Effects of geographic area, feedstock, temperature, and operating time on microbial communities of six full-scale biogas plants

Biogas production is a hot topic, which has globally gained interest from many researchers over the past years. This fact is mainly due to the depletion of fossil fuels and environmental concerns regarding wastes disposal. Anaerobic Digestion (AD) represents a biological way to obtain both energy (in form of biogas) and waste discard, by converting the polluting organic matter. The overall process relies on a syntrophic chain where different microbial consortia produce the feed necessary for the final methanogenic step. Cheese whey has been largely investigated for AD treatment, since is a high polluting waste derived from the cheese-making process. However, there is a less-known waste originating from the portioning and shaving phases of long-ripened hard-cheese. This study aimed to investigate the microbiome of anaerobic digesters processing dairy industry wastes, such as cattle manure, cheese whey and hard-cheese powder wastes. In particular, the effects of process parameters, reactor configurations and type of dairy wastes, on the microbial populations, have been analyzed. The goal was achieved by means of culture-independent methods and high throughput sequencing, which allowed quantifying and identifying the main species present, as well as their differential gene expression in relation to hydrogen injection for biogas upgrading purposes.