2. Calculatory interest rate, i: assumed rate of interest for evaluating the cash flows (income and
expenditure) generated by a biogas plant during its technical service plant. Proceeding on the
assumption that the expenditures are all the more burdensome, the earlier they fall due, while
income is all the more valuable, the earlier it is earned, all cash flows occuring in connection with
the investment are compounded/discounted at an assumed rate for a fixed point in time. Please
refer to chapter 8.4 for the calculation procedure.
3. Investment costs (incl. wages):
- planning
- land aquisition/leasing (as applicable)
- civil works
- building and structures/digester
- modification of animal housing
- gas appliances/aggregates
- slurry spreading implements
- assembly and commissioning
- customs, taxes, duties, fees
- transportation
4. Manpower costs for:
- feeding the plant
- spreading the digested slurry
5. Maintenance and repair:
- spare parts/materials
- wages for maintenance/repair work
6. Energy revenues
- market value of replaced energy
- energy supplied
- production induced with extra energy (market value)
7. Revenues from fertilizer:
- market value of replaced inorganic fertilizer
- revenues from sales of digested slurry
- higher cash-crop yields due to fertilizing with digested slurry
8. Time saved (real financial income only) for additional:
- wage work
- work on the farm (included additional incom)
9. Depreciation (annual for linear depreciation):
= investment costs / n (technical service life)
In this example, the technical service life of the plant is conservatively estimated at only 10 years.
10. Depreciation and capital-servicing costs (interest on loans): neither of these two factors is
included as a cost factor in the dynamic models presented in chapter 8, because the cost of
investment is equal to the sum of cash values from depreciation and interest (cf. Brandt, 1982, for
details). In this example, it is assumed that no external capital is needed, i.e. that the biogas plant is
fully financed with internal capital.
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