Steam Energy Carries Heat To Arsenal
October 26, 2011
REDSTONE ARSENAL, Ala.--High-tech energy often begins with low-tech input.
That's the case for the unique waste-to-energy facility that provides steam to Redstone Arsenal to heat and cool its buildings. Huntsville's steam plant, owned by the city's Solid Waste Disposal Authority, relies on vary basic input -- municipal solid waste, also known as household garbage -- to manufacture energy that travels in the form of steam through seven miles of export line to the Arsenal.
"In 1990, when this steam plant opened, it was leading edge technology. It still is leading edge today. There are not a lot of these facilities in the country," John "Doc" Holladay, executive director of the Solid Waste Disposal Authority, said.
The Huntsville steam plant is one of 90 in the U.S. It is the only waste-to-energy steam facility in Alabama. Built and operated in its early years by Ogden Martin Industries, it is now managed and operated on behalf of the city by about 40 employees of Covanta Energy.
In the late 1980s, the waste-to-energy steam plant satisfied significant needs for both Huntsville and Redstone Arsenal that still exist today.
"The landfill was filling up and the city was running out of disposal capacity. At the same time that Huntsville was looking for alternative disposal technologies to free up landfill space, Redstone's old coal-fired steam plant needed to be updated or completely rebuilt," Holladay recalled.
"Redstone and Huntsville partnered up to make things happen, and an agreement was reached for Huntsville to supply Redstone with steam energy for the next 25 years."
A waste-to-energy steam plant was a solution to Huntsville's landfill issues and was a steam energy solution for Redstone. As part of the agreement, Redstone transports up to 50 tons of waste each day to the steam plant to be turned into steam energy. In addition, the charges Redstone pays for that steam energy are used by the Solid Waste Disposal Authority to pay for operating the steam plant and to invest in steam plant improvements.
In July 1990, the waste-to-energy steam plant began supplying steam energy to Redstone. The steam plant, located on 20.5 acres on the northeast side of the Arsenal along Triana Boulevard, is designed to process up to 690 tons per day of municipal solid waste, commercial waste and limited amounts of dried sewage sludge to provide a consistent source of 400,000 pounds of steam energy per hour to Redstone.
"All garbage in Huntsville and Madison County -- including Madison city -- is delivered here," Holladay said. "To make something like this successful, you have to have two things -- a consistent source of fuel and an energy customer."
In its early years, the waste-to-energy steam plant accepted both municipal waste, and construction and demolition debris from its customers. But that mix has changed over the years.
"Construction and demolition debris has a high energy content," Holladay said. "But because the amount of household waste kept growing, we had to start taking construction and demolition debris back to the landfill."
On Redstone, big consumers of steam energy include NASA's Marshall Space Flight Center, the Sparkman Center, the Aviation and Missile Research Development and Engineering Center, the Von Braun Complex and, most recently, the Army Materiel Command/Security Assistance Command headquarters.
"We are working to concentrate our steam customers along Martin Road," Mark Smith, the Garrison's energy manager, said. "We want to use this renewable energy as efficiently as we can. Because of energy loss in our steam lines, we are pruning off some lines that aren't in a concentrated area. We are trying to maximize efficiency using steam energy."
While steam energy usage grows along the Martin Road corridor, some lines have been eliminated in the northeastern section of the Arsenal near the motor pool and in the old schoolhouse area near Gate 10.
At the same time, some new buildings, such as those located at the Von Braun Complex, are using a combination of steam energy and gas to heat and electricity to cool because of efficiencies.
"The bottom line is we want to use energy that is most efficient and cost effective for us," Smith said. "Our energy has to be more cost effective and at a cost the Garrison is willing to pay."
Redstone is only one of a few Army installations that use steam as energy, Smith said. He knew of only one other installation -- Aberdeen Proving Ground, Md. -- that uses steam energy today.
"It is pretty rare in the Army," he said. "(During the World War II era) we started using steam energy because we were in munitions production and steam energy was a safe way of heating that wasn't explosive. We are not in munitions production anymore, but we continued to use that system of heating."
In those days, the Arsenal's steam energy was produced from coal. In 1990, Huntsville's waste-to-energy steam plant replaced two of the Arsenal's coal-fired steam plants.
