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City could turn wastewater into energy

In an effort to turn garbage into gold, the City of Petaluma is exploring ways to convert the wastewater generated by its industrial users into energy.

Just five months after several local food processors said they could no longer afford Petaluma's wastewater costs, the city has hired an outside consultant to study the sewer plant's capacity and efficiency. The ultimate goal: Retrofit the facility to accept high-density waste from industrial users and turn it into electricity that the city can use to offset energy costs.

Kennedy Jenks Consultants — a Santa Rosa-based firm that built the original Petaluma Hopper Street wastewater plant in 1930 — is tasked with assessing the ability of the Ellis Creek Wastewater Treatment Facility to accept the thick, sludgy waste that food and beer producers generate. There is a growing number of such businesses in Petaluma. Kennedy Jenks will also oversee a $4.5 million required upgrade to the plant's equipment to meet higher state water quality standards.

Public Works Director Dan St. John said that the firm's final report to the city will include a proposal to create a methane digester that turns waste into energy.

"It's state of the art technology," said St. John. "It encourages the food and beer industries to stay in Petaluma, but to do so in the environmentally friendly way that reflects this city's long-term goals."

News of exorbitant costs to food processors and breweries for wastewater treatment surfaced earlier this year, prompting the Petaluma City Council to discuss the matter at its annual goal setting session in February. After several businesses threatened to leave Petaluma if a cheaper solution did not present itself, the council told city staff to pursue solutions. St. John immediately began soliciting local consulting firms to assess operations at the three-year-old, $120 million plant.

"During our hiring process, we discovered that Petaluma's industrial users generate approximately 40,000 gallons of high density waste every day," said St. John. "That's roughly 12 huge tanker-truck loads that are driven to Oakland — where they have a methane digester — every day. That means costs to the businesses, wear-and-tear on our roads and damage to the environment through greenhouse gas emissions."

Lagunitas Brewing Co., one of Petaluma's largest high-density waste producers, said that they spend about $1.2 million each year on trucking costs. As their operation grows, that figure is projected to rise significantly. While the hometown brewery has no plans to leave Petaluma, they said earlier this year that having a local place to dispose of their waste would help.

"We want to help the city find solutions because it will take our 3,000 trucks off the road each year," said Lagunitas Chief Financial Officer Leon Sharyon.

If the city decides to retrofit the plant, St. John said it would require a commitment from the city's high-density waste producers to bring enough waste to the plant to make the project worthwhile. Generating electricity from converted wastewater requires collecting enough high-density waste to make the project cost-effective. St. John said he thinks Petaluma's industrial users currently generate enough waste to support the city building its own methane digester.


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