‘Complicated choice’ looms in Sonoma County over next compost operator
This story was originally published Aug. 12, 2018:
Every week, hundreds of thousands of Sonoma County residents dutifully gather grass clippings from their yards and food scraps from their kitchens, toss them into green bins and then cart them to the curb alongside their garbage and recycling.
Tons of this so-called “green waste” is then hauled, at a cost of $5 million per year, to other counties, where it is chopped up, often mixed with chicken guts, encouraged to rapidly decompose, and then sold as compost.
The process takes place entirely outside Sonoma County - mostly in Mendocino, Napa and Marin counties - ever since Sonoma Compost, the county's longtime compost operation atop the Central Landfill, was shut down nearly three years ago for wastewater violations.
Now local officials face a complex but crucial decision about the future of composting in Sonoma County, one that will have major implications for the life of the county landfill, the rate of emission of greenhouse gases and the size of people's garbage bills.
That decision is whether to encourage the construction of a new, modern composting facility here, with costs of $50 million or more, or whether to continue hauling the material to existing facilities elsewhere indefinitely.
“This is one of the biggest decisions we're going to make in the past several years,” said Henry Mikus, the former head of the Sonoma County Waste Management Agency, which oversees recycling, household toxic and e-waste programs.
Mikus, now engineering manager for the city of Sebastopol, is chairman of the 10-member board overseeing the waste agency, a joint-powers authority including representatives from all nine cities and the county.
On Wednesday, the board will consider whether to grant a contract with a new composting enterprise, likely located southwest of Santa Rosa or east of Petaluma. It also could ink a deal with an existing composting operation outside the county, or craft some combination of the two.
The decision is complicated for a number of reasons. Each of the eight long-term composting solutions up for consideration have their own unique set of technological, financial, environmental and commercial benefits.
To make the decision easier, waste agency staff narrowed down the 12 original proposals, ranking each on a 100-point scale.
The result of that effort was five proposals all within a tight range of five points of each other. The top-ranked proposal, with 78.9 points, was a group called Renewable Sonoma, a team put together by the same people who ran Sonoma Compost for 20 years.
Their plan is to build a modern compost facility north of the Santa Rosa Laguna Treatment Plant on 13 acres of property leased for 20 years from the city of Santa Rosa. The facility would use two different composting technologies.
One, covered aerated static pile composting, entails pumping air through piles of compost to accelerate the decomposition process while capturing the odors.
The other is anaerobic digestion, which takes place in sealed tanks starved of oxygen, a key byproduct of which is biogas. It could be used by the water treatment plant, which already uses biogas derived from human waste. That gas is burned in large industrial turbines that produce electricity for the plant, providing a low-cost and emergency source of onsite power.
Even though the rankings of the top five proposals fall within a tight range, Sonoma County Waste Management staff favored Renewable Sonoma's proposal for several reasons.
The company plans to have a robust outreach and education campaign about the need to increase diversion of food scraps from the garbage into the green bin, according to the staff report. It also plans to accept biosolids from the treatment plant, which is the organic material left behind after human waste is put through the anaerobic digestion, water removal and composting processes.
Biosolids are often applied to farmland as fertilizer, but regulatory constraints on such applications have made doing so increasingly challenging for the city.
A number of questions have been raised, however, about the waste management staff's recommendation to begin exclusive negotiations with Renewable Sonoma.
Some are surprised the county would go through a year-and-a-half-long selection process only to end up picking the same people who operated the previous composting site atop the landfill for 22 years before it was shut down in 2015 for environmental reasons.
Neighbors complained about odors, truck traffic and releases of nutrient-rich wastewater running from the open-air facility into local creeks. A lawsuit alleging violation of the federal Clean Water Act ultimately forced the operation's closure.