Lifecycle Cost Analysis for Single-Use Systems - Less complicated single-use systems have more favorable lifecycle economics. - BioPharm International
Lifecycle Cost Analysis for Single-Use Systems
Less complicated single-use systems have more favorable lifecycle economics.
 Nov 2, 2008 BioPharm International Supplements

Calculating Lifecycle Costs

 Table 4. Lifecycle cost worksheet Year
Table 4 indicates how capital and operating costs are combined to calculate a lifecycle cost expressed as net present value (NPV). The NPV reflects the sum of cash flows for each of the 10 years studied; each of the cash flows is discounted and expressed in today's dollars. The combined capital savings from Tables 1 and 2b show up as a negative capital outlay (capital savings) of \$8,122,000. Operating costs and savings from Tables 2b and 3c are calculated for each of the 10 years studied. Capital cost is straight-line depreciated over 10 years. A corporate tax rate of 10% is used to adjust incremental profit or loss and a discount rate of 10% is used to account for the cost of money. These factors vary widely between companies and locations, especially tax rates which often reflect incentives from local governments. The calculated NPV for this alternative is an impressive savings of eight million dollars. This indicates the use of single-use bags to supply buffer is a clear winner over the stainless-steel buffer storage tanks.

Assessing Various Combinations of Stainless-Steel and Single-Use Equipment

 Table 5. Lifecycle cost analysis of single-use scenarios
For our case study, this methodology was used to evaluate lifecycle economics for other single-use alternatives as shown in Table 5. For each scenario, NPVs were calculated for three different capacity scenarios, including the base projection from Table 3c, a more conservative scenario involving fewer batches (downside), and a more optimistic scenario (upside).

Scenario 1 examines replacing a seed train consisting of a 50-L and 250-L stainless-steel fermenter with a single 250-L single-use fermenter. In this scenario, the single-use fermenter would be inoculated initially at a 50-L volume and then topped off with additional media to produce 250-L of seed. It was reasoned that spreading the cost of the single-use fermenter bag over the two seed steps would produce more favorable economics than paying for both a 50-L and 250-L single-use fermenter bag. This illustrates an important point in evaluating single-use alternatives, which is that you don't always need to consider a like-for-like replacement. What makes sense in a stainless-steel world may not be the optimum design in a single-use world. Similarly, in the earlier buffer hold example, the favorable economics for single-use bags results mainly from a change in operating philosophy to produce buffer for multiple purification lots at the same time. This makes sense in a single-use world because it doesn't increase capital costs. In a stainless-steel world, costs increase with the size and number of storage tanks.