Co-Digestion – The Path to Success Template Revised 15 March 2011 November 2015 Blair Wisdom

Agenda Co-Digestion Overview Feasibility Ensure Success of Receiving Stations and Pretreatment Safeguard for Stable Digester Performance

Co-Digestion overview

Black & Veatch | November 2015 What is Co-Digestion? It takes shape in many forms. Essentially, it is the addition of high strength waste (HSW) to anaerobic digesters Commonly practiced with the brown grease (BG) portion of fats, oils, and grease (FOG) Increasing focus on industrial and pre- consumer wastes Dairy whey Fruit/vegetable wastes Institutional food wastes Corn silage

Why would you Co-Digest? Black & Veatch | November 2015 Why would you Co-Digest? Excess capacity in digesters may afford opportunity for revenue from tip fees. Regional haulers (FOG and others) may need an outlet (encourage them to keep it out of collection system. Control where HSW are injected in plant – turn from waste that consumes energy to an enhancement Increased load can make energy recovery more attractive Energy

stabilization technologies Black & Veatch | November 2015 Organic Resources-to-Energy CO-LOCATION/(CO)-DIGESTION AND GAS UTILIZATION Sludge WWTP EXISTING DIGESTERS CO-GEN GRID DEDICATED DIGESTERS GAS UPGRADING RNG FLEET PIPELINE stabilization technologies COMMERCIAL ORGANICS SOURCE SEPARATED ORGANICS/ ORGANIG FRACTION OF MSW FOG

Co-Digestion Can Enhance Overall Sustainability Black & Veatch | November 2015 Co-Digestion Can Enhance Overall Sustainability Reliable systems provide valuable service to industries Increased revenue On-site power production provides greater reliability Flexibility for multiple energy uses

Pros/Cons of Co-digestion Black & Veatch | 2 September 2015 Pros/Cons of Co-digestion ADVANTAGES Synergistic effects (location, infrastructure) Qualified & experienced personnel on site Improves digester performance thanks to symbiotic behaviors Increase in revenues through tipping fees Self-sufficient generation of renewable energy on-site achievable Biosolids contain less contaminants, more nutrients, and are more suitable for agricultural use than conventional biosolids Increased in gas production and quality Improved economics, benefitting rate payers for publically owned treatment works + stabilization technologies Co-digestion dilutes the inhibitory effects of substrates, balance the micro and macronutrients, increase the organic loading with consequent higher methane yields per unit of digester volume; lastly diversify and synergize the microbial communities which play pivotal role in the methanogenesis. Source: Braun, Wellinger (2003); Grasmug, Braun (2003); Schmelz (2007); STOWA, (2006) adapted

Pros/Cons of Co-digestion Black & Veatch | 2 September 2015 Pros/Cons of Co-digestion DISADVANTAGES Capital costs; feedstock receiving station and conditioning/removal of contaminants before feeding digester and increased mixing may be required Increased chemical oxygen demand (COD)/nutrient load of digestate’s filtrate Foam formation and scum layers in digester Odors Dewaterability: increased amount of biosolids Hygienization may be required Deposition of material (pipe & valve blockage; reduced digester volume) Mixing Challenges - stabilization technologies Source: Braun, Wellinger (2003); Grasmug, Braun (2003); Schmelz (2007); STOWA, (2006) adapted

Feasibility

Process Capacity

Rock River Water Reclamation District Black & Veatch | November 2015 Rock River Water Reclamation District Drivers: Combat rising energy costs Institute sustainable practices Fully utilize equipment capacities Capacity evaluation: Average 32 day SRT 100 ppd of VS/kcf

Rock River Existing Stabilization and Gas Handling Black & Veatch | November 2015 Rock River Existing Stabilization and Gas Handling Excess Gas Treatment Capacity Excess Digester Capacity Excess Engine Generator Capacity Limited Gas Handling Capacity

Availability of HSW

Significant Biogas potential in high strength wastes Black & Veatch | November 2015 Significant Biogas potential in high strength wastes

Organic Feedstocks & Properties for AD Black & Veatch | November 2015 Organic Feedstocks & Properties for AD MANURE, SEWAGE SLUDGE; FOOD PROCESSING WASTE INDUSTRIAL SLUDGE (e.g. Thin Stillage from EtOH Production); BG (FOG) SLAUGHTER HOUSE WASTES COMMERCIAL FOOD WASTES (Restaurants; Cafeterias) COMMERCIAL FOOD WASTES (Groceries; Packaged Waste) RESIDENTIAL SOURCE SEPARATED ORGANIC WASTE; ORGANIC FRACTION OF MSW Increase in total solids (TS) content Decrease in homogeneity Increase in contamination (non-digestible) stabilization technologies

