Effect of silage preparation on methane yields from whole crop maize silages

Additives for silage preparation were tested on their effect on the composition of whole crop maize silage and their potential to improve methane production from energy crops in anaerobic digestion plants. Treatments included ensiling without additives, inoculation with silage starters containing homofermentative lactic acid bacteria or a mixture of homoand heterofermentative lactic acid bacteria and the addition of amylase. Additionally the effects of improper silage preparation like insufficient compression of the material and the addition of the spoilage organism Clostridium tyrobutyricum were evaluated. Good silage qualities were obtained in all experiments, only the addition of Clostridium tyrobutyricum resulted in high concentrations of butyric acid. Methane yields were generally higher after 119 days of storage compared with 44 days of storage. Addition of C. tyrobutyricum could significantly improve methane yields based on volatile solids. Methane yields based on freshly harvested material were calculated with respect to the storage losses observed in the experiments. Although C. tyrobutyricum caused the highest storage losses, this was compensated by the elevated formation of methane. It remains to be investigated, whether storage losses in laboratory experiments are significant for the technical scale.