Cold Regions Geoenvironmental Research Facility

2004 Winner: Innovation In Agricultural Science Sponsored By Dow AgroSciences Canada Inc.

Waste-Treatment Technology Creates Useful Products From Manure

Intensive livestock operations have come under pressure due to concerns over manure management and potential adverse effects such as odour, surface and groundwater contamination, and impact on rural drinking water quality. Two statistics illustrate the magnitude of the problem: Alberta has a swine population of 2.14 million, and an 80,000-head pig operation can produce more waste than a city of one million people. Far more manure is generated than can be transported economically for crop fertilization.

Dr. Kevin Biggar and his team in the University of Alberta’s Faculty of Engineering have developed an innovative, economically feasible waste-treatment technology that uses Alberta’s cold winter and existing infrastructure to provide an environmentally sustainable solution that creates value-added products from pig manure.

The Innovative Technology

The technology is a freeze-separation process that operates on the same principle used to produce ice beer. As water freezes, pure ice crystals form while impurities are rejected into the remaining unfrozen liquid. As cooling continues, more ice forms and the remaining liquid becomes increasingly concentrated with impurities. Dr. Biggar’s group uses a method called thin-layered freezing. The manure is placed in a storage lagoon in layers 50 to 75 mm thick. Each layer is allowed to freeze before the next layer is placed. Fluid containing concentrated nutrients such as nitrogen, potassium and sulfur migrates downward, resulting in a thin layer of highly concentrated nutrient-rich fluid. This fluid forms vertical channels through the ice, draining to a collection system at the bottom of the pit. This concentrated fluid is stored in a separate facility.When the ice starts melting in spring, the first melt flushes remaining impurities with it leaving nearly pure ice. Melt water from this ice is collected and stored separately. The solids are later removed and treated.

Useful Products

In the laboratory and in field tests over an Alberta winter, freeze separation of hog manure has concentrated nutrients into 10 to 40 per cent of the original fluid volume, allowing it to be economically transported greater distances for use on crops. The remaining liquid has very low concentrations of impurities and may be able to be reused for irrigation, washing or animal drinking water. The solids can be composted. The process also seems to significantly reduce odours.

This freeze separation technology offers the economic advantages of using natural cooling and heating and existing lagoon systems, while producing three value-added products – nutrient-rich fluid, reusable water and compostable solids. The technology is particularly attractive in light of anticipated regulatory changes regarding intensive livestock operations and their environmental impact.