pms and one or more gates to the pms are closed run off i e percolate containing hydrolytes from the pm may be delivered to a process tank pt prior to transfer to the mr in certain embodiments degassed liquid from the mr is returned to the pt from which it may be sprayed onto the organic matter in the pm the percolate from the pm may be fed back to the process tank through a drain in the bottom of the pm in one embodiment the process module is operated under anaerobic conditions during percolation excess percolation liquid now containing hydrolytes may be fed through a coarse filter and introduced into the mr where the methanogenesis takes place separation of fresh and degassed percolate may take place using a principle of leveling in the reactor tank percolate may be continuously taken out of the mr and heated in a heat exchanger when the ph of percolate coming out of the process module has reached a defined level and the solid fraction in the pm has been inoculated by methanogenic bacteria the methanogenesis may start in the pm after a period of time the methane production or accumulation in the pm is.