Conducted at the Massachusetts Institute of Technology (MIT; Cambridge, MA), a team of researchers led by Timothy Gutowski surveyed 20 manufacturing techniques, looking at everything from traditional processes like the casting, grinding, and machining of metals; the injection molding of plastics; as well as more recent techniques, like the use of lasers and water jets to shape materials. Also included were fabrication techniques from the microelectronics sector like chemical vapor deposition and sputtering. The researchers hoped to better understand energy waste (energy that did not convert a raw material into a finished product), as well as material waste (raw material that was lost in the conversion process).
The researchers found that except for methods that involved melting metal, the overall power requirements for each process were similar, ranging from about 5 to 50 kilowatts of electricity. Where large variations were seen was in the amounts of material processed, ranging from hundreds of kilograms per hour or more for the older processes to just a few milligrams per hour for newer techniques. As the processes were assessed the researchers recognized a theme:
A striking trend emerged: as processes become more technologically sophisticated, they tend to manipulate smaller and smaller quantities of material at slower rates, but since power consumption per process has stayed about the same, the amount of energy needed to generate a given quantity of finished product has been growing fast.
At one time, the researchers noted, the efficiency of converting energy into finished goods might not have garnered much attention. Today, however, as carbon taxes are considered and power consumption is tracked at every stop, energy efficiency will bear as much importance as output rates in manufacturing techniques. For the record, injection molding rated as a pretty efficient process, overall.
