September 19, 2011 | General

Web Extra: Food Waste Critical To San Francisco’s High Diversion

When the city made residential and commercial composting mandatory in 2009, the amount of organics diverted rose from 400 to 600 tons a day.
Part II
Dan Sullivan

SAN Francisco’s mammoth undertaking to recycle 220,000 tons of organics a year into approximately 150,000 cubic yards of compost centers around the notion that it benefits the environment to recycle organics back into the earth than to send them to the landfill.
SAN Francisco’s mammoth undertaking to recycle 220,000 tons of organics a year into approximately 150,000 cubic yards of compost centers around the notion that it benefits the environment to recycle organics back into the earth than to send them to the landfill. Since residential and commercial composting became mandatory in October 2009 (See “Zero Waste On San Francisco’s Horizon, Part I,” July 2011), composting volume has increased substantially while demand for the end product has held pace.
Recology, an employee-owned company contracted to collect and process San Francisco’s compostables, recyclables and trash, hauls the organics to either its recently purchased Grover Environmental Products facility in Vernalis, California (acquired in early 2010), or to its long-established Jepson Prairie Organics facility near Vacaville. The latter site sits next to and is managed by Recology in tandem with the Hay Road Landfill, which primarily serves Solano County, including the cities of Dixon and Vacaville. According to San Francisco and Recology officials, when all expenses are accounted for, it costs roughly the same – dollars-and-cents-wise – to compost, recycle or send trash to the landfill.
“The city set a goal of getting to zero waste to landfill – we are the major service provider to the city, and we’re going to do everything we can to help San Francisco achieve its goal,” says Recology spokesman Robert Reed. “Recycling and composting is our business model. We have 15 or 16 recycling and composting facilities and three small landfills on the West Coast. It’s how we are making our mark in the industry. We engage in best management practices, and recycling and composting are preferred alternatives to landfilling.”

Recology collects San Francisco’s food waste and green waste together. Food waste is about two to three times the volume of green waste due in large part to small residential yards and an exuberant restaurant scene. “There are 5,000 restaurants here,” says Reed. “It’s America’s favorite food city.”
Residential and commercial organics, recyclables and trash are collected in 32, 64 or 96-gallon green, blue or black bins with lids. Organics bins only go up to 64 gallons because of the weight when filled. Color-coded Dumpsters, roll-off containers and compactors are available for larger generators. Residents pay $27.55 for any size recycling and organics bin and a 32-gallon black “Landfill” bin. The rate doubles if they want a 64-gallon black bin and triples for a 96-gallon one, an option hardly anyone uses. Commercial customers receive a diversion discount of up to 75 percent depending on how much of their total volume is recycled. Double-bay compacting trucks pick up recycling and trash in one pass; single-bay trucks are used to collect organics, typically on the same day. Frequency is determined by the amount of material generated.
Organics – including food waste and green waste (residential and commercial landscape debris) – go to either Jepson Prairie or Grover. Recology also collects green waste only from Vallejo, Vacaville, Dixon, unincorporated Solano County and East Bay as well as food waste only from Folsum State Prison, the Vacaville California Medical Facility (another prison), University of California Davis and Safeway Corporation.
San Francisco’s recyclables are taken for processing to the 200,000-square-foot Recology-operated Recycle Central sorting facility in San Francisco. Garbage is consolidated at the transfer station, loaded onto 18-wheelers and taken to Waste Management’s Altamont Landfill in Alameda County. One motivating factor for San Francisco to aggressively compost and recycle – in addition to its goal of zero waste by 2020 – has historically been a favorable tipping fee with Waste Management that would have been up for renegotiation once the city had disposed 15 million tons of trash. But the San Francisco Board of Supervisors recently approved a 10-year, $112 million deal with Recology to haul the trash by train to Recology’s Ostrom Road Landfill north of Sacramento beginning in 2015.

