Codigestion Case Studies Enhancing Energy Recovery From Sludge Dale Gabel, PE, BCEE MWRD PWO Seminar 1 May 23, 2012
What is Codigestion? Direct addition of high-strength organic wastes to municipal wastewater anaerobic digesters Typical high-strength organic wastes Fats, oils, and grease (FOG) Restaurant food scraps Food processing wastes Off-spec cola syrups Dairy wastes Cheese Wastes Brewery Wastes Winery Wastes Others 2
Advantages of Codigestion 3 Technical Removes FOG from sewer collection systems Removes FOG materials from headworks and primary clarifiers Removes organic loadings on liquid treatment train Increases digester utilization Economic Produces more biogas for beneficial uses (CHP, dryer, vehicles, etc.) New revenue streams from tipping fees Reduces O&M costs for headworks and liquid treatment trains Environmental Reduces landfilling of high-strength wastes (HSW) Reduces emission of greenhouse gases
Challenges of Codigestion Possible need for digester upgrades Additional capital and O&M costs for FOG/HSW receiving and processing Additional paperwork for permitting, waste receipts, billings Debris removal and disposal Potential negative anaerobic digester performance impacts Potential anaerobic digester toxicity from HSW Potential increase in nutrient concentrations in sidestreams 4
Key Elements of an Effective FOG Waste/HSW Processing System Material Delivery Control/Traceability Volume of Material and Storage Requirements FOG Waste/HSW Unloading Considerations Storage and Conditioning Odor Control Feed Strategies 5
Material Delivery Control and Traceability Develop Application Process Collaborate with Haulers and WWTP Operators Train Drivers on Delivery/Unloading Procedures Sample Collection and Testing Record Keeping Security 6
Volume of Material and Storage Requirements Research Market Number of potential hauling companies Estimate deliveries per day Delivery truck capacities Billing: Basis and Method Develop Storage and Feed Strategy Design for anticipated peak day loads Develop acceptable delivery schedule Continuous feed or single shift 7
FOG Waste/HSW Unloading Considerations Access Control and Automation Unloading Method Debris/Sediment Removal Pumping Clean up 8
Key Components of a Receiving Station FOG Storage Tanks Influent/Mixing Pumps Heat Exchangers Odor Control Rock Trap/ Grinders Digester Feed Pumps 9
Codigestion Case Studies Des Moines Metropolitan Wastewater Reclamation Authority, Iowa. 136 mgd, various HSW Douglas L. Smith Middle Basin WWTP, Johnson County, Kansas 14.5 mgd, FOG/HSW Gloversville-Johnstown Joint WWTF, New York 13 mgd, yogurt/cheese whey 10
11 Des Moines Metropolitan Wastewater Reclamation Facility (DMMWRF) 50 mgd (134 mgd Capacity)
HSW Processing System Truck weigh stations (3) Rock traps (3) HSWs received and blended in HSW receiving tank HSW then blended in another tank with primary and waste activated sludge and fed sequentially to the digesters 12
Unloading into Underground HSW Receiving Tank Up to Three Trucks Can Be Received Simultaneously 13
Foaming Control Foaming events from selected HSW controlled by reducing accepted quantities of these wastes corn oil and isopropyl alcohol (IPA) Ongoing digesters upgrades expected to reduce foaming Submerged-fixed covers Internal draft tube mechanical mixers 14
Feed Volumes Average (Minimum- Maximum) Volumetric Fraction PS (gal/day) 132,000 (42,000 180,000) TWAS (gal/day) 98,000 (0 204,000) HSW (gal/day) Est. 160,000 (93,000 297,000) 35% 26% 42% Digesters HRT Based on Blended Sludge (days) 33 (22 49) Predominant load is due to HSW 15
Selected Data for Codigested Waste Streams Packing Biodiesel Trucked Brown Plant DAF Production Municipal Grease Float Waste Sludge Tipping Fee, $/gal $0.0148 $0.026 $0.027 $0.0148 Wastes Accepted 24/7 24/5 24/7 24/5 Digester Feeding 24/7 24/7 24/7 24/7 Flow, gpd 16,700 33,300 32,300 20,100 ph (1) 4.7 5.7 5.8 5.1 (4.0 7.0) (5.3 6.5) (5.2 8.1) (5.0 5.1) COD (1), mg/l 40,000 (700 30,8000) TS (1), % solids 5.45 6.68 0.3 2.95 (2.04 9.24) (0.91 12.77) (0.08 0.68) (1.49 4.11) VS/TS (1), % 88.8 83.7 76.3 (75.8 95.7) (64.9 92.8) (72.1 80.4) (1) Average (Minimum Maximum) 16
Cargill Financed Part of the Project and Purchases a Fraction of the Produced Biogas for Use in Its Boilers Digesters Cargill 17
Biogas Production and Utilization Annual Biogas, cfd Annual Total, cf Distribution, % Used in CHP (1) 524,000 174,000,000 35 Used in Boilers 94,000 50,000,000 10 Sold to Cargill 706,000 239,000,000 48 Flared 8,660 24,000,000 5 Total biogas 1,423,000 500,000,000 100 (1) About 8,800 MWh produced and 25,000 MWh purchased. 18
19 Financial Benefits Capital Cost New HSW tank $1,750,000 WRA Investment in Cargill biogas utilization project $1,100,000 New submerged fixed concrete digester covers $6,000,000 New digester mixing systems $6,500,000 Annual Revenue TOTAL = $15.4 million HSW tipping fees revenue $200,000-400,000 Biogas sold to Cargill $300,000-800,000 Annual power produced $370,000 (1) TOTAL = $0.9-1.6 million (1) Calculated as 8,800 MWh produced annually at $0.045/kWh; expected to increase significantly with planned CHP engines and expected power price increase
