Balancing Biogas Production and Energy Demand
Determining the biogas production
The quantity, quality and type of biomass available for use in the biogas plant constitutes the
basic factor of biogas generation. The biogas incidence can and should also be calculated
according to different methods applied in parallel.
• Measuring the biomass availability
• Determining the biomass supply via pertinent-literature data
• Determining the biomass supply via regional reference data
• Determining biomass supply via user survey
It should be kept in mind that the various methods of calculation can yield quite disparate
results that not only require averaging by the planner, but which are also subject to seasonal
variation.
The biomass supply should be divided into two categories:
8. quick and easy to procure
9. procurement difficult, involving a substantial amount of extra work
Measuring the biomass availability (quantities of excrement and green substrate)
This is a time-consuming, cumbersome approach, but it is also a necessary means of
adapting values from pertinent literature to unknown regions. The method is rather
inaccurate if no total-solids measuring is included. Direct measurement can only provide
indication of seasonal or fodder-related variance if sufficiently long series of measurements
are conducted.
Determining the biomass supply via literature data
According to this method, the biomass supply can be determined at once on the basis of the
livestock inventory. Data concerning how much manure is produced by different species and
per liveweight of the livestock unit are preferable.
Dung yield = liveweight × number of animals × specific quantity of excrements [ kg/d ]
Often, specific quantities of excrement are given in % of liveweight per day, in the form of
moist mass, total solids content or volatile solids content
Determining the biomass supply via regional reference data
This approach leads to relatively accurate information, as long as other biogas plants are
already in operation within the area in question.
Determining biomass availability via user survey
This approach is necessary if green matter is to be included as substrate.
Determining the energy demand
The energy demand of any given farm is equal to the sum of all present and future
consumption situations, i.e. cooking, lighting, cooling, power generation etc. The following
table helps to collect all data concerning the energy demand.
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