Area Specific HSW Survey industries in service area Black & Veatch | November 2015 Area Specific HSW Survey industries in service area Evaluate characteristics & value of available wastes pH Total and Volatile Solids (TS and VS) Total and Soluble COD Total Ammonia Nitrogen (TAN) Total Kjeldahl Nitrogen (TKN) Volatile Fatty Acids (VFA) Long Chain Fatty Acids (LCFA) Alkalinity Gas Production and Composition Capillary Suction Time (CST) and Sludge Dewatering Biosolids Odors Determine loading and any adverse effects

Increased Competition for FOG – Long term outlook? Black & Veatch | November 2015 Increased Competition for FOG – Long term outlook? Increased interest in yellow grease for biodiesel Gasoline price fluctuations Carbon footprint/offsets Increased use of yellow grease in Animal feed Cosmetics Increased consideration as substrate for industrial anaerobic Digestion Grant/offset benefits Renewable energy generation Reduced restaurant generation from recession Pricing to attract haulers 3rd bullet is most applicable to plant JB: FOG is the term under which brown grease (BG) and yellow grease (YG) falls; typically only BG is used for co-digestion whereas YG is increasingly used for biodiesel production due to its higher purity/value; YG is typically not used for co-digestion; the trend I have seen is that rendering firms that collect the BG try to discharge the BG for the lowest price; so if one WWTP’s receiving fee is too high then they go to another receiving place where the cost per gal is lower = WWTPs may start to compete for haulers; best to have long-term contracts with less haulers in place if possible to secure supply

Commercial and Residential Source Separated Organics - Co-Digestion Black & Veatch | November 2015 Commercial and Residential Source Separated Organics - Co-Digestion OBJECTIVES & MEASURES: Increase of Waste Diversion towards Zero Waste Goal (meet local, state and federal landfill diversion and/or organics ban requirements) Closing Carbon and Nutrient Loop Cheap and plentiful feedstock for energy production Educate food establishments, food processors, retailers, and residents of organics collection stabilization technologies

Availability of HSW Contacted 50 companies in surrounding area Black & Veatch | November 2015 Availability of HSW Contacted 50 companies in surrounding area Conclusions of HSW Survey Abundant supply of Non-FOG high strength wastes Thin stillage, dairy wastes, distillers syrups 4,000 to 5,000 gallons per day of FOG waste generated within the district’s service area Another 20,000 gallons per day of FOG waste generated Around the district’s service area Adequate Supply for 20,000 GPD HSW Facility

Assess the Benefits

What are the Operational Costs and Benefits? Black & Veatch | November 2015 What are the Operational Costs and Benefits? Operational Costs Some added maintenance Added loads to the plant Potentially added biosolids disposal costs Operational Benefits Increased biogas Increased waste heat from engine generators Tipping fees Service to customers B&V - 22

Ensure Success of Receiving Stations and Pretreatment

Hauling Considerations Black & Veatch | November 2015 Hauling Considerations What type of wastes are being processed? Processed source separated food wastes? “Liquid” high strength wastes? Efficient truck unloading Hauling schedules? Multiple trucks at a time? Cleaning stations Weigh scales Hauled load management and billing

Pre-treatment and materials handling issues Black & Veatch | November 2015 Pre-treatment and materials handling issues Pretreatment: Rock traps, screens, grinding, depackaging (industrial wastes) Remove non-biodegradable materials Protect downstream equipment Reduce particle size to optimize digestion Storage tanks Mixing Site specific heating Heat tracing, HEX, mixing with warm sludge JB: FYI - The slide you’re showing for Pacific Biodiesel is a demonstration plant at the Oceanside WWTP of San Francisco; the previous installation at that side funded by the CA Energy Commission with Black Gold failed to make biodiesel from brown grease; I do not know if they are actually making vehicle-fuel grade biodiesel from it or off-spec biodiesel that can be used as boiler fuel.

