Trace elements (TE) are know to be of importance for the function and efficiency of the biogas process. From process data and functional analyses it appears as the main effects of TE addition is caused by enhanced degradation rate of different organic acids and methane production. Some data exists on effect on microbial community structures by TE addition by no expression studies have so far been done, which is the main aim of this project. To reveal further information on the positive effect on trace metal addition in biogas processes we have generated both metagenomic and metatranscriptomic data from non supplemented and TE supplemented processes. This data will be used for comparative analysis to generate information of up regulated functions and effect of community structure.