The following discussion on energy, cost and carbon emission will only focus on comparison between Powders 2 and 3. The total cost reduction, including the cost of citrate addition will have to be considered when calculating the savings for Powder 3. Citrate is used as a processing aid that leads to an increased in total citrate of 1.8 g/kg FCMP. This increase is well below the natural variation of citrate in milk powder which is 13.2–20.8 g/kg (Gaucheron, 2005). In this study, 0.2 mol citrate per kg of cream was added in the form of 1 M trisodium citrate (73.8 g per kL of milk). At an average cost of around A$850.00/ton (Alibaba.com Hong Kong Limited (2013)) for citrate, the resulting additional cost per kL of raw milk processed is A$0.06/kL. This means that the cost savings for Powder 3 accounting for citrate addition becomes
A$3.90/kL. For a 10 ton/h spray dryer requiring 12 kL raw milk feed/h it represents a cost savings of around A$46.80 per hour or A$205,000 per annum if the plant was running 50% of the year.