The City of Edmonton estimates that about 50 per cent of single-family residential waste could be composted, and yet, only about six to eight per cent is.
Most municipalities aim to capture about 80 per cent of their organic waste, environmental engineer Daryl McCartney said.
When they start a compost program, they’ll typically capture about 30-50 per cent but with time, practice and public education, municipalities can push that rate up to 80 per cent, the University of Alberta professor explained.
“Less education, the lower the capture rate and higher contamination as well,” he said.
Seattle is the gold standard, according to McCartney.
The 2018 Seattle Public Utilities Waste Prevention and Recycling Report states in that year, the city had an overall recycle rate of 56.5 per cent. Out of 796,822 tons of waste, 450,500 tons were diverted from the landfill and 346,322 tons were disposed of. That same year, Seattle’s residential recycling rate for all types was 62.8 per cent. The city’s 2022 goal is to reach 75 per cent.
During its most successful years, Edmonton was able to divert about 60 per cent of its waste from the landfill too, McCartney said, but its contamination rate was higher — meaning there was still garbage mixed with the organics.
Green cart, black cart, blue bag
Seattle, which is one of the few cities to share waste data publicly, has residents separate their organic waste from their other garbage — and they do quite a good job. Seattle has an incredibly low contamination rate for its organic waste: two to three per cent in peak summer months and four to five per cent the rest of the year.
Calgary launched its green cart composting program in June 2017. Calgarians already separated their recycling into blue bins and their garbage into black bins for curb-side pickup. The green carts added separation of organics.
“It’s the tale of two cities,” McCartney said. “It’s kind of ironic. Edmonton was way ahead… and Calgary waited and it’s built the latest and greatest.
“Calgary’s facility is good… their final product is a good, clean product. I’ve done some testing and I wouldn’t hesitate to recommend that… It’s quite an economical process as well.”
The Edmonton Cart Rollout pilot program was launched in April 2019. Eight-thousand homes received a green cart for food scraps (organics) and a black cart for garbage. Residents were asked to continue separating their recycling and setting it out in blue bags. Yard waste collection is collected at Eco Stations twice in the spring and twice in the fall and is composted at the Edmonton Waste Management Centre (EWMC) cure site.
Edmonton Cart Rollout was supposed to expand city-wide in summer 2020 but the COVID-19 pandemic postponed the launch. The pilot phase will continue into spring 2021, when the city-wide rollout is expected to begin.
“All remaining single-unit homes in Edmonton will follow a similar routine once they receive a food scraps (green) cart from March to fall 2021,” Anna Kravchinsky, spokesperson for the city’s waste services, told Global News.
Edmonton has a few things coming down the pipe in 2021 that will improve its composting numbers: more food scrap (organic, or green) carts, the new High Solids Anaerobic Digestion Facility operating at full capacity and processing capacity from regional partners becoming available.
“At that time, the majority of the city’s organics will be diverted from landfill,” Kravchinsky explained.
In May 2019, the Edmonton Composting Facility closed due to the roof being structurally unsound. The city said it’s currently “almost fully deconstructed.”
That means there’s less processing space at the EWMC, where the separating and sorting of organics from general garbage takes place (at the Integrated Processing and Transfer Facility inside the EWMC).
“As a result, green cart organics from the pilot program and yard waste are prioritized in the remaining EWMC facilities,” Kravchinsky said. “Where possible, the IPTF is used to add additional organics to those locations when capacity allows.”
Source or central separation
McCartney started consulting in the field of composting in the late 1980s, when programs were just starting to roll out in major Canadian cities. In 1993, he began researching organic waste systems and composting.
Generally, Canadian cities use two main ways of separating organic waste from other garbage: source separation (when residents are asked to separate food waste from other garbage at their homes before the city collects it) and central separation (when all residential waste is collected and brought to a city facility, where organics are separated from other garbage).
“The City of Edmonton doesn’t have a source separated program,” McCartney said, but with the green cart pilot project, it’s moving in that direction.
Right now, organics arrive at the EWMC in garbage bags, green carts, yard waste, and even from Eco Stations. Crews at the facility sort through residents’ waste, recovering the organics in the garbage and sending it to the composter through a mechanical screening process.
“Currently, most organics are commingled with other refuse in black bags,” Kravchinsky said.
“These organics are mechanically pre-processed or separated from the other refuse, and then sent to one of the processing areas at the EWMC. Organic waste that is not commingled with other refuse is sent directly for processing.
“A small amount of the organics that is commingled in black bags is also extracted for use in the High Solids Anaerobic Digestion Facility (HSADF).
“In spring 2021, Waste Services expects to have agreements in place with processing partners in the Edmonton region to ensure additional organics processing capacity.
“This will ensure that organics collected in the city-wide Edmonton Cart Rollout get processed and diverted from landfill.
“This will also free up capacity at the EWMC to process a larger fraction of the commingled organics,” Kravchinsky said.
In 1999, Edmonton was the first to build a large-scale composting facility, McCartney said. At the time, it was the biggest in the world.
“They were leaders in that regard,” McCartney said.
“They had this notion that using the large drums and slowly breaking open the bags that they could sort the organics… The technology worked quite well for about 50 per cent of the organics.”
But the other half of Edmonton’s organic waste was still mixed with the garbage.
“Trying to get that out was quite difficult,” McCartney explained. “It’s still not easy to get the systems pure… Unfortunately, that little bit of contaminant is problematic.”
Even a little piece of plastic or other waste in a supply of compost means it can’t be sold.
Comparing costs of each sorting method
You can compare source- and central-separation techniques by looking at cost per tonne, McCartney said. With source separation, it’s residents doing the separating, which saves the city money, but people have to be taught to correctly, accurately and consistently separate their household waste, which means investing in public education.
“The general agreement in the industry is that you need to spend between 20 and 25 per cent of your entire waste budget on education and public awareness,” McCartney told Global News.
With central separation, cities have to invest more in sorting resources and technology but not as much in public education.
McCartney says another measure is the capture rate (the percentage of organic matter that’s correctly captured) and the contamination rate (how much non-organic waste ends up in the compost product).
The City of Edmonton can’t compare home-sorted versus centrally-sorted waste since the pilot only includes 8,000 residences. However, the Waste Services department agrees that having residents separate their organics at home first results in “a much lower contamination level and the removal of of remaining contaminants at the EWMC is much easier.”
“Organics commingled with other waste in black bags results in a high level of contaminants, making the sorting process more difficult,” Kravchinsky said.
“As a result, organics from green carts are much easier to process at the facility and produce higher quality compost when compared to organics that are commingled in black bags.”
Learn from Seattle
Seattle has been able to increase its capture rate and lower its contamination rate by investing in creative public education campaigns, McCartney said.
“They’re looking at all the things that cause contamination and developing programs to address them.”
Those little plastic stickers on fruits and vegetables, for instance. The peel is compostable but the sticker is garbage. In response, Seattle created fruit sticker bingo. When a family filled all 20 spots with fruit stickers, they received a free bag of compost.
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