Biomedical Engineering Reference
In-Depth Information
Hydrogenotrophes
Acetoclasts
Figure10.2
Themethanisationofbiowaste
•
Stage II: Carbon dioxide, hydrogen and free fatty acids levels peak; nitrogen
levels fall to around 10%; cellulose begins to be broken down.
•
Stage III: Carbon dioxide decreases and plateaus to hold at around 40%;
methane production commences and achieves steady state at around 60%;
free fatty acids decrease to minimum levels; cellulose breakdown continues at
a linear rate with respect to time; nitrogen levels fall to near zero.
•
Stage IV: Carbon dioxide and methane continue in steady state at circa 40 and
60% respectively; cellulose component reduces steadily.
•
Stage V: Cellulose becomes fully decomposed, ultimately leading to zero
methane and carbon dioxide production; oxygen and nitrogen revert to atmo-
spheric levels.
Although beyond the scope of the present discussion and therefore not appro-
priate to address fully, the position of hydrogen as a regulator of methane produc-
tion warrants a brief mention. In the earlier examination of anaerobic digestion
the obligate syntrophic relationship between the hydrogen producing acetogenic
bacteria and the hydrogen-utilising methanogens, was described. Essentially,
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