ECONOMICS OF ANAEROBIC DIGESTION. Tim Raibley

HDR ORGANICS MANAGEMENT PRACTICE Industrial treatment of Waste Water Non-municipal high strength waste water treatment (Food manufacturers and Confined Animal Feeding) Waste Water Treatment Co-digestion of food, FOG (municipal sewage, WWTP digestion) Solid Waste Management Municipal Organics (yard and green wastes, Composting, Dry fermentation)

State of the Practice/Drivers Other Considerations Modeling Assumptions Conclusions Digestion Technologies Cost Comparisons

STATE OF THE PRACTICE / DRIVERS

STATE OF THE PRACTICE Organics Management E.U. Common practice reflecting EU directives Canada Growing since late 1990 s o 45% of all households composted kitchen waste, 60% of them through curbside collection. Over 50% of SFD and 22% of MFD composted kitchen waste o In Ontario, 80% of large municipalities have curbside food waste diversion, serving over 9 million residents, 2.4 million homes U.S. Beginning to grow o 36 million tons of food waste generated/year, around 5% (less than 2 million tons) composted o Growing curbside programs, across 16 states, majority in the West and North East US. o Large metropolitan areas are first adopters

DRIVERS AND TRENDS Why digestion of municipal organics? Organics diversion policies Beneficial use of resources Air quality initiatives Low carbon fuel requirements Landfill bans

MODELING ASSUMPTIONS

MODELING ASSUMPTIONS For cost comparisons Population of 100,000 residents Food waste o 4,000 tons per year o 30% moisture o VS/TS: 80% Financial o Capitalization: 20 year term at 4% o Byproduct value: $0 o Electricity sales: $0.10/kWh Digestion performance o Biogas production varies by technology type Collection Mode o Not modeled

VARIATIONS IN FEEDSTOCK o Pre-consumer industrial/agricultural o Post-consumer food waste o Co-collected green/yard/food o Source separated food waste o Organic fraction of Municipal Solid Waste o Fats, Oils, and Grease (FOG)

DIGESTION TECHNOLOGIES

DIGESTION TECHNOLOGIES CONSIDERED Dry Fermentation Mixed Tank Co-digestion at WWTP Covered Lagoon

DIGESTION TECHNOLOGIES PRO/CON Type of Digestion Pros Cons Dry Fermentation Mixed Tank Co-digestion at WWTP Covered Lagoon Accepts green/yard waste yard waste collection compatibility Highest VS/CH4 production Food/beverage waste compatibility Use of excess capacity Already sited Low cap and ops cost Agricultural waste compatibility Requires bulking for porosity Lower VS/CH4 production High cap and ops cost Lower range of Total Solids Requires removal of glass/metals Challenges incorporating systems, increased solids, etc. Requires large footprint Requires long HRT

DIGESTION COSTS

DRY FERMENTATION Typical Feedstock: Mostly Agricultural history in EU Stackable feedstock Batch bunker/garage HRT: 21 to 28 days Cap Cost ($M) O&M ($K) $/ton (pre-revenues) Biogas Generation (Km 3 /y) Electricity Sales ($K/y) Total System Cost ($/ton) $ 2.1 $ 82 $ 57 349 $ 66 $ 41

MIXED TANK DIGESTION Mostly Industrial/Agricultural Food/Beverage wastes, High solids but pump-able feedstock (10% to 15% ) Continuous HRT: 15 to 28 days Cap Cost ($M) O&M ($K) $/ton (pre-revenues) Biogas Generation (Km 3 /y) Electricity Sales ($K/y) Total System Cost ($/ton) $ 3.5 $ 130 $ 94 485 $ 91 $ 72

CO-DIGESTION USING WASTE WATER TREATMENT PLANTS (WWTP) Typical feedstock: Waste water (sewage) Low solids feedstock (4%) Continuous HRT: 20 to 28 days Cap Cost ($M) O&M ($K) $/ton (pre-revenues) Biogas Generation (Km 3 /y) Electricity Sales ($K/y) Total System Cost ($/ton) $ 2.8 $ 114 $ 79 456 $ 86 $ 58

COVERED LAGOON Typical feedstock: Animal manures Low solids feedstock (4%) Continuous HRT: 80 120 days Cap Cost ($M) O&M ($K) $/ton (pre-revenues) Biogas Generation (Km 3 /y) Electricity Sales ($K/y) Total System Cost ($/ton) $ 3.2 $ 80 $ 77 349 $ 66 $ 61

COST COMPARISON SUMMARY Covered Lagoon Co digestion WWTP Mixed Tank Total System Cost post revenues ($/ton) Total Cost pre revenues ($/ton) Dry Fermentation $ $20 $40 $60 $80 $100

OTHER CONSIDERATIONS

GENERATORS AND COLLECTION Variations in material quality and quantity relate to program performance o Combined or separate food and yard materials o Use of film plastic or compostable bags o Quantity of contamination need for pretreatment Programs that capture more organics tend to have higher contamination Increase participation and diversion when: o Provide BINS o Allow BAGS o Restrict garbage (Limits on quantity, Bi-weekly collection)

GENERATORS AND COLLECTIONS Collection method (automated, manual, curbside placement etc.) needs to reflect neighborhood Options to reduce cost of adding food waste collection o Weekly co-collection of garbage and organics o co-collection of garbage/organics week 1 and recyclables/organics week 2 o bi-weekly (every other week) garbage collection Typical weekly food waste collection cost ranges: o $20 to $25/HHD/annum (co-collection) to o over $35/HHD/annum (separate collection)

PRE-PROCESSING Getting to the Organics Match technology with attributes of organic stream/generator o Source control (collection) is key to minimizing contamination o Degree of contamination affects pre-processing and processing options Consider integration with existing system o co-processing with yard waste o co-processing with IC&I organics

OTHER TECHNOLOGY COSTS Key Issues Feedstock quality/contaminant level Odors and odor management Area/site size requirements Utilities: power, water usage and wastewater Potential permitting issues Proven operations on similar feedstock Ancillary costs: chemicals, effluent Maintenance, staffing, fuel, water, power requirements By-product compatibility

CONCLUSIONS

FINAL THOUGHTS No one-size/technology fits all AD is not cheap Match technology to organic stream Consider upstream issues (Collection) Consider downstream issues (Effluent, Digestate, Gas Markets) Costs vary due to economies of scale Offsets for carbon credits, low carbon fuel, etc., can reduce cost