OLDS, Alta. – The benefits of composting could be compared to pasteurizing milk.
“Composting is a process that eliminates pathogens,” Frank Larney of Agriculture Canada told the Olds College composting conference.
He has been involved in a series of compost trials at the Lethbridge Research Centre. Researchers investigated the effects this process has on eliminating dangerous organisms and weed seeds.
At the Lethbridge site, they used an open windrow system where the materials take three to six months to break down. The temperature must be higher than 55 C for 15 days or longer and the compost must be turned a minimum of five times to be effective.
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They worked with compost based on manure mixed with straw or wood shavings.
If the windrows are not turned, the pathogens living on the outside of the pile may not be killed because they are not exposed to enough heat.
A 1998 study showed E. coli was
effectively killed if the windrows got hot enough and were turned regularly. All traces of this bacteria were killed after seven weeks.
A 1999 study found protozoa like giardia and cryptosporidia were killed within 42 days in straw-based windrows. Windrows based on wood chips took 56 days to kill the microbes.
“The difference seems to be temperature related. The straw-bedded windrows were warmer.”
Many farmers are reluctant to spread fresh manure on their fields because of fears it may introduce new weed seeds.
But composting can destroy a number of common weeds.
A 1997 trial showed composting kills pigweed seeds in 50 days. Wild buckwheat is harder to eliminate and may take up to 70 days because it has a hard outside coat.
In 1999, researchers checked 13 weed species with varying results. Wild mustard and scentless chamomile died in seven days while round leaf mallow survived for 42 days.
However, they found after 12 weeks of composing all viable weed seeds were gone.
