than 50 percent.

Between site preparation and construction there should be plenty of work. "We'll use some existing roads and possibly some foundation work, but the site was abandoned a long time ago and not in ready use," Stauder says. "Essentially, we'll go in there, take down buildings and structures that we don't need, construct a new power plant that will process 500,000 to 750,000 tons of waste per year, and produce 90 megawatts of power to be sent to the BC Hydro grid."

A project economic impact analysis by Roslyn Kunin and Associates Inc., which was performed using the British Columbia provincial government input/output model, determined that economic activity in British Columbia would be boosted by $79 million during the three-year construction of the facility. Tax revenue would increase by $32 million, and more than 1,600 jobs would be generated during that period. Once in operation, it would add $32 million to the provincial economy, $1.5 million to provincial tax revenue and create about 195 full-time jobs.

Construction of the $500 million Gold River Region project, which has been received enthusiastically by the surrounding community, is anticipated to begin by the end of the year. "We'd like to get a shovel in the ground before then, but it's very tough these days, no matter what you're building, to get all your permits," Stauder says. "When you're building any kind of power plant it's even that much more difficult. There are a lot of regulations, a lot of processes to run through to get all your approvals so you can start the process. Everything seems to take a little bit longer."

Technology and Proximity

Covanta has licensing rights to the German thermal waste treatment technology Martin GMBH, which is used in many plants around the world. The majority of Covanta's facilities use the Martin system, according to Stauder.

The core component of the Martin system Covanta deploys is a reverse-acting combustion grate, which is comprised of several stair-like grate steps equipped with surface-ground grate bars. Every second step is moved up and down against the grate inclination, which constantly rakes and agitates the fuel bed and mixes the red hot mass with newly fed waste. As the waste burns, the fuel bed temperature reaches 1,000 degrees Celsius (1,800 degrees Fahrenheit) and higher, and it is combusted to inert mineral ash through the slow and uniform mixing and agitating motion of the fuel bed.

Burned-out combustion residues are transferred by a slowly rotating roller at the grate discharge and into the Martin residue discharger where they are quenched. The thermal heat is converted into steam to turn a turbine and create power.

Stauder says the majority of the facilities are located in close proximity to landfills and populated areas where electricity is needed, and Covanta typically contracts waste management companies to truck the waste, with one exception-the company's plant in Dickerson, Md. This facility processes an average of 1,500 tons per day of solid waste, generating up to 55 megawatts, enough to power 40,000 homes.

At Dickerson, MSW is first delivered to the Shady Grove Transfer Station in Derwood, Md., compacted into intermodal steel waste containers, and gantry cranes are used to load it onto railcars. Each day CSX Corp. assembles a train that transports the MSW 22 miles to the facility in Dickerson. There the containers are off-loaded and trucked from the on-site rail yard to the facility's enclosed refuse building.

Rail is also used after the Martin process, when the remaining ash material (according to the U.S. EIA, a ton of garbage is reduced to approximately 300 to 600 pounds of ash) is loaded back into sealed containers and shipped to a landfill in Brunswick, Va., thereby not adding to the truck traffic on the rural roads leading to the facility.

Although many of Covanta's plants are located in the Northeast, where demands for power are high, others are scattered all over the country-from Detriot to Long Beach, Calif., to Minneapolis and even in Honolulu.

Reliability is the Ticket

Collectively, Covanta Energy's plants produce approximately 5 percent of the nonhydro renewable power in the U.S. The beauty of waste-to-power applications and what makes it superior to other renewable energy technologies is its reliability-waste is always being generated, Stauder says. "We always look at how we are able to provide renewable power that is very reliable-we will run at about 90 [percent] to 92 percent of availability, whereas if you evaluate a wind plant, that will run at about 25 [percent] to 30 percent of the time, simply because the wind isn't always blowing; it's unreliable and you never know when it's going to create power," he says.

Even the output from hydropower plants fluctuates with the seasons, depending on rain and water flows, Stauder says. "Being consistent and reliable, we're beneficial to the electrical infrastructure in the country and the growing need for power. On top of that, people might say �well, you're a power plant, so you can't be good,' but we look at our process compared to the alterative process for waste disposal. When you are landfilling, you're taking a garbage truck of waste and putting it into the ground-it's going to decompose and turn into methane, which is 20 to 25 times more potent a greenhouse gas (GHG) than any other out there."

He adds that while avoiding methane and GHG creation, Covanta Energy also doesn't add to truck traffic and diesel emissions associated with transporting truckloads of trash to landfills that are typically farther away from the communities they serve than renewable energy plants. "You need more trucks, more diesel, and on top of that you're not going to produce as much power out of a ton of trash, as you will at one of our plants," he says. "Out of 1 ton of trash, we'll produce about 600 kilowatts, whereas a landfill gas plant-if the landfill has one-will only produce between 75 and 150 kilowatts per ton. So those are some huge benefits-when you consider all of those things, we're actually a GHG reducer compared to the alternatives, and we pride ourselves on what we do-we provide a service that is exceptionally good for communities, the economy and the environment." BIO

Anna Austin is a Biomass Magazine associate editor. Reach her at [email protected] or (701) 738-4968.