Cost analysis — In fermentor system costing, the annual depreciation is typically what percentage range of the installed capital cost?

Introduction:
Economic evaluation of bioprocess plants requires estimating annualized capital charges, including depreciation. Thumb rules provide reasonable ranges for early-stage feasibility studies where detailed tax and depreciation schedules are not yet set.

Given Data / Assumptions:

• Installed capital includes vessels, utilities tie-ins, and instrumentation.
• Straightforward rule-of-thumb budgeting stage.
• Industry-typical service life and salvage assumptions.

Concept / Approach:
For preliminary estimates, annual depreciation is often approximated as a percentage of installed capital. A common range used in bioprocess conceptual design is 6–10 percent, capturing typical asset lifetimes and salvage values before full discounted cash flow models are built.

Step-by-Step Solution:
Identify the commonly cited range from design heuristics.Select the choice that spans expected variability in equipment types and lifetimes: 6–10%.Note that detailed financial models may shift the effective rate.

Verification / Alternative check:
Texts on process design list annual capital charges (including depreciation and interest) often totaling 15–25 percent; the depreciation subcomponent is frequently taken as 6–10 percent for quick estimates.

Why Other Options Are Wrong:

• Narrower bands like 5–6% or 6–7% may understate typical variability.
• 8–10% covers the upper slice but omits lower common values.
• 12–18% is too high for depreciation alone in most bioprocess contexts.

Common Pitfalls:
Confusing depreciation with total capital charge (which may include interest on investment and maintenance); assuming tax code specifics without jurisdictional detail.

Final Answer:
6–10% of capital cost