ARCHIVED - Finding Gold in Garbage

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March 07, 2007— Ottawa, Ontario

When you pass a cow field or garbage dump, the first thing you notice might be the smell. But hidden within those steaming manure piles and rotting kitchen scraps is something of great value — a clean source of energy.

Methane gas is belched out by the natural bacteria that break down organic wastes from crops, sewage, animal waste and garbage. Usually methane escapes into the atmosphere, where it becomes a greenhouse gas. But if collected and purified, methane can also be used to create energy — and profit.

Anaerobic digestion is already used in parts of Europe to process industrial waste. These anaerobic reactors at a newsprint mill in Germany process methane from industrial wastewater.
Anaerobic digestion is already used in parts of Europe to process industrial waste. These anaerobic reactors at a newsprint mill in Germany process methane from industrial wastewater.

"Once it has been properly purified, you can sell methane directly into the natural gas grid," says Dr. Serge Guiot, leader of the environmental bioengineering group at the NRC Biotechnology Research Institute (NRC-BRI). "Or you can use the raw gas in modified engines that run electricity generators. You can then use that electricity yourself or sell it to the grid."

This type of energy is called biogas. Not only is biogas a potential source of profit, it is renewable and produces far fewer greenhouse gases than fossil fuels. The process for extracting biogas — called anaerobic digestion — is emerging as a green alternative for cities and industries that are struggling to manage the growing volume of organic waste in landfills and wastewater treatment plants. Anaerobic digestion, or AD, offers a way of treating organic waste that's far cleaner than traditional methods such as composting, landfilling or incinerating.

Dr. Guiot leads an NRC project that will take the concept of AD on the road. His group is building a trailer-size mobile AD unit that will travel to several sites in Quebec that handle organic waste, including a municipal wastewater treatment plant, a pulp and paper mill, and a landfill site. "The unit will demonstrate anaerobic digestion at real sites, on real waste," says Dr. Guiot.

NRC's unit will spend about six months at each site. Operators will get a pilot scale demonstration of how AD technology can extract methane from their own waste. The same process could be used on an industrial scale to produce enough methane to generate revenue. "We will be able to tell them how much methane they could extract on a large scale," says Dr. Guiot. "That will show them the economic benefit of this process over incinerating the waste or putting it in a landfill." The goal is to convince the people who manage these facilities that there's money in methane. "The data should be convincing because it will be based on processing their own waste in a real context," says Dr. Guiot.

But methane faces a major hurdle to become our next green energy source. Although it is well known that anaerobic digestion is a good option for treating sewage sludge and industrial wastewater, and agricultural operators have used it on a small scale for years to generate energy for farm buildings and equipment, it has been a harder sell convincing decision makers of AD's potential for large scale treatment of other types of waste, and for generating energy.

This anaerobic digester on an Ontario dairy farm produces power from the farm's manure. Photo courtesy of Ontario Ministry of Agriculture, Food and Rural Affairs
This anaerobic digester on an Ontario dairy farm produces power from the farm's manure. Photo courtesy of Ontario Ministry of Agriculture, Food and Rural Affairs

"The tools are there," says Dr. Guiot. "But there is a gap between the science and its practical implementation." A major reason for this gap is money. The short-term cost of anaerobic digestion is higher than traditional options such as landfilling, incinerating and composting. "For anaerobic digestion, you have to invest in processing and purifying the biogas, and the equipment to turn the methane into electricity," says Dr. Guiot.

But when well managed, anaerobic digestion can be more cost effective in the long run.

Dr. Guiot knows of one landfill operator who has invested in a purification station and now sells methane to the TransCanada Energy Company. He now makes a profit from methane that formerly would have drifted into the atmosphere. Ontario Power offers financial incentives to farmers who generate electricity from biogas, paying them about 12 cents per kilowatt hour. This is higher than the market value of electricity at 6 to 8 cents per kilowatt hour.

NRC's mobile unit is part of a larger project led by Natural Resources Canada with funding from the Canadian Biomass Innovation Network (CBIN). This project is looking at several ways to convert waste into energy. According to Jody Barclay, of Natural Resources Canada, the project offers two main benefits. "It's creating renewable energy," she says. "It's also disposing of what is typically considered waste. If we can find a use for the organic components of industrial and municipal solid waste, we can reduce the burden on landfill sites."

Dr. Guiot says these types of demonstration projects give scientists the chance to play an important social role. "If we can make scientific knowledge more accessible to practitioners, we can help them to make good decisions," he says, and hopefully one day develop a clean source of energy by finding gold in our garbage.


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