City

Where does Berkeley’s green waste go?

Up to 23 moderately smelly tons of green brush, food waste and non-compostable debris is dumped at a Central Valley site. All photos: Sean Gin

By Jim Rosenau

At our house, it happens every Monday night. We wheel our green waste to the curb to be hauled away. But just where is this “away” anyway? And what happens when it gets there? I got curious, then I got gas money and a photographer from Berkeleyside. Here’s what we learned.

At around 4:30 a.m. each weekday the first of four to five 48-foot tractor-trailer trucks pull up to the city’s transfer station at Second and Gilman. They load  the vehicles with up to 23 tons of Berkeley’s green waste, collected from our curbs and 300 commercial addresses. From there, the trailer trucks travel 69 miles over Altamont Pass, via Highway 580, on their way to the edge of the Central Valley. Here, land is less costly and noses less fussy.

This 124-acre composting space, with the Delta Mendota canal to its west and a dry wall recycling facility to the east, sits amid orchards and grain fields. Here, composting is conducted on an industrial scale, which is not economically or politically practical anywhere close to a town. And here, it is possible for nearby farms to buy compost in quantity.


Before Berkeley began collecting residential green waste in 1990, if you wanted to compost anything — be it the easy stuff, like kitchen scraps or tougher material, like woody prunings, you learned to do it yourself in your own yard. And, all through the 70s and 80s, the likes of Mother Earth News and Organic Gardening magazines provided heaps of encouragement for DIY composting.

In their heyday, these publications printed one article after another on “the best way” to make compost. For me, it was as close to a religious rite as anything I have put into daily practice. Decades of culling, turning and screening went into my piles. But once the city handed out those green pails for kitchen waste, I had to reexamine the bother, given that they would take everything I’d ever put in my pile, even my nail clippings.

Everything larger than 3″ is sent down a short conveyer belt non-compostable waste is hand-culled as it passes.

Berkeley began industrial scale composting early, thanks to a 1984 ballot initiative that sought to accomplish a 50% waste diversion by 1991. Municipal composting was conducted variously at the city’s landfill (now Cesar Chavez Park) by Urban Ore, across the tracks north of Gilman by another company, then out in the valley by yet another company, before Grover Landscape Services (now a subsidiary of Recology, the former NorCalWaste Systems) won the contract.

The regional compost heap grew much faster once state law pushed other cities to participate. Byron Sher’s AB 939, passed in 1989, called for the state to divert 25%  of its solid waste by 1995 and 50% by 2000.

It’s hard to imagine that operations like Recology’s would exist without the state mandate. Berkeley’s share of Recology’s tonnage represents just 14% of current operations. The rest of their material is collected from Livermore, San Francisco and the Davis St. transfer station in San Leandro, which collects from most of western Alameda County.


Judging from the operation this reporter observed on a day in May, and statistics provided by city staff, Berkeley is doing a good job diverting its green waste. In 2010, the city collected 13,650 tons of residential food and green waste and 6,500 tons of food scraps from commercial customers. All school cafeterias divert food scraps, too.

A 2008 County study found almost no plant debris in Berkeley’s residential waste stream. And a “lid flipping,” study conducted in 2009 showed Berkeley has one of the highest residential food waste participation rates among Alameda County cities.

“Food is a far greater source of methane generation in landfills than woody plant debris,” said Tom Padia, the director of source reduction for Stopwaste.org. Atmospheric methane is thought to have a far more potent climate change impact than carbon dioxide.

It’s difficult to know what this really costs. Recology collects $33.50 per ton hauled from the Second Street transfer station. In addition, the transfer station accepts another 11,000 tons from landscapers and arborists, charging a minimum of $67 per ton for compostable loads. That’s easy to quantify. But Berkeley, unlike most cities in the region, uses city staff and vehicles to collect  green waste from residences, along with 300 commercial sites. No cost breakdown for collection was available from city staff, though a study is planned later this year.

Still, without local and state regulatory intervention, it would cost less to collect unsorted garbage on one truck, haul it to a landfill and collect some of the methane from decomposing organic matter. But the benefits are real and widely appreciated, though also hard to precisely quantify. “Aerobic composting produces no methane (a far more potent greenhouse gas than CO2) when done right and results in a soil amendment that helps conserve water and reduce need for chemical applications,” Padia said.


