Environmental Engineering Reference
In-Depth Information
3.10 Start-up scheme for continuous laboratory experiments, showing
the daily gas production per m
3
of reactor volume according to a rise in
organic loading rate (OLR) (adapted from VDI 4630).
(once or twice per week). After every increase in OLR, the VFA
concentration will rise and then decline again, which shows the adaptation.
In the beginning, the OLR can often be increased faster than when coming
near to maximum stable OLR. A sudden change in H
2
concentration, a
sudden rise in total VFA or an increasing amount of propionic acid
compared to acetic acid can indicate problems in microbial process stability.
In response, the OLR should not be increased; it could even be slightly
decreased. An absolute interruption of feeding for some days, however, can
have negative impact on process stability, especially if the substrate is easily
degradable. In addition, an experienced operator can give the microbes a
period at low or medium OLR to adapt to a special substrate.
3.5
Detailed feedstock evaluation
3.5.1 Estimation of energy recovery potential
Estimation of the potential for energy recovery from a certain biogas
feedstock can be carried out in different ways, some more accurate than
others.
Literature data
The literature documents the biogas yields of different feedstocks; see, for
example, Chapter 2 of this topic. However, these data can vary
considerably. To calculate the potential, it is generally better to consider
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