Development and Adoption of Solar-Disinfection Composting Latrines in Developing Nations

1. Development and Adoption of Solar-Disinfection Composting Latrines in Developing Nations • Craig Adams, Joe Rendall, Mario Medina, Mary Adams, Emily Robbins, Sarah Eberhart, Matt Williams • University of Kansas Presentation to University of Oklahoma International WaTER Conference October 24, 2011

2. Water Supply and Sanitation Collaborative Council (WSSCC)

3. Unicef Progress Report See unicef, Progress for Children, #5 (9/06)

4. Open Defecation • Unfortunately, very common • Dangerous with respect to spread of disease • Simply providing latrines will not change behavior

5. Azacilo, Bolivia:A Small Aymaran Village in Andes above La Paz

6. Working with Community

7. VentilatedImproved Pit (VIP) http://www.accessgambia.com/information/small/latrine-vip.gif http://tilz.tearfund.org

8. Human Composting Latrines The Humanure Handbook

9. Human Composting Latrines • Advantages over pit latrines and septic systems • Creates valuable compost • Does not promote leaching into groundwater (as can septic systems and pit latrines) • Disadvantages: • Must be operated properly (e.g., addition of grass and ash) • Key issue is achieving full disinfection of human parasites (e.g., ascaris) Prep4md.blogspot.com

10. Composting Latrines • Options • ECOSAN Toilet • Dehydration approach (www.ecocan.co.za) • Below grade • Double vault composting latrine • Solar disinfection composting latrine

11. Our Solar Composing Latrine Design

12. Disinfection Requirements Pathogen disinfection data fit from Cairncross and Feachem 2nd Ed. • Time/temp requirements for disinfection of Ascaris eggs. • Ultimate goal is to achieve complete disinfection: • in one time interval • Without internal (composting) heat being required

13. Approach to Our Solar Composting Latrine Research • Two primary heat sources • Composting heat • Best to insulate and keep all heat in • Solar heat • Best to allow as much in as possible • What is best balance, and what design achieves this? • Constraints • Local materials, building practices • Sustainable operation and maintenance • Material handling and usage • Goal • Achieve complete disinfection regardless of composting heat (so that all parts of pile are known to be disinfected). • Requires achieving critical “Time x Temperature” everywhere in pile • Improve disinfection and compost quality • Requires significant increases in temperatures ~2x side losses during day

14. OBJECTIVES • Develop and optimize solar composting latrines • Develop design criteria and options for solar compartments for various regions • Calibrate and validate the thermal models APPROACH • Phase 1: Non-insulated slab • Simulated compost (to determine worst-case temps) • What temperatures can be achieve at various depths? • What are the temperature profiles? • Phase 2: Insulated slab • Simulated compost (to determine worst-case temps) • Phase 3: Insulated and non-insulated slab • Actual compost

15. LaboratoryStudies • The lab experiment used to test different sustainable insulation materials. Heat Flux of Wood and Concrete Block Base Materials

16. Field Station Nelson Environmental Study Area – KU Experimental Field Station

17. Field Station • 10 slabs • Data • Outside parameters: • Ambient temperature (shade) • Ground temp (@ 4”) • Total solar radiation (at angle of lids) • Compartments all instrumented with: • 10 Thermocouples in soil (5 readings) • 2 Thermocouples in compartment air • Selected compartments also have • Slab temperatures • Cover interior surface temperature • Soil moisture • Additional Thermocouples • Data collection • Agilent 34980A Logger • 60 channels collected (of 120 available) at 5 min intervals • Meteorological station also on site

18. Experimental Matrix(47 permutations) • Baseline • Mounded compost pile (covered with Black & Translucent 6 mil plastic sheet) • Sides: • Single and Double Wood, • Concrete, • Single and Double ¼” PC • Covers • Single and Double 1/16” PC (corrugated) • Single and Double ¼” PC (flat) • Unpainted and Black Metal (corrugated) • 6 mil Translucent plastic sheet • White fiberglass (corrugated) • Insulation • None vs. Hay • Moisture • Dry (10%) vs. 30-50% • Internal Heat • None vs. 100 W/compartment (~ 200 W/m2)* • Interior Walls • Uncovered vs. Al-foil covered “Energy Generation in Compost” Locascio, Katinka; Wolfson, Richard

19. Thermally Inert Soil Assumption • Typical composting heat generation: 200 W/m2 (Cornell Univ.)

20. Reproducibility in Designs • Comp. 1 & 2: Straw Insulated Concrete • Comp. 5 & 6: Straw Insulated Double Wood • Comp. 4 & 7: Uninsulated Double Wood • Comp. 8 & 9: Single Sided Wood

21. Temp. Profile of Uninsulated Concrete w/ Dbl 1/16” PC Cover~28°C DAY

22. P18: Uninsulated Double Wood -Single 1/16” Clear PC Uninsulated Wood – Single 1/16” PC (DRY) Infiltration issues X Date: 8/25/2011 Max Solar Radiation: 8.01 kWhr-m2 Max ambient T: 28.2 °C (82 °F) Pathogen disinfection data fit from Cairncross and Feachem 2nd Ed. 1 yr

23. Discussion • Building materials • Insulated wood and concrete both effective. Infiltration should be prevented. • Cover Materials Double Clr PC > 6mil Plastic sheet ~ Single Clr PC > White Fiberglass > Black Metal > Metal • Moisture • Moisture required for composting • Moisture decreased temperatures by ~5C (evaporation) • Reflective interior (foil) • Increased soil temps ~3C • Clear sides • Increased solar heating • Increased solar heating may be offset by increased heat losses • May be impractical

24. Discussion • Internal heat generation highly beneficial • Infiltration and exfiltration potentially significant heat loss mechanism • Turning piles • Lower parts of pile cycled up to top of pile to be disinfected • Can not assure that parts of pile aren’t left on bottom • Requires increased handling – health implications

25. Acknowledgements • Funding – DOD ARO, Constant DP funds • Matthew Maksimowicz, Jay Bernard, Jim Weaver • Aurelien Jean • KU Exp. Field Station / NESA: Dean Kettle, Bruce Johanning • Many EWB-KU students who have contributed to building latrines working with Azacilo, Bolvia • EWB-USA • SumajHusaiand Engineers-In-Action • People of Azacilo, Bolivia

26. Questions/Comments/Discussion?