"But we produce our own steam still from remote locations," Smith said. "We have nine or so boiler plants fueled by natural gas or fuel sources. We still have loss in distribution. But it's not cost effective to change because gas prices are so cheap. Cost is an issue. So, too, is energy reduction and energy efficiency. We want to manage our own resources and do it smartly."
For Chris Spence, chief engineer for Covanta Energy, the waste-to-energy steam plant has a lot of untapped potential.
"About 70 percent of manufacturing processes in the country use steam as a primary source of energy," he said. "Of the 90 steam plants in the U.S., Covanta manages 41. There are a lot more waste-to-steam plants in Europe."
For many communities, the high cost of building a waste-to-energy steam plant must be weighed against the more traditional use of landfills for waste disposal.
Understanding the waste-to-energy steam plant is popular fodder in Madison County for school-age children who often go on field trips to the plant. The entire process -- from the garbage trucks arriving at the tipping area to dump refuge into the waste storage area to the giant claw that mixes and grabs trash to send through the steam process system to the end product of steam for the Arsenal and ash for use in the landfill -- makes for some good classroom discussions pertaining to environmental science issues.
In the waste storage area, the plant's claw mixes the waste to ensure a consistent energy source is fed into the chutes that travel to the burners.
"Coal, fuel and natural gas are very consistent for heating. Trash is not. What's wet, what's dry, what burns well and what does not burn so well all affect the consistency of trash as an energy source for heating buildings," Holladay said. "If you mix that trash correctly, then you will get heat release that is consistent."
The claw is much like a crane, picking up the waste and dumping it into chutes. The waste travels onto the grates of two mass-burn furnaces where temperatures exceed 2,000 degrees Fahrenheit.
The incineration process cuts waste volumes by 90 percent, reducing the waste of one fully loaded residential garbage truck into ash that can fit into a wheelbarrow. The steam created by the incineration process is shipped through seven miles of pipeline to the Arsenal while ash remaining from the combustion process is transported to the landfill where 14.5 tons of ferrous metals and 1 ton of non-ferrous metals are removed and recycled daily.
"We use the ash to cover garbage," Spence said. "Alabama regulations require the coverage of all municipal solid waste every day. As opposed to using dirt or some other synthetic material to cover waste, we use the steam plant's ash."
Because of the waste-to-energy steam plant, the amount of waste being transported to the city's landfill located just south of Airport Road is now mostly construction and demolition material, reducing the amount going in the landfill by 75 percent in weight and 90 percent in volume. In addition, the absence of household waste also means there is no production of methane gas, which is an issue at waste-filled landfills.
The last remaining elements of the process -- the acid gases resulting from the waste combustion -- are neutralized in a dry flue gas scrubber. Any particulate matter is captured by a fabric filter baghouse.
"Our air pollution equipment exceeds what our permit requires," Spence said. Reports indicate that in most all categories the steam plant produces about 90 percent less than the allowable air pollutants.
Holladay said the Solid Waste Disposal Authority is considering expansion of the steam plant to better accommodate the growing need for waste disposal.
"We are right at the time when we need to be looking at the expansion of the plant," he said. "We could add a new boiler and provide more steam. But we need to have a manufacturing operation nearby that needs steam to make that feasible. The other option would be to generate electricity from waste."
Existing boilers at the steam plant produce steam at a temperature and pressure that is far less than the higher temperature and pressure needed to produce electricity.
"We need to establish what our real need is," Holladay said. "The issues of energy resiliency -- the need for energy backups and how quickly energy can be resumed once a source has been lost -- and distributive energy -- the need to generate energy close to where it is used -- are two things we need to consider for our future investments. As we increase the demand for electricity, there is a growing demand for having resiliency and energy sources that are close to the demand."
Smith said the Arsenal would consider being a customer of electricity from the steam plant as long as it is cost effective. In the Army's move to make installations Net Zero, meaning they produce as much energy as they use, new alternatives to energy from the steam plant would gain the Arsenal credit toward a Net Zero status, he said.
Holladay would like to see the steam plant grow into an operation that co-locates the production of steam and electricity for energy usage on the Arsenal.
"There is more potential for us to be more efficient," he said. "We've been blessed with the collaboration we've had with the Garrison commanders at Redstone. This is probably the closest thing this community has to a true partnership between the city and county, and the federal installation.
"Redstone is important to our future growth. This steam plant has done everything we've asked it to do. Now, we need to start looking at where we go from here for the future."