Rows of compost are turned 15 times in a 10-week cycle before being harvested

Grover Landscape Services, which started as a family business in 1986, initially made compost when they could not buy enough quality soil amendments for their landscaping projects. Over the years, their equipment and expertise enabled them to compete for the growing municipal compost trade, collecting both tipping fees and sales of finished compost.

The daily deluge arrives at Grover’s Central Valley site on tractor trailer rigs, each unloading up to 23 moderately-smelly tons of green brush, food waste, and non-compostable debris.

Scraps of plastic, pressure treated boards, even golf balls come in, but, despite the pace, the staff does its best to remove unwanted material, according to Adam Grover, the site manager. As the trucks are dumping, they yank out obvious bags of trash for disposal. They’ve even got a pile of banged-up green cans that fell into collection trucks.

The real sorting begins after the green waste has been dumped. First, all material is filtered down to particles of three inches or less in a rotary screen that winnows about half the material, ready for composting without further treatment. A blower and vacuum remove much of the lighter plastics. Everything larger than three inches is sent down a conveyer belt where a crew of four or five men hand-culls the waste for still more plastics, metals, batteries and whatever else they can grab as it passes.

The remaining coarse material is loaded into a hammer mill to be ground further, then it’s remixed with the fine material and is ready to be composted.

Finished material is ejected from a filter at the Central Valley site of Recology

When you make, say, one thousand tons of compost a day, you can forget about bins and piles. On this scale, windrows are what you want. Six-foot-high rows up to 540 feet long are turned and watered by 3 Aeromaster SP 170’s, made in Illinois. Not only do they turn and aerate the compost, they water it during each turn to replace moisture lost to evaporation and the thirsty bacteria.

You might think of the process as dedicated culture for bacteria, not unlike a cow’s stomach. Microbes eat the green waste, taking in oxygen and water, excreting humus and carbon dioxide. Aeration releases the CO2 and replaces the O2. Row temperatures must reach at least 131 degrees for 15 days. The heat kills most plant pathogens and weed seeds; in a small pile at home it’s tough to maintain those temperatures for long. I never did. Scale matters. The rows are turned 15 times in the 10 weeks cycle before compost is harvested.

Once finished, the compost, which has lost about 40% of its initial volume, is loaded into another screen to filter out coarse, insufficiently composted material.

Again, a blower and vacuum winnow off more plastic. The remaining coarse matter is cleaned with a water bath to separate woody bits from rocks and foreign matter and then sent either to be burned at a biomass generator or ground again and remixed on site when extra carbon is needed to balance wet, green matter.

Finished compost, sold as WonderGrow, is blended on site with calcium and other inputs to make custom soil-amendments to suit each grower

On average, about 13% of what Grover receives is burned for electricity, 80% leaves as finished compost, five percent as low-grade compost; and two percent leaves as trash, sent to landfills.

Most of the finished compost, sold as “WonderGrow”, is blended on site with calcium and other purchased inputs to make custom soil-amendments. The rest is sold to regional dealers like American Soil Products for further blending, or returned to senders.

Berkeley receives under its contract up to 5% finished compost for the tonnage we ship. This material, valued at $42,000 per year, is used in parks, school and community gardens, and is distributed to city residents at the Marina for free on the last Saturday of the month between February and October. And at that price, it goes fast. Figure a day or two at most, in summertime.

“We order 80 to 120 yards each month and have 150 to 400 cars and trucks show up,” said John Mann, the city’s waterfront director.

Though Berkeley’s green waste travels 150 miles round trip over two county lines, and is co-mingled with that of a host of other communities, what comes back is a high- quality soil amendment, clean enough that it’s certified by an independent lab for use on organic farms. Given all this, I asked Vince Tye, Recology’s sales manager at the site why anyone should make their own compost at home. His take, “It’s like people who make their own wine.”

But given how fast it gets scooped up upon delivery, I’m thinking I’ll have to find room for yet another bin — this one to hoard some WonderGrow when I get my hands on it.

Jim Rosenau is an artist who lives and works in Berkeley. He previously wrote for Berkeleyside about the 72-acre Berkeley Meadow.

Photographer Sean Gin graduated with a fine art degree from UC Berkeley in 2010. He lives and works in Berkeley and his work can be seen on his website, SeanGin.com. See more of the shots he took for this story here.