Tag Archives: composting latrines

Composting latrine vs. flush toilet: A crowd-funded study

Composting latrine vs. flush toilet: A crowd-funded study | Source: by Rob Goodier, EngineeringForChange, Aug 2014 |

Excerpt: What we know is that composting toilets have clear ecological and economical advantages over flush toilets. They turn waste into compost, and the compost can fertilize crops, completing a circle of nutrients that saves soils and saves money. They save money in the costs of sewage and in fertilizer. Importantly, they also require much less water.

In this composting pit latrine design, when waste has filled the first pit, the latrine is moved over the second pit. The first pit converts to compost and can be emptied to fertilize fields. Credit: E4C Solutions Library

In this composting pit latrine design, when waste has filled the first pit, the latrine is moved over the second pit. The first pit converts to compost and can be emptied to fertilize fields. Credit: E4C Solutions Library

Those arguments for composting latrines are well documented and have been made for years, but how do they compare in hygiene and how do they fare within the cultures of the different people who use them? Do they limit the spread of disease as well as a flush system with a septic tank or a sewer might? And do they feel as comfortable for families to use? Are they as accessible? And are they really the most sustainable solution in global sanitation?

To answer these questions, Jeff Deal the director of health studies at the water and sanitation engineering non-profit Water Missions International, is raising money through the site that crowdfunds scientific research, experiment.com. The goal is $22,000, which Water Missions International will match to pay for the study.

Pathogen destruction and solids decomposition in composting latrines

J Water Health. 2011 Mar;9(1):187-99.

Pathogen destruction and solids decomposition in composting latrines: study of fundamental mechanisms and user operation in rural Panama.

Mehl J, Kaiser J, Hurtado D, Gibson DA, Izurieta R, Mihelcic JR. SourceCivil & Environmental Engineering, Michigan Technological University, Houghton, Michigan, 49931, USA.

The relationship between temperature, high pH, desiccation, decomposition, pathogen destruction, and user operation in active double vault urine diverting (DVUD) composting latrines located in the Bocas del Toro region of Panama was assessed. Latrine samples were analyzed for temperature, pH, % moisture, carbon-to-nitrogen (C/N) ratio, and presence of specific pathogens. Surveys and visual inspections were used to verify use and type of dry material desiccant added.

Measurements supported findings that compost latrines do not reach temperatures sufficient to destroy all pathogens. pH measurements showed that many latrines were operating within the range for ideal aerobic decomposition, a pH of 7.5-8.5, but only 17% of latrines measured pH 9 or above. Almost 100% of composting latrine users added sawdust and wood ash, to lower moisture level and provide carbon for decomposition.

However, the recommended amount of desiccant added was insufficient to reduce moisture to the suggested 25% for pathogen destruction and C/N ratios remained in the range of raw human faeces. Importantly, pathogens, mainly helminths, were still present in compost stored for the 6-month contact time. The latrines have conflicting goals of pathogen destruction and aerobic decomposition. Recommendations are made regarding operation of composting latrines and disposal of composted material.