Eighteen years after it was first proposed, an ordinance regulating the controversial use of treated sewage sludge for crop fertilizer will go before the San Luis Obispo County Board of Supervisors on Tuesday.
Sludge, or biosolids, are the mulchlike solid material left over from sewage treatment that can be used as fertilizer. The land application of sludge is controversial because it can contain harmful heavy metals such as zinc, cadmium, selenium and copper that are not removed by the sewage treatment process and can accumulate in soils with repeated applications.
On Tuesday, supervisors will discuss a draft ordinance governing the application of biosolids on land in the county. An environmental impact report is also being drafted for the proposed law.
The proposed ordinance contains a number of safety requirements to minimize the risk of environmental damage. A key condition is an application limit of 10 tons per acre over three years, which county environmental health authorities say should prevent many of the problems associated with the use of sludge.
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Rich Lichtenfels, supervising county environmental health officer, said it should take about nine months to complete the EIR.
“A final ordinance could be in place as early as spring of 2017,” he said.
The use of sludge first came to local attention in 1998, when residents expressed concern about plans to apply the materials to grow alfalfa at a ranch near San Miguel. Since then, two separate task forces were formed to help guide the development of an ordinance, according to a staff report on the proposed ordinance.
A major stumbling block in developing a permanent ordinance was the cost of an environmental impact report, which estimates have put at as much as $200,000. In 2004, an interim ordinance was adopted that limits the use of sludge to historic levels and is so restrictive that it has eliminated its use in the county, Lichtenfels said. Only 1,500 cubic yards of sludge a year can be applied in the county.
“No land application projects have been applied for since the interim ordinance was enacted,” he said.
In the meantime, the county’s 20 wastewater treatment plants continue to generate approximately 12,000 tons of biosolids a year. About a quarter of that amount is disposed of in landfills and another quarter is trucked to the San Joaquin Valley to be used as compost. The other half of the sludge is trucked to a composting facility in Santa Maria.
Critics of land application of biosolids, such as David Broadwater of Atascadero, are urging the county to consider a broad set of alternative uses for the material. At a recent Board of Supervisors public comment period, Broadwater recommended using biosolids as cogeneration fuel, thereby reducing the amount that goes into landfills or on the land.
He said biosolids can produce 10 times the amount of energy than it takes to treat, and it has the potential to supply 20 percent of the nation’s energy needs.
“This is a serious issue, and it’s something we have not taken a serious look at,” he said.