The following alternative modes of calculation are useful:
Determining biogas demand on the basis of present energy consumption, e.g. for
ascertaining the cooking-energy demand. This involves either measuring or inquiring the
present rate of energy consumption in the form of wood, charcoal, kerosene and bottled gas.
Calculating biogas demand via comparable-use data: Such data may consist of
• empirical values from neighboring systems, e.g. biogas consumption per person and
day,
• reference data taken from literature, although this approach involves considerable
uncertainty, since cooking-energy consumption depends on local cooking and eating
habits and can therefore differ substantially from case to case.
Estimating biogas demand by way of appliance consumption data and assumed
periods of use: This approach can only work to the extent that the appliances to be used
are known in advance, e.g. a biogas lamp with a specific gas consumption of 120 l/h and a
planned operating period of 3 h/d, resulting in a gas demand of 360 l/d.
Then, the interested party’s energy demand should be tabulated in the form of a
requirements list. In that connection, it is important to attach relative priority values to the
various consumers, e.g.:
1. priority: applies only when the biogas plant will cover the demand.
2. priority: coverage is desirable, since it would promote plant usage.
3. priority: excess biogas can be put to these uses.
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