An investigation on biogas generation from Maltese diary farmyard manure, in relation to the cows' feeding ration characteristics

Abstract

The objective of the project is to assess the quality of dairy manure in Malta and analyse its potential of generating biogas through anaerobic digestion. Biogas production is a very promising option to generate renewable energy. Currently, specific parameters on the anaerobic digestibility of animal manures are unavailable which restricts the exploitation of the promising potentials. The aim of this study was to assess whether there is a correlation between the potential biogas generated from cow manure in Malta and the respective feeding ration. Each farm follows a different feeding strategy based on concentrates and fodder. The quality, type and amount of each specific feed ration vary for all four farms. An experimental analysis was conducted involving the incubation of manure samples collected from four dairy farms. Four batch-type anaerobic digesters were operated simultaneously at 37.8 °C for a retention time of 9 days. From the results it transpired that the feeds supplied to the cows affected the C/N ratio of the resultant manure, which subsequently contributed to the biogas yields. The diet ration comprising of just concentrates and local fodder produced manure with a C/N ratio of 25: I, which eventually generated the highest biogas yields. The lowest biogas yields were generated from a substrate with a C/N ratio of 38:1, of which cows were fed on a rather similar feeding ration. However, there were other parameters which contributed to the Jisparity in both the C/N ratio and the respective biogas.