• biogas;
  • fixed capital investment;
  • Lang factor


Sub-Saharan African countries are well-suited for the biogas digester technology because of their warm climates and availability of animal manure. This technology could serve as a means to overcome energy poverty, which poses a constant barrier to economic development in Africa. A generative type of capital cost estimation based on knowledge of flowsheet and major equipment, which can be used by investors to indicate the magnitude of the proposed investment and help to provide other information, including the profitability of the project, was employed. In this study, three operating, small to medium scale biogas plants and one commercial scale biogas was used to determine the cost structure. Analysis of the breakdown of the fixed capital investment (FCI) cost, based on the principle of factorial method of capital cost estimation and using Lang factor (fL) analysis was used to create an econometric model for calculating FCI. A Lang factor (fL) value of 2.63, 2.91, and 3.04 has been obtained for small/medium scale biogas plants in two African locations. Calibration of the factors revealed that fL value of 2.63 gives a better cost prediction. The verification of the correctness of the performance model also revealed that the model satisfies all the three Conte's criteria indicating that the model is sufficient for the purpose of effort estimation. An estimated fL value of 1.79 was obtained for the large scale biogas plant. © 2009 American Institute of Chemical Engineers Environ Prog, 2009