Waste No Energy, LLC, (WNE) owns and operates a biomass anaerobic digester located east of Monticello, Indiana. WNE creates green energy, heat, and fertilizer from food and food processing waste, oil and grease, livestock manure, and farm residual waste through anaerobic digestion. We offer an alternative to organic waste disposal, thereby reducing the carbon footprint of generators of organic waste.
Anaerobic digestion is the breakdown of waste products in the absence of oxygen. Material is decomposed by bacteria leaving residual gases and solid material. The gas, sometimes called biogas, is mainly methane and can be captured and used as fuel either for heating or for electricity production. Post digestion effluent is used for agricultural fertilizer and commercial uses.
Currently, organic waste products are most commonly disposed of in landfills, incinerated, or applied directly to land. All three of these methods can contribute to the pollution of the air, soil, and water in local communities while providing zero net benefit. The Waste No Energy® digester improves the local environment by transforming these organic waste products into clean, renewable energy and useful, nutrient-rich fertilizer substitutes, ultimately reducing the community’s carbon footprint.
True to its name, the digester will take organic waste feedstocks (such as outdated grocery and bakery goods, used fats, oils and greases from restaurants, excess commodities from food manufacturing facilities, swine and cattle manure) and convert those waste products into clean, renewable energy and liquid organic fertilizer, with little to no waste products.
The mixed feedstocks are pumped into the digester periodically throughout the day according to a defined and automated feeding schedule. While inside the digester, which is heated to 100oF, the contents are continuously mixed in a gentle stirring motion to promote anaerobic activity using recycled heat from the combined heat and power (CHP). Biogas will be produced and captured in the variable volume membrane roof. From there it is piped to the biogas conditioning unit.
The digester tank is an aboveground bolted stainless steel complete mix style system with approximately 1.25 million gallons of live load. The digester is always operated within 95% of full as fresh feedstock is periodically pumped into the system and completed digestate is periodically removed from the system.
The digestion process breaks down the volatile organic compounds (VOC’s), fats, carbohydrates, and proteins to create biogas. The VOC’s in the feedstock are generally responsible for the majority of the odor associated with the waste products. The anaerobic digestion process breaks down the VOC’s and consumes their components during the process of methane creation, which in turn produces a byproduct that is free of noxious odors and stabilized. The process does not destroy the nutrients, allowing the effluent to be used as an organic fertilizer source.
Methane gas, the main constituent of biogas, is produced as a result of the anaerobic digestion process. Gas produced through the digestion process is stored in the dome of the digester tank within a flexible dual membrane roof structure. The gas holder is comprised of two membranes: a gas membrane and a weather membrane. Air is continuously forced between the two membranes to keep the exterior weather membrane inflated, while allowing the interior biogas membrane to rise and fall with variable gas production. A small fraction of air is pumped inside the gas membrane in a stoichiometric ratio acting as a catalyst and reducing the concentration of hydrogen sulfide gas contained with the biogas.
The entire facility is tied into one human machine interface (HMI) system to operate the facility via programmable logic controller (PLC). This allows for safe and efficient operation of the facility at all times. Flow meters, level sensors, high level floats, temperature sensors, pressure sensors, and other instruments are located on each piece of equipment and communicate with the PLC. All electronic or hydraulic motors communicate with a motor control center (MCC), which is connected to the PLC for control. Start, stop, local, and remote control are all available to the operator on the HMI. The automated program monitors each instrument, trends critical items, operates the plant, and sends alarms to operators in the event of an abnormal condition. By trending operating conditions, the operator can maximize gas production and plant efficiency.