Is My Waste Suitable for Anaerobic Digestion?
This is a frequent question we receive in our emails, from those considering installing agricultural AD systems.
We found one possible approach to answering this which we would like to bring to your attention and it is available as a slide in an excellent free downloadable presentation from a TUHH, Department of Waste Management Workshop in Anaerobic Digestion and Production of Biogas, Prof. Dr.-Ing. R. Stegmann, Dipl.-Ing. Olaf Bade, Chimatra Workshop 2005.
It appears to originate from Linke, Leitfaden Biogas 2000.
Our readers must certainly verify the numbers on the graph, nevertheless, we think that the plot is useful to demonstrate the interaction between volume load, detention time and substrate concentration for biogas plants.
Volume load is the amount of daily supplied substrate per volume of the digester.
First, we have the variability of the calorific yield from the particular biomass feedstock, and from the above it is clear that for a lower calorific yield agricultural waste such as chicken manure the volume load will need to be significantly higher than for a higher calorific yield waste feedstock such as pig manure.
Even so, the assumption is made that the economically viable substrate concentration will be higher for the low calorific feedstocks than for the higher calorific ones. In this example pig manure is shown as viable down to 60 kg/m3, but don’t rely on these numbers, obtain verification yourself.
Detention times within the reactor also need to be within a reasonable range, and the author has assumed 20 to 30 days, for optimum methane production. However, this optimum period varies with each feedstock, as is shown on the preceding slide in the above presentation. (We think that this slide refers to mesophilic fermentation but again you must check this yourself.)
We cannot be sure for how long the presentation will be available online, but while it is click here.
Of course the economic viability of any project will vary according to many more parameters than those discussed above, but at least we have the basis in the above for a first pass assessment.
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The above is for general informational purposes only, it shall not be used for the basis for any decision making processes, and we take no responsibility for any error or inaccuracies in the information provided.
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