King County & Brown Grease

1. King County & Brown Grease Local sewer agencies have a need to address restaurant grease trap waste. In response, there is the potential of a renewable energy fuel source and opportunity to invest in sustainable waste management technologies.

2. Wastewater Treatment Division (WTD) • 34 local jurisdictions feed wastewater to King County WTD’s system • 3 major treatment plants serve 1.5 million across 420 sq. miles • 600 employees manage the treatment of about 175 million gallons of sewage each day • Our challenge: integrating sustainability into urban sanitation systems

3. In Evaluation of Emerging Technologies • Level of technology development • Applicability to WTD system • Potential benefits to WTD facilities or environment • Potential impacts to WTD facilities or environment • Potential for recovery of valuable resources • Consistency with King County policies & directives

4. A Business Need for Energy Management • WTD represents 58% of all King County government’s facility energy use • Target #1: Achieve a 10% normalized net reduction in energy use • Target #2: Produce, use or procure renewable energy equal to 50% of use • Target #3: Maximize the cost-effective conversion of waste to energy 2010 Wastewater Treatment Energy Use by Type

5. WTD Already Produces 610,000 MMBtu’s of Digester Gas South Plant • Digester gas scrubbed. 20% of it used on site for process heat. 65% sold directly to PSE [85% use, 15% flared] West Point • New cogen plant expected to generate 18,000+ mega-watt hours of ‘renewable energy’ every year, nearly 1/3 of the plants yearly electricity consumption • Plant will use 60% of digester gas to produce electricity for sale to SCL – two engines, capable of producing 2.3 MW each (combined 4.6 MW installed power) • 44% of digester gas energy used on-site for process needs including raw sewage pumping [total adds to >100% as cogen process also generates all process heat required for the plant]

6. Why South Plant for Brown Grease? • Relatively easier plant access for trucks visiting brown grease receiving site - must be self serve • Centrally located in Renton • Digester capacity

7. Local Sewer Agencies’Proposed Preferred Pumper Program If PPP moves forward: • Potential for “new” brown grease coming on market • Standardization and improved record-keeping helpful • Would need public & private involvement to leverage resources/support beneficial reuse

8. 2006: Food Waste Co-Digestion Study Benefits: • Increased energy production Concerns: • Uncertain supply with private composter contracting for restaurant food waste • High onsite cost to unload and store incoming waste; screen out metals and glass; mix and grind Conclusions: • 2006 report recommended looking at liquid waste as potentially more cost-effective

9. WTD Approach to Study • Experience available: nationally, agencies/consulting firms have implemented full-scale grease co-digestion projects • Plants currently accepting brown grease by truck (partial list): Riverside, CA East Bay Municipal Utility District, CA Millbrae, CA Oxnard, CA Watsonville, CA So. Bayside Authority (Redwood City), CA Lincoln, NE Pinellas County, FL

10. 2012: Brown Grease Co-Digestion Study Q1: How much brown grease can the current wastewater processing facilities manage? Q2: How much would an appropriately-sized brown grease receiving facility cost? Q3: What are the estimated operating costs and revenues?

11. Q1: How much grease can current wastewater processing facilities manage? • Capacity of solids processing facilities (digesters, biosolids mngt., etc.) - OK • Capacity of biogas handling systems could be limited by waste gas burners - ?? • Capacity of biogas-to-energy systems - OK • Practical operational limit to daily truck deliveries onsite - maximum 10–20 trucks/day

12. Q2: How much would an appropriately-sized brown grease receiving facility cost? • Representative site selected • Identified facilities needed • Truck offloading facilities, grease receiving tanks • Screening, heating, mixing, pumping • Modular design to facilitate expansion if needed • Capital cost estimate: $2M

13. Q3: Identify estimated operating costs and revenues Cost estimates prepared for facility to manage 15,000 - 30,000 gpd (10 – 20 trucks/day) Costs • Cap’l recovery: ~$135,000/yr • O&M cost: $400,000/yr to $500,000/yr Revenues • Energy revenue: $100,000/yr to $200,000/yr • Tipping fee required to break even

14. Next Steps • Market assessment • How much brown grease is currently being collected by haulers? • Can a sufficient quantity of grease be secured to recover costs? • Is the PPP moving forward? • Further verify key grease co-digestion process assumptions • Seek grant funding

15. WTD Considerations Moving Forward • Must be cost-effective for ratepayers • Ability to help WTD meet energy targets • Need assurances that supply won’t disappear • Is this something better done by private sector? • Brown grease can create storage and pumping issues • Must be O&M cost neutral • Ensure trucks don’t create safety & security issues • Digester and scrubber capacity is not unlimited