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Climate change mitigation potential in sanitation via off-site composting of human waste

Nature Climate Change volume 10, pages 545–549 (2020)Cite this article

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Abstract

Approximately 4.5 billion people lack access to safely managed sanitation globally, and 1 billion live in slums, often relying on anaerobic waste containment in pit latrines. Providing access to safely managed sanitation may lead to reduced GHG emissions and thus simultaneously address both Sustainable Development Goals. Here we measure cumulative GHG emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) during the off-site composting of human waste to estimate scalable emission factors. We find that CH4 emission factors are one to two orders of magnitude smaller than IPCC values for other excreta collection, treatment and disposal processes. After accounting for GHG emissions throughout the sanitation cycle, including transport, urine and compost end-use, the climate change mitigation potential is 126 kg of CO2-equivalent per capita per year for slum inhabitants. If scaled to global slum populations, composting could mitigate 3.97 Tg CH4 yr−1, representing 13-44% of sanitation sector CH4 emissions.

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Fig. 1: Competing linear and circular models for sanitation and the associated environmental interactions from local to global scales.
Fig. 2: GHG emission rate dynamics during three stages of thermophilic composting.
Fig. 3: GHG emission rates during paired-pile management experiments.
Fig. 4: Local- to global-scale climate change mitigation potentials at different levels of waste diversion to composting.

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Data availability

The datasets generated and/or analysed during the current study are available from the corresponding author on reasonable request. Source Data for Figs. 2 and 3 are provided with the paper.

Code availability

The code for the figures and analysis in the current study are available from the corresponding author on reasonable request.

References

  1. Rose, C., Parker, A., Jefferson, B. & Cartmell, E. The characterization of feces and urine: a review of the literature to inform advanced treatment technology. Crit. Rev. Environ. Sci. Technol. 45, 1827–1879 (2015).

    Article  CAS  Google Scholar 

  2. Berendes, D. M., Yang, P. J., Lai, A., Hu, D. & Brown, J. Estimation of global recoverable human and animal faecal biomass. Nat. Sustain. 1, 679–685 (2018).

    Article  Google Scholar 

  3. Graham, J. P. & Polizzotto, M. L. Pit latrines and their impacts on groundwater quality: a systematic review. Environ. Health Perspect. 121, 521–530 (2013).

    Article  Google Scholar 

  4. World Health Statistics 2018: Monitoring Health for the SDGs, Sustainable Development Goals (WHO, 2018).

  5. The Sustainable Development Goals Report 2019 (United Nations, 2019); https://doi.org/10.18356/55eb9109-en

  6. Zhenmin, L. & Espinosa, P. Tackling climate change to accelerate sustainable development. Nat. Clim. Change 9, 493–496 (2019).

    Article  Google Scholar 

  7. Kulak, M., Shah, N., Sawant, N., Unger, N. & King, H. Technology choices in scaling up sanitation can significantly affect greenhouse gas emissions and the fertiliser gap in India. J. Water Sanit. Hyg. Dev. 7, 466–476 (2017).

    Article  Google Scholar 

  8. Reid, M. C., Guan, K., Wagner, F. & Mauzerall, D. L. Global methane emissions from pit latrines. Environ. Sci. Technol. 48, 8727–8734 (2014).

    Article  CAS  Google Scholar 

  9. Ryals, R., McNicol, G., Porder, S. & Kramer, S. Greenhouse gas fluxes from human waste management pathways in Haiti. J. Clean. Prod. 226, 106–113 (2019).

    Article  CAS  Google Scholar 

  10. Haug, R. T. in The Practical Handbook of Compost Engineering Vol. 1 Ch. 1 (Routledge, 2018).

  11. Saunois, M. et al. The global methane budget 2000–2012. Earth Syst. Sci. Data 8, 697–751 (2016).

    Article  Google Scholar 

  12. van Eekert, M. H. A. et al. Anaerobic digestion is the dominant pathway for pit latrine decomposition and is limited by intrinsic factors. Water Sci. Technol. 79, 2242–2250 (2019).

    Article  CAS  Google Scholar 

  13. Syakila, A. & Kroeze, C. The global nitrous oxide budget revisited. Greenh. Gas Meas. Manage. 1, 17–26 (2011).

    Article  CAS  Google Scholar 

  14. Tian, H. et al. Global soil nitrous oxide emissions since the preindustrial era estimated by an ensemble of terrestrial biosphere models: magnitude, attribution, and uncertainty. Glob. Change Biol. 25, 640–659 (2019).

