Methane: Gas from past may have future

BY ROBERT IRWIN

A $250,000 Cambridge-area manure digester is all powered up, but the methane it generates has no place to go. Sound like deja vu all over again?

The system at John Pittens' 80-cow dairy operation had gathered dust for 10 years, its components slowly corroding. The scene was similar to those at a dozen other Canadian farms, where similar digesters were eagerly constructed during the energy crisis in the early 1980s.

Ray Stickney, who supervised the installation of six Ontario on-farm methane digesters for Canviro Consultants Ltd. back in the '80s, says the original units were eventually abandoned "because there were other opportunities on the farm for farmers to make more money with their time."

But last year Ontario Hydro plowed a few thousand dollars into recommissioning Pittens' digester. It was part of a demonstration aimed at firing up interest in methane production on Ontario farms again.

The methane produced by Pittens' dairy manure is supposed to run an adjacent 90-hp Caterpillar engine connected to a modest 35-kilowatt generator.

The farm is equipped with a matched pair of hydro meters. One measures electricity going from the generator to Ontario Hydro lines. The other measures power incoming from Hydro.

Pittens' system can produce more electricity than he needs, so as part of the demonstration Hydro has agreed to pay him for any surplus he generates. "By the year 2000 there will be an open market policy, so anyone can sell power," Ontario Hydro Technologies senior research engineer Francis Chang explains.

Chang sees farm methane digestion as a viable business but cautions, "don't look at it as a cash cow." Most experts agree the operation of a methane digester requires the same dedication as raising livestock or growing crops.

Pittens earns extra revenue from his digester by accepting potato waste from a nearby Humpty Dumpty potato chip plant. Anaerobic digestion satisfies government regulations for the processing of waste from imported potatoes to remove the threat of plant disease and permit land spreading.

But right now, the methane Pittens produces is wasted: The system has to run on purchased propane pending a final engine tune up and system review by Hydro experts. He's beginning to wonder if he may have to foot the rest of the bill.

Hydro staff haven't been calling lately. The giant utility has axed direct financial support of many research projects in the wake of a recently announced $6-billion deficit, the largest in Canadian corporate history.

"I agreed to work with Ontario Hydro as long as I didn't have to spend too much money," says Pittens, who at 65 says he has no plans for expansion. He's a little discouraged by his latest propane bill, which totalled $800.

Chang admits Hydro has no more money available now for Pittens' digester, but says the utility remains committed to methane and will lend its expertise to anyone interested. At current prices for electricity, he says Pittens' operation is too small to be profitable on power alone. His department is turning its attention to digesters that can handle larger volumes. Chang suggests the output from a 2,000-hog operation could pay back the original investment in seven years.

In fact, Chang and Ontario Ministry of Agriculture, Food and Rural Affairs manure expert Don Hilborn are looking into the possibility of locating a community digester in an area with large numbers of livestock. "Somewhere like Perth county," Chang speculates.

The concept would see a digester capable of generating as much as two megawatts fed from livestock operations in up to a five-square-mile area. Manure would be pumped through an eight-inch municipal manure pipeline. Returns would come from electricity produced as well as heat and composted manure, which would be sold or made available to participants.

The process converts inorganic nitrogen to an organic form. Hillborn says basically all nutrients remain in composted manure, but the nitrogen is more available to crops and "not as hot," meaning it is less threatening to the environment in the event of a spill or leaching through tiles.

"Hopefully you get rid of the pathogens, too," he points out.

Chang's calculations show heat generated could represent an additional 70 per cent over the value of the electricity produced. Heating greenhouses or supplying a dryer are among possible uses.

Both Chang and Hillborn say the anaerobic digestion process should make livestock producers more popular with neighbours: It removes much of the odour from manure. Nonetheless, if as envisioned 60 per cent of the land base around the digester is occupied with livestock production facilities, exhaust fans would still create odour.

The output of such a system represents a fraction of the potential of one of Hydro's ill-fated nuclear plants. Yet Chang says every little bit helps the system.

"Most incentive comes from it being a green energy," he explains. Power from methane would replace power from environmentally harmful sources like coal.

He won't speculate on the likelihood of hydro rates rising. But if industry analysts are correct in their predictions of sharp increases beyond the year 2000, he says methane's future in Ontario will be even brighter.

