Another Kind of Recycling

On May 10, the city of Santa Rosa, California's Laguna Wastewater Treatment Plant will inaugurate a small pilot project that relies on native algae and marsh plants to purify sewage and produce methane. The gas will run a generator that charges a fleet of four electric maintenance vehicles.

Nationwide, there’s a rush to extract more energy from wastewater treatment, but Laguna boasts that it is the only operation in the U.S. harvesting algae for fuel. The city has published a coloring book about its “F.A.B” (Fuel from Aquatic Biomass) project, featuring Algae, a smiley, if scummy, little fellow.

Algae-to-fuel is a side operation at Laguna, but it has garnered top honors from the Association of California Water Agencies. In addition, Laguna has won state and federal awards for recycling and quality control. Ninety-nine percent of its biosolids — treated, nutrient-rich sewage sludge — are spread on the land, either as fertilizer on fodder or as compost on city parks and playgrounds. Only 1 percent is trucked to a landfill. Apart from the algae operation, 25 percent of the plant’s electrical bill is offset by methane from biosolids.

Last year, Ventura Regional Sanitation District, serving Ventura County, began converting biosolids into dried pellets for fuel. And in a pilot project, the city of Los Angeles started injecting some of its biosolids into wells a mile under the ocean floor at Terminal Island, where they will degrade into methane for fuel.

In northern San Diego County, the Encina Wastewater Authority now converts its biosolids into dried pellets for sale to a cement manufacturer in Victorville. The Encina treatment plant, like Laguna, is certified by the National Biosolids Partnership.

“We’ve gotten our ratepayers out of the game of paying millions of dollars to haul biosolids more than 200 miles to Yuma, Ariz.,” said Kevin Hardy, the general manager. “Instead of five trucks to Yuma, we’re sending one truck a day to Victorville. That’s half the distance. And we’re getting to beneficially use the product as fuel.”

Similarly, Los Angeles and Orange counties are hoping to recycle a third of their biosolids as pellets at the Rialto SlurryCarb Facility, which opened last June. The plant is designed to produce twice as much energy as it consumes.

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