A back-end solution to an energy crisis

ILDERTON, ONTARIO - The hundreds of black and white Holstein cows milling about the barn at Laurie Stanton's dairy farm may not look like a valuable source of energy, but each animal on the hoof has a lot of potential.

In the search for a way to deal with the vast quantity of manure his big herd generates and to do something useful with it, Mr. Stanton, a third-generation dairy farmer, had a quirky idea: why not try to turn the dung into a valuable commodity, like electricity?

Later this summer, Ontario electricity consumers will start using power that Mr. Stanton's herd will contribute to the provincial grid. Each of his cows is expected to produce enough manure to keep three 50-watt light bulbs constantly illuminated.

The sprawling dairy operation, located near London, Ont., is poised to become the largest source of farm-biogas-derived electricity in Canada, with its cow manure turned into methane, the active ingredient in natural gas, and burned in a miniature power plant to produce electricity.

"There is huge potential for it," Mr. Stanton said of his scheme. "We're absolutely sold on this system."

The idea of turning cow waste into electricity, according to its boosters, which include the Ontario government, the source of $2.5-million in financing for the venture, sidesteps one of the biggest quandaries in agriculture today.

It's the question of whether it is good sense or folly to turn valuable human food, such as corn and soybeans, into renewable fuels, such as ethanol or diesel, to use for cars.

The rush to make ethanol from corn has more than doubled the price of the agricultural staple, and although it has also helped to curb petroleum use, it has prompted global worries about food-price inflation.

But in the case of manure, it is a material nearly no one wants; while farmers typically spread it on their land as a substitute for fertilizer, the activity is often a source of complaints from neighbours offended by its pungent smell, and worried about its potential to pollute groundwater.

There is something alluring about getting energy from "materials that are not really competing with food," observes Franco Berruti, director of the University of Western Ontario's Institute for Chemicals and Fuels from Alternate Resources. The institute, along with two other Ontario universities, will conduct research at the Stanton farm, tracking its progress in turning agricultural wastes into energy.

Dr. Berruti says society should be looking for a "sustainable type of biomass that can be converted into value-added products, and manure is certainly one of those."

He thinks people should view manure and other similar materials in the same way they'd view a crop.

"When you look at farms, agriculture operations, nothing is waste. Everything is a resource. It's just a matter of harvesting," he said.

The province announced funding for the $5-million project earlier this month, saying it hopes the Stanton's on-farm power plant will suggest a possible way of dealing with some of the nearly 50 million tonnes of biomass, or waste residues from plants and animals, that Ontario produces annually.

If converted to energy, the biological waste could produce enough power to meet the needs of seven million homes, according to a Ministry of Research and Innovation estimate.

Manure is used to produce energy in many developing countries, although the operations are often primitive, little more than covered pits with pipes for methane collection. But in Germany, considered the Western leader of the technology, biogas projects are currently producing about the same amount of electricity as a large nuclear plant.

In Canada, only a handful of farms produce electricity from their waste material, in part because building small power stations is expensive and because it requires large-scale agricultural operations to be economically worthwhile.

The Stantons, with 750 milking cows, operate one of the biggest dairy farms in the country.

Ontario's electricity grid is also at capacity in many areas, leaving little or no room for new suppliers to hook up to it.

Yet given the huge potential for biomass energy, John Wilkinson, Minister of Research and Innovation, said he thinks agriculture can produce both food and fuel, if it uses waste materials for energy.

"It is not food or fuel. We believe innovation is the key to food and fuel," he said recently when announcing the grant to the Stanton farm.

Contractors are currently putting the finishing touches on the power plant, sited near the farm's dairy barn, in the middle of a vast expanse of waist-high corn plants.

After having been washed and scraped from the cow stalls into a series of sewage pipes that run under the barn, a series of eight, three-story-high steel tanks, located at the heart of the power plant, will be used to ferment the manure.

Once in the holding tanks, bacteria naturally present in the manure will decompose it, giving off methane gas, which will be collected at the top after bubbling through the slurry.

The gas will then run through pipes into a diesel generator that has been converted to run on natural gas, where it will be burned to produce electricity.

Although the operation will start small - with an initial capacity of 300 kilowatts, Mr. Stanton hopes it will eventually produce about 1.3 megawatts- enough to provide for the electricity needs of about 800 typical homes.

A kilowatt is the amount of electrical capacity needed to supply 10 light bulbs, each rated at 100 watts.

To boost the power output to the higher figure, the farm plans to mix manure from its cows with food waste trucked in from canneries and elsewhere in the London area.

The process of producing the methane is also known as anaerobic digestion because it takes place in the absence of oxygen.

Bacteria thrive best at temperatures of around 37 degrees, the same as normal human body temperature, so the slurry will be heated and kept at that level for the five days it is expected to take the microbes to chomp through the cow dung.

The long period of heating kills most pathogens, and eliminates the manure smell that many people often complain about, Mr. Stanton said.

After being run through the digester, the leftover liquid will be used as fertilizer, reducing the farm's need to buy plant nutrients on the open market, he said.

The solid bits the bacteria can't digest are going to be strained out to produce a matted, grey-coloured material that resembles peat moss and is going to be used on the farm as a bedding for the cows.

Under Ontario's preferential pricing system for electricity from green sources, the farm will receive 11.7 cents for every kilowatt hour delivered onto the grid.

Although the price is about double the current market level, Garry Fortune, an energy consultant for the Stantons, said it should be raised to 18 to 20 cents per kwh to reflect the big environmental benefits of getting rid of manure.

The province announced funding for a $5-million anaerobic digestion power plant at Laurie Stanton's dairy farm in the hopes that it will suggest a way of dealing with some of the nearly 50 million tonnes of biomass, or waste residues from plants and animals, that Ontario produces annually. If successful, Mr. Stanton's farm will produce about 1.3 megawatts, enough to power about 800 typical homes.

How it will work:

1. BARN: Slurry of manure is washed and scraped from cow stalls into a series of sewage pipes that run under the barn. The manure is mixed with other food wastes.

2. DIGESTER: The slurry is heated to around 37 degrees and kept at that level for the five days needed for the microbes to decompose the cow dung. This process gives off methane gas, which bubbles through the slurry and is collected at the top.

3. DIESEL GENERATOR: The gas runs to the generator, where it is burned to produce electricity to power the digester and the farm, and to feed into the grid.

4. SOLIDS SEPARATOR: Leftover liquids are used as fertilizer and the solids are strained to make a material to be used as bedding for the cows.


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