May 2004

Municipal Composting Gains Acceptance; Provides Relief for Landfills
by James I. Miller

Imagine a time when a significant portion of the solid waste stream we create quickly biodegrades into a valuable, new resource. Through the continued success and growing popularity of municipal composting programs, that time may not be so far off.

In spite of the obvious benefit, producing a saleable, organic product may not be the most significant payoff of municipal composting in the long run. In conjunction with curbside or community recycling efforts, successful programs involving composting are becoming an important and beneficial tool for diverting solid organic waste from our nation’s landfills.

Among the most successful municipal recycling programs that includes composting is that of the City of San Francisco, where more than 63% of the city’s waste – including its bio-waste – was recycled in 2002. That means the people of San Francisco now recycle considerably more waste than is sent to landfills in the area. Considering the population density of the Bay Area region, that’s an extraordinary accomplishment, and composting is an important part of that success.

Most municipal recycling programs – including those considered highly effective – typically do not come close to achieving this level of success. So why is this program so different? Gloria Chan, public information officer for the city and county of San Francisco’s Department of the Environment says, “The people make it work. It takes people that care about their environment and understand the importance of what they’re doing,” she said.

Implementing a municipal recycling program in a dense population center such as the Bay Area takes a coordinated effort. Introducing composting to the program was even more challenging. “San Francisco is divided into 12 geographic regions,” said Gloria Chan. “We began our pilot program in 1999 in just one region and went full scale in year 2000. In addition to our recycling program, the city issued free bags for residents to collect organic waste for composting. We later introduced incentives to encourage more participation to meet benchmarks along the way. There was a significant increase in 2002 from construction and demolition recycling which helped boost our numbers, but education, awareness and desire are the key ingredients for our core success,” she added.

San Francisco generated 1,882,490 tons of solid waste in 2002. Of that figure, only 702,012 tons were landfilled. More than 1,180,478 tons were diverted from area landfills through the city’s recycling and composting program.

Municipal composting and organic recycling is more than a responsible practice – it makes economic sense as well. Gloria Chan continues, “With fuel costs at $2.50 per gallon in the Bay Area, composting our food waste and other organic materials saved a lot of money, and extended our landfill volumes, allowing more room for non-recyclable materials,” she added. In the process, new revenue can be generated from the sale of a product perfectly suited for gardening, landscaping and many other beneficial uses.

Homeowners have been composting in small quantities for as long as anyone can remember. But larger scale operations involving large, urban populations hold the most promise for long-term landfill relief.

Barbara Petroff, project manager for Sturbridge, Massachusetts based U.S. Filter, creators of the IPS composting technology in place in a growing number of U.S. cities said, “It’s refreshing to see the number of municipalities that are already committed to adding composting to their recycling programs, or are giving serious consideration to composting in the future.”

In Rapid City, South Dakota, city administrators launched a small-scale composting program back in 1993. At that time most of the material included yard clippings and similar green waste. Since then, the recycling of yard waste has grown to approximately 4,000 tons per year.

But in 2003, Rapid City took composting to another level. A major initiative was undertaken to combine municipal composting with its established MSW program.

Dallas Wasserburger, president of the Alliance of Architects and Engineers of Rapid City, designed the $7.2 million dollar compost and recycling facility for the city. According to Mr. Wasserburger, “We designed the Rapid City composting hall to handle projected volumes 20 years into the future. At full capacity, we will be composting more than 213 tons of material per day.” The system converts pre-processed solid wastes from the city’s MRF and biosolids from the city’s water reclamation facility into valuable compost, suitable for a wide variety of applications.

The new facility consists of several buildings. Automated collection trucks deposit MSW onto the tipping floor of a 40,000 square foot receiving building. There, any unsuitable material is pulled from the waste stream. The balance is transported to one of two Dano rotating drums where biosolids from the water treatment plant are mixed in.

After processing, dual trommel-type screens capture larger items at the end of the drums. Smaller material is moved by front-end loader to the composting hall and distributed in composting bins by a screw auger. The main composting facility houses nine bays. Each bay measures 10 feet wide, 8 feet deep and 280 feet long. Two 100 horsepower agitators turn the compost periodically in the bays.

To properly aerate the mix, four 100 horsepower fans pull air from the building through a chemical scrubber and into a wood-chip biofilter before exhausting to atmosphere. The entire composting process is a balance between oxygen, moisture and temperature. The Rapid City installation is in full compliance with all EPA regulations.

“Through our composting program, we are accomplishing in just 30 days what used take 5 or 6 months to achieve,” said Mr. Wasserburger. “In another 12 months, we expect to be diverting as much as 60% of Rapid City’s municipal solid waste stream from our landfill.”

The resultant compost is sold to area residents and/or used for municipal projects of all kinds. In addition, due to composting, Rapid City realizes considerable cost savings in other areas of its MSW program. There are no tax dollars consumed to maintain the new facility.

The composting system is expected to extend the useful lifetime of the Rapid City, South Dakota municipal landfill by more than 30 years.