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Research pegs distillery stillage as a promising turfgrass fertilizer

Early experimentation into an alternative form of turfgrass fertilizer is showing promise. A science student from the University of Ottawa is leading an ongoing research project in which distillery stillage is being used to help grow grass.

Jessica Gaudet shared her findings online in February with an audience attending the Ontario Turfgrass Symposium in Guelph.

The project – a collaboration between Almonte-based Dairy Distillery and the University of Ottawa – has been conducted in two parts. The first was to transform a dairy waste product into ethanol while the second part was the transformation of distillery waste into a plant fertilizer.

When milk is transformed into such products as butter and cream, the fats and proteins are removed, leaving a lactose sugar solution, or milk permeate, behind.

Gaudet has been working with Parmalat’s Winchester, Ont.-based plant which gets its milk supply from dairy farms in the vicinity. About 100,000 litres of milk permeate are produced daily, but it’s a waste product that requires proper disposal at a cost. It isn’t permissible to pour the permeate down the drain because of its high sugar content.

Instead, an arrangement has been made with Dairy Distillery to take the sugar source and transform it into vodka. Gaudet said that when making vodka, if 20,000 litres of milk permeate stillage are used, 20,000 litres of ethanol aren’t being created. The new waste product is called distillery stillage which can be used as fertilizer.

She said some research has already been done in this field, so it’s not new.

“It’s been especially popular in Brazil where they have a huge production of sugar cane.”

The milk permeate no longer contains lactose because it was broken down during the fermentation process in making vodka. What remains is a “dead yeast” that accumulated during fermentation.

Gaudet said it, too, can’t simply be poured down the drain because the yeast has a high biological oxygen demand. The distillery will drain it but will pay a higher fee to the municipality for the water treatment. If the distillery wishes to deal with a higher volume of the waste product, it must pay a fee for its proper disposal.

The research project was to determine if a fertilizer product could be developed from the stillage.

Gaudet said the stillage is a nutrient-rich solution – a fact that triggered interest in the product as a possible fertilizer in the first place. The stillage was particularly analyzed for its nitrogen, phosphorus and potassium content and was compared with Miracle-Gro – a consumer product readily available in most garden stores.  She said the goal was to determine if a fertilizer could be developed from distillery stillage that would be as effective as other available products.

High phosphorus, potassium content
Analysis revealed a somewhat higher nitrogen content was found in the stillage than that found in Miracle-Gro, but the amounts of phosphorus and potassium were significantly higher in the stillage. There was also a lot of salt, and plants weren’t faring well during the initial stages of the research project.

It was determined the stillage needed to be diluted to approximate what was found in Miracle-Gro. The dilution process, however, decreased the nitrogen content which prompted Gaudet to add nitrogen as urea. It wasn’t a significant amount but, without it, good growth wouldn’t have been realized, she said.

Greenhouse experiments at the University of Ottawa initially focused on pepper plants before turfgrass was added to the study. The latter was done as a side experiment. 

Consequently, less data has been generated from the turfgrass experiment.

“But we got such good results that we decided to see what we can do with it, but most of our data was for fruit-producing plants.”

For the turfgrass experiments, seeds were planted into small cones to compare results from inputs of only water, Miracle-Gro and distillery stillage. The experiment was conducted over an eight-week period during which the individual cones were fertilized once a week. The turfgrass was clipped when deemed necessary.

At the experiment’s conclusion, the turfgrass was dried to obtain the dry shoot rate. Little growth was realized with the cone that was watered only. The cones fertilized with Miracle-Gro and distillery stillage produced significant growth, and no notable difference was acknowledged between the two.

Gaudet said she was excited by the results. A small area at the University of Ottawa was set aside last summer for a six-week field experiment in which two rectangular plots were stripped of their previous cover and, with more soil added, were seeded and watered until germination was realized. There wasn’t sufficient space for a plot to allow Miracle-Gro to be applied, but the one in which the distillery stillage was applied weekly produced a thick, green cover.