    Article  Google Scholar 

  15. Höglund-Isaksson, L. Global anthropogenic methane emissions 2005–2030: technical mitigation potentials and costs. Atmos. Chem. Phys. 12, 9079–9096 (2012).

    Article  Google Scholar 

  16. Brink, S. et al. Methane Mitigation Opportunities in China: The Woodrow Wilson School’s Graduate Policy Workshop (Princeton Univ., 2013).

  17. IPCC 2006 IPCC Guidelines for National Greenhouse Gas Inventories (eds Eggleston, H. S. et al.) (IGES, 2006).

  18. Preneta, N., Kramer, S., Magloire, B. & Noel, J. M. Thermophilic co-composting of human wastes in Haiti. J. Water Sanit. Hyg. Dev. 3, 649–654 (2013).

    Article  Google Scholar 

  19. Heijnen, M., Rosa, G., Fuller, J., Eisenberg, J. N. S. & Clasen, T. The geographic and demographic scope of shared sanitation: an analysis of national survey data from low- and middle-income countries. Trop. Med. Int. Health 19, 1334–1345 (2014).

    Article  Google Scholar 

  20. Berendes, D., Levy, K., Knee, J., Handzel, T. & Hill, V. R. Ascaris and Escherichia coli inactivation in an ecological sanitation system in Port-au-Prince, Haiti. PLoS ONE 10, 1–14 (2015).

    Article  Google Scholar 

  21. Piceno, Y. M. et al. Bacterial community structure transformed after thermophilically composting human waste in Haiti. PLoS ONE 12, 1–30 (2017).

    Article  Google Scholar 

  22. Moya, B., Parker, A., Sakrabani, R. & Mesa, B. Evaluating the efficacy of fertilisers derived from human excreta in agriculture and their perception in Antananarivo, Madagascar. Waste Biomass Valorization 10, 941–952 (2019).

    Article  CAS  Google Scholar 

  23. Pardo, G., Moral, R., Aguilera, E. & del Prado, A. Gaseous emissions from management of solid waste: a systematic review. Glob. Change Biol. 21, 1313–1327 (2015).

    Article  Google Scholar 

  24. Powelson, D. K., Chanton, J., Abichou, T. & Morales, J. Methane oxidation in water-spreading and compost biofilters. Waste Manage. Res. 24, 528–536 (2006).

    Article  CAS  Google Scholar 

  25. Vergara, S. E. & Silver, W. L. Greenhouse gas emissions from windrow composting of organic wastes: patterns and emissions factors. Environ. Res. Lett. 14, 124027 (2019).

    Article  Google Scholar 

  26. Langergraber, G. & Muellegger, E. Ecological sanitation—a way to solve global sanitation problems? Environ. Int. 31, 433–444 (2005).

    Article  CAS  Google Scholar 

  27. Trimmer, J. T., Miller, D. C. & Guest, J. S. Resource recovery from sanitation to enhance ecosystem services. Nat. Sustain. 2, 681–690 (2019).

    Article  Google Scholar 

  28. Galatowitsch, S. M. Carbon offsets as ecological restorations. Restor. Ecol. 17, 563–570 (2009).

    Article  Google Scholar 

  29. Schlesinger, W. & Bernhardt, E. S. Biogeochemistry: An Analysis of Global Change 419–444 (Academic, 2013).

  30. Black, M. & Fawcett, B. The Last Taboo: Opening the Door on the Global Sanitation Crisis (Cromwell, 2008).

  31. 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories (eds Calvo Buendia, E. et al.) (IPCC, 2019).

  32. Population Totale, de 18 Ans et Plus Menages et Densites Estimes en 2015 [Total Population, 18 Years and Older Households and Estimated Densities in 2015] (ISHI, 2015); http://www.ihsi.ht/pdf/projection/Estimat_PopTotal_18ans_Menag2015.pdf

  33. Luquero, F. J. et al. Mortality rates during cholera epidemic, Haiti, 2010–2011. Emerg. Infect. Dis. 22, 410–416 (2016).

    Article  CAS  Google Scholar 

  34. Pinheiro, J., Bates, D., DebRoy, S., Sarkar, D. & R Core Team nlme: linear and nonlinear mixed effects models. R package v.3.1-141 https://CRAN.R-project.org/package=nlme (2019).

