Fats, Oils, and Grease: Nuisance to Opportunity for Sioux Falls

Patti Craddock, PE Presents: Fats, Oils, and Grease: Nuisance to Opportunity for Sioux Falls CSWEA 88th Annual Meeting, Oakbrook Terrace, Illinois Ma...
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Patti Craddock, PE Presents:

Fats, Oils, and Grease: Nuisance to Opportunity for Sioux Falls CSWEA 88th Annual Meeting, Oakbrook Terrace, Illinois May 20, 2015

Presentation Outline • Fats, Oils, and Grease (FOG) – nuisance to opportunity concept for Sioux Falls • Sioux Falls WRF business case evaluation and improvements plan

Fats, Oil, and Grease (FOG): Nuisance • Nuisance – Collection System – Treatment Facility

• Stop it at the Source Campaigns – Public outreach – Ordinances

FOG Program Outreach Education

Fats, Oil, and Grease (FOG): Opportunity • Yellow grease – Used cooking oil – Already a market

• Brown grease – Grease – down the drain (interceptors) – Evolving market – Energy rich waste stream

Grease as Energy Source at WWTFs • FOG is highly volatile – high energy/unit volume • Benefit – energy recovery – Anaerobic digestion – Incineration (thermal oxidation)

• Example: anaerobic digestion – Direct feed to digesters – co-digestion – VS Content: FOG-95%, Municipal-70-85% – VS Destruction: FOG-90%, Municipal-66%

Co-Digestion Drivers for Sioux Falls Aging Assets/Underutilized Assets CO2 Wastewater Sludge

CH4

CH4

CO2 Stripping CNG

CNG Vehicle Fuel Heat

CO2

• Digester heating • Energy recovery • Use at WWTP • Use on Base

Engine Liquid Wastes

Electricity

Sludge Liquor

Feed Stocks

• Return to WWTP • Liquid Fertilizer

Anaerobic Digester At WWTP Residuals

Solids Solid Wastes

• Soil Amendment • Further Energy Extraction

Co-Digestion Drivers Improved Collection System Operations CO2

Wastewater Sludge

CH4

CH4

CO2 Stripping CNG

CNG Vehicle Fuel Heat

CO2

• Digester heating • Energy recovery • Use at WWTP • Use on Base

Engine Liquid Wastes FOG

Electricity

Sludge Liquor

Feed Stocks

• Return to WWTP • Liquid Fertilizer

Anaerobic Digester At WWTP Residuals

Solids Solid Wastes

• Soil Amendment • Further Energy Extraction

Co-Digestion Drivers Power Savings Wastewater Sludge

CH4

CH4

CO2 CO2 Stripping CNG

CNG Vehicle Fuel Heat

CO2

• Digester heating • Energy recovery • Use at WWTP • Use on Base

Engine Liquid Wastes

Electricity

Sludge Liquor

Feed Stocks

• Return to WWTP • Liquid Fertilizer

Anaerobic Digester At WWTP Residuals

Solids Solid Wastes

• Soil Amendment • Further Energy Extraction

Co-Digestion Drivers Renewable Fuel Wastewater Sludge

CH4

CH4

CO2 CO2 Stripping CNG

CNG Vehicle Fuel Heat

CO2

• Digester heating • Energy recovery • Use at WWTP • Use on Base

Engine Liquid Wastes

Electricity

Sludge Liquor

Feed Stocks

• Return to WWTP • Liquid Fertilizer

Anaerobic Digester At WWTP Residuals

Solids Solid Wastes

• Soil Amendment • Further Energy Extraction

Co-Digestion Drivers Community Green Goals CO2

Wastewater Sludge

CH4

CO2 Stripping CNG

• Landfill Diversion CNG Vehicle Fuel • Less TruckHeat Traffic• Digester heating

CH4

CO2

• Energy recovery

• Smaller Carbon Footprint

• Use at WWTP • Use on Base

Engine Liquid Wastes

Electricity

Sludge Liquor

Feed Stocks

• Return to WWTP • Liquid Fertilizer

Anaerobic Digester At WWTP Residuals

Solids Solid Wastes

• Soil Amendment • Further Energy Extraction

Co-Digestion Drivers Reduced Residual Biosolids CO2

Wastewater Sludge

CH4

CH4

CO2 Stripping CNG

CNG Vehicle Fuel Heat

CO2

• Digester heating • Energy recovery • Use at WWTP • Use on Base

Engine Liquid Wastes

Electricity

Sludge Liquor

Feed Stocks

• Return to WWTP • Liquid Fertilizer

Anaerobic Digester At WWTP Residuals

Solids Solid Wastes

• Soil Amendment • Further Energy Extraction

Utility Drivers to Capture Grease and Co-Digest • Aging assets (with capacity) • Energy efficiency and sustainability practices – Additional energy for onsite and other energy use – Reduce aeration system costs for FOG entering collection system or with hauled waste – Part of utility/community sustainability metrics

