Methane production potential from anaerobic co-digestions of different animal dungs and sweet corn residuals

摘要

The sweet corn planted areas in Thailand are estimated more than 2.8 million acres and they are also likely to increase by an average about 0.9% each year. These lead to increase the amounts of sweet corn residuals such as trees, leaves, cobs and husks, are accumulated into the fields for burning management more than 35,000 tons per year. The renewable energy production by using biogas technology should be instead of burning for treatment of sweet corn residuals. Seeds, corncobs and cornhusks were used as materials for dry anaerobic digestion using co-digestion technology with 3 types of dung; pig dung, cow dung and goat dung. Corncobs and cornhusk were grinded into 2-3 cm of length and pretreated with alkali pretreatment at room temperature for 48 hr. After pretreatment, hemicellulose and lignin were reduced form original plants by using 2%(w/v) of NaOH. The digestions were performed at 1:1 of dung and corn residual ratio, at 37±2 °C, 74±3% humidity, 25% of initial total solid, and C/N ratio at 3-10:1. The results showed that anaerobic co-digestion between pig dung/seed (PS), goat dung/husk (GH) and cow dung/husk (CH) showed the highest efficiency of COD removal at 79.80%, 74.37% and 72.49%, respectively. While GH, goat dung/cob (GC), and PS had maximum biochemical methane potential at 68.20%, 60.58% and 24.11%, respectively. Moreover, GH had highest methane concentration at 46 vol%, and also produced the volume of methane at 5,045.8 ml/gVS. These values were equivalent to heating value at 16.53 MJ/m3. Meanwhile pig dung/seed (PS) and cow dung/cob (CC) had methane concentration at 19 vol% and 9.10 vol%, respectively. However, the amount of H2S at 30 day of dry digestion using pig dung, cow dung and goat dung were equal to 160 ppm, 58.33 ppm and 25 ppm, respectively.