Distinguishing fact from fiction in manure separation
By David Manly
Recent research by the Prairie Agriculture Machinery Institute (PAMI) suggests that solid-liquid separation could help minimize phophorus pollution from runoff. The research was done in collaboration with the Manitoba Livestock Manure Management Initiative, Manitoba Agriculture, Food and Rural Initiatives, Agriculture and Agri-Food Canada, the University of Manitoba, the National Centre for Livestock and the Environment and the Puratone Corporation.
The agriculture projects manager for PAMI, Lorne Grieger, says that this research was done in order to address the inherent challenge in removing phosphorus from liquid hog manure. Therefore, the experimenters compared two different methods for separation and evaluated their performance.
“One system evaluated used high speeds and centrifugal force to separate the solid particles from the liquid manure, the other used a filtration method with rotating screens to separate the solids from the liquid,” he said. “The separated solids, which are rich in phosphorus and have a reduced moisture content, can be transported greater distances than liquid manure.”
The resultant solid and liquid compontents from the separation can both be used as valuable sources of nutrients for crops in Manitoba by being used as a fertilizer. In fact, Grieger said that the province of Manitoba was the perfect setting for these experiments, as there are regulations that dictate the total amount of phsophorus that can be applied to the land as fertilizer, and therefore the amount of manure that can be used. And if the total phosphorus content could be decreased, more fertilizer would be able to be used per acre.
“This is an issue for livestock producers located in areas of Manitoba where livestock numbers are high and the amount of phosphorus in the manure exceeds the amount of land available near barns were the manure is produced,” he said. “Because Manitoba is a net importer of phosphorus, an effective method of treating the liquid manure is required to allow a redistribution of phosphorus from areas where there is an excess to other areas of the province that are deficient.”
But, he cautioned, in order to minimize the risks of phosphorus pollution, there could be a substantial cost commitment to separate, ship and store the resultant high phosphorus solids to prevent contamination. If it were to get into the watershed, excess phosphorus can cause explosion algal growth, which can reduce water quality and harm the animals that live nearby.
According to Grieger, the next step in the research is to improve the phosphorus removal efficiency of existing treatments, of which data will become available this summer.