Goal is to meet higher air, water requirements
AMERICAN CANYON — The garbage collector for Napa and unincorporated areas of southern Napa Valley is putting the finishing touches on a new master plan for its main recycling and composting facility at the end of Tower Road, adding reuse of water, conversion of waste to wattage and reduction of compost gas emissions.
Those projects are all part of intertwined efforts to hit city and state targets for reducing greenhouse, noxious and diesel engine emissions; trimming the tally of trash ending up in landfills and keep more rainwater and treated process waste water on site, according to Greg Kelley, general manager of Napa Recycling & Waste Services and Napa County Recycling & Waste Services (707-255-5200, naparecycling.com). The estimated cost for all the upgrades is about $20 million.
“After 18-plus years, things have changed and regulations have changed and (waste) processing has changed,” he said. “It is costly, but it is a long-term investment, because we will always have yard waste.”
The city of Napa hired engineering consulting firm CH2M Hill to evaluate what needs to be done to the 20-acre site to get it up to the latest air-and water-quality regulations. That report is due back to city officials shortly so the master plan can be completed in mid-August.
One change to the existing site master plan is different handling of stormwater. Currently, all rainwater and process waste water is collected in three basins that allow problematic particulates and other compounds to settle out to clean the water before it is discharged.
The latest state stormwater rules are still in draft form but have been trending toward keeping most rainwater on a property through various means.
Another planned change to the plant is designed to improve air quality during composting operations. As bacteria break down food and plant waste during composting, the microorganisms release greenhouse gases, volatile organic compounds (VOCs), reactive organic gases (ROGs), dust and ammonia into the air. Yet, composting also cuts down on the odor, pathogens and bulk of rotting organic material as well as locks carbon into the cell structure of the microbes, so composting can help the state meet its GHG-reduction goals, according to the California Air Resources Board.
So being considered for the plant upgrades are a reverse air circulation system that would suck air through the compost, pulling any gases into a pipe and filter, according to Mr. Kelley. The intent is to remove 95 percent of the VOCs emitted.
“Compost, in general, uses water and air to get heat to activate the bacteria,” Mr. Kelley said. “We have blowers blowing air through the piles, so we don’t have to turn them manually, like most compost operations. With current food-waste collection, forced air is the easiest to adapt to.”
The combination of blowing air and covering the piles with finished compost helps trap odors in the piles, he said.
The operation has been experimenting with food-waste recycling for the past year and a half, but collection of such scraps from commercial customers is just getting started, according to Mr. Kelley. Currently, the company has more than 60 commercial food waste customers, but the service area could yield 300 to 400 commercial accounts.
A driving forces for that part of the project is the state goal of recycling 75 percent of the solid waste that would go to landfills. After programs to reuse construction and demolition debris, collect yard and landscaping trimmings and provide single-bin household and business recycling, the next target is food and other organic waste.
“That’s the largest part of the waste stream left that can be diverted,” Mr. Kelley said.
Napa currently diverts 55 percent of its solid waste from its contracted disposal site, the Keller Canyon Landfill in Contra Costa County.
A third major part of the planned American Canyon compost and recycling center is recovery of natural gas — methane — from rotting organic material to use as energy. Out of seven vendors of dry anaerobic bacterial digestion technology — biodigesters that work on mostly solid waste without addition of water — the city and Napa Recycling is looking at the semimobile SmartFerm system designed by Zero Waste Energy in the East Bay and made by North Carolina-based Environmental Solutions Group.
Napa Recycling currently has seven vehicles converted to use compressed natural gas purchased from Pacific Gas & Electric Co. The planned harvesting of biogas from as much as 20,000 tons of organic waste could provide fuel for 16 to 20 diesel-powered garbage and recycling trucks, according to Mr. Kelley.
The goal is to have all fleet vehicles using natural gas, because natural gas is less expensive, burns cleaner and will help avoid the costly upgrades to diesel-burning engines now required in California, he said. For the past few years, on-road large diesel trucks have been required to have engines replaced with the newest cleaner-burning versions or upgraded with special filters. The downside of running diesel engines hotter to burn more particulates and other emissions is a reduction in mileage and higher maintenance on engines, he said.
“A new diesel engine for our trucks comes with a radiator that is twice the size of current ones,” Mr. Kelley said.
Funding possibilities for the project being considered are California Pollution Control Bonds, city or private financing, and grants from the California Energy Commission for biogas use in vehicles. Lower tipping fees at the compost plant versus the transfer station — $40 a ton versus $65 a ton — could attract more revenue there, which with lower open-market purchases of natural gas, could help offset some of the cost of the project, according to Mr. Kelley.
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