Drinking water that was just extracted from hog slurry may not be your cup of tea but it’s real handy on the hog farm
Politicians and media were photographed drinking freshly processed hog slurry water in an experimental facility. The event was the grand opening of Solugen’s first pig slurry purification plant last fall.
VIPs were not enthusiastic about the new beverage product, but most were brave enough to at least try a little sip. They all conceded the Solugen clear liquid was tolerable, although nobody asked for seconds or placed an order for bottled beverage.
Solugen is a Quebec startup with a system that extracts 85 percent of phosphorus found in pig slurry. In doing so, it also extracts 84 percent of the water from slurry, says Patrick Vidal, a director with the new company.
“There is no taste to this water because it’s pure water. There’s no salts or minerals as normally found in water. Our process leaves nothing but two molecules of Hydrogen bonded to one molecule of Oxygen,” says Vidal.
“The basic science behind the process is called azeotropic distillation. (See sidebar.) But before we get there, we need to separate the liquids from the solids. We use a unique centrifuge technology we developed ourselves to deal with pig slurry. That gives us the liquid, but it’s still full of many chemicals that need to be removed entirely.
“So the liquid goes into the azeotropic distillation process, where we add a specific kind of solvent that promotes evaporation of the liquid. We bring this liquid up to a certain temperature.
“Using azeotropic distillation, we go through a process of concentrating these liquids which isolates many components. But mainly we isolate pure water, and that’s what we’re looking for.”
Vidal says that when dealing with pig manure, the process isolates, extracts and captures two different types of liquids. The first is liquid ammonia nitrogen. The other is a liquid concentrate of potassium, which holds other elements such as residual phosphorus.
The process is continuous. Vidal says this eliminates the expensive and odorous stage of storing slurry in large, round, open-air pits. Slurry is continuously transferred from the pig barns to the Solugen processing plant.
Within the facility, the slurry never stops. It is in a non-stop state of processing from the moment it enters until the moment all the individual elements exit the facility. Vidal points out that storage at any point in the process is expensive and disruptive of the system.
“We eliminate up to 95 percent of the bad smell associated with the storage and spreading of manure. We also eliminate up to 95 percent of those greenhouse gases produced during the storage and spreading of manure. A major part of our design requires the manure be pumped from the husbandry directly to the processing facility.”
The prototype processing plant is located on a hog farm at Ste-Agathe de Lotbinière in Quebec. The 50-by-60 foot building is located about 400 metres from the hog barn. The prototype plant has been processing since October. The current plant only uses half the building, leaving room for a twin processor that could be added to double capacity, which is in the plans for this farmer.
The basement of the building is a concrete pit that accepts slurry being pumped from the barn. Slurry is run through the Solugen centrifuge, which rotates slowly, says Vidal.
He explains that the slow speed is vital to keep maintenance costs low. The plant needs to shut down only four times a year for preventive maintenance.
“The centrifuge extracts all kinds of solid material. We see plastic gloves, pieces of wood, nails, anything you might imagine. The dirty liquid we have now is charged with colloidal foreign elements, which we must get rid of.
“The second step of pre-treatment is to add lime. We use about 10 kilos of lime to treat one cubic metre of this liquid. This lime will flocculate and aggregate those colloidal elements so we can retrieve them from the liquid and send them back into the solid fraction. Then we proceed with treatment of the cleaner liquid.
“There is a huge concentration of phosphorus in the solid fraction. We discovered that about 85 percent of the phosphorus contained initially in the manure will be found in the solid fraction. This solid fraction constitutes only 10 percent of the initial volume of manure. That means 85 percent of the phosphorous is found in 10 percent of the initial volume of manure.”
Vidal says the more phosphorus is isolated and extracted, the more it can be managed and exported beyond the phosphorus-saturated fields around pig barns.
He says many pig producers are forced to go further and further to find a farmer willing to have slurry injected into his land. It’s also more of an environmental problem and a safety problem with big tanker trailers on rural roads.
“We use electricity to carry out further treatment. We require about 30 kilowatts to treat one cubic metre of solid manure. Here in Quebec we pay $2.10 in electrical costs to treat one cubic metre of the solid manure. The cost of lime is about 50 cents for one cubic metre of manure. So that’s a cost of about $2.60 to treat one cubic metre.
“In comparison, pig farmers in Quebec have a cost ranging from $4 or $5 to treat one cubic metre of manure, all the way up to 10 dollars. Some farmers have a very high cost in transporting manure a great distance.”
From an economical point of view, Vidal says it only pencils out if a pig farmer produces a minimum 10,000 cubic metres of manure annually, which would require about 1,500 sows. A Solugen processing plant to handle that volume would cost $850,000.
The other option is a larger facility that processes 20,000 cubic metres of manure annually. It’s priced at $1.35 million. Neither price includes the building.
Vidal says Solugen contacted pig farmers throughout Quebec and Ontario, as well as Europe, however COVID-19 has put those plans on hold for now.
They haven’t taken their technology to Western Canada yet, but that is in the long-term plan. Solugen also started working with local governments to bring their technology to municipal sewage treatment plants faced with difficult challenges.