Leveraging An Agency s Assets. Anaerobic Co-Digestion FOG, Food Waste and More

Transcription

1 Leveraging An Agency s Assets Anaerobic Co-Digestion FOG, Food Waste and More

2 Anaerobic Co-Digestion Energy CO 2 Use existing WWTP Infrastructure CH 4 CO 2 Stripping CNG Wastewater Sludge CO 2 Heat CNG Vehicle Fuel Digester heating Energy recovery CH 4 Use at WWTP Use on Base Engine Electricity Liquid Wastes Sludge Liquor Return to WWTP Feed Stocks Anaerobic Digester At WWTP Residuals Solids Soil Amendment Further Energy Extraction Solid Wastes

3 Key Features of a WTE Program Digester set up to handle challenging waste streams Energy-rich waste streams FOG, food waste, food processing waste, high strength waste streams Receiving facilities at the WWTP/digesters Use(s) for renewable fuel power production, vehicle fueling, utility gas.

4 Address Digester Mixing and Heating First

5 Potential Waste Streams Looking for readily-digestible volatile solids Low cellulose content High COD, highly concentrated Difficult to treat or dispose FOG Food waste, sorted (large restaurants, cafeterias) Food processing waste High strength waste streams

6 Targeted Wastes Fats, Oils, Grease (FOG) Pumped waste from interceptors Food Waste Pre-consumer Post-consumer with pre-treatment Typical grease interceptor Kitchen grinder Ground food waste

7 Bringing in Grease and Minimizing Risk Regulate Waste Haulers Issue permits Require Bill of Lading or other form of documentation Secure long term delivery contracts

8 How Much Grease or FOG is Out There? Some Trap Grease Production Rates*: National Avg. = 13.4 lbs/year/person Sacramento, CA Avg. = 11.2 lbs/year/person Provo, UT Avg. = 26.6 lbs/year/person * Source: Wiltsee, G. Urban Waste Grease Resource Assessment. NREL. November 1998

9 How Much Food Waste is Out There? Findings Commercial 0.25 lb/day per capita Residential 0.79 lb/day per capita % Solids 25 to 40% Volatile matter is 80 to 95% Digestible 80 90% of volatile Better Anaerobic Digestability than Municipal Sludge

10 Who is Doing Food Waste Digestion? U.S. EBMUD Since 2003 Commercial Food Waste, Operating Capacity of 40 T/D, Future Capacity of 200 T/D Milwaukee Since 2005, Operating Capacity 10 T/D West Lafayette, Indiana, since 2009, currently 2-3 T/D Central Marin Sanitation Agency (in construction) Europe Denmark > 200 operating Germany > 10 Italy, Rome Poland

11 Case Studies South Bayside System Authority (SBSA) Redwood City, CA FOG Co-Digestion since 1986 City of Millbrae WWTP Millbrae, CA FOG Co-Digestion Solids Reduction Due to Co-Digestion FOG City of West Lafayette WWTP West Lafayette, IN FOG Co-Digestion Food Scrap Waste Co-Digestion

12 Grease Trap Deliveries at SBSA Grease Trap Deliveries at SBSA 1,200,000 1,000, , , , , Annual Gallons Received Year Annual Gallons Received 86 32, , , , , , , , ,080, ,000,000 / yr

13 SBSA Experience FOG Co-Digestion Digester # 1 Digester # 2 Characteristic (Grease) (No Grease) ph Total Solids (%) Volatile Solids / Total Solids (%) Volatile Acid (mg/l) Alkalinity (mg/l) Volatile Acid / Alkalinity Ratio Volatile Solids Loading (lbs/ft 3 /day) ~ 0.10 ~ 0.07 Detention Time (days) Gas Production (1000 ft 3 /day) ~ 182 ~ 130 Methane (%) Volatile Solids Destruction (lbs/day) 12,200 8,300 Gas Production (ft3/lb. vol. solids destroyed) 15 15

14 SBSA Receiving Station Used for FOG and Septage Receiving Underground tank

15 Millbrae FOG Receiving Facility

16 Millbrae: Reduced Solids Production Wet metric Tons Biosolids Disposed 1, Wet Metric Tons 1,400 1,200 1, Wet Metric Tons WET WEIGHT, METRIC TON 2007 average AFTER IKG RECEIVING Average FY 93 - FY 06 0 FY 93 - FY 06 Average 2007

17 West Lafayette FOG and Food Waste Project included: Digester Improvements (mixing and heating) New Gas Handling Equipment New Gas Conditioning System New Cogeneration System FOG Receiving Facility Food Waste Receiving Facilities New improvements operating as of Spring 2009 Featured project on 17 August EPA Greenpower Partnership webinar

18 Gas Treatment and Microturbines Unison Gas Treatment Skid Capstone Microturbines

19 West Lafayette FOG Receiving Station Existing Grit Tank New Truck Scale

20 Food Waste: Source Separated High quality food waste available from Purdue University University dining halls separate food waste Plate Scraping Trough Macerator/Pulper Classifier

21 Purdue Food Waste Processed Food Waste Bags are placed in 33 gallon rolling totes

22 Food Waste Pilot (Spring 2009)

23 West Lafayette Other Waste Streams Thin stillage very high strength Food waste from high schools Cooking oil washdown Vegetable juice

24 West Lafayette Reduced Residual Solids

25 Project Reduces Carbon Footprint Less CO 2 than landfill or composting Less CO 2 from shorter truck halls Renewable energy replaces energy from fossil fuels

26 A Sustainable Solution Cost effective projects with reasonable payback A local renewable energy source Reduces truck traffic on the roads Diverts waste from landfills Increases WWTP s value as a community asset Reduces carbon footprint