Effect of ratios of manure to crop on dry anaerobic digestion for biogas production

To make clear the impact of ratios of manure to crop on dry anaerobic digestion would be of great significance to promote the practical progress of dry anaerobic digestion project. Four experiments were set at total solids(TS) of concentration of 30%: (A) pig manure alone; (B) straw alone; (C) the mass ratio of pig manure to straw of 2:1; (D) the mass ratio of pig manure to straw of 1:2. The experimental temperature was controlled at (35±1)℃. Over 62 days, operation period, the results showed that the biogas production to time curves of experiment (A), (B), (C) and (D) reached the inflection point at 48th, 40th, 26th and 25th days’ respectively. The total biogas yields of experimental (C) and (D) were 15715 and 13186 mL, respectively. According to the biogas yields of experiment (A) and (B) with the materials separately, it could be calculated that the biogas production potentials of (C) and (D) were 15168 and 13838 mL, respectively. There was no significant difference between the experimental results and the calculated values. The improvement of ratio of manure to crop could promote digestion efficiency by improving the digestion speed. But no obvious effect was found on enhancing the biogas production potential. Thus, the advantages of dry anaerobic co-digestion may be of improvement to material structure and of adjustment to material nutrient, but not of enhancement of the biogas production potential.