Make Your Own Fertilizer
Contract with local farmers, who use the spent grains as livestock feed. Spent grains can also be used as fertilizer.The grains can be dried to extend shelf-life and reduce shipping cost, but drying requires energy and is expensive. Still, both wet and dry grains are used. Another waste product that poses problems for the industry is the spent filter material used as filter aids. Alternative filtration systems that do not require filter aids or that use materials that can be recycled are now available.
Water supply to the plant is either ground water (wells), surface water (lakes, rivers), or city water. Raw water is typically contaminated with salts, oils, various organic substances, calcium, clay, silica, magnesium, manganese, aluminum, sulfate, fertilizers, ammonia, insecticides, carbon dioxide and, of course, bacteria and pyrogens. A city water treatment plant removes most of these impurities, but adds chlorine or chloramines and fluoride. Table 1 summarizes the level of contaminants by type of raw water.
The three marketable wastes from breweries are spent grain, spent hops and yeast. The spent grain is recovered from the mash tun and is then sold as animal feed either after pressing in a wet state or after drying in rotary driers. Alternatively, the wet grain may be used in the preparation of silage for cattle. The possible markets for hops are restricted. Some are used as a fertilizer or as a low-grade fuel. Yeast can be separated from beer by filtration or centrifuging. The yeast slurry is then dried in drum driers. Some of the yeast may be mixed with brewers' spent grains to produce a feed material with a slightly higher protein content than normal brewers' grains. The yeast may also be used directly as a source of vitamins. If it is to be used as a human food it must be debittered to remove the hop bitter substances absorbed on to the yeast cells. The cells are then washed in an alkaline solution, washed with water and drum dried. Although bakers' yeast was originally obtained as...