Anaerobic Degradation of Halophyte Biomass for Biogas Production

Anaerobic degradation of wild halophytes (Kalidium caspicum, Salicornia europaea and Climacoptera lanata) from solonchaks of Kyzylkum desert in comparison with conventional glycophyte Panicum coloratum was studied. Lab-scale reactors were fed with dried and milled plant biomass. Tests were operated under batch and continuous mode at mesophilic (M) and thermophilic (T) temperatures. High concentrations of chlorides, sulphates, sodium and potassium and low contents of nutrients were revealed in the biomass. Batch-tests showed that total methane-yields at M and T conditions were similar. Maximum biogas was produced in result of anaerobic digestion of Kalidium caspicum (about 1000 mL CH4 from 1L of sludge at T and M-conditions); 950/900 mL/L was obtained in result of digestion of Salicornia europaea at T and M respectively; digestion of Panicum coloratum produced about 900/800 mL/L and Climacoptera lanata 880/700 mL/L. It was revealed that 72-90% of organic fractions of K.caspicum and 54-90% of S.europaea can be decomposed to CH4 at 35oC within 30-days whereas approximately 50-70% of organic matter was decomposed due to anaerobic degradation of C.lanata and P.coloratum. At T-conditions about 60-70% organic matter of the biomass was conversed into methane. Incubation at 55oC accelerated the CH4 conversion rate up to 2 times. Time differences of the anaerobic decomposition of various halophytes are related to variation of lignin content, different concentrations of nutrients and other chemical compounds in the biomass. Preliminary studies of anaerobic digestion of plant biomass under continuous mode demonstrated that it is possible to get about 300-500 mL CH4 from 1L of anaerobic digestion sludge per day.