As real-world educational experiences go, it doesn’t get more truer-to-life than this. Last year, Donald Kirk, a professor in chemical engineering, asked 12 of his fourth-year students to design a plant that could transform Toronto’s trash into energy – a task that propelled the team right into the murky heart of the city’s garbage crisis.
With the help of EnQuest Power Corporation, an upstart waste-to-energy company, the students developed a detailed proposal for a gasification plant. The team proposed feeding garbage into a huge cylindrical kiln that’s heated to 800 Celsius, and subjecting it to steam. In this super-hot, oxygen-starved environment, plastic and organic waste reduces to a synthetic gas that can be used as fuel. The small amount of material that doesn’t break down would be dumped at a landfill site.
What struck Professor Kirk is that the design team didn’t focus on the engineering aspects of the project, but rather on the environmental and socio-economic consequences. “They came up with ideas for community buy-in that I thought were more innovative than the engineering,” he recalls. One idea involved setting up a plant at a decommissioned landfill site, where the energy produced from the gasification process would generate heat for a greenhouse. “They were thinking broadly, about how you would make this technology attractive to the public,” says Kirk.
Every Canadian knows that Toronto has world-class garbage problems. A growing number of Torontonians feel uncomfortable about shipping garbage to distant landfill sites, and public opinion polls show a growing interest in garbage disposal alternatives such as gasification and high-tech incineration, as practised in Europe.
Many local politicians and environmentalists remain skeptical. They cite concerns with toxic emissions, reliability, cost and the potentially negative impact such systems could have on recycling programs. On the other side of the debate, proponents say that the GTA municipalities need to reduce their dependence on landfills, which emit greenhouse gases and depend on a steady stream of dump trucks spewing diesel exhaust. They also say new technologies can generate energy, providing cities with economic and environmental payoffs.
Since 2001, Toronto has been increasingly proactive about diverting garbage from landfill. In 2005, the city’s diversion rate reached 40 per cent, thanks to expanded recycling, hazardous waste drop-off programs, and household green bins for organic waste. Toronto is now one of North America’s greenest municipalities, and city officials hope to break through the 60 per cent mark by 2008.
It won’t be easy. Half of the city’s residents live in apartments, and many highrises don’t have adequate recycling or green bin facilities. Another headache is finding a way to dispose of toothbrushes, mattresses and old electronics – and all the other stuff that can’t be tossed into recycling bins. Even if Toronto achieves a 60 per cent diversion rate, it will still have to dispose of 400,000 tonnes of residual waste each year. Until 2010, our trash will continue to be shipped to Michigan, and then it will be dumped at a newly purchased landfill site near London, Ontario. But within the next four or five years, the city wants to choose an alternate method for dealing with residual waste.
Over the coming year, the Community Environmental Assessment Team will work with Toronto’s city council to evaluate the options. Philip Knox, the team’s chair, wants the University of Toronto to play a role. “We’d like to get professors and students to come out and help us look at these issues,” he says.
When John Rowswell (MEng 1986) was elected mayor of Sault Ste. Marie in 2000, he took over a city with serious economic problems. He set out to attract new business to the Sault – in particular, businesses that focus on waste management and energy. Rowswell travelled to Forssa, Finland (Sault Ste. Marie’s sister city), for a quick education on new approaches to energy, recycling and waste management. Forssa diverts two-thirds of its trash, and uses the energy generated from it to power a district heating system.
Inspired by Forssa, Sault Ste. Marie launched a daring experiment last year. The city partnered with EnQuest to builda demonstration gasification plant at the local landfill, with an eye to generate energy from waste. The firm plans to separate recyclables at one facility, and then gasify the remaining hydrocarbon-based materials, such as plastics, wood and paper. EnQuest claims its technology can reduce garbage mass by up to 90 per cent. Sault Ste. Marie is now seeking environmental approval to process one tonne of garbage a day, with the possibility of ramping up to 275 tonnes a day if the technology proves viable.
Cities have been burning garbage since the 19th century. The rap against old-style incinerators is that they pollute the local environment with lead, mercury and the dioxins they create during the burning process. Knox says that Toronto’s environmental assessment team will evaluate thermal processing techniques such as incineration and gasification, but it’s a touchy issue. For decades, an incinerator rained heavy-metal ash on downtown neighbourhoods until it was mothballed in 1988.
In the 1990s, countries including Germany, Sweden and Denmark pushed through tough new rules limiting emissions – forcing municipalities to invest heavily in technology to capture all but the slightest traces of toxins in the ash. “It’s not a problem to have a very clean incinerator,” says chemical engineering professor Charles Jia, who has been developing scrubbing technologies for both industry and municipalities. Waste is mechanically pre-sorted to remove hazardous materials, such as batteries, and substances that burn poorly or not at all, such as glass, aluminum and wet organics. Carbon-activated sponges can absorb mercury vapours that are released during incineration, and alkaline filters can neutralize the acid gases. In some countries, the bottom ash – about 20 per cent of the original volume of the garbage – is stabilized by mixing it with cement to form concrete.
Do these new technologies produce safer incinerators? The jury is still out, but a growing number of toxicologists think they do. The thornier problem is the hefty capital and operating costs associated with incinerators, and the composition of the waste being fed into them. Clean incineration is almost twice as expensive as dumping in landfill. But there’s an off-setting benefit: the heat generated by five tonnes of waste can provide enough power for a typical household for one year.
