Upcycling Dairy Industry Byproducts: Transformation of Distillery Stillage into Fertilizer

Abstract

The dairy industry is dealing with the disposal of a costly by-product, called milk permeate, when creating a variety of dairy products such as cheese, yogurt and butter. Milk permeate is a solution high in lactose that is costly to dispose of because of its high biological oxygen demand (BOD) and chemical oxygen demand (COD).

We addressed this issue in two parts; one by using milk permeate with a lactose-fermenting yeast, Kluyveromyces marxianus, to create ethanol to be sold vodka, by fermentation and distillation processes. The fermentation and distillation eliminates the lactose from solution, but it creates a secondary waste product that is high in yeast biomass, therefor still contains high BOD and COD. This secondary by-product, distillery stillage, was repurposed into a fertilizer and tested in greenhouse cultivation of Capsicum annuum (bell pepper).

The transformation of milk permeate was successful at creating a profitable ethanol product and reducing waste, after fermentation with K. marxianus. The usage of repurposed distillery stillage as a fertilizer shows promise as it was applied to C. annuum plants in a greenhouse setting and showed results comparable to commercial fertilizer available on the market.

The work accomplished demonstrated how transformation and upcycling successfully reduced waste in the dairy industry by applying it to two different waste products, milk permeate, followed by distillery stillage. This has reduced the environmental footprint of dairy waste streams and created new revenue opportunities while promoting sustainable agriculture.