Sludge composting plant starts up
A plan 12 years in the making has finally arrived: A facility to compost Los Angeles county sewage sludge is up and running in Kings County.
The $100 million plant, owned and operated by the Sanitation Districts of Los Angeles County, located on pancake-flat land southeast of Kettleman City and dubbed “Tulare Lake Compost,” started processing small amounts of the pre-treated sludge in January.
The facility mixes sludge from 78 Southern California cities with mostly agricultural green waste and composts it in large heaps. The result, according to engineers, is safe, “exceptional quality” fertilizer approved by the U.S. Environmental Protection Agency for application on any farm crops, garden plants and lawns.
The product is intended for distribution to Central Valley farmers as a fertilizer.
The project has taken a long road to fruition, clearing multiple hurdles to get there.
After it was approved by the Kings County Board of Supervisors in April 2004, the proposal faced environmental lawsuits alleging the sludge was unsafe.
Those lawsuits were settled by the end of 2006. As part of the settlements, the Los Angeles County sanitation districts agreed to use natural gas powered trucks to haul in the sludge. The districts also agreed to give $30,000 a year to West Hills Community College District to support engineering programs.
The original plan was to start operation in 2007, but according to Division Engineer Ann Heil, the project ran into an unexpectedly complex hurdle: The soil the plant is built on.
“The soils here were more challenging than we thought they would be,” Heil said.
Heil said the soil is corrosive, meaning it tends to eat concrete foundations. Clay in the soil expands when wet, which can crack pavement and foundation material.
Heil said the facility had to formulate and test a special composition for the ground under the 177-acre facility to make it work.
The facility also had to get permits from the San Joaquin Valley Air Pollution Control District and the Central Valley Regional Water Quality Control Board.
The result is a sprawling site that includes a massive, odor-proofed building. The trucked-in sludge is dumped inside and mixed with green waste. From there, it goes outside on conveyor belts to a huge paved composting area.
The mixed material is covered with special tarps. Oxygen is pumped in from below. The process of microbes digesting the material heats it up, killing nearly all the remaining pathogens.
The final composted product gets sifted and cured. It looks like a bag of fertilizer you’d buy at a lawn-and-garden store.
“You can touch it,” Heil said. “You can buy similar stuff at Home Depot.”
The challenge for the facility, which is producing a limited amount of compost and is still in the testing phase, is to find takers for the finished fertilizer, which is expected to be ready for shipment starting July 1.
All the product being made is, for now, staying on site.
The facility is currently operating at a capacity equivalent to 20,000 tons of sludge a year – a small fraction of the 500,000 tons a year the facility would process at full build-out.
That would be enough to process nearly all the sludge produced by the 78 Los Angeles County cities in the sanitation districts association (The city of Los Angeles itself, a separate entity, is not included).
The original plan was to spread the fertilizer on 12,000 acres of Westlake Farms land not far from the facility.
But that was before severe drought hit from 2007-2009 and again from 2012 to the present, forcing many Westside growers, including Westlake Farms, to fallow much of their ground.
It’s not clear how much irrigated farmland in Westlake is currently available to take the fertilizer.
Westlake officials couldn’t be immediately reached for comment.
Officials at Tulare Lake Compost said Tuesday that the plan is to market and sell the compost to growers throughout the Central Valley.
“We anticipate the [agricultural market] is robust enough,” said Supervising Engineer Melissa Fischer.
According to Heil, the agreement with Westlake is still in place.
According to Fischer, marketing plans for the compost “have yet to be determined.”
As far as the green waste that the facility needs to operate, there’s no shortage of that, according to Riley Jones, a consultant for the project.
The plant is taking wood chips from ground-up almond and citrus orchards that have been removed, as well as tree trimmings, according to Jones.
“There’s an overabundance of wood right now,” he said.
One of the project’s main goals, according to Heil, is to comply with mandates to reduce the amount of organic waste that goes into landfills.
Another objective is to trap carbon in the soil that would otherwise be released into the atmosphere and contribute to global warming, according to Heil.
Heil said that if the sludge were buried in a landfill, it would produce methane, a potent greenhouse gas.
Fischer described the finished product as superior to artificially-manufactured nitrogen-based fertilizers widely used in the agricultural industry.
But she acknowledged that some people have misgivings about turning human waste into fertilizer and using it on crops for direct human consumption.
“If you can get past the social stigma, absolutely, this is the better fertilizer,” Fischer said.
“We were looking at long-term sustainable options that were reliable,” said Heil. “I think we’ve come a long way as far as how the compost is perceived by farmers.”
The reporter can be reached at snidever@hanfordsentinel.com or 583-2432. Follow him on Twitter @snidever.
