**5.5 Batch reactors**

Batch reactors are quick, require inexpensive equipment, and are the simplest to operate since they are fed with feedstock and left for a longer period before being emptied. No mixing, stirring, and pumping required, low input in terms of process and mechanical demands, and low capital cost, but they are channeling and clogging and these types of reactors have larger volume and lower biogas yield. The methane production is commonly the highest at the beginning and decreases toward the end of the process as the substrate is being utilized [117, 140, 142].
