Unit 5.3: Computer Decision Tools for Digester Economic Assessment

Background and Guiding Questions

The third unit discusses two computer decision tools that are available for doing an economic assessment of an AD system, and how to use them to make projections about the return on investment.

Guiding Questions

  • The net present value (NPV) and the internal rate of return (IRR) are popular criteria for evaluating an investment.  If an investment yields an NPV of just slightly more than zero, how will the IRR for that investment compare with the cost of the capital invested in the project?
  • What combination of electricity price, bedding value per cow, and grants would make a digester profitable if expected biogas yield is 80 cubic feet per cow per day and operation and maintenance costs are 3% of installed cost per year?



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