Santa Rosa open to new composting operation at Laguna wastewater site

Santa Rosa is open to a large-scale composting operation on city-owned property near the Laguna wastewater treatment plant, an option that could provide curbside garbage customers some monthly savings.

The Sonoma County Waste Management Agency has been looking for a new site for an organic composting facility since a longtime operation atop the Central Landfill west of Cotati was shut down by regulators in 2015 over water pollution concerns.

Since then curbside customers have been paying millions of dollars to have their organic garbage hauled out of the county, an expensive, wasteful process that local officials want to end.

The county waste agency invited composting companies to submit proposals for a new facility in late May. As part of that process Santa Rosa made it known it might be willing to allow such an operation on surplus property north of the treatment plant.

The city interviewed potential operators, reviewed their plans, and winnowed the list to four companies it felt would be the best fit, said Emma Walton, water reuse engineer for the city.

The four finalists were San Diego-based BioMRF, the multinational firm Sacyr, StormFisher, which is headquartered in Ontario, Canada, and a Petaluma-based venture called Renewable Sonoma, which appears to have partnered with SCS Engineers in Santa Rosa.

The city’s Board of Public Utilities last week agreed to let the four firms submit proposals to the agency using city land. The proposals are due next month.

Putting a composting operation near the wastewater plant makes a lot of sense, Walton said.

“It seems like a good location for it to me because there are so many synergistic benefits that could arise out of co-locating it with the treatment plant,” she said.

For one, the city already composts about a third of the 28,500 tons of organic waste processed by the plant each year. The plant processes an average of ?18 million gallons of wastewater per day from ?230,000 residents in Santa Rosa, Rohnert Park, Cotati, Sebastopol and unincorporated portions of Sonoma County.

It composts that material during the rainy winter months when applying it to fields - the cheapest option - is not allowed because of concerns about runoff. Having another composting operation nearby could allow the city to increase its composting of bio-solids, she said.

The city plant produces a lot of treated wastewater, and that water could be used to keep the compost piles at the moisture level needed to keep the composting process going. The plant also produces excess heat from its four big gas-fired engines that produce electricity for the plant, and that heat could be used to boost the composting process, Walton said.

Some composting operations also produce methane, which, under the right circumstances can be captured and burned by those same engines to generate even more electricity, making the plant more self-sustaining, she said.

Finally, any stormwater that runs off the roof or parking lot of the facility could easily be treated at the plant, Walton said.

That runoff proved to be the problem for the former Sonoma Compost operation, which piled up grass clippings, leaves and table scraps in large outdoor windrows at the county landfill. When it rained, the water sometimes flowed off the site untreated into a ?local creek.

It’s not clear how large the proposed operations would be, what type of composting they’re considering, or how much land they’ll need. The city has 26 acres it says it might be willing to lease for the purpose. The details of the proposals remain confidential, Walton said.

While the Llano Road plan is located in a lightly populated area about ?9 miles southwest of downtown, there are still residents who live along Walker Avenue who could protest such a use. The Sonoma Compost operation was shuttered largely because of legal challenges by nearby residents. It’s unclear how Llano Road residents might respond to the idea of a compost operation taking root in their area.

Proposals are due to the waste agency by Jan. 16, and a final decision about an operator will be made by the agency’s board. Separately, the city’s Board of Public Utilities would have to approve a lease for the compost site.