Debris in Hauled Wastes Black & Veatch | November 2015 Debris in Hauled Wastes

stabilization technologies Black & Veatch | November 2015 FOG/BG CO-DIGESTION EXAMPLE: WATSONVILLE WWTP stabilization technologies Source: Kester, G. (2008) PLANT DESIGN CAPACITY: 12 MGD FOG CO-DIGESTION: 3,000 – 10,000 GAL/DAY

Example – Des Moines WRA - 170,000 Gallon Receiving Tank Black & Veatch November 2015 Example – Des Moines WRA - 170,000 Gallon Receiving Tank JB: what facility?

Des Moines WRA - Receiving/Storage Tank Black & Veatch | November 2015 Des Moines WRA - Receiving/Storage Tank Mixed via recirculation pumps and nozzles Lined for corrosion control JB: what facility?

Black & Veatch | November 2015 Summary of receiving concepts Basic or Sophisticated Systems – No two are the same! Simple systems with rock-boxes - traps grit/debris before larger tank Mechanical systems for removing debris Some have storage while others go straight to digesters Heating? Is it needed? CDM – rock boxes No standard design

Safeguard for Stable Digester Performance

Opequon WRF – Frederick Winchester Service Authority (FWSA) Black & Veatch | November 2015 Opequon WRF – Frederick Winchester Service Authority (FWSA) Current Solids Treatment: Lime-Stabilized biosolids – landfill disposal Frame and Plate Filter Presses Design Solids Process: Two mesophilic primary digesters and one secondary digester

Black & Veatch | November 2015 Solids Process

Solids Design Summary Substrates for co-digestion: Wastewater sludge Black & Veatch | November 2015 Solids Design Summary Substrates for co-digestion: Wastewater sludge Kraft Foods waste Dairy whey waste GTW and DAF Float Food waste Solids retention time, days Maximum Month Annual Average   15 20 VS Loading Rate, ppd/kcf 154 132 Expected Volatile Solids Reduction, % Average Annual 45

Pilot Testing - Digester Set up and Operation Black & Veatch | November 2015 Pilot Testing - Digester Set up and Operation 4 digesters with working volume of 9.75L, 15 day SRT Mesophilic temperature (370C) Seeded with 8 Liters of digester effluent from Christiansburg WWTP Schematic Diagram showing Digester setup

Parameters analyzed pH Total and Volatile Solids (TS and VS) Black & Veatch | November 2015 Parameters analyzed pH Total and Volatile Solids (TS and VS) Total and Soluble COD Total Ammonia Nitrogen (TAN) Total Kjeldahl Nitrogen (TKN) Volatile Fatty Acids (VFA) Long Chain Fatty Acids (LCFA) Alkalinity Gas Production and Composition Capillary Suction Time (CST) and Sludge Dewatering Biosolids Odors

Waste Characteristics (Part II) Black & Veatch | November 2015 Waste Characteristics (Part II) High Strength Waste Total COD (mg/L) TS VS GTW 50,000 40,000 37,000 Whey 87,000 78,000 56,000 DAF 600,000 300,000 285,000 Juice waste 76,000 44,000 43,000 Sludge Mix ~35,000 ~30,000 ~23,000   Part I: Feed contained Juice Waste and Whey Waste only. Digester performance was assessed and the roles of alkalinity and VFA concentrations were evaluated Part II: Carried out in three phases with increasing concentrations of all the food wastes listed in the table above.

Total Time of Operation: 310 Days Black & Veatch | November 2015 Total Time of Operation: 310 Days The above mentioned compositions were attained on Day 180 Juice processing waste underwent a sudden, drastic change on Day 240 New waste much “stronger” Digester 4 which was receiving the highest HSW load by volume exhibited failure

Volatile Solids (mg/L) Failure Caused by Shock Load to Digester Wastes being added were acidic in nature, especially the juice processing waste The sudden change in the nature of the waste seems to have inflicted a “shock load” on the digester that exhibited failure   “Old” Juice waste “New” Juice Waste pH 4.10 3.10 Total Solids (mg/L) 32,000 72,000 Volatile Solids (mg/L) 31,000 68,000 Total COD (mg/L) 66,000 208,000

Acidic wastes can reduce buffering capacity of anaerobic systems. Black & Veatch | November 2015 Acidic wastes can reduce buffering capacity of anaerobic systems. The nature of the wastes to be added as co-substrates to anaerobic digesters is therefore something that must be thoroughly studied Similar Juice mix with supplemental ammonia did not show failure Variability in the nature of the HSW must be monitored as sudden changes in the HSW feed might push digesters to failure

Biomethane Potential Analysis Black & Veatch | November 2015 Biomethane Potential Analysis

Page - 3 April 29, 2014