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Giving a Crap: How a Simple Toilet and Load Cells are Tackling Global Ills

According to the World Health Organization, over 1.7 billion people worldwide do not have access to even the most basic sanitation facilities. An even greater number lack access to safely managed sanitation or sewerage systems. The ripple effect leads to some staggering statistics. Almost a million people die annually of preventable, communicable diseases, including almost a quarter of a million children under 5. About a third of the world’s school-aged children, mostly girls, miss class or drop out because of a lack of hygienic resources (a predicament that can lead to embarrassment, harassment, and threats to their safety). These and other sanitation equity-related conditions perpetuate the cycle of poverty, epidemics, and even climate change. The team at change:WATER Labs, led by CEO and inventor, Diana Yousef, hopes to address these with their innovative, waste-shrinking, waterless toilet system, the iThrone. And Tacuna Systems is proud to be part of their efforts.

The iThrone Concept

The idea behind change:WATER’s iThrone system is simple — evaporation. Human waste is mostly water. What if, instead of flushing it using valuable, drinkable water sources, it was desiccated? Could that waterless toilet promote the evaporation of its liquid content, releasing pure water molecules into the atmosphere? What if this could be done so efficiently that it would leave only a small amount of dry solids?  Perhaps these dry solids could be used for energy production, fertilizer, or other useful applications.

a conceptual diagram of the iThrone waterless toilet system that shows how a special membrane within allows pure water to evaporate
An artist rendering of the internals of the iThrone waterless toilet (Source – change:WATER)

The iThrone waterless sanitation system “does its business” exactly through this process, borrowed from the evaporation mechanism found in plants. Each self-contained unit has bags made of a special, 95% compostable micro-porous membrane that collects human waste and releases pure, molecular water, leaving behind just a small amount of residual solids. Bags that collect these solids need to be replaced only once or twice a month, the company estimates, depending on usage. The iThrone operates without any water or external power source. Instead, it derives its required energy from the collected waste itself.

Cost is another advantage of the system. Unlike other portable toilet solutions, the iThrone is cheaply and easily serviceable. Rather than having to pump liquids out of tanks, the iThrone simply requires the collection of these small, dry, compostable bags. And unlike alternatives which have to be emptied almost daily, the waste-shrinking iThrone only has be to be serviced monthly. Likewise, the iThrone is less expensive to produce than alternative waterless toilets. These lower production and maintenance price points make the system more accessible to the areas that most need it.

iThrone Live Testing Take One: Uganda

A big issue with a big idea such as this one is, of course, proving its viability. Live testing is a big part of this effort. Just before the global pandemic, the change:WATER team began its pilot test in Uganda.

The results were promising. Unlike composting toilets, the team found that the iThrone portable toilets produced little to no odor, didn’t discharge any waste onsite, and actually shrank daily waste collections significantly. They behaved as expected, turning waste into a small amount of residue. Users were thrilled with their new facilities.

However, the team encountered issues collecting measurements that would allow them to refine their design. “We had good analog data but unreliable real-time data on the amount of waste collected in the system and how fast it was evaporating,” explained Yousef. The team had added load cells (and a power source for them) to measure the waste’s mass reduction over time, but they found that the load cell quality was not up to the task. “The most critical data is minute-by-minute,” Yousef continued. “We needed to understand how the surrounding environmental conditions affect performance in real time.”

Then came the pandemic. The field deployment team actually had to be evacuated from Uganda on March 13, 2020 and, due to COVID shut-downs, the team had to put live testing in Uganda on hold.

iThrone Live Testing Take Two: Panama

While the world became consumed with managing a global virus, a Central American construction company was busy working on providing adequate housing for indigenous populations in Panama. They were looking for a no plumbing toilet. To them, the iThrone stood out as a potential solution to this daunting task.

The change:WATER team welcomed the opportunity to join this effort, but they knew there would be challenges. Unlike Uganda, the Panamanian climate is extremely humid all the time and this could affect the iThrone’s performance. They knew they needed an accurate, robust way to measure evaporation continually over time. The measuring system had to operate accurately in high humidity and have liquid ingress protection. It needed to produce a high confidence result – in other words, it needed low error and a high signal-to-noise ratio. And, it had to be affordable.

This is where Tacuna Systems entered the scene.

The Panama test requirements

For the Panama project, Yousef and her team wanted to be able to remotely monitor the collection bag’s weight to derive three vital pieces of information: (1) when the toilet was used, determined by weight increases, (2) any leaks, determined by rapid weight decreases, and (3) evaporation rates, indicated by slow and predictable weight decreases. The first two would allow the team to check for malfunctions. The third would allow them to make any design adjustments needed to suit environmental conditions. A robust system with high-quality load cells was key. But the team’s expertise was not load measurement. And as Yousef recalled, “you don’t know what you don’t know.” The design team needed help knowing where to start.

Finding a supplier who is also a partner

Not sure where to turn, the change:WATER team reached out to our chief engineer, Chris Lange, for advice. “Chris was responsive to our issues, like a partner,” said Yousef. “He was really helpful and his advice was critical to our project.” Interestingly, they came across the Tacuna Systems company website by performing a simple internet search for a particular kind of load cell.

After consulting with Lange, they settled on a design of 8 load cells per toilet, connected via a junction box, with amplifiers. To reduce load cell costs, the team chose units with an IP65 rating, adding further ingress protection in the iThrone design itself. The load cells, data acquisition system and data transport were all powered using solar generation.

iThrone in Panama: A Work in Progress

To date, the Panama project is ongoing. The builder has incorporated the iThrones in newly-built outhouses behind the principal dwellings and the change:WATER team has established their testing system. Using pilot data, the design team has made some structural improvements to their system. The modified units will be the source of further usage and performance data over the next few months. For completeness, the team also collects feedback from users to influence further design modifications.

In the future, given the promising test results, the units could be incorporated into more formal structures. Meanwhile, the change:WATER team is continuing its development efforts with important partnerships including the MIT Solve initiative and MIT D-Lab.

Solving Myriad Global Ills with Waterless Sanitation

While the innovative iThrone is still undergoing design refinements based on live test results, its promise for improving the future is great. In full production, the simple, highly portable waterless toilet will allow access to safe, inexpensive sanitation where it has not existed before. For poor, rural communities, schools in under-resourced areas, and refugee camps, the iThrone’s benefits could be life-changing. Yet even in developed areas, the iThrone could offer a far more environmentally friendly solution to off-the-grid sanitation than what is available today.

Even beyond expanding sanitation options, the change:WATER approach has many upsides. It would lessen the spread of many of the diseases borne by human waste — germs that don’t survive without water. Also, in the absence of water, bacterial methane emissions would significantly diminish, reducing greenhouse gasses from human activity. By eventually replacing other portable toilet options or even flush toilets in areas with modern plumbing, the iThrone could potentially lessen water shortages, pollution and emissions from water treatment facilities, and harmful chemical usage.

In fact, Yousef estimates that the iThrone could address nearly half or more of the 17 Sustainability Development Goals (SDG) outlined by the United Nations. From providing sanitation equity and access, reducing poverty, promoting gender equality, increasing sustainability, and reducing greenhouse gas emissions to promoting economic growth, iThrone is poised to make a significant impact on the planet.

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