Sludge a success story for Whitecourt-area farmers

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They say great ideas start with the planting of a seed — and that’s precisely what happened after employees at Alberta Newsprint Company noticed tomato plants growing in a pile of pulp sludge.

The result is a ‘superfertilizer’ that area farmers can’t get enough of. The phone at the Whitecourt plant rings off the hook from farmers asking about the availability of the organic fertilizer, and some have even stopped the trucking contractor delivering the sludge to ask how they can get some.

And there’s no mystery about why.

One project at a site near Mayerthorpe showed a one-time sludge application at 50 tonnes per hec-tare yielded the same quality and quantity of barley as application of 200 kilograms per hectare of 35-10-0 fertilizer applied annually for three years.

And given the pulp sludge is free, it’s no wonder farmers stop delivery trucks.

Chad Merrifield

Chad Merrifield
photo: Supplied

Whitecourt-area farmer, Chad Merrifield is a longtime user of the product.

“With our program, I would say that our nitrogen savings are probably sitting around 60 per cent,” said Merrifield. “That will be reduced somewhat because it has to be incorporated.”

Merrifield plants about 650 hectares into canola and wheat — some located close to the Millar Western Forest Products mechanical pulp plant. He’s been applying mechanical pulp sludge from both Millar Western and Alberta Newsprint Company since the mid-1990s.

The material is applied with spreader trucks, and is provided at no charge by both companies within a 45-kilometre radius of their plants. (Diverting the sludge has saved Alberta Newsprint Company the expense of building two landfills.)

Millar Western both delivers and applies the pulp sludge, with incorporation handled by Merrifield. Along with lower fertilizer costs, he gets a bonus of higher-quality soil.

“We have found that there are a lot more earthworms in the soil because it is a lot softer and more pliable,” he said. “It doesn’t bake at all and holds water appropriately because it (pulp sludge) is adding the fibre back in.”

Years of research

The sludge, a byproduct of the mechanical pulping process, has been described as a porridge-like material. It’s about 80 per cent water, but also contains short lignin fibres, is high in carbon, and contains nutrients such as nitrogen and phosphorus. And unlike kraft pulping, it doesn’t contain high concentrations of harmful chemicals.

After tomatoes were spotted growing in the pulp sludge more than two decades ago, Alberta Innovates Technology Futures (AITF, formerly the Alberta Research Council) began conducting studies. The evidence concerning the sludge’s potential as organic fertilizer got better and better as scientists progressed from lab work to field trials to actual full-scale land application. Along the way, the Mechanical Pulp and Paper Consortium was also formed to help finance and guide the research.

Among the findings was that because the nitrogen is in organic form, the sludge acts as a slow-release fertilizer and delivers nutrient benefits for up to five years. It also improves soil structure and tilth, thereby increasing water-holding capacity.

Its chemical composition is about 45 per cent carbon, between 1.5 and 3.0 per cent nitrogen, and 0.3 per cent to 0.5 per cent phosphorus, said Dani Degenhardt, an AITF researcher.

Merrifield took part in some of the early studies to establish an optimum range of tonnes per hectare to achieve the best production results — which was found to be between 50 to 100 dry tonnes per hectare per application.

Application is ‘quite manageable’ as it is thinly applied and can be incorporated immediately to avoid any odour issues with neighbours. Merrifield applies it post-harvest every six to eight years, and said he’s seen benefits last for up to 12 years.

Test results

The pulp sludge had greatly improved his soil, he said. Just in fibre content alone, many Prairie soils register at between three and five per cent. On Merrifield’s land where the pulp sludge has been applied, it’s between 15 to 18 per cent.

In another Alberta Innovates study, application of 50 tonnes per hectare increased brome grass productivity by fivefold compared to control plots, and this increased yield was sustained for six growing seasons. The study used Magna smooth brome grass, and researchers calculated the volume increase by cutting hay on both a control site and a pulp sludge application site.

“The (test) site was a coarse-textured site and the carbon-to-nitrogen ratio before application of sludge was around 16 to 21,” said Degenhardt. “It increased to 33 to 38 post-application.”

Merrifield has also applied and incorporated pulp sludge on hay ground prior to seeding.

“You have a slow-release nitrogen for a number of years,” he said. “So it reduces the need for supplemental fertilizer.”

Another key factor is that it has neutral pH.

Although the material is a biological form of fertilizer, it’s not certified organic.

“Unfortunately, because the sludge is an organic waste product from an industrial process, it would be very challenging to get the status changed so that the organic producers could still use it,” said Degenhardt. “We’ve tried in the past and were not successful.”

One obvious concern is the impact of less desirable elements in the sludge. Degenhardt said at the time of application, there is a slight increase in electrical conductivity, sodium absorption ratio, nitrate, nitrite, and metals such as copper, nickel and zinc, but they are not long lasting. Merrifield’s only concern was with the hydrogen peroxide content, but once incorporated, it breaks down to hydrogen and oxygen.

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