Don’t Worry, Use Slurry

For the layperson, a product composed of pig excrement, urine, and leftover feed and water might be hard to embrace. For farmers and scientists, however, slurry holds much promise in addressing emissions. 

“Slurry has long been recognized as a great fertilizer with a proven ability to maintain production levels on farm. Unfortunately, too much application in regions of dense animal production has given slurry some bad press,” says Dr. Marie-Pierre Létourneau Montminy, Canada Research Chair in sustainable animal protein production and assistant professor at Université Laval. 

Using four feeding regimens with various ratios of phosphorus (P) and nitrogen (N), the study is generating four types of pig manure and applying them to crops as fertilizer. 

“A pig trial was performed - using twelve environmentally controlled stalls housing four pigs per dietary treatment - to test the interaction between N and P. Over four weeks, the treatments were evaluated for growth performance, water intake, body composition, gas emissions, and slurry volume, including its concentration in N and P, and its pH. 

N and P have an environmental impact when applied in excess, while high pH increases ammonia losses 

As a result of these trials, four slurry types have been produced and sent to the University of Manitoba, where soil scientists are evaluating them for leaching and runoff potential, as well as GHG emissions. 

At Université Laval, Dr. Lofti Kiari is gauging the fertilizer potential of the samples compared to chemical products and determining which slurry would be most effective in that regard.  

Work is also ongoing with Agriculture & Agri-food Canada at the Sherbrooke Research and Development Centre to assess the slurry samples for biogas production. Biogas is a renewable energy source produced from raw materials such as agricultural waste and manure. 

“Thus far, we have confirmed that we can alter N to P ratios without impacting growth performance. Using a simulation model, we predicted the retention and excretion of N and P by pigs and compared that to what occurred on farm.” 

This is notable for producers, as it means that science can design diets and accurately predict the N to P ratio in the resulting slurry.   

Starting in February of 2026, a second phase of the study begins, focused on fiber and protein digesting enzymes in swine diets.  

“In general, the more fiber is digested by an animal, the less it can be emitted as methane. Protease [a type of enzyme needed to digest protein} is also of interest. It is produced naturally by the body but can also be supplemented in animal feed. If we can further degrade proteins, we may be able to reduce emissions. Combine that with better digestion of fiber, and there should be a marked benefit to the environment.” 

Though manure science may lack glamour, it places green ag squarely in the spotlight. 

“When you consider the environmental impact of swine production, it is due largely to manure and manure’s use as fertilizer. For that reason, we have made manure a priority in our project. While we have already developed some strategies to lower emissions with feed, crop production is also a factor, as chemical fertilizers affect both feed and manure. By producing manures with a better balance of N and P, we could reduce the need for chemical fertilizers going forward.” 

To further aid the planet, this study is also crafting strategies to lower methane emissions during the storage of slurry. 

In the months ahead, work will continue on two fronts, which include modelling in the lab and applying strategies on farm under real world conditions. The latter includes testing various methods of using manure for biogas production to find the most efficient option.  

The end goal of this project mirrors the linchpin of SIP’s agenda: Finding practical solutions that address industry issues and aid the bottom line. 

“We want to identify the best strategies for producers, but if those approaches are too costly, no one will implement them, so we really need producer input and involvement along the way.” 

Apart from supporting a greener planet, this study positions pork production as efficient, conscientious, and committed to a brighter future. Plus, if there is a carbon tax to contend with, or a premium paid for sustainability, the results could save producers money or strengthen competitiveness by reducing their environmental footprint. What’s not to love?