• Reduce collection system maintenance and related costs

Sioux Falls FOG Receiving and Digester Complex Improvements • FOG Opportunity incorporated with aged infrastructure improvements • Study completed in 2013 with Sioux Falls, SEH and Kennedy/Jenks Consultants (KJ) team • Design/construction of phased improvements in progress

Digester Improvements Require Coordination for Success • Digester mixing • Digester covers

• Heat exchangers • Engine generators

• Gas conditioning • FOG receiving

Improvements Plan 5

2 6

3

4 Project 1 2 3 4 5 6 7 8

Capital Improvement Heat Exchangers Secondary Digester Cover Digester Gas Conditioning Digester Mixing & Cover #3 Digester Mixing & Cover #2 Digester Mixing & Cover #1 Feedstock Receiving and Processing Energy Recovery

7 Weigh Stationlocation to be determined

Heat Exchanger Replacement Tube-in-Shell – 1980s

Replaced with Spiral

Secondary Digester Cover Replacement • Floating cover-1980s replaced with fixed steel cover • Ability to convert to primary digester

Digester Mixing • Maximum active volume

• Maximum volatile solids destruction • Effective and energy efficient process control

• High reliability Effective mixing is critical with FOG - No grit build-up - No mat build-up

Digester Improvements - Mixing

Digester Gas Conditioning Required for Engine Performance • Quality Issues – Hydrogen sulfide > 2,000 mg/L – Siloxanes

• New Facilities – Biofilter to reduce hydrogen sulfide – Iron sponge for polishing hydrogen sulfide – Activated carbon for siloxane removal

FOG Receiving and Processing

Weigh Stationlocation to be determined

FOG Processing

Digester

Dosing Pumps

Recirculation Pump Grinder Mixing Pump

Mixing Nozzles

Fog Receiving Tank

Rock Trap

Business Case Evaluation Criteria Units Base Value Description Planning Period years 20 Discount Rate 4% FOG Capture Rate 75% Electricity Current Rate $/kWh $0.072 Escalation Rate per year 5% FOG Program Administration per year $100,000 Collection Sys Maint Deferred per year ($200,000) Tipping Fee $/gal $0.10 3% Tipping Fee Escalation Engines/MT Energy Recovery (Future-Engines and/or Microturbines (MT)) Electrical Efficiency 38%/31% Generation Uptime 90%/95% Cost to Operate $/kWhr $0.034/$0.023 OTHER: Labor, Maintenance, Solids Disposal, unit process power costs

Biogas Production and Energy Savings $800,000

400

$700,000

350

$600,000

300

$500,000

250

$400,000

200 Energy $-FOG

$300,000 $200,000

Energy $-Base Biogas-FOG

150 100

Biogas-Base $100,000

$-

50

0

Biogas Production, cfm

Annual Energy Produced, $

Capacity of Existing Primary Digesters (337 cfm)

FOG Co-Digestion Annual Costs and Benefits $1,000,000

$500,000 O&M-CHP/Dig

Annual Cost/Benefit, $

$-

Solids Handling O&M-FOG

$(500,000)

Power Demand Tipping Fees

$(1,000,000)

$(1,500,000)

$(2,000,000)

$(2,500,000)

Power Benefit

FOG Receiving Facility Payback Analysis 18 Cost

16

Revenue

Savings=$4.5M

14

2023 - 2027

Millions

12

10 8 Cumulative Cost

6

Breakeven = 7 years

4 2

Cumulative Revenue

0 2015

2017

2019

2021

2023

2025

2027

Sensitivity Analysis Savings Over 20 years, $ Millions

Sewer Tipping Fee FOG Capture Maintenance $8 $7

5

5

$6

7

$5

7

7

$4

$3 $2 $1 $0

9

9 11

12

Payback Period, years

Improvements Summary • Aging Assets – – – –

Heat exchangers Digester mixing Secondary digester cover Energy recovery (future)

• Process Performance/Optimization – – – –

Digester gas conditioning Primary digester covers Feedstock receiving and processing FOG ordinance & enforcement

Co-Digestion Maximizes Asset Value & Achieves Sustainability Goals • Digestion equipment - end of useful life • Digester & energy recovery systems have capacity • Annual benefits exceed costs • City initiatives for sustainability – Waste minimization – Water resources – Energy

Nuisance

Opportunity

Thank You!

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