| Summary: | The absence of sewers and roads at backcountry sites makes the management of human
excreta offensive, intensive, and expensive. Proper management is essential in order to
prevent deleterious pathogen and nutrient discharge. The dearth of resources, vague
certification standards, absence of monitoring, and erroneous popular perception have caused
misapplication of systems and mismanagement of end products. Elevated environmental
impacts, human health risks, and management costs have resulted.
The diversion of urine from urinals and by urine diversion seats significantly reduced the
mass of helicopter extracted excrement. However, until a more robust urine diversion system
is developed that does not clog, only urine from urinals should be diverted.
Composting toilets failed to produce safe, stable, and mature end-product at all sites surveyed.
They should be re-named sawdust toilets, following European nomenclature, to avoid further
confusion. Performance was dramatically improved with urine diversion, elimination of
bulking agent, and optimization for vermicomposting. Despite improving mineralization and
reduction of volatile solids, operating costs, exposure risk, and E. coli, Eisenia fetida
earthworms did not reduce Ascaris suum ova concentration or viability. Vermicomposting
toilets, unlikely to produce residuals approved for unrestricted discharge, should be designed
to minimize waste, costs, hazards, and environmental impacts. This approach is seemingly
opposite from sawdust toilets, which at considerable cost, strive against unfavorable
biochemistry and thermodynamics to produce ‘compost’ for onsite disposal despite
precautionary federal regulations.
Solvita® test paddles, useful in the assessment of end-product, could be used with
vermicomposting toilets, to ensure low ammonia is present in feedstock (values 4-5) and to
ensure stability (values 7-8) prior to disposal. Pit toilets, commonly excavated to depths greater than seasonal high ground water, carried the
greatest risk of pollution. These were conceptually redesigned to prevent disease
transmission and treat nutrients with septic fields. In order to reduce the risks of
eutrophication and ammonia toxicity, fields should: be oversized by at least a factor of 10
based on daily urine output; maximize the depth of unsaturated soil with curtain drains where
necessary; lie >60m from surface water; and where appropriate use natural wetlands such as
moist, acidic, productive and phenotypically plastic graminoid meadows.
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