Analysis and characterisation of biogas feedstocks - The Biogas: Science, Production and Applications - page 66

3.7 Examples of BMP degradation curves (adapted from VDI 4630 and
DIN 38 414 (S8)).

addition, a BMP measurement should never exceed 350Nm 3 /t COD added ,
which is the theoretical maximum according to Speece (1996). According to
VDI 4630, the representativity of the results of BMP tests can be tested by
using microcrystalline cellulose for reference samples.

3.4 Additional laboratory analysis of feedstocks
In addition to the essential feedstock analysis described in Section 3.3, extra
analyses used in the field of biogas feedstock characterisation are now
described. Depending on the specific situation, one analysis may be more
appropriate than another. A summary of the different procedures for
analysis can be found in Section 3.7.

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3.4.1 Trace element analysis

The analysis of trace elements is described in EN 13346 (sludges) and
ISO 11885 (wastewater), as well as in APHA 3120 C. For biogas feedstocks,
drying and milling (e.g. ball mill) is recommended before analysis. The
sample is then digested in a boiling aqua regia (EN 13346). If some
indigestible solid particles remain, they should be removed by filtration. For
subsequent elementary analysis, AAS (atomic absorption spectroscopy),
ICP-OES (inductively coupled plasma - optical emission spectroscopy) or
ICP-MS (inductively coupled plasma - mass spectroscopy) can be used. This
analysis allows a very broad range of elements to be analysed; for details see
EN 13346 and ISO 11885 (see Section 3.7).
The determination of trace elements can be useful if some trace elements