Location: Dairy and Functional Foods
Title: Computer simulation to predict energy use, greenhouse gas emissions and costs for production of fluid milk using alternative processing methods Authors
|Datta, N. -|
|Nutter, D. -|
|Sampedro, F. -|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 11, 2014
Publication Date: N/A
Interpretive Summary: Greenhouse gas (GHG) emissions from fluid milk production have significant environmental impact. ARS researchers in Wyndmoor, PA, in collaboration with the dairy industry, developed a computer model of the fluid milk process so that milk processors can test changes to their plants to lower CO2 emissions and to calculate the energy cost savings and equipment costs to implement the changes. This model was expanded so that processors may determine if the use of alternative processing technologies, which use less heat than the traditional fluid milk process, will help lower energy costs, GHG emissions, and water use in their plants. The computer model may help the dairy industry realize its goal of reducing CO2 emissions by 25% per gallon of milk by the year 2020.
Technical Abstract: Computer simulation is a useful tool for benchmarking the electrical and fuel energy consumption and water use in a fluid milk plant. In this study, a computer simulation model of the fluid milk process based on high temperature short time (HTST) pasteurization was extended to include models for processes for shelf-stable milk and extended shelf life milk, milk products that may prevent the loss or waste of milk that leads to increases in the greenhouse gas (GHG) emissions for fluid milk. The models were for ultrahigh temperature (UHT) processing; crossflow microfiltration (MF) without HTST pasteurization, crossflow MF followed by HTST pasteurization, and crossflow MF followed by HTST pasteurization with partial homogenization; and pulsed electric fields (PEF) processing, and were incorporated into the existing model for the fluid milk process. Simulation trials were conducted assuming a production rate for the plants of 113.6 million L/yr of milk to produce only whole milk (3.25%) and 40% cream. Results showed that GHG emissions in the form of process-related CO2 emissions and specific energy consumptions (SEC) for electricity and natural gas use for the HTST process alone were 37.6 g CO2e/kg milk, 0.14 MJ/kg and 0.13 MJ/kg, respectively. CO2 emissions, and SEC for electricity and natural gas use were highest for the PEF process with values of 84.0 g CO2e/kg milk, 0.37 MJ/kg, and 0.10 MJ/kg, respectively, and lowest for the UHT process at 31.6 g CO2/kg milk, 0.10 MJ/kg and 0.17 MJ/kg. Estimated net operating costs though that were associated with the various processes were lowest for the HTST process or for use of MF alone at $0.51/L and highest for the UHT process at $0.60/L. The increase in shelf life associated with the UHT and MF processes may eliminate some of the supply chain product and consumer losses and waste of milk and compensate for the small increase in GHG emissions noted for these processes over HTST pasteurization alone. Water usage was also calculated for the processes. The water usage for the HTST and PEF processes were both 0.245 kg water/kg of milk. The highest water use was associated with the MF process followed by HTST which required 0.333 kg water/kg of milk, with the additional water required for membrane cleaning. The simulator model is a benchmarking framework for current plant operations and a tool for evaluating the costs of process upgrades and new technologies that improve energy efficiency and water savings.