10.3.2 Recommendations to Perform BMP and Validate
Correctly the Results
This part presents the diverse items that intensely affect the results of BMP tests. To
increase the possibility of finding authenticated and reproducible BMP test results,
some recommendations are made, referring especially to the inoculum, the substrate,
the test setup, data analysis, and reporting.
10.3.2.1 Inoculum
The inoculum must be obtained from an anaerobic digester, which is active at the
time of sampling and is digesting complex organic substrates. Sampling of the
inoculum should be performed at steady state.
Quality control of the inoculum is performed through its characterization, which
is mainly based on the following:
– The analysis of pH
– The analysis of volatile fatty acids (VFA) concentration
– The analysis of ammonium concentration
– The analysis of alkalinity
Another way to check inoculum quality is that of analyzing the operational
parameters of the digester, from which the inoculum itself is taken. Optimal values
for operational parameters are as follows:
– pH: >7.0 and <8.5
– NH4
+
: < 2.5 gN_NH4 L
À1
– VFA: < 1.0 gCH3COOH L
À1
– alkalinity: > 3 gCaCO3 L
À1
All the routines to analyze the inoculum activities are presented in the work of
Angelidaki et al. (2009). The inoculum usually has the most important characteristic
that of producing low quantities of methane, so to have a reduced content of organic
load. The final aim of the inoculum is in fact to provide the microbial flora to the
digester and limit organic matter load. Total methane production of the inoculum
should be below 20% of the production of the substrate. If the inoculum has too high
organic load, a pre-incubation period could be requested to bring it down. Other
possible pretreatments of the inoculum can be sieving and dilution with nitrogen
flushed deionized water. For sieving, usually a mesh of 1–5 mm is used. Dilution is
performed in the case the volatile solid concentration reaches very high values, such
as higher than 100 g L
À1 . Storage of inoculums should be performed at ambient
temperature for a maximum of 4–5 days.
10 Substrate Characterization in the Anaerobic Digestion Process
325
Correctly the Results
This part presents the diverse items that intensely affect the results of BMP tests. To
increase the possibility of finding authenticated and reproducible BMP test results,
some recommendations are made, referring especially to the inoculum, the substrate,
the test setup, data analysis, and reporting.
10.3.2.1 Inoculum
The inoculum must be obtained from an anaerobic digester, which is active at the
time of sampling and is digesting complex organic substrates. Sampling of the
inoculum should be performed at steady state.
Quality control of the inoculum is performed through its characterization, which
is mainly based on the following:
– The analysis of pH
– The analysis of volatile fatty acids (VFA) concentration
– The analysis of ammonium concentration
– The analysis of alkalinity
Another way to check inoculum quality is that of analyzing the operational
parameters of the digester, from which the inoculum itself is taken. Optimal values
for operational parameters are as follows:
– pH: >7.0 and <8.5
– NH4
+
: < 2.5 gN_NH4 L
À1
– VFA: < 1.0 gCH3COOH L
À1
– alkalinity: > 3 gCaCO3 L
À1
All the routines to analyze the inoculum activities are presented in the work of
Angelidaki et al. (2009). The inoculum usually has the most important characteristic
that of producing low quantities of methane, so to have a reduced content of organic
load. The final aim of the inoculum is in fact to provide the microbial flora to the
digester and limit organic matter load. Total methane production of the inoculum
should be below 20% of the production of the substrate. If the inoculum has too high
organic load, a pre-incubation period could be requested to bring it down. Other
possible pretreatments of the inoculum can be sieving and dilution with nitrogen
flushed deionized water. For sieving, usually a mesh of 1–5 mm is used. Dilution is
performed in the case the volatile solid concentration reaches very high values, such
as higher than 100 g L
À1 . Storage of inoculums should be performed at ambient
temperature for a maximum of 4–5 days.
10 Substrate Characterization in the Anaerobic Digestion Process
325