Sustainable milk powder production using enhanced process integration and 100 % renewable energy

Abstract

This paper presents a Total Site analysis of the requirements to integrate 100 % renewable energy into a 10 t/h ultra-low energy milk power factory of the future in New Zealand and California. The location of the factory is important for selecting renewable energy options and therefore three case studies from three different locations are reported. In New Zealand the best option is to use renewable electricity from wind, hydro and geothermal for the factory electrical needs, and high temperature geothermal energy when available for process heating up to 210 °C and low temperature geothermal energy with MVR technology upgrading for process heating up to 180 °C. When no geothermal energy is available the best option is renewable electricity driven heat pumps for heating up to 85 °C, and biomass (wood residue) for high temperature heating up to 210 °C. Biomass production, however, will require 35 % more land than the farms require for producing the milk. In California renewable energy is best met using biogas from anaerobic digestion of cow manure and solar thermal. Biogas converted into biomethane on farm fuels a combine cycle gas turbine with a heat recover steam generator (HRSG) to meet process heating needs above 80 °C and all factory and biogas compression electrical needs. Solar thermal with day-night storage provides hot water utility. A cow manure collection rate of 37 % is required to meet both process heat and electricity needs.