Biomethane Recovery from Fresh and Dry Water Hyacinth Anaerobic Co-Digestion with Pig Dung, Elephant Dung and Bat Dung with Different Alkali Pretreatments

Biomethane was produced from water hyacinth (Eichhornia crassipes (Mart.) Solms), an aquatic weed plant, comprising of cellulose, hemicellulose and lignin by using two steps of methods. The first was that fresh and dry water hyacinth in the length of 1 cm, were pretreated with 2 different alkali solutions; 2%(w/v) of NaOH and 10% (w/v) of Lime. The optimum condition was selected from 100, 120 and 140oC for 4 hr at ratio of 1g plant per 15 ml of treatment solution. The yields of sugar from NaOH pretreatments were higher than lime conditions. The highest of sugar yield at 60 g sugar /g substrate was observed from 140oC by using dry water hyacinth, whereas fresh hyacinth had yield at 36.7 g sugar /g substrate. The second method was 12 sets of anaerobic co-digestions with 3 types of dung; pig dung, elephant dung and bat dung, and 2 types plants; fresh and dry hyacinth that pretreated by sodium hydroxide and calcium hydroxide. The mixtures of sugar solution and treated plant solid from both hyacinths were used as substrates by using 200 ml of waste water from sweet corn industrial as starter. The co-digestions were achieved at 1:1 ratio of dung and mixture solutions and at 37±2°C under anaerobic condition for 45 days. The COD removal in rang of 51-69% were absorbed from all 12 conditions. The digestions from all lime treated plants showed higher methane concentration than NaOH treated plants. The lime treated fresh hyacinth had highest values of biochemical methane potential (BMP) and methane concentration were at 59.3% and 63.65 vol.%, respectively. They were equivalent to heating value at 12.58 MJ/m3. The second was lime treated dry hyacinth that showed 32.4% BMP and 43.15 vol.% of methane, respectively.