Turning Sewage Sludge into Fuel

Casella Organics wants to dry sewage sludge into pellets and bring them into Pennsylvania to be used as a fuel at coal-fired plant.

This would be Casella’s first foray into the biosolids-as-powerplant-fuel concept and it comes from the company’s desire to diversify, said Jen McDonnell, director of sales and marketing.

Most of its biosolids are applied to land as fertilizer or for other purposes, she said. Commercial dryers in the Northeast can get most of the water out of sludge.

Cement kilns, which use a lot of energy, have used this kind of material as fuel, she said, and the company wanted to know if it would make economic and technical sense to develop a product line for coal-fired power plants.

“I think the objective is to make it attractive to an industry as an alternative [fuel],” she said. “You want to be able to compete with whatever fuels are out there.”

Ms. McDonnell said she doesn’t know if the emissions from biosolid burning would be more or less than those from coal alone.

“That’s part of what we have to find out in the permitting process,” she said, “If we can get through this pathway when everybody is comfortable with trying it as a fuel, then we can look closer at some of these opportunities.”

The Pennsylvania Department of Environmental Protection is reviewing Casella’s application to transport the biosolids into the state. It would be up to the power plants to apply for a permit to burn the stuff. Currently, there are no facilities permitted to do that, the DEP said.

Ms. McDonnell said Casella has talked to some power plant operators but doesn’t have any contracts in hand yet. “With these new ideas, it’s really one step at a time,” she said.

In Pennsylvania, unlike in some states that have restricted the practice, spreading sewage sludge biosolids on land is still an option, said Ed Johnstonbaugh, a renewable energy educator with Penn State Extension-Westmoreland.

For it to be worthwhile to transport biosolids, they have to be packed with enough heat content to override the cost or there must be other incentives for the fuel, he said.

“The only potential for something like that is if they can get it classified as a renewable fuel,” he said.

Pennsylvania has alternative fuel standards that require utilities to get an increasing amount of their electricity from renewable and other sources, such as waste coal, biomass, and landfill gas. It’s not clear how the state would treat biosolids from sewage sludge.

Nils Hagen-Frederiksen, a spokesman for the Pennsylvania Public Utility Commission which administers the state’s alternative energy portfolio standards, said no one has tried to claim biosolids as an alternative fuel yet, but if someone wants to argue it fits under the biomass category of an alternative fuel, they can petition the PUC.

Ms. McDonnell said Casella might explore that route.

A few years ago, Michigan-based DTE Energy approached the Allegheny County Sanitary Authority about using its biosolids as fuel in coal plants, said Douglas Jackson, director of operations and maintenance.

Mr. Jackson said he believes it was the alternative fuel standards that piqued DTE’s interest. “They had some coal-fired units and they were looking for sources of biosolids,” he said.

The conversations were brief and never went anywhere, he said.

Alcosan produces 110,000 tons of biosolids each year, and sends about half of that to be applied to land for agricultural and reclamation purposes once it’s blended with lyme. The rest it burns in its incinerator, which produces steam to heat the facility and ashes sent to a landfill.

Its biosolids are still about 70 percent water, Mr. Jackson said. They would need to be further solidified in an industrial dryer to be compatible as a fuel for coal plants, he said. That would add the cost of transporting the sludge and the energy-intensive expense of drying it.

Source: Power Source