The perfect ethanol feedstock.

Milk is a miracle food. It contains fats, proteins and sugar.  The sugar in milk is a disaccharide composed of galactose and glucose. During dairy processing, lactose is separated and aggregated in a byproduct called permeate. The most common source comes from cheese making when the proteins in whey are concentrated. The water and lactose permeates through the filter to make whey permeate. To improve efficiency, processors concentrate the proteins in skim milk and as part of the filtration process create a byproduct called milk permeate. Whey and milk permeate have a similar composition being mostly water (5% solids) and lactose.

In the past, dairy products like whey or permeate was discharged in waterways or spread on fields. This practice was banned due to environmental damage created by the permeate’s high biological oxygen. The additional cost of waste management has forced many smaller creameries to stop production.

Permeate is perishable so it must be used or disposed of within days. Transporting permeate is expensive due to Its low solids content. The most common use for liquid permeate is animal feed. But due to transport costs and its lower solids content, permeate used for animal feed provides little value to dairy processors beyond disposal.

Liquid permeate can be dried into a powder or further refined to make pure lactose. Last year, 550,000 tonnes of permeate was dried in the US and 85% of it used for low value animal feed, mostly in China. Dryers are very expensive to build and operate. They are also carbon intensive with 670kg of carbon emitted for every tonne dried. The high cost and low margin of drying permeate makes drying not an option for many dairy processors. 

During the oil crisis of the 1970s, several plants were built in New Zealand, Ireland and the US to convert whey permeate into fuel ethanol. Three of these plants are still in operation today. While these plants were built to address energy security, DD Biofuel looked at permeate with the goal of making low carbon ethanol.