Trouble free and more efficiency biogas production due to liquid feeding system

Case Study - Ronconi Giacomo biogas plant, Italy

“We have a large livestock farm, consisting of 130,000 pigs and 2,000 dairy cows. To round out our activities, we have built two 1 MW biogas plants which we feed with slurry, cattle dung, processed water from the company and a small percentage of silage. Both anaerobic digestion plants are fed with the same input material but have two very different feeding systems. We installed a vertical mixer with screw conveyor to feed the dry solids directly into the digester of the first plant. In the second plant, we use a liquid feeding system so the substrates are well mashed with a liquid when fed into the digester.”

In the second plant, Ronconi installed a Vogelsang PreMix solid matter feeder to prepare and mash the input material. A screw conveyor delivers the solid matter to the PreMix. In a single operation, it chops up fibrous residues, eliminates foreign matter and mixes the solids with digestate or slurry into a homogeneous suspension where it’s finally fed into the digester.

After more than two years of operation since January 2018, Mr. Giovanni Ronconi was able to compare the two methods statistically, analyze production results and manage differences.
Ronconi sums up the results as follows: “What is most evident is the very clear reduction in manpower required to maintain the digester and mixers. Before, we had to dismantle them nearly every month in the plant without pre-mixing to remove ropes, fibers and straw stalks. However, the digester using the PreMix has never needed measures like these. The maintenance of the machine itself is also minimal. So far, we haven’t needed to do any work on the progressive cavity pump, while only the cutters and sieve have been replaced on the macerator. At the same time, the liquid feeding system prevents the formation of layers and improves the gas yield. This makes it possible to reduce the quantities of input material without affecting daily production. Finally, the PreMix requires less energy than the vertical mixer and reduces the energy requirements of the mixers, which are no longer forced to handle long-fiber materials as is the case with manure.”