Chalida U-tapao Steven A. Gabriel, Christopher Peot and Mark Ramirez

1. Identification of optimal strategies for energy management and reducing carbon dioxide emission at the Blue Plains Advanced Wastewater Treatment Plant (AWTP) Chalida U-tapao Steven A. Gabriel, Christopher Peot and Mark Ramirez Dept. of Civil & Env. Engineering, University of Maryland, College Park, Maryland District of Columbia Water and Sewer Authority, Washington DC 13 November 2009

2. Outline • Overview of energy, wastewater treatment • process and objective of this research • Flowchart of modeling decisions/processes • (the Blue Plains AWTP is case study) • Ongoing work

3. U.S. Primary Energy Overview • Imports fill the gap between U.S. energy use and production • Petroleum is the major imported fuel (Source: EIA, Energy perspective , June 2009)

4. U.S. Energy Consumption by Energy Source, 2008 • More renewable energy will decrease imported petroleum, coal and natural gas • Many renewable energy sources can be selected (Source: EIA, Renewable Energy Consumption and Electricity 2008 Statistics)

5. Wastewater Treatment Process • Contaminated substances are separated in solid form • Almost all solids are biomass (Source: DC Water and Sewer Authority)

6. Biosolids is a Significant Renewable Energy Source • Biosolids is biomass that is renewable energy source (Source: DC Water and Sewer Authority)

7. A Huge Plant Such as The Blue Plains AWTP Has Great Potential to Produce Renewable Energy (Source: DC Water and Sewer Authority)

8. Objectives of this research • Find optimal strategies for energy management • Use energy sources that can reduce the carbon footprint at the Blue Plains AWTP

9. Flowchart SEWAGE Investment $ Operations/Investments PB=% of sewage to be converted to biosolids $ $ IWASA WASA Operations PE,W=% of power from methane to be used at WASA $ Iwind Isolar Idigester PG,W=% of methane to be used at WASA 1-PB PB 1-PG,W Biosolids Methane Outside sales transp. indust. Biogas Other clean energy wind, solar, etc PG,W Use at WASA Electricity Land application natural gas grid/market 1- PE,W PE,W Outside sales carbon allowance market Use at WASA electric power grid/market

10. The Blue Plains AWTP operating process 330 MGD 736,087 kWH/day GHG (CO2) GHG (CO2 CH4 ,N2O) GHG (CO2) Odor Biosolids 1,163 tons/day (Source: Gabriel, S.A., et al., Statistical Modeling to Forecast Odor Levels of Biosolids Applied to Reuse Sites. Journal of Environmental Engineering, 2006).

11. Average 1,163 tons per day

12. Average 239 tons per day

13. The Anaerobic Biodegradation Production Process Active biomass + C-substance CH4 + CO2 + stabilized biomass + H2O Biogas composition Methane gas 55-65% Carbon dioxide 30-40% Water vapor, traces of H2S and H2 0-5% (Source: Appels, L., et al., Principles and potential of the anaerobic digestion of waste-activated sludge).

14. The Relation Between Biogas Production and Retention Time ODS : organic dry solids of the sludge (wt%) (Source: Appels, L., et al., Principles and potential of the anaerobic digestion of waste-activated sludge). Biogas is 0.4 x 239 x 1000 = 95.6 x 103 cubic meters per day Methane is 60 % = 57.3 x 103 cubic meters per day Carbon dioxide is 35% = 33.5 x 103 cubic meters per day

15. Historic Daily Power Consumption Data for The Blue Plains AWTP Average 2008 = 736 x 103 kilowatt hours per day

16. From Methane Gas to Electricity • Methane 1 ft3 = 1,028 BTU • 3,412 BTU methane = 1 kWH • Blue Plains AWTP will have almost 534 x 103kilowatt hours per day from methane gas ( Source: http://tonto.eia.doe.gov/kids/goodstuff.cfm?page=about_energy_conversion_calculator-basics) • Plant needs 736 x 103 kilowatt hours per day (not enough)

17. Other Renewable Options are at Blue Plains • Methane from biosolids generate electricity that is not enough for the Blue Plains AWTP operations (Need 736 x 103 kilowatt hours per day but it is able to generate only 534 x 103 kilowatt hours per day ) • Other options more than methane or electricity is to invest in renewable energy source (e.g., wind, solar, hydropower and geothermal)

18. Prediction of Carbon Dioxide (CO2) Credits • 0.8 tons CO2 credits per dry ton biosolids (Brown, S., H. Gough, and et al., Green Aspects of Biosolids Processing and Use 2009) • 0.8 x 1,163 tons biosolids per day • CO2 credits are 930 tons per day

19. Financial Benefit from CO2 Credits Transaction Volume and Value, Global Carbon Market, 2008 108.9/27.4 = $ 3.94 per ton CO2 Source: Ecosystem Marketplace, New Carbon Finance • The Blue Plains AWTP • $3.94 x 930 tons per day = $ 3,692 per day • = $1.3 million per year

20. Summary • Biosolids from the Blue Plains AWTP is a significant renewable energy source. It has a high efficiency to generate methane and electricity Methane is 57.4x103 cubic meters per day Electricity is 534.5x103kilowatt hours per day • CO2 credits is 930tons CO2 per day • Financial benefit from CO2 credits is about $ 3,692 per day • Methane for transportation grid • Selling Electricity to Grid Electric Power

21. Ongoing Work • Build a multiobjective optimization model in order to make best decisions to: • minimize DCWASA’s CO2 footprint • minimize energy usage • minimize costs • other considerations (as appropriate) • Will consider both investment decisions as well as operational ones