Source Separated Organic Materials Anaerobic Digestion Feasibility Study Prepared for Ramsey/Washington Counties Resource Recovery Project Board And the St Paul Port Authority By Foth Infrastructure & Environment

Scope v Review AD processes & current development v Examples of large scale AD plants v Option for biogas generation and use v Energy market status v Availability/composition of SSOM in metro area v Facility Design Considerations v Permitting and Environmental Considerations v Economic Analysis v Schedule

Definitions v Process to degrade organic material in the absence of oxygen. v Microorganisms transforming degradable organics into water, carbon dioxide, and methane v Degradable portion forms biogas v Non-degradable portion forms digestate

State of the Technology v Most facilities used on MSW feedstocks are located in Europe v Anaerobic digestion of MSW sources not yet common in US v Report examined process types, technology suppliers, and selected vendors v Project focused on systems at 100,000 tpy

Biogas Use Options v Direct use – typically provides best economics, requires user proximity v Electric generation – proven technology, scalable, renewable v Combined heat and power – benefits of both direct use and electricity v Fuel cells – unknown with AD of MSW or SSOM v Pipeline quality – treatment required, expensive

SSOM Supply Assessment v Notable current recovery programs: Backyard composting Food waste direct to livestock Food waste manufactured into animal feed SSOM composting v Significant amount of SSOM still disposed in the mixed MSW waste stream

Estimated SSOM and Yard Waste As Disposed Material TypeResidential (tons) Commercial (tons) TOTAL (tons) Source Separated Organic Material 189,000200,000389,000 Yard Waste (+Smaller Wood Waste) 47,00013,00060,000 TOTAL236,000213,000449,000

Facility Design Considerations v Originally intended to work with experienced system vendors to describe and develop cost estimates v Did not happen v Developed preliminary facility design assumptions and costs via building up components

Facility Design Considerations v Process Flow & Scalability v Mass Balance v Receiving & Preparation v Processing v Site Needs

Facility Design Considerations v Ideal = scalable & redundant (2 lines) v Conveyors, bag breakers, trommels, metal separation, shredder, blending tanks, digesters, gas conditioning, end use, digestate handling v Scalable – # of lines, # of digesters, etc v 21 days in digesters v Biogas yield of 400,000 to 525,000 MMBTUs per year v 165 tons per day of dewatered compost

Site Needs v 8 acres v Digesters require high soil loading support v Utilities – electricity, steam, compressed air, sewer v Site security - typical

Permitting and Environmental Considerations v No current AD facilities operating with MSW as a feedstock v Permit needs anticipated to include: EAW EIS Emissions: air, water, solids Other Federal, State/MPCA Local PUC

Economic Analysis v Capital costs System vendor response lacking Published sources Plant build up estimate v O&M costs Published Plant build up v Revenues

Economic Analysis v Capital costs – published sources Adjusting for scope, cost range is $30M to $45M for 100,000 tpy facility v Capital Cost – Plant Build Up $38,580,000 v O&M Published Sources Typical $20 to $60 per ton v O&M Plant Build Up $53/ton for direct use option $58/ton for electrical generation option

Economic Analysis v Revenues Electrical generation: >$3M/yr or $30/ton (assuming $0.06/kWh) Biogas sales: $2.28M to $4.24M/yr or $23 to $42/ton (assuming $6- $8/MMBTU) v Anticipated Tip Fees Debt Service estimated at $30 per ton Estimated Net cost per ton $55-$60

Schedule v Siting3 - 6 mo v Funding mo v Prelim engineering3 mo v Permitting mo v Construction mo v Startup/commissioning3 - 4 mo v Total42 – 57 mo