Yet not all garbage is created equal. The most energy-efficient waste includes wood, paper and plastic, says Jia. But municipalities have become increasingly adept at recycling these materials, and environmentalists are loath to roll back those gains. “One of the major arguments against incinerators
is that they need to be fed to get your money’s worth out of them,” says Phil Byer, a professor of civil engineering. “I don’t see any good argument for burning packaging.”
Kirk has a different way of looking at this issue. He agrees that it’s much more energy efficient to recycle paper and metal products than to make them from scratch. But he points out that some of the materials collected in blue boxes end up in landfills, because they can’t be reprocessed. Plastics come in so many different chemical forms, he says, that some can’t be properly sorted. Instead of recycling plastics, Kirk advocates converting them into usable synthetic gas (also known as “syngas”). “The question I ask is, ‘How much energy does it take to recycle compared to the amount of energy you can get out of the process?’”
In class, Kirk walks his students through a life-cycle analysis, which calculates the total energy used for recycling trucks, sorting equipment, secondary shipments of contaminated materials to landfills and the greenhouse gases created by landfills. “Most come around to the view that we should be using the plastics for their fuel value,” says Kirk.
ALTHOUGH INCINERATION and gasification garner most of the media attention, some waste-management firms believe there’s a less risky solution to our garbage problem. The alternative relies more on decomposition than high-tech facilities operating at blazing temperatures.
In the early 1990s, Eastern Power Corporation, a Toronto energy company founded by brothers Gregory (BASc 1982) and Hubert Vogt (BASc 1980) and Herman Walter, developed two facilities for capturing the methane gas that escapes from landfills, and using it as fuel. Having completed those ventures successfully, Eastern shifted focus.
They reasoned that if the decomposition process could be accelerated, they could alter the entire logic of municipal waste management. Through a subsidiary called Subbor, Eastern designed an “anaerobic digestion technology” capable of rapidly converting garbage into a peat-like substance. According to Eastern’s studies, anaerobic digestion is the best bet for minimizing greenhouse gases and maximizing the energy produced from municipal solid waste.
In Subbor’s system, municipalities collect all solid waste in“super blue boxes” and truck it to a central processing facility. A series of filters and mechanical separating machines remove the metals, paper and recyclable plastics so they can be sent to recycling facilities. The remaining material is ground down and goes through a two-stage “digestion” process that uses bacteria to accelerate natural decomposition. This digestion takes place at 55 Celsius. The process yields a bio gas that can be used to operate the facility or produce electrical power for a local utility. It also yields a peatlike substance. After sorting the peat to remove undigested residuals, such as plastic scraps, it can be sold for compost, landfill cover or agriculture.
In 1998, Subbor approached the City of Guelph about building a $30-million demonstration facility capable of processing 480 tonnes of garbage a week. But even after Subbor built the plant, anaerobic digestion continued to be a tough sell. Three years after signing the contract, Guelph cancelled the deal when city officials determined that Subbor couldn’t handle the volume of waste generated by the city. Subbor sued for breach of contract, but the city maintained it didn’t violate the terms of the agreement. A judgment is pending, but Subbor’s plans to build more facilities are on hold for the time being.
York and Durham regions also rejected anaerobic digestion as an option following an environmental assessment conducted last spring. The assessors concluded that it would be difficult to find a sufficiently large site and warned that such plants – because they must be capable of storing large quantities of decomposing waste – have the potential to damage local ecosystems.
Despite the setbacks, Vogt remains optimistic. “Technology can help us in this area,” he insists. “When, I can’t predict. But we have learned to be patient.”
What’s clear with all of these technologies is that the City of Toronto won’t be able to consider them in isolation from other key policy decisions, some of which fall under the purview of other levels of government. “Waste management has to be seen as a system,” says Byer. “It is a question of a package of options and activities.”
A major consideration will be packaging rules, says Knox. Germany and Sweden, for example, have much tougher national rules requiring manufacturers to take responsibility for the full life cycle of the packaging they use. Knox says that without tough regulations, there will be little motivation for manufacturers to reduce their dependence on plastic and paper wrapping.
Then there’s the role of established recycling programs. For many environmentalists, these are sacrosanct because they have forced citizens to think about the three Rs – reduce, reuse, recycle. But as Knox and Kirk point out, some of the stuff that goes in the recycling box ends up in landfill, only by way of a more circuitous route. “It’s amazing, when you start to peel back the layers of the onion, the things you find underneath,” Knox says.
Beth Savan, the director of the university’s Sustainability Office, says that the decision to adopt new technologies must be guided by a handful of key factors: toxin emission levels, the health of waste management workers, location, the risk of failure and the mechanics of transporting waste to the disposal facilities. “This is always going to be a value-laden decision,” she says. “There will never be a universal system where everyone can agree on the assumptions.”
Yet both Byer and Kirk say it will be critical for Toronto to evaluate the various technologies in a scientifically rigorous fashion. Byer, who has previously advised the city on waste management technology, knows that the claims and counter-claims of the proponents of various systems need to be tested carefully, especially when it comes to incineration and gasification. He says the university is well-positioned to offer dispassionate expert advice. “We need to be openminded about these technologies, but we must also take a hard look at them.”
John Lorinc (BSc 1987) is a Toronto journalist. Penguin Canada recently published his book The New City.
By bringing artificial intelligence into chemistry, Prof. Aspuru-Guzik aims to vastly shrink the time it takes to develop new drugs – and almost everything else