Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract Only
Publication Acceptance Date: 6/6/2013
Publication Date: 7/9/2013
Citation: Tomasula, P.M., Yee, W.C., Mcaloon, A.J., Bonnaillie, L. 2013. Computer simulation to predict energy use, greenhouse gas emissions and costs for production of extended shelf-life (ESL) milk using microfiltration. Joint Meeting of the ADSA, AMSA, ASAS and PSA. 96:E-Suppl. 1,78. T221.
Technical Abstract: Extended shelf-life (ESL) milk has a shelf life between that of high-temperature short-time (HTST) and ultrahigh temperature (UHT) pasteurized milk. ESL milk is usually pasteurized at temperatures exceeding 125 deg C which may give the milk a cooked taste. ESL milk produced using crossflow microfiltration (MF) prior to HTST pasteurization at 72 deg C produces milk with the fresh taste of HTST milk and depending on raw milk quality, packaging and cold-chain handling, may have a shelf-life of up to 30 d. Little information is available on the additional energy use, greenhouse gas (GHG) emissions and operating costs of installing MF in an existing HTST processing plant. The objective of this study was to develop a model for milk MF and incorporate it into a computer simulation model of the fluid milk process that was recently developed for processors to benchmark their current energy use, GHG emissions, and capital and operating costs. MF was modeled as two MF skids in series, each containing the housings for 1.4 micron membranes. In the simulator, skim milk leaves the separator at 55 deg C as the feed to the first skid. The retentate from the first skid fed the second MF skid. Permeates from both skids were blended with cream and HTST pasteurized to produce 3.25% whole milk. Retentate (3% of the total feed stream) was added to the remaining cream stream and heated to 130 deg C before storage. Simulations conducted for medium – sized milk plants processing 27,300 L/h of milk showed GHG emissions, electricity and natural gas use were 88.6 g CO2eq/kg milk, 0.38 MJ/L and 0.12 MJ/L using HTST pasteurization alone and 93.6 g CO2eq/kg milk, 0.38 MJ/L and 0.14 MJ/L for the HTST/MF plant, demonstrating the additional electricity and natural gas used by the MF process and for heating of the cream/retentate stream. The difference in operating costs between HTST and HTST/MF was estimated as 0.10 cents/L which is in agreement with literature estimates. This study demonstrates that computer simulation allows rapid assessment of process changes and an evaluation of new technologies in an existing processing line without costly pilot testing.