Recology has been producing compost since 1996, says Reed, adding that the company has put “a lot of energy and resources into improving our techniques and into new equipment.” All preprocessing equipment at both Jepson Prairie Organics and Grover is electric due primarily to air quality considerations. Primary contaminants are film plastic and glass; these are removed mostly by hand. Feedstocks that come in separately are ground separately.
Once material is ground – with more contaminant removal during that process – it is placed with Caterpillar front-end loaders into an Engineered Compost Systems (ECS) covered AC Composter negative aerated static pile system complemented by a CompDog pipeless above-grade aerated floor system. The negatively aerated static piles are approximately 100-feet long, 30-feet wide and 12-feet high. The material is processed in about 60 days. The ECS system, installed in 2009, replaced enclosed (in Ag-Bags) aerated static piles.
Since San Francisco mandated organics recycling across all sectors in 2009, the city’s diverted organics have increased from approximately 400 tons daily to 600 tons/day (tpd). A main driver for composting system improvement has been the Yolo-Solano Air Quality Management District (AQMD) and pressure to lower ozone-creating emissions. Jepson Prairie’s permit from the Yolo-Solano AQMD is based on VOC emissions from processing 400 tons/day (tpd). But the facility’s permit from the state Department of Resources Recycling and Recovery (CalRecycle) was set at 600 tpd.
With the new ECS system, the facility has been able to successfully demonstrate – by cutting its VOC emissions in half – it can operate at 600 tpd and stay well under the threshold of allowable VOC emissions at 400 tpd under the old (Ag-Bag) system. “We were successful in obtaining approval through the local air board,” says Paul Yamamoto, who oversees Recology’s composting and landfill operations. “It’s not completely final, but it’s on its way.”
While Jepson Prairie Organics works on expanding its permit to meet the city’s growing volume of food waste, the surplus – actually more than half, say San Francisco Department of Environment officials – is going to Grover Environmental, which had traditionally been a green waste compost only site. “Grover has the permits to handle the additional food scraps volume,” explains Jepson Prairie facilities manager Greg Pryor. Adds Department of Environment Zero Waste Coordinator Jack Macy: “We’re looking forward to Jepson Prairie getting all the approvals to utilize their new 600-ton-a-day permitted capacity, especially considering the close proximity of the farms and vineyards that utilize this compost.”

