Pit Latrine Emptying and Dehydration Technology

A portable toilet
Opportunity

Available for Licensing
TRL: 3

IP Status

PCT Patent

Inventors

John Mizia

Morgan DeFoort

Reference No: 2020-093
Licensing Manager

Steve Foster
Steve.Foster@colostate.edu
970-491-7100

At a Glance

Researchers at the Advanced Biomass Combustion Lab and the Rapid Prototyping Lab at CSU have designed a simple yet effective method for drying wet fecal sludge in a low energy consumption process that relies on ambient drying and physical capture.  This technology can be used in off-grid sanitation devices, providing an energy-neutral solution to the problem of transport and remediation of pit latrine waste material.

 

Background

Sanitation remains a large hurdle in remote, rural, or developing communities. Worldwide, 2.5 billion people lack adequate sanitation facilities. Pit latrines are commonly used in areas that lack access to the large infrastructure needed for effective sanitation but are difficult to maintain due to moisture content of fecal matter. Dry fecal biomass contains energy on par with wood pellets, but that energy content is reduced by as much as 10 times when the biomass is wet. Furthermore, the amount of energy present in wet fecal material is less than the amount of energy required to evaporate all moisture present. 

Overview

Researchers have developed an energy efficient system to dry the fecal matter for subsequent downstream energy capture. The prototype dehydration technology is a chain that increases the surface area of the fecal matter, thus reducing the moisture content.

Bentonite clay was used in as an experimental surrogate for wet fecal sludge due to its similar physical properties and its incredible ability to absorb and hold a large amount of water.  As shown in Figure 1, below, while heated and forced air dried the clay the quickest, the outdoor test showed the second fastest drying. These data sets reinforce the theory that a relatively low velocity air flow and small temperature gradients are effective means to dehydrate human waste.

A graph of drying times in different conditions

 
Figure 1. summarizes the drying of bentonite clay (proxy for fecal matter) for the different test conditions, including air at different temperatures and flow rates being passed over the chain from a lower inlet tube. 
Benefits
  • Energy neutral system for dehydration of fecal matter
  • Ease of containment and transport of pit latrines
  • Enhanced safety and sanitation of pit latrines
  • Dry fecal matter produced for combustion and safe, sustainable energy production
  • Simple design allows for ease of integration, scale up, and scale down for multiple sizes
Applications
  • Pit latrines in rural or remote areas, such as outdoor recreation, military bases, and construction sites
  • Pit latrines in developing countries

Last updated: November 2022