Published investigations into the economics of SCCO2 cleaning show that operational costs of SCCO2 cleaning are quite reasonable and often lower than solvent vapor degreasers or aqueous cleaning systems. CO2 is relatively inexpensive and can be reused in most SCCO2-cleaning systems. Waste treatment due to cleaning is minimal, as no waste stream is generated besides the actual contaminants removed from the parts being cleaned. Unfortunately, the initial capital costs for SCCO2 systems are usually higher than other alternatives — sometimes by a significant amount. Findings on economics include:

• Researchers at Los Alamos Laboratory conducted a study to measure the total electrical costs associated with operation of a 60-liter capacity SCCO2 system at temperatures between 30 degrees C and 50 degrees C and pressures between 1,500 and 3,500 psi. Based on electricity costs of 10 cents/kilowatt hour, costs ranged from $0.90 to $2.80 per hour. This would result in between $1,872 and $5,824 per year in electrical costs if the unit ran for 2,080 hours per year. The researchers concluded that utility costs for the unit will be relatively insignificant when compared to operations and maintenance labor costs. (Ref. 10)

• Texas Instruments completed a predictive total cost assessment analysis based on bench-scale tests of SCCO2 cleaning to replace a trichloroethylene (TCE) vapor degreaser with a SCCO2 system. It was found that a full-scale system would have a negative net present value and a 10-year payback. The biggest item that made payback so long was extremely high initial capital costs. Year-to-year operational costs showed the SCCO2 system to be less expensive than the TCE vapor degreaser. (Ref. 6)

• An economic analyses done after bench-scale testing based on cleaning 150 bearings per year showed annual savings of only $1,400 on a $75,000-100,000 investment. Therefore, the SCCO2 system could not be economically justified for this application. Even at 1,000 parts per year, the investment would have a simple payback of eight years — longer than is typically acceptable for manufacturing companies. It appears that a much higher volume application would be required to justify the SCCO2 system. (Ref. 11)

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