Recology sells finished compost to vintners, farmer, landscapers, garden centers and the general public for anywhere from $9 to $10/cy (about 90 percent of its business, says Reed) to $30/cy and higher for custom blends. It can mix in rock phosphate, wood chips, lime and other amendments purchased offsite, as well as other soil products made on site – and special preparations (such as those used in biodynamic agriculture). While the economics of hauling compost can begin to look tentative when one considers service outside of a 100-mile radius, Recology has an advantage of its operations being situated in the heart of California agriculture.
Napa Valley’s nationally-renowned Chateau Montelena is a Recology compost customer. The macro and micronutrients in the compost combine with Chateau Montelena’s geography and climate to give the wine grapes their particular terroir, says Dave Vella, longtime vineyard manager. Compost is incorporated annually right after harvest in the rows between the grape vines at a rate of up to 3 tons/acre. At the same time, cover crops are being planted, including clovers, mustards and grains, to stimulate the soil microbiology and also for weed suppression.
“It’s amazing, the impact compost makes,” says Vella. “We do soil testing every year, and if we find we are lacking in any nutrients – phosphorous, potassium, sulfur, zinc, calcium, copper, boron, etc. – Recology will custom blend it into the compost for us.” He adds that the biggest advantages of having a complete soil amendment are the time saved in terms of both labor and the hours put on equipment as well as less soil compaction. Without the custom-blended compost, he says, a tractor might have to pass through the vineyard three times or more, applying such necessary amendments as lime to resolve low-pH issues, organic fertilizer blends and other necessary micronutrients.
Soil Health And Compost
THE way Bob Shaffer sees it, food scraps “are the most valuable resource that we have for building great compost.” Shaffer, a long-time farmer and founder of Soil Culture Consulting in Glen Ellen, California, Is a consultant to Recology – San Francisco’s waste hauler and processor – for its composting operations at Jepson Prairie Organics and the more recently acquired Grover Environmental Products (see main story). “As I studied soil ecology and the live biomass in soil, I began to work more effectively with farmers as a consultant,” he says. “Because, if you’re going to raise great crops you need to understand the life in soil, and if you understand the relationship between crop health and soil life you end up using compost.”
Residential, institutional and commercial food wastes offer the perfect “superfood” for the composting process, he adds. “It’s so important for us as farmers and for those of us who take care of the soil to have access to recycled organic matter, like food scraps, that are loaded with nutrients. After all, this is human food that we’re recycling. This food is raised on our best land for farming, with great skill and with the intention of being dense in minerals, protein, carbohydrates and oils. This nutrient density supports our health and, in fact, supports the health of microbes in compost better than other compostable forms of organic matter.”
The composting process also sequesters carbon in the soil, says Shaffer. Recology estimates that the 900,000 tons of compost it has produced since 1996 has been the equivalent of removing all traffic off the Bay Bridge for 777 days.
Food Waste Digestion
THE city of San Francisco is exploring possibilities for anaerobically digesting at least a portion of the 220,000 tons of organics it generates annually in order to reduce VOCs while producing biogas, heat and electricity for its recycling and recovery operations and/or for the grid.
San Francisco is working with its organics waste hauler Recology and East Bay Municipal Utility District (EBMUD) located in Oakland, which – despite treating the wastewater for most of the East Bay – has excess capacity in its anaerobic digesters. “We’re providing EBMUD with processed food scraps from the city of San Francisco,” explains Paul Yamamoto, a Recology vice president who oversees the employee-owned company’s composting and landfill operations. “East Bay Municipal Utility District’s water treatment plant accepts the processed food scraps into one of its digesters and is already producing biomethane for a power-plant operating onsite.” In collaboration with Recology, EBMUD was the first sewage treatment facility in the nation to convert postconsumer food scraps to energy via anaerobic digestion, according to the U.S. EPA. (See “Green Energy From Food Wastes At Wastewater Treatment Plant,” January 2008.)
The food scraps are picked free of major contaminants and go through size reduction before delivery to EMBUD, explains Recology Director and Vice President of Technology Chris Choate. “EBMUD rehydrates it at their site – they need to take it to about an 8- to 12-percent solids content. They dump it into a vat of water and mix it up until it’s about the consistency of chocolate milk.” A paddle finisher takes out nondigestibles such as sticks before the slurry goes into the digester.
“The EBMUD project lets us start digesting food scraps quickly and with low capital investment – we can then assess the economics of these projects and technology considerations as we expand our investments in organics processing in the years to come,” says Choate. He adds that Recology is firmly committed to the EBMUD’s AD project as demonstrated by the company’s investment in the infrastructure required to meet its 10 year commitment to provide and process food waste feedstock. As for where that gained knowledge will be applied next, Recology has held preliminary discussions with Solano County about locating a digester at its Jepson Prairie Organics composting facility. Another possibility is Recology’s transfer station on the outskirts of San Francisco. “We are looking at multiple options – there are a lot of moving pieces,” says Yamamoto, confirming that the arrangement with EBMUD has been largely about gathering information for eventual application.
“Anaerobic digestion helps to reduce contaminants and also reduces volume through the digestion process,” says Greg Pryor, facility manager at Jepson Prairie, which has traditionally processed the bulk of San Francisco’s food and green waste into compost. Because commercial and institutional food waste tends to be wet and have a high bulk density, it can be difficult for some facilities to compost, says Choate. Pretreatment with AD is an option that holds the additional benefit of producing energy, he notes. “Food waste is a big source of volatile organic compounds, so if you’re able to stabilize it before it goes out to the compost facility, it’s going to help with VOC emissions.”
How San Francisco Calculates 77 Percent Diversion
THE City of San Francisco announced it had shattered its solid waste diversion goal of 75 percent by 2010 – the current figure is 77 percent, with an even higher number soon to be released. That rate is calculated with a formula used to measure solid waste diversion dictated by the California Integrated Waste Management Act of 1989 (AB 939), which mandated municipalities across the state meet at least 25 percent diversion by 1995 and 50 percent by 2000. “All California cities use the same metrics,” says San Francisco Department of Environment Zero Waste Manager Jack Macy. “We use and report a diversion percentage to really make sure we have met and continue to meet our 75 diversion goal by 2010. This is a way to track our progress.”
But the city’s more important goal is zero waste, adds Macy. The numbers speak for themselves, he says, pointing to a tonnage reduction cleaved in half between 2000 and 2010. The diversion rate includes all residential and commercial solid waste as well as about 50 percent of construction and demolition debris (C&D). “C&D is considered restricted waste; we’re able to include it if we can show that we know it was not happening before 1990.” And like all cities in California per the metrics of AB 939, the diversion figure includes biosolids.
“Disposal has not only gone down by half since 2000, over each of the past three years we’ve had the lowest disposal on record going back to early 1970s,” Macy says. Another important consideration, he notes, is that San Francisco’s base population of 800,000-plus increases by roughly 50 percent daily because of commuters and tourists. California does not consider waste-to-energy (burning trash) as diversion.

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