Effect of magnesium ions on biogas production characteristics of lettuce and potato peelings in anaerobic digester

In order to improve utilization rate of raw materials, shorten period of fermentation and increase gas production rate, the effects of magnesium sulfate on biogas production performances were investigated in an anaerobic digester with anti-scum device using asparagus lettuce peelings and potato peelings. Results showed that the optimal addition amount of magnesium ions with the asparagus lettuce peelings and potato peelings were 0.30 g and 0.10 g per liter gas slurry, respectively. The cumulative total amounts of biogas were enhanced by 71.4% and 41.6%, compared to the comparison. Correspondingly, with the asparagus lettuce peelings and potato peelings the highest volumetric production rate of biogas reached 0.398 m³/(m³·d) and 0.804 m³/(m³·d), and the methane content of biogas maintained at about 70% and 68% in the end of the biogas fermentation, respectively. The results indicated that adequate magnesium ions supplemented could significantly shorten the startup time of fermentation and enhance the daily biogas productivity and methane content of biogas.