  35. R: A Language and Environment for Statistical Computing v.3.5.2 (R Core Team, 2018).

  36. Dubber, D. & Gray, N. F. Replacement of chemical oxygen demand (COD) with total organic carbon (TOC) for monitoring wastewater treatment performance to minimize disposal of toxic analytical waste. J. Environ. Sci. Health A 45, 1595–1600 (2010).

    Article  CAS  Google Scholar 

  37. Cao, Y. et al. Mitigation of ammonia, nitrous oxide and methane emissions during solid waste composting with different additives: a meta-analysis. J. Clean. Prod. 235, 626–635 (2019).

    Article  CAS  Google Scholar 

  38. Mihelcic, J. R., Fry, L. M. & Shaw, R. Global potential of phosphorus recovery from human urine and feces. Chemosphere 84, 832–839 (2011).

    Article  CAS  Google Scholar 

  39. Ryals, R., Kaiser, M., Torn, M. S., Berhe, A. A. & Silver, W. L. Impacts of organic matter amendments on carbon and nitrogen dynamics in grassland soils. Soil Biol. Biochem. 68, 52–61 (2014).

    Article  CAS  Google Scholar 

  40. Ryals, R. & Silver, W. L. Effects of organic matter amendments on net primary productivity and greenhouse gas emissions in annual grasslands. Ecol. Appl. 23, 46–59 (2013).

    Article  Google Scholar 

  41. Bargout, R. N. & Raizada, M. N. Soil nutrient management in Haiti, pre-Columbus to the present day: lessons for future agricultural interventions. Agric. Food Secur. 2, 1–20 (2013).

    Article  Google Scholar 

  42. Myhre, G. et al. in Climate Change 2013: The Physical Science Basis (eds. Stocker, T. F. et al.) Ch. 8 (IPCC, Cambridge Univ. Press, 2013).

  43. Neubauer, S. C. & Megonigal, J. P. Moving beyond global warming potentials to quantify the climatic role of ecosystems. Ecosystems 18, 1000–1013 (2015).

    Article  Google Scholar 

  44. FAOSTAT Statistical Database (FAO, 2019); http://faostat.fao.org/

  45. Peal, A., Evans, B., Blackett, I., Hawkins, P. & Heymans, C. Fecal sludge management (FSM): analytical tools for assessing FSM in cities. J. Water Sanit. Hyg. De. 4, 371–383 (2014).

    Article  Google Scholar 

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Acknowledgements

This work was supported by the Department of Natural Resources and Environmental Management at the University of Hawaii at Mānoa, the Department of Life and Environmental Sciences and the Blum Center at the University of California, Merced, and a donation from J. Wick and P. Rathmann. We thank the staff and interns at Sustainable Organic Integrated Livelihoods in Cap-Haïtien, Haiti, for their assistance with coordinating travel and experimental logistics. We also thank S. Crow, J. Wells and S. Hart for access to a gas chromatograph, K. Porterfield for laboratory assistance and J. Bravo for graphic design.

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Authors and Affiliations

  1. Department of Natural Resources and Environmental Management, University of Hawai’i at Mānoa, Honolulu, HI, USA

    Gavin McNicol & Rebecca Ryals

  2. Sustainable Organic Integrated Livelihoods, Cap-Haïtien, Haiti

    Julie Jeliazovski, Junior Jules François & Sasha Kramer

  3. L’Université Antènor Firmin, Cap-Haïtien, Haiti

    Junior Jules François

  4. Department of Life and Environmental Sciences, School of Natural Sciences, University of California, Merced, Merced, CA, USA

    Rebecca Ryals

  5. Department of Earth System Science, Stanford University, Stanford, CA, USA

    Gavin McNicol

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Contributions

G.M. and R.R. designed the study and wrote the manuscript. J.J. assisted with the sample collection and site logistics and contributed to the manuscript writing. J.J.F. contributed to the site logistics and organized the sample collection. S.K. contributed to the study design and manuscript writing.

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Correspondence to Gavin McNicol.

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The authors declare no competing interests.

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Peer review information Nature Climate Change thanks Mathew Reid, Guillermo Pardo and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–6 and Tables 1–3.

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McNicol, G., Jeliazovski, J., François, J.J. et al. Climate change mitigation potential in sanitation via off-site composting of human waste. Nat. Clim. Chang. 10, 545–549 (2020). https://doi.org/10.1038/s41558-020-0782-4

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