Process Flow Summary:
Green waste substrates are delivered via truck to the Receiving Building, which is equipped with seven receiving areas, including: two liquid material tanks with hose connections; two grease trap receiving bins; two food waste receiving bins; and one yard waste receiving bin. The Receiving Building provides ample storage capacity so multiple trucks can unload their waste directly into the bin at the same time. The waste receiving system is critical during EISENMANN’s proprietary process, since it screens, prepares and blends the substrates in order to provide the desired feedstock for the Main Digesters. The system’s bins and tanks utilize load cells and flow meters to regulate the appropriate amount of material into each Main Digester. The digesters e process temperature. The digester vessel is properly sized in order to achieve the necessary residence time for the optimal production of biogas.
The mixture leaving the Main Digesters is pumped to the Solid / Liquid Separator Unit. Solids are pressed into a wet cake and the remaining liquid stream is directed to the Post Digester Tank (or the Final Storage Tank). The Post Digester Tank is designed with a double membrane roof so it can yield ample biogas storage capacity. The biogas quality and flow is constantly monitored and tracked to ensure consistency in the mix. The biogas travels from the Post Digester Tank to a condensate trap before being routed to the Combined Heat and Power Units (CHP Units). The CHP Units convert the biogas to electrical power, which is sent to the utility grid and/or thermal energy. A portion of the biogas is scrubbed to pipeline quality and injected into the natural gas pipeline or compressed and marketed as Renewable Compressed Natural Gas (RNG) for use as transportation fuel. Any condensed moisture are continuously fed with organic material during a typical operating shift.
In the Main Digester, the material is mixed to ensure homogenous blending of substrates and microbial culture while assisting in the release of biogas. Hot water is circulated through heating coils in the Main Digester to maintain an appropriate temperature.