Biogas a going concern in Denmark

The Danes are world leaders in their approach to biogas production, according to Dr. Les Gornall, an internationally recognized environmental consultant who has been involved with biogas in many countries.

He claims a 100 per cent success rate with a half-dozen plants, all still running, that he constructed in his native Northern Ireland over the past two decades. It was in Denmark, though, where his 0.5 megawatt combined farm/industrial digester won a Thermie award and demonstrated unprecedented efficiency.

"Centralized biogas plants in Denmark are seen to support local industry, clean up the odour around the town, produce electrical power, produce hot water for their district heating system and make employment from a waste," Gornall says. He plans to be in Canada this month to consult on "a large but commercially sensitive project."

Gornall attributes some of the Danes' success to "an advanced social structure." He claims the fact that 75 per cent of national taxation is distributed through local town and village councils prompts greater interest in sustainability.

"My guess is that in the future all organic wastes will be treated in digesters in Denmark and land spread as enhanced fertilizers," he predicts. His latest Danish project at Vaarst-Fiellerad combines wastes from farms, food factories and the organic fraction of municipal solid waste, and co-digests the material at 56 C for a minimum of eight hours.

Gornall calls the output "a pasteurized fertilizer product." He claims the process generates seven volumes of gas per volume of digester per day.

"It's probably a world record for a high solids digester," Gornall asserts.

Why do farm digester projects sometimes fail? "There comes a point when the harvest is more important than the next maintenance job - it's a slippery slope from then on to the closure of the plant," Gornall observes.

He says farmers have to realize the digester is "another animal, not another tractor. In general, tractors do not die when left for a week without attention."

More hot gas from Ottawa

The regional municipality of Ottawa Carleton is the latest Canadian community to join the methane club.

A $4-million digester fired up at the city's sewage treatment plant last November is generating electricity worth about $1 million annually, says process engineer Scott Hall.

Methane-powered Caterpillar engines run three 800-kilowatt generators at Canada's second-largest secondary treatment plant. Hall says net savings amount to $650,000 after deducting operating and maintenance costs.

Maintenance includes oil changes every 750 hours. Heat recovered from the engines heats the process and buildings.

The plant's treated bio solids have become popular with local cash croppers in recent years.

Feds developing large-scale technology

Methane enthusiasts are watching Agriculture and Agri-Food Canada (AAFC) researcher Dr. Daniel Masse. He's getting a growing number of calls from farmers in Ontario and Quebec anxious to use his methane technology to solve odour problems.

Masse's low-cost, practical methane production system, proven out in AAFC's Lennoxville, Que., laboratory and on a 200-pig farm test, will soon be ready for launch on a large commercial scale.

Project details remain sketchy because of confidentiality agreements with a private company, which along with the Quebec pork board has funded his methane work. Masse's process appears to be based in part on specially developed micro-organisms that can be added to manure.

"We are using a different approach," explains Masse. He contends that digesters built on Canadian farms two decades ago cost too much and mistakenly relied on a high-temperature process that required manure to be kept at temperatures between 35 and 65C.

"We have a very, very cold winter, and during the winter you have to heat the manure." He says much of the energy produced with early systems went to create the heat that kept the digesters going.

Another problem Masse sees with high temperature digesters is "process stability. If the farmers uses antibiotics when the animals are sick, that m ight have an effect on the microflora," he explains.

Masse also found stability in high temperature digesters required continuous feeding. "That means seven days a week, 24 hours a day, which means the farmer can't use existing manure handling equipment."

He says pumps have been used to meter in manure, but they boost costs and have been difficult to keep properly calibrated under field conditions. The harsh environment results in high failure rates and repair bills, too.

High temperature systems need time- consuming monitoring and sampling. "You have to check the concentrations of volatile acids and pH almost daily," Masse points out.

"If a farmer makes more than $1,000 an hour harvesting corn, he's not going to sit beside a bio reactor that brings him $300 a day," Masse reasons.

Hog manure leaving barn pits and gutters normally averages between 12 and 20C, exactly the operating range of Masse's process. His system is designed to produce hot water, which can be used to clean or heat buildings.

He predicts it will replace the propane used on many farms. He says this approach makes the system affordable, because there is no investment in costly electrical generating equipment.

What advice does Masse have for farmers who want to produce methane? "I tell them to wait" a little longer, he says.

© copyright 1998 Agriculture Publishing Company Limited.


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