Lowering Food-Waste Co-digestion Costs through an Innovative Combination of a Pre-Sorting Technique and a Strategy for Cake Solids Reduction

Bringing new strategies to make co-digestion cost effective to enhance biogas energy production

Kennedy/Jenks Consultants

Recipient

Irvine, CA

Recipient Location

37th

Senate District

74th

Assembly District

beenhere

$1,382,677

Amount Spent

closed

Closed

Project Status

Projects Updates/The Results

Project successfully demonstrated two complementary approaches to lower the overall cost of co-digestion: a new technology to lower preprocessing cost of food wastes (FW), and a new strategy for the addition of Fats, Oil, Grease (FOG) or FW to lower the mass of cake solids requiring disposal. The technology uses an organic waste separation technique known as an organic extrusion press (OEP/OREX) for selective extrusion of organic materials that has a higher efficiency than conventional techniques. Also, the technology is more economical than typical source separation programs since it requires minimal preprocessing. Results indicated 54% savings compared to source separation and polishing of FW currently practiced. Economic evaluation of a 100 MGD plant indicated $8.9 to $9.3 million worth of energy savings by energy recovery, due to increased gas production.

The Issue

Energy generation potential through the digestion of municipal sewage at wastewater treatment plants (WWTP) and the co-digestion of fats, oils and grease (FOG) and food wastes is estimated at more than 600 megawatts (MW). While combined heat and power generation systems using digester gas are highly beneficial, several barriers exist that impede the installation of these systems. Among the key barriers for food waste co-digestion are the challenges in pre-processing food wastes prior to their addition to the digesters.

Project Innovation

The project demonstrated two complementary approaches to lower the overall cost of co-digestion: a new technology to lower preprocessing cost of food wastes, and a new strategy to lower the mass of cake solids requiring disposal. The new technology for the preprocessing of food wastes uses an organic waste preprocessing technique known as an organic extrusion press (OEP) for selective extrusion of organic materials and is capable of recovering 95% of organics. The project applies a new strategy in operating co-digestion systems that involves optimizing the organic waste loading in a way that will lower the mass of cake solids requiring disposal relative to the conventional process.

Project Goals

Demonstrate OREX food waste pre-processing technology that can lower pre-processing cost by at least 10 percent
Demonstrate potential for increase in biogas production in anaerobic digesters by approximately 70 percent
Demonstrate optimum co-digestion operating condition that can lower the wet mass of dewatered cake by at least 5%

Project Benefits

This project developed a reliable and cost-effective bioenergy from wastewater treatment plants (WWTP) through the integration of an organic waste preprocessing technique known as organic extrusion press and co-digestion of locally available food waste and restaurant fats, oil, and grease (FOG) in an optimized manner that lowers the mass of cake solids that needs disposal. Though there is some seasonal variation, the supply of wastewater, food waste and FOG are very reliable.

Environmental & Public Health

Environmental & Public Health

The technology from this project has the potential to reduce greenhouse gas emissions by 443,345 MTCO2e/year at a modest 10% market penetration. Furthermore, a lower volume of sludge requiring disposal will lower the emissions from trucks used for hauling sludge.

Greater Reliability

Greater Reliability

Applying the results of this project to waste water treatment facilities will reduce grid imports and provide a reliable generation source for these facilities and the grid. With the technology advancement supported by this project, the estimated increase in annual energy production at the demonstration facility is approximately 7,400 MWh.

Key Project Members

Ganesh Rajagopalan

Ganesh Rajagopalan

Manager - Applied Research Group
Bhargavi Subramanian

Bhargavi Subramanian

Staff Scientist
Kennedy Jenks Consultants

Subrecipients

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