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higher production,” Lowe explains, so the grain needed to be separated from the water. To complicate matters, any water piped to the municipal wastewa- ter treatment system needed to be free of solids content and have a pH in an acceptable range. Multiple ways to separate grain from water evaluated The stillage produced by some dis- tilleries contains grain that remains intact and can therefore be separated from water using a settling and rinsing process called ‘lautering.’ However, the ne grain particles resulting from the grinding process employed by 8 Feathers precludes lautering as a means of separation. Also ruled out was occulation, which causes particles to clump using chemical additions that would render the dewatered grain unsafe as animal feed. Mechanical separation emerged as the logical choice. Options included lter presses, screw presses, circular vibratory screeners and cen- trifugal screeners, Lowe said. “Initially, all mechanical options appeared as viable choices. “The lter press offered excel- lent performance but the cost of the press, air diaphragm pumps to ll the press, and a compressor to run the pumps put the total cost at more than double that of a screw press or centrifugal separator,” Lowe says. “Further, without adding some form of chemical solids coagulator into the ow, the lter cloths would require extensive cleaning after each use. Chemical use would also contaminate
The Centri-Sifter centrifugal sifter separates about 3400 kg per week of ne grain particles from 8 Feathers stillage. The dewatered solids pass through the chute in foreground. The water gravity- discharges into the 7570L vat below Stillage separation Going green with centrifugal sifting
8 Feathers Distillery, founded in 2004 at Boise, Idaho, USA, produces premium whiskeys from locally-sourced grains, and water from a nearby arte- sian well. The company disposes of its grain slurry waste sustainably and eco- nomically by separating the grain from water using a centrifugal sifter. The grain is donated to a local farmer as livestock feed, while the water is treated before being safely piped into the public wastewater system. W aste produced from the distillation process, called stillage, is about 40 percent grain solids and 60 percent water by weight, says distiller Greg Lowe. The distillery processes 1363kg
of grain weekly, which produces roughly 3,409kg of stillage. A local farmer previously picked up eight 1136 litre totes per week of the watery grain mixture, but at 423kg, the totes were dif cult to transport, and required covers to prevent spillage. “This wet approach would not scale for
8 Feathers Distillery produces small batch spirits made from pure water and locally sourced grains in Idaho. An artesian well underneath the distillery supplies high quality water
56 ● BREWER AND DISTILLER INTERNATIONAL I november 2019
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