By Dr Jolly Kabirizi and Joshua Kato
The high moisture content of brewery spent grains (80 to 85%) together with polysaccharides and protein makes it particularly susceptible to microbial growth and subsequent spoilage in a short period of time (7 to 10 days).
Where storage may be required for downstream processing of brewery spent grains, then deterioration through microbial activity is perceived as a potential problem, unless the brewery spent grains can be stabilized post-production. Wet brewery grains can be preserved through: (a) silage making and; (b) dehydration/drying.
Silage is a good method for storing wet spent grains for a long period, particularly since ensiling does not alter their nutritive value. Wet spent grain silage can be done without additives or other raw material provided that the grains are put in plastic tank or tube; pit/trench silo or plastic tanks as soon as possible.
Process of Ensiling Spent Grain
- Fill the silo at once.
- Provide flow to the juice.
- Do not use too broad and tall silos.
- Quickly cool and press before ensiling
- Protect from rain and cover the grains with plastic film.
- The silo should have proper drainage to collect runoff.
- Packing and ensiling characteristics can be improved by blending the wet spent grains prior to ensiling with dry materials such as dry forage (chopped maize/sorghum stover; rice/wheat straws or soybean hulls, or with a source of fermentable carbohydrates such as molasses or cereal grains. Adding carbohydrates accelerates fermentation, releasing more acids and resulting in a stable silage. Ensiling spent grains with whole crop maize improves fermentation and stability.
- Pack uniformly but not excessively so as to eliminate air pockets between the job and the tarp.
- Brewer’s grains silage is ready within 3 weeks and can be used over 6 months, and longer if a silage additive is used. Storage time can be improved by storing in a shaded or cool place
- They naturally acidify (pH <4.5) In the case of prolonged use (6 months), use a preservative for silage.