This is one of the biggest concerns most breweries have – disposing of their bioactive yeast.
While its common for breweries to re-use their yeast from previous brewery runs (e.g., re-use 50% from previous run + 50% new yeast), a brewery that produces approximately 8 Tons of spent grains per week, can produce 80-200 kg / week (varies on production cycle).
Quick definition first
BOD – The organic content of wastewater is expressed and measured as BOD. BOD is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample
Typically, breweries dispose of their yeast with waste water which contributes BOD into municipal water systems. In Toronto, there doesn’t seem to be any regulation for breweries to pre-treat their effluent prior to entering the municipalities water systems. Cities like Toronto will measure and charging extra for treatment of BOD that enter their systems.
Typical of Brewery Wastewater Composition (from Hawaii Water Environment Association) include the following:
- Wort – Liquid extracted from the mashing process.
- Beer – When the good stuff goes bad and needs to be wasted.
- Trub – Solids composed mainly of heavy fats, coagulated proteins, and inactive yeast.
- Propylene glycol – Used to control temperature during fermentation cooling of beer. Could be in discharge due to leak.
- Label glue – Used in bottling operation, the clean-up wastewater can be high in BOD.
- Defoamer Used to control foam during the fermentation process.
- Cleaner Caustic, Phosphoric Acid, Nitric Acid, Peracetic Acid, Quaternary Ammonium Compounds
- Hydrogen sulfide may also be detected in brewery wastewater
- Detergents Soap
Spent yeast diversion options:
1. As a brewery, investigate waste water management systems / side streaming that help reduce BOD entering municipal systems.
2. As a food waste transformer, look for partners like local soup manufacturers or bakeries to take the wet yeast as is so that breweries don’t need to invest in drying infrastructure. Potential market rate for spent yeast C$20-$40/Ton according to McNess (2018)
However, most re-users of spent yeast will likely prefer it dried.
Contact a local drying facility, one that handles spray drying of milk or potatoes for instance. If in Ontario, University of Guelph food scientist might be a good start for leads. There is a US based Wisconsin(?) based dryer that can help dry yeast that Molson uses.
There is great potential to tranform spent yeast – for instance, did you know that Marmite’s major ingredient is an extract from brewer’s yeast?
Learn more about New products that have been made by incorporating Spent Yeast
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