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close this bookBioconversion of Organic Residues for Rural Communities (UNU, 1979)
close this folderAnalysis of energy cost of integrated systems
View the document(introduction...)
View the documentEnergy cost and energy requirement
View the documentWhy energy analysis?
View the documentNet energy intensity
View the documentWhat criteria are offered by energy analysis?
View the documentConclusion
View the documentReferences

What criteria are offered by energy analysis?

It is assumed that the criteria of social acceptability and pollution levels are analyzed separately. Energy analysis is a tool that offers three types of criteria:

a. A statement about actual energy use, direct and indirect. This is an accounting process. It is not difficult to do, but is often done inaccurately through failure to consider all factors. It can be used to interpret the impact of energy prices on costs.

b. A criterion of economic attractiveness. Here the task is to compare the GER of alternative methods, or to optimize around the least energy-intensive route per unit product, taking into account the GER of all inputs. However, this cannot be considered independent of the production intensity required. Table 3 and Figure 2 show how, even with skilful husbandry, intensification demands an energy requirement.

c. Evaluation of the net energy of biomass systems.

TABLE 3. Output of Selected Natural and Other Systems

  Energy ratio (output/fossil fuel input) Net energy GJ/ha-yr
Kung Bushman, Kalahari Desert infinite .003
Shifting cuttivators, Congo infinite .52
Tsenbaga tribe, New Guinea - yams infinite .47
sweet potatoes infinite .40  
Dodo tribes, Uganda 5.0 .64
Subsistence agriculture, indict 14.8 9.6
Rice, Tanzania 23.4 3.6
Corn, Mexico 30.6 28.5
Peasant farming, China 41.1 274.