New odour control system allows yeast plant to re-open

By Martin Slepkov

Lallemand was founded in Montréal at the end of the 19th century and now develops, produces and markets enriched active/inactive yeast, bacteria and derivatives of micro-organisms for bakeries, wine, beer and other alcohol beverage producers. The company also supplies industries such as animal and human nutrition, pharmaceutical, other food manufacturers and the agriculture industry.

Today, Lallemand is a global leader in yeast and bacteria production, with 26 manufacturing sites throughout the world, employing over 2,800 people.

The company’s Bio-Ingredients Division was formed in 1984 to develop value-added products while optimizing the seasonally available extra capacity in the yeast fermentation plants, and to recover biomass from fermentation. Lallemand Bio-Ingredients purchased an out-of-commission powdered food ingredient facility located in Tara, Ontario.

In 2014, it began to convert the Tara plant to dry food and feed yeast by upgrading the facility’s existing equipment. Recruiting staff that had been employed at the plant two years earlier and using local contractors, an engineering team from the Quebec facility brought the once dormant production plant back to life.

Yeast products are made in various forms, including powder, liquid and paste. Functions of inactive yeast and yeast extracts include water-binding, emulsifying, and adding nutritional value such as vitamins D and B-complex. It is a high quality protein that is also used as a taste enhancement. Manufacturing such a product is done with strict quality compliance for safety and consistency and testing is conducted throughout production, meeting Halal and Kosher certifications.

Drying yeast products is very tedious and the byproduct can be rather odorous. Receiving liquid yeast via tanker trucks from the Montréal facility, the raw material is pumped into a gas box dryer. Gas from the drying process is exhausted to atmosphere. Separated wastewater flows to a 530 m³ treatment basin across the street, at a rate of 12 to 15 litres per minute when the plant is in full operation.

As the plant began operation, the surrounding community began to experience odours and expressed their concerns. One issue was that the plant’s odour control system burner did not have sufficient capacity to treat the drying process’s 18,000 cfm exhaust stream. So, Lallemand made plans to increase the burner’s capacity by installing additional ports to improve its efficiency. This would also increase exhaust retention time, allowing the retrofitted oxidation equipment more time to achieve its goals.

However, it was soon apparent that the wastewater treatment basin was the major odour source and not the dryer exhaust stack discharge. When wastewater entered the treatment basin, it released aerosolized sodium selenite (Na₂SeO₃). This inorganic compound is robust, very heavy and smells like horseradish and rotten eggs. It can travel long distances, following low lying ground.