Whoooooosssshhhhhh! Humans around the world use toilets six to eight times per day, accompanied by the familiar sound of the water flush. Since 40% of the world’s population remains without access to toilets, international attention on sanitation problems, hence the upcoming United Nations Water World Toilet Day on November 19. However, a new challenge has emerged: as climate change and resulting droughts threaten the world’s water supply, can we afford to keep flushing our problems away? Nonprofit RTI International has developed an incinerator toilet—entirely self-sustaining in energy efficiency—that will revolutionize water use in human waste disposal.
The world’s most terrifying problem is climate change. Water stress in lower mid-altitude arid and semi-arid regions, caused by climate change-stimulated droughts, is among climate change’s most pressing problems. The southwestern United States faces massive water shortages despite large and growing populations, presenting an intractable quandary. Should fresh water supplies be transported from elsewhere—and further drain already strained reservoirs in other locations—or should desalination be used to convert seawater, but destroying oceanic ecosystems in the process?,  Both options are extraordinarily energy and capital intensive, requiring immense upfront investment. The optimal choice is unclear, but one conclusion follows: humans must find new ways to use less water.
Empowered by a research grant from the Bill and Melinda Gates Foundation, RTI International sees opportunity in adapting to water scarcity. RTI’s toilet requires no electricity, water, or sewer connection. It works by mechanically separating solid and liquid waste and burning solid waste using a combustion unit. Thermal energy produced by combustion is then used to disinfect liquid waste using electrochemical treatment. As of October 2016, RTI is beta testing a prototype toilet in India.
Figure 1. The sustainable RTI incinerator toilet.
Figure 2. The RTI prototype in Ahmedabad, Gujarat, India.
Incinerator toilets offer significant advantages over alternative options for sustainable toilets. For example, no-flush toilets lead to sludge in sewer systems and bad odors.  Although they also require no water or electricity, they are largely limited to urinals. Freezing toilets require electricity, which limits sustainability.
Considering billions of toilets exist worldwide, even at high unit price, the Total Available Market for incinerator toilets is massive. Over 4 billion people use toilets every day, resulting in as much as 51.2 billion gallons of water used daily by toilets. Today, RTI’s incinerator toilet can be operated for less than $0.05/day in India, which is less than the approximately $0.08/day low-flush toilets currently cost in the U.S.,  However, incinerator toilets are costly relative to existing toilets—which have still not reached the entire world population—limiting the Serviceable Available Market and Serviceable Obtainable Market (SOM).
In order to address challenges associated with converting research prototypes to mass market products, RTI must focus on four tasks following successful development. First, RTI must reduce unit cost in order to maximize SOM; much future market growth is in developing economies, and the longevity of toilet product life has led to low replacement rates. Second, RTI must find manufacturing partners who can produce the toilet, including in or near international markets currently or imminently facing water scarcity, and develop a supply chain that can both meet demand and sustainably source materials. As a nonprofit, like IKEA, RTI can utilize net income to fund sales growth and further sustainability research. Third, RTI must market and sell the toilet aggressively worldwide, including by partnering with the United Nations and nongovernmental organizations already working to raise climate change and sustainability awareness. Lastly, in order to gain a toehold in the market, RTI must lobby for government, tax, and regulatory changes to incentivize incinerator toilet installation. RTI toilets offer a complete solution to a real problem, and the world must invest now or confront impossible costs later.
 World Economic Forum, Climate Adaptation in 2014: Seizing the Challenge, p. 25, http://www3.weforum.org/docs/GAC/2014/WEF_GAC_ClimateChange_AdaptationSeizingChallenge_Report_2014.pdf, accessed November 2016.
 Scientific American, “The Impacts of Relying on Desalination for Water,” https://www.scientificamerican.com/article/the-impacts-of-relying-on-desalination/, accessed November 2016.
 Roman Kilisek, “Climate Change, Desalination and the Water-Food-Energy Nexus,” Breaking Energy, January 24, 2014, http://breakingenergy.com/2014/01/24/climate-change-desalination-and-the-water-food-energy-nexus/, accessed November 2016.
 RTI International, supra note 3.
 Lauren K. Ohnesorge, “RTI Opens Indian Subsidiary, Tackles Toilets, Cancer,” Triangle Business Journal, February 24, 2016, http://www.bizjournals.com/triangle/blog/techflash/2015/02/rti-international-opens-indian-subsidiary-rtp.html, accessed November 2016.
 Phil Matier & Andy Ross, “Low-Flow Toilets Cause a Stink in SF,” San Francisco Gate, February 28, 2011, http://www.sfgate.com/bayarea/matier-ross/article/Low-flow-toilets-cause-a-stink-in-SF-2457645.php, accessed November 2016.
 Estimate assumes approximately eight daily flushes per person. Since low-flush toilets use under 1.6 gallons/flush and are now common worldwide, the 1.6 gpf figure was used to be conservative.
 Ohnesorge, supra note 12.
 Fairfax County Water Association, “Is Water Free?”, https://www.fcwa.org/story_of_water/html/costs.htm, accessed November 2016.