McGill tames acrid manure smell

Macdonald researcher creates new system that helps neutralize nature's fertilizer

Spring can make Quebec's 5,000 pork producers a little nervous. Why? Because this is the season when farmers can dispose of pig manure – accumulated during winter – by applying nature's fertilizer to their fields.

Trouble is, the nutrient-rich substance has a pungent odour that few people appreciate. If Suzelle Barrington has her way, however, spring will soon smell sweeter for everyone. And pig farmers won't have to field complaints from their non-farming neighbours.

Barrington is a professor of bioresource engineering at McGill University's Macdonald Campus and Farm. She has developed an anaerobic method of digesting the brown liquid. Rather than it being stored in the open round cement vats one sees in the country, Macdonald Farm's manure is sealed under a plastic cover that is inflated as the manure ferments. Barrington's manure digester, distinguished by its green dome roof, is clearly noticeable from Highway 40 in Ste-Anne-de-Bellevue.

Reduces greenhouse gases, pathogens

Keeping the air and the oxygen enclosed within the manure dome is what reduces its odour. The device also fosters the creation of natural gas, which better preserves the manure's nitrogen and enhances its value as fertilizer. The dome's slower breakdown of manure also means its carbon is released in the soil, not in the air, thereby reducing the greenhouse emissions normally associated with the fertilizer.

"With anaerobic [without air] digestion, the nitrogen-rich proteins don't break down and smell as much," explains Barrington. "When the manure is applied to the fields, the breakdown is slower and the nutrients are better absorbed by the soil."

Another advantage to the manure dome is how it fosters the breakdown of antibiotics given to livestock, while killing pathogens or parasites in the fertilizer. Barrington is currently investigating ways the dome's methane gases, which now escape into the atmosphere, could be used to heat water or farm buildings.

Barrington predicts the higher quality fertilizer produced by the manure dome and its reduction of methane gas in the environment are good reasons to encourage farmers to adopt the system. Later this month, Barrington will meet with a major pork producer near Quebec City who will be the first commercial farm to convert to anaerobic digestion. The Quebec government also plans to fund a study of the impact of the Barrington method this fall.