| dc.description.abstract | Anaerobic digestion technology can convert agricultural waste into biogas. Taiwan′s mushroom industry has a large output value, and the disposal of spent mushroom substrates (SMS) becomes a problem. SMS are rich in lignocellulose, so it is suitable for converting it into biogas.
The use of SMS for anaerobic digestion to produce biogas will face the problem of too high C/N ratio, leading to insufficient nutrition in anaerobic digestion. Therefore, through the process of co-digestion, urea is used to balance the C/N ratio. However, the addition of urea tends to increase the ammonia concentration, causing the pH to rise too high, so this experiment will try to add a buffer solution to control the pH.
Mesophilic operation can increase anaerobic activity but reduce the rate of methanogenesis. Thermophilic operation can increase the rate of methanogenesis, but anaerobic bacteria are not stable. Therefore, this experiment will combine the advantages of two temperature intervals for anaerobic digestion to establish a two-stage temperature controlled anaerobic digestion system.
This experiment explored the co-digestion of SMS and urea, and the results showed that the optimal C/N ratio was 20. Through the addition of the buffer solution after the acid production phase, stable pH control resulted in a methane yield of 442.8 mL, an increase of 31%. By activating the cells in an 8-hour mesophilic environment, methane production increased, and methane production reached 502.5 mL, an increase of 83%.
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