10.3.2.2 Substrate
The sampled substrate has to be representative of the final feedstock which will be
digested on an industrial scale. The preparation of sample to be used in the tests has
to be well documented, e.g., describing the sampling process and technique in brief
details and by taking pictures. In the German guideline VDI, a complete explanation
of sampling processes is provided. Usually, sample preparation has to be reduced to
leave its properties and its digestibility similar to those of the original substrate.
These are the most followed procedures:
– Coarse materials and inert materials (e.g., plastics, gravel, and sand) have to be
removed.
– If the particles in the organic fraction are too large, grinding or shredding might
be required. To avoid heating too much the sample during grinding, freeze
grinding or cryogenic grinding can be performed. Optimal diameter of particles
is lower than 10 mm. To obtain this length, the sample can be filtered; in this way
the big particles will be separated and then milled.
– All the pretreatments have to be noted carefully in the laboratory book by the
staff.
– The storage of the substrate can be performed for a maximum og 2–5 days at 4
C.
If longer storage periods are required, the samples can be frozen at À20
C.
Drying of the sample for storage purposes has to be avoided (Kreuger et al. 2011).
– Before performing BMP tests, the complete characterization of the substrate has
to be performed. The most important analyses are represented by volatile solids,
total solids, pH, Kjeldahl nitrogen, alkalinity, ammonium, and volatile fatty acids.
Another key parameter is represented by chemical oxygen demand (COD),
Raposo (Raposo et al. 2009); Raposo (Raposo et al. 2008); Noguerol-Arias
(Noguerol-Arias et al. 2012), together with elemental composition (CNHX) and
total organic carbon.
10.3.2.3 Test Setup
In this section, the conventional setup most used for BMP tests it is described;
accordingly, other previous setups can be found in the German guideline VDI and in
the work of Guwy (2004).
The volume of the vessels used to perform the BMP tests depends on three
factors:
1. The degree of homogeneity of the substrate
2. The volume of biogas which will be produced
3. The precision of the techniques used for gas measurement
For homogenous substrates, smaller volumes (%100 mL) can be used, whereas
for heterogeneous substrates, larger volumes are preferred, in the rage of 500 mL to
2000 mL.
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PietroBartocci et al.
The sampled substrate has to be representative of the final feedstock which will be
digested on an industrial scale. The preparation of sample to be used in the tests has
to be well documented, e.g., describing the sampling process and technique in brief
details and by taking pictures. In the German guideline VDI, a complete explanation
of sampling processes is provided. Usually, sample preparation has to be reduced to
leave its properties and its digestibility similar to those of the original substrate.
These are the most followed procedures:
– Coarse materials and inert materials (e.g., plastics, gravel, and sand) have to be
removed.
– If the particles in the organic fraction are too large, grinding or shredding might
be required. To avoid heating too much the sample during grinding, freeze
grinding or cryogenic grinding can be performed. Optimal diameter of particles
is lower than 10 mm. To obtain this length, the sample can be filtered; in this way
the big particles will be separated and then milled.
– All the pretreatments have to be noted carefully in the laboratory book by the
staff.
– The storage of the substrate can be performed for a maximum og 2–5 days at 4
C.
If longer storage periods are required, the samples can be frozen at À20
C.
Drying of the sample for storage purposes has to be avoided (Kreuger et al. 2011).
– Before performing BMP tests, the complete characterization of the substrate has
to be performed. The most important analyses are represented by volatile solids,
total solids, pH, Kjeldahl nitrogen, alkalinity, ammonium, and volatile fatty acids.
Another key parameter is represented by chemical oxygen demand (COD),
Raposo (Raposo et al. 2009); Raposo (Raposo et al. 2008); Noguerol-Arias
(Noguerol-Arias et al. 2012), together with elemental composition (CNHX) and
total organic carbon.
10.3.2.3 Test Setup
In this section, the conventional setup most used for BMP tests it is described;
accordingly, other previous setups can be found in the German guideline VDI and in
the work of Guwy (2004).
The volume of the vessels used to perform the BMP tests depends on three
factors:
1. The degree of homogeneity of the substrate
2. The volume of biogas which will be produced
3. The precision of the techniques used for gas measurement
For homogenous substrates, smaller volumes (%100 mL) can be used, whereas
for heterogeneous substrates, larger volumes are preferred, in the rage of 500 mL to
2000 mL.
326
PietroBartocci et al.