The Anaerobic Digestion of Cattail Weeds to Produce Methane Using American Cockroach Gut Microorganisms

The objective of this study was to characterize anaerobic batch digestion of cattail weeds botanical fractions singly and in combination using American cockroach gut microorganisms as an inoculum. The effects of increasing concentration of cattail weeds expressed as percentage of total solids (TS) from 5, 15, to 30 and 60% on methane yield was investigated at ambient temperature of 29±1°C. The results showed that highest methane yields were obtained at 5% TS for both individual and mixed cattail botanical fractions. A maximum methane yield of 447 CH4 ml/g volatile solids (VS) and 288 ml/gVS added were obtained from leaves and whole cattail weeds (comprised of spikes, leaves, stems rhizomes and roots each 20% wet weight), respectively. An average methane content in the range of 72 and 79% was obtained in the biogas produced at 5 to 60% TS for both separate and mixed cattail botanical fractions. Lower TS % led to faster onset of biogas production and higher methane productivity. Blending of cattail botanical fraction at 5 to 60%TS in general did not improve the methane yield compared to that obtained from separate botanical fractions. Methane yield obtained from whole cattail weed was less by a factor of 1.6 compared to that of leaves at 5%TS. It was concluded, that anaerobic digestion of cattail weed is feasible and could serve the dual roles for producing biogas, a clean renewable energy and reducing the weed as part of its management.