Two possible extraction processes can be applied:
– Continuous solvent extraction method: Goldfish method
– Semi-continuous solvent extraction method: Soxhlet method
These are quite well-known processes which do not need to be discussed further.
10.2.16 Proteins
To measure proteins, different methods can be employed, among them:
– Nitrogen-based methods
– Infrared spectroscopy
– Colorimetric methods
– Methods using ultraviolet absorption
– The determination of nitrogen which is nonproteic
Among those, one of the most used is the Kjeldahl method.
10.2.17 Summary
For the biogas feedstock analysis, the available normative is of fundamental importance to standardize the process. Table 10.6 shows a brief overview of the most
significant available standards and approaches.
Table 10.5 Solvent characteristics
Number
Feature
1
High affinity for lipids
2
Low affinity for proteins and carbohydrates
3
It has to evaporate readily and to leave no residue
4
Low boiling point is required
5
Nonflammable and nontoxic solvents are preferred
6
E f ficient penetration of sample particles
7
Low cost solvents are preferred
8
Non hygroscopic materials are also preferred
10 Substrate Characterization in the Anaerobic Digestion Process
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