Composting Key to Meeting Landfill Organics Ban

The Halifax Regional Municipality (HRM) in Nova Scotia took a giant leap in 1998 to reaching a 50 percent diversion goal by 2000. Between July and November, 1998, organics collection carts were distributed to almost 100,000 households in the region. In December, two new composting facilities designed to process those materials, as well as feedstocks from the commercial sector, opened their doors.



“The Halifax Regional Municipality’s new integrated solid waste-resource management system is ‘leading edge’ in all of North America,” says Mayor Walter Fitzgerald. “We are successfully converting previously designated waste into a valuable resource.” Eventually, the system is expected to achieve diversion in the 65 percent range.



The composting initiatives are due in large part to the province of Nova Scotia’s ban on disposing of compostable organics in landfills and incinerators. The ban became effective on November 30, 1998. To comply, all municipalities have to develop a composting infrastructure (see “Nova Scotia’s Organics Disposal Ban Takes Effect,” November, 1998).



Both composting facilities utilize in-vessel technologies. Originally, one of the two was designed as an open air windrow operation. But Nova Scotia Ministry of the Environment guidelines that place more stringent requirements on large-scale, open air windrows, combined with community concerns about that type of facility, led the vendor, New Era Farms, to rethink its approach and proceed with an in-vessel system.



Contracts between HRM and the haulers determine the flow of residential organics to the composting sites. There is a minimum throughput guaranteed by a put or pay agreement with HRM. Feedstocks from the institutional/commercial/industrial (ICI) sector are directly solicited from generators by the facility owners. No ICI feedstocks were being received as of January, 1999, because of HRM requirements that the plants had to pass performance tests prior to handling ICI material. Estimates by HRM show that flow to both sites will be roughly 55 percent residential feedstock and 45 percent from the ICI sector.



NEW ERA FARMS



The New Era Farms compost facility in Halifax has a capacity of 27,500 tons/year. It is sized to allow expansion by an additional 11,000 tons. The system prototype was first developed about four years ago in Colchester County, Nova Scotia (see accompanying article).



The new facility, which is located in a business park, has three main areas: A receiving and preprocessing building, composting pad and curing structure. Feedstock is unloaded onto the tipping floor, where workers remove oversized items and evident contaminants. Next, material is loaded in a hopper that feeds a conveyor. On the conveyor, hand sorters remove recyclables and residuals that ended up in the organics stream. A magnet with a manual scrape pulls out ferrous.



The conveyor feeds a slow speed rotary shredder that reduces material to a two-inch size. The residential mix is loaded directly into containers for composting. Once ICI feedstocks are received, it may be necessary to mix in amendments prior to composting.



The New Era facility has 24 Stinnes-Enerco containers (each about 30 feet long by 10 feet wide by 8 feet high). After being loaded, containers are placed in an outdoor area connected to a system of process air and water piping. Six additional containers are open at the top and used as biofilters containing a mix of compost, peat moss and bark. Rolled compacted concrete was used for the pad surface.



Processing in the containers takes about ten days. Given the current mix (residential only that is fairly high in carbon), it takes two to three days to reach 55ƒC. After the initial composting phase, the container is moved to a 440 foot by 72 foot wide building with a domed, fabric roof (made from a polymer manufactured in Nova Scotia) where the material is unloaded, furthe