Could Anacortes sewage one day become fuel or some other product the city could sell?
The Anacortes City Council explored this question and other options that could replace the aging fluidized bed incinerator of the Anacortes Wastewater Treatment Plant, based on information presented by the environmental engineering firm Brown and Caldwell.
Director of Public Works Fred Buckenmeyer has favored the idea of hydrothermal liquefaction, a new technology with some pilot programs installed in Vancouver, B.C. The process turns sewage sludge into biocrude oil and biogas which can be used as fuel.
The fluidized bed incinerator now in use has a yearly maintenance cost of about $500,000, Buckenmeyer said. It also has not been meeting air quality regulations.
The city still has a few years to make a decision, he said.
“We’re going to be able to keep it running, barring catastrophic failure,” Buckenmeyer said.
The reason why the council might decide to act now is to take advantage of a U.S. Department of Energy grant that would pay for half of the hydrothermal liquefaction project, with the deadline quickly approaching. To receive the grant, the city must produce an engineering report that explores hydrothermal liquefaction and two other options.
Additional funding may be available through the state Department of Ecology.
The replacement options presented to the council were ranked based on reliability, sustainability, social impacts, cost and regulatory factors.
Hydrothermic liquefaction was ranked as the best option, slightly ahead of temperature-phased anaerobic digestion. That process, chosen by Bellingham to replace its incinerator, turns the sludge into biosolids that can be sold for use as fertilizer. The city of Edmonds is looking at gasification to replace its incinerator. In that process, the sludge is also turned into usable biofuel.
Among the other options reviewed were raw solids composting, supercritical water oxidation, mesophilic anaerobic digestion and alkaline stabilization.
The wastewater treatment plant’s current method, fluidized bed incineration, ranked 11th out of 12 options considered.
Some council members were hesitant about the hydrothermal liquefaction option due to costs. One downside is the high startup costs and future upgrades that might become necessary to bring the facility into compliance for nitrogen-limiting regulations.
While initial capital costs are unknown, one estimate said in the meeting suggested it was closer to $20 million than it was to $10 million.
It was mentioned that Marathon Anacortes Refinery has signaled interest in purchasing future biocrude oil produced, as well as Parkland Fuel’s Burnaby Refinery in B.C.
“I appreciate the enthusiasm for new tech here… but if we don’t produce enough, could they even use it?” Councilmember Ryan Walters asked.
Councilmember Matt Miller also expressed concern about maintenance and operation costs for the facility.
The council will return to the issue at next week’s session to make a decision on whether to move forward with the grant application for hydrothermic liquefaction, and if so, what two other options might be explored.