BioCycle January 2010, Vol. 51, No. 1
Hamilton, Ontario utilizes in-vessel technology to compost residential food waste within the city limits.
IN December 2001, Hamilton City Council in Ontario approved the Solid Waste Management Master Plan, which called for 65 percent waste diversion by 2008. The legislation was in response to dwindling landfill space, and a growing concern about the costs and environmental implications of citing a new landfill. A green cart program for household organics was identified as having the potential to divert over 40 percent of the waste going to the landfill. In 2006, the first phase of the program was rolled out, with green carts delivered to all 150,000 single-family residences (properties with up to five units). All food waste, including meat and dairy, soiled paper products and yard trimmings are permitted in the green bin.
In 2007, rollout of the green cart program began for apartment buildings and condominiums (with five or more units). “There are roughly 1,000 apartment buildings in Hamilton that fit this category, with a total of about 60,000 units,” says Beth Goodger, Director of Waste Management for Hamilton’s Public Works Department. “We finished the green cart rollout to this sector in 2009, and now are working on the next phase, which involves Hamilton’s commercial sector. We estimate that will include about 5,000 businesses.”
The city of Hamilton has a mix of urban, suburban and rural residences, with a total population of 504,000. There are six collection zones, with public/private waste collection service providers. Organics from the green bin are collected weekly using a split truck with garbage (40/60), and taken to the city’s Central Composting Facility. In addition to the green bin, residents can put out up to two additional bags of yard trimmings year round. During spring and fall there is also a separate collection of yard trimmings due to the volume, which is composted at a separate facility adjacent to the city’s landfill site.
As part of the city’s waste reduction program, progressive limits were placed on residential trash setouts after organics collection was in place. When the program was first initiated in 2006, single-family residences were restricted to a maximum of three garbage bags per week, in addition to the green cart and blue bin for recyclables. Previously, residents had unlimited garbage setouts. In 2010, the restriction will become tighter, limiting residents to just one garbage bag per week. Extra garbage will be left behind with a tag explaining the program. “These constraints are intended to encourage greater utilization of the recycling and organics stream collections,” explains Goodger. “About 43 percent of our residential waste is organics. By making the constraints gradual, we allowed people to realize how diverting organics results in less garbage. The restriction will reinforce this behavior, and help Hamilton reach its goal of 65 percent diversion.” There is a 70 percent green cart participation rate for single-family residences, based on cart setouts at the curb.
The majority of residents receive 32-gallon IPL, Inc. green carts, whereas inner city locations (without driveways) receive smaller 10-gallon bins. In addition to the curbside cart, households are given a kitchen collector for food waste and a guide called “Green Cart Smart.” The guide uses colorful illustrations and rhyming verse to inform residents about the new program, explaining why participating is necessary: “Whether German, Italian, Chinese or Hispanic … all of us have waste that’s mostly organic.” The guide also spells out what should be included in the green cart, and what excluded: “All kinds of stuff that’s hard on your noses, like meat that is rotten (or your ex-boyfriend’s roses). No diapers, or ‘Girl Things’ or animal poop, but all other kinds of gross, smelly gloop. Fuzzy blue guck from the back of your fridge, but no plastic or glass…not even a smidge. That stuff still goes in your handy blue boxes. The green cart’s for things like your bagels and loxes.”
Initially, the program did not allow the use of compostable bags, due to possible confusion with noncertified “biodegradable” bags. “We were concerned that allowing compostable bags in the program would open the door to contamination,” notes Goodger. “There is still public confusion about the difference between compostable and conventional plastics, not to mention biodegradability vs. compostability.” However, when apartment buildings and condominiums were added to the green cart program, compostable bags were allowed. A page was added to the “Green Cart Smart” guide for apartments, explaining that residents are only to use bags approved by the Biodegradable Products Institute (BPI).
In 2008, Hamilton’s Central Composting Facility (CCF) began receiving organics from the Region of Halton and County of Simcoe, which also allow use of compostable bags. “We started accepting organics from the Region of Halton and County of Simcoe in order to have our facility run at capacity,” says Joel McCormick, Project Manager at the composting facility, and Acting Supervisor of Waste Processing for the Public Works Department. “We found that allowing compostable bags in Hamilton’s program contributed to a slightly higher rate of contamination, increasing to just under five percent. However, this number is dropping again, with expanded education programs.”
