Thermophilic digestion is not an option for simple plants. The pH of the fermentation slurry indicates whether
the digestion process is proceeding without disturbance. The pH should be about 7 [4]. This means that the slurry
should be neither alkaline nor acid. Biogas can in principle be obtained from any organic material. Cattle
manure can be used as a “starter”. Feed material containing lignin, such as straw, should be pre-composted and
preferably chopped before digestion [5]. More than ten days’ preliminary rotting is best for water hyacinth. Gas
production is substantially improved if the preliminary rotting time is twenty days.