20 Johnson County, Kansas Middle Basin WWTP 12.5 mgd (14.5 mgd Capacity)
Process Flow Diagram FOG/HSW are blended sequentially with primary sludge and thickened WAS 21
22 FOG/HSW Receiving Facility
FOG/HSW Received Daily Receipts Highly Variable 30,000 Volume of Wastes Received, gallons 25,000 20,000 15,000 10,000 5,000-23
Foaming Overflow Events During Codigestion Startup Were largely eliminated by reducing mixing energy 24
Digester Parameters Parameter Value Digester dimensions, ft 55 (diameter), 30 (SWD) Number of digesters 3 VSLR (design), lb VS/cf-d 0.15 VSLR (actual), lb VS/cf-d 0.12 HRT (actual), d 21.8 Mixing type Jet mix Mixing energy input per digester, HP 40 (1) Gas Production Rate, cfd Above 250,000 (2) (1) Cycled 1-hour on and 4-hours off in the primary digesters (2) Before FOG/HSW codigestion (2009) it averaged 125,000 cfd 25
Digester Gas Production Increased with Addition of FOG Waste and Other High Strength Wastes 400,000 Digester 4 Start-up Foaming Loss of HSW 350,000 300,000 Start FOG Addition 250,000 Digester Gas Produced, cubic feet/day 200,000 150,000 100,000 50,000-1/1/2009 3/1/2009 5/1/2009 7/1/2009 9/1/2009 11/1/2009 1/1/2010 3/1/2010 5/1/2010 7/1/2010 9/1/2010 11/1/2010 1/1/2011 3/1/2011 5/1/2011 7/1/2011 9/1/2011 11/1/2011 1/1/2012 3/1/2012 26 Total Digester Gas 7 per. Mov. Avg. (Total Digester Gas)
27 Digester Gas Cleaning, Storage and Utilization
Project Financials Capital cost of codigestion and cogeneration Improvements Annual FOG/HSW tipping fee revenue $10,000,000 $300,000 Annual electrical power from biogas $400,000 28
Gloversville-Johnstown Joint WWTF, New York (GJJWWTF) - 6.7 mgd (13 mgd Capacity) 29
Codigestion Process Flow Diagram Trucked Cheese Whey Yogurt Whey Pumped from Industrial Park Whey Flow Equalization Tanks Primary Sludge WAS Ferric Sludge Blending Gravity Belt Thickening Blended Raw Sludge Recuperative Thickening Recycle Primary Digester Secondary Digester Day Tank BFP Dewatering Cake to Landfill Dairy Washwater Pumped from Industrial Park Microstraining and DAFT Pretreatment Thickened Dairy Waste (considering re-routing to the whey equalization tanks) Sludge blending/equalization Whey equalization Recuperative thickening 30
Yogurt Whey has the Lowest COD Concentration but Offers the Major Contribution to Loading and Gas Production Source Cappiello Whey (cheese) Flow (mgd) COD (lbs/d) TSS (lbs/d) TKN (lbs/d) 0.012 10,010 270 110 FAGE Whey (yogurt) 0.056 23,600 3,020 470 Euphrates (cheese) 0.007 5,840 280 90 Yogurt whey COD ~ 30,000 mg/l and cheese whey COD ~ 100,000 mg/l 31
2002 vs. 2011 Performance Comparison Parameter 2002 2011 (1) VS Loading, lb/cf-d 0.06 0.21 Hydraulic Retention Time, days 34 Solids Retention Time, days 34 Volatile Solids Reduction, % 40 Digester gas Generation, cfd 83,000 310,000 Digester Gas Production, cf/lb VSR 13 Methane Content, % 68 Annual Electrical Production, MWh 816 5,000 Cake TS, % solids 18 20 14 (1) Projected based on January 2011 data 32
Revenue from HSW Receiving Trucked & Pumped Waste Revenue $1,000,000 $800,000 $600,000 $400,000 $200,000 $0 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 $1,000,000 annual revenue for 6.5 mgd facility 33
Facility is Largely Energy Self-Sufficient Remains connected to the power grid for reliability 34
Capital Cost Total Project Cost $11,500,000 NYSEDRA Grant Funding $1,400,000 ARRA/NYSEFC Grant Funding $6,000,000 Total grand funding $9,600,000 Net Cost $1,900,000 35
Project is Highly Profitable Incremental Cost Incremental chemical cost $100,000 Incremental dewatered $300,000 solids landfill disposal cost Incremental CHP O&M due $100,000 to increased CHP capacity Biogas drying $50,000 Revenue Power generated $640,000 Pumped-trucked waste $992,000 receiving fees (1) Power @ $0.12/kWh Annual revenue significantly exceeds cost 36
Conclusions The three analyzed facilities had different Capacities Codigested HSWs Cost structure (tipping fees, unit power cost, biosolids disposal cost) All three facilities realized significant increase in biogas production and electrical power savings Benefits included Financial gains Serving the local communities and industries Environmentally sound utilization of the HSWs An increasing number of HSW codigestion facilities are expected to continue being implemented 37
Acknowledgements John Kabouris, PhD, PE, CH2M HILL Tim Shea, PhD, PE, BCEE, CH2M HILL Larry Hare, Des Moines Metropolitan Wastewater Reclamation Authority, Iowa; Doug Nolkemper, Douglas L. Smith Middle Basin WWTP, Johnson County, Kansas; Operations staff at Gloversville-Johnstown Joint WWTF, New York 38
Questions? Codigestion Case Studies Enhancing Energy Recovery From Sludge Dale Gabel, PE, BCEE MWRD PWO Seminar 39 May 23, 2012