CENTRAL COMPOSTING FACILITY
The CCF is located within city limits in the industrial section of Hamilton. Close to both downtown and Lake Ontario, CCF uses an in-vessel system and is totally enclosed in a building under negative pressure to control odors. Air curtains above the tipping floor doors help maintain negative pressure at all times. The building is constructed of concrete and galvanized steel to prevent corrosion.
CCF’s annual capacity is 60,000 metric tons, with a peak of 90,000 metric tons, which translates to approximately 255 tons/day, with a peak capacity of 381 tons/day. The facility is owned by the city, but operated by Maple Reinders, a waste management service contractor, and employs seven people. Project groundbreaking was in February 2005, with full operation starting in June 2006. Total construction costs were $30 million CAN ($28 million USD).
Trucks are weighed to determine tonnages, and unloaded inside the composting building. Front-end loaders scoop up the organics and drop them into a Komptech Terminator, a slow-speed shredder. This opens bags and reduces particle size, but does not fragment plastic, making it easier to screen out at the end of the process. “Glass can be an issue, because it can shatter into many pieces. We combat this by educating the public not to put glass into the green cart,” says McCormick.
After shredding, organics are blended with oversized woody materials (screened out of previously composted material) to give structure to incoming material and allow air to pass through the composting mass more easily. This mixture is fed via conveyor into a tunnel for the first of three composting phases. “Our composting process was designed by Christiaens Group, and uses aerated tunnels for both primary and secondary composting phases,” explains McCormick. “The first phase lasts 14 days in a series of 10 tunnels, during which a 35 to 45 percent volume reduction occurs. Organics are then moved to a separate set of 6 tunnels for the second phase, where they are composted for an additional 7 to 10 days.”
The system uses in-floor aeration, with 21 channels of air per tunnel. Spigots in the floor serve a dual purpose, pushing air out and collecting leachate. The leachate is reused in the first phase, but fresh water is introduced for the second phase. The building is under negative pressure, with air pulled into an above ground, covered, biofilter that measures 30 by 50 meters (98.4 by 164 feet). “The biofilter media consists of large stringy wood pieces, which is replaced approximately every three years,” says McCormick.
Christiaens can monitor and control the composting process remotely. “We have a control room for monitoring operations at the facility, but we aren’t a 24-hour facility, so the remote capabilities are important,” says McCormick. “If the system detects an error, it calls the composting operator’s phone with a message about what is wrong. Christiaens also monitors the process from Holland.” The system measures temperatures in three zones of each tunnel, oxygen levels, tunnel pressure, air circulation, input of fresh material, biofilter performance and the watering system.
After the second composting phase, organics are screened to 1-inch minus using a Komptech star screen and sent through an air classifier. Overs are processed in an electric, horizontal Vermeer grinder and mixed with incoming organics. “This grinding stage for overs was added in 2009 to make the carbon more accessible for the composting process,” reports McCormick. Fines from the screen are fed via enclosed conveyor to a semi enclosed curing building, where they remain until marketed. The cured product is sold to soil blenders for residential landscaping.
As of November 2009 the city’s residential diversion rate was 45.4 percent, but efforts are being made to increase this percentage. “The one garbage bag limit being implemented in 2010 will bring Hamilton closer to the 65 percent diversion target,” concludes McCormick.
COMPOSTING EDUCATION CENTER
Hamilton’s Central Composting Facility (CCF) has a classroom for hands-on education, which showcases recycling, organics collection and waste management in the city. School groups come to the CCF education room on a weekly basis, and learn about the basics of Hamilton’s curbside collection programs, such as the one bag of garbage rule, how to sort material into the proper bins, etc.
There are several interactive displays for engaging the students, such as a child-sized model of a collection truck that demonstrates how a cart tipper works. A play kitchen has common household items to help children identify organics and recyclables. Students learn about landfills and how to keep curbside bins tidy. Windows in the room offer views of the composting operation, including the tip floor and the shredder. This allows students to see first hand where the organics they place in their household green cart are turned into compost, instead of being sent to the landfill.
January 19, 2010 | General
Steady Progress Toward 65 Percent Diversion
BioCycle January 2010, Vol. 51, No. 1