Pieces of a puzzleThere are a number of other techniques being explored and being tested. They include the use nanomaterials to separate usable water from fecal sludge and thicken the feces for further treatment; electrochemistry to break down fecal solids into fertilizer and sanitize the water to be reused for flushing or irrigation; and hydrothermal carbonization, which converts fecal sludge into an aqueous suspension of charlike material that is safe to handle and easily separated from the liquid phase.Another BMGF-funded device is the omni-processor, a wastewater treatment plant device that treats a community’s waste to a safe end product at little to no energy cost and creates safe drinking water that’s good enough for Bill Gates to drink.While early-stage toilet technologies may eventually provide sustainable sanitation for many communities, the solution to the world’s toilet problem has no single solution. Approaches by the private sector and those promoted by universities and foundations around the world are all pieces to the puzzle.Despite the basic facts of life that we all need to rid our bodies of waste, this is not an easy problem to solve, and we have not evolved quickly enough to keep up with our own poop. While demand must originate from local communities, innovations in technology will keep us imagining what the possibilities are, and if we can meet the UN’s SDGs, then maybe everyone can enjoy a little “me time” in the bathroom. Karl Linden is a professor of environmental engineering and the Mortensen Professor in Sustainable Development at the University of Colorado. This post originally appeared at The Conversation. RELATED ARTICLES Does a Composting Toilet Stink Up Your House?Do Low-Flow Toilets Really Work?Collection and Use of Urine Niagara’s Innovative 0.8 gpf “Vacuum-Assist” Stealth ToiletCan Switching to a Dual-Flush Toilet Save Heat?Q&A: Composting toilet in a Passive House? Sustainable sanitation technologiesSanitation systems protect human health by providing facilities and services for the collection and disposal of human urine and feces, ensuring a clean environment and breaking the cycle of disease. In order to be sustainable, sanitation technologies must be economically viable, socially acceptable, and environmentally sound.Economic viability ensures that a sanitation system can be built, operated, and maintained without outside subsidies. Social acceptability determines adoption and proper operation and maintenance. Environmental sustainability refers to the technology’s ability to reduce harmful pollution, use limited resources (water, land, energy), and recover resources contained in human waste.Sanitation technologies include anything from pit latrines to flush toilets connected to septic or sewer systems. But in many cases, existing systems have technical or operational problems.Pit latrines are socially unacceptable due to odors, and they are environmentally unsustainable since they only collect waste and do not treat it. Flush toilets connected to septic tanks or sewers must not only transmit the waste away but also treat it in centralized facilities. That requires major infrastructure, which uses precious water resources and is not possible in areas that need sanitation the most. Construction, operation, and maintenance of sewer infrastructure and treatment plants represent prohibitive costs for many parts of the developing world.What, then, is a better alternative?The world needs sanitation systems that are socially acceptable, reduce water consumption, take advantage of renewable energy, operate off-grid with little maintenance, and harvest useful products from human waste. The introduction of sustainable sanitation technology would result in greatly improved health, a cleaner environment, and energy conservation for both the developing and developed world. The United Nations Millennium Development Goals (MDGs), a 25-year effort that wrapped up in 2015, aimed to “halve, by 2015, the proportion of the population without sustainable access to safe drinking water and basic sanitation.” While the goals for “access” to safe drinking water have been met, the UN revealed that 1.8 billion people still use drinking water that is fecally contaminated, connecting the dots between lack of adequate sanitation and contamination of drinking water.Since the MDGs have ended, the world is now striving toward the Sustainable Development Goals (SDGs), a 15-year effort to achieve universal and equitable access to safe drinking water and sanitation.How can we achieve safe sanitation? One way is through innovation. How is it possible that 2.4 billion people lack access to improved sanitation facilities in 2015?While many westerners use their bathroom time as “me time,“ 40% of the world’s population may be pooping outdoors, in an unsanitary latrine, or in a plastic bag and launching flying toilets to dispose of their waste.The environmental impact of the worldwide sanitation situation cannot be underestimated. Not only do the unsanitary conditions and noxious odors of many latrines pose a health hazard for fecal-transmitted diseases, but in many cases the fecal matter ends up in the environment, untreated.Recent analysis by the World Bank reported that in a study of 12 cities, an average of 69% of the fecal sludge was released untreated into the environment – that is, only 31% was safely treated. In places like Dhaka, Bangladesh, only 2% of the fecal sludge is safely handled, while 98% is dangerously released into the environment. Toilet techIn parallel with efforts to change the face of conventional latrines, there is a wide effort underway to completely rethink what a toilet is and how we can recover the value in waste.The Bill & Melinda Gates Foundation (BMGF) in 2011 launched the Reinvent the Toilet Challenge and funded 16 teams around the world to dream big and re-create the toilet paradigm. (The BMGF is a funder of The Conversation Media Group.) Clearly, business as usual is not working, and given society’s experience in other sectors, why not develop “leapfrog” technologies that leave our 20th-century toilet behind?While technology is not the single solution to the worldwide sanitation crisis, it does have the potential to reshape the landscape and create new ways to do your business.The 21st-century toilet must provide a safe and hygienic environment, effectively treat the waste for safe handling, and recover resources embedded in the waste. It should also do all this while using no water resources or electrical energy.To meet this challenge, our group at the University of Colorado Boulder developed the Sol-Char Toilet, which uses concentrated solar energy to destroy the pathogens in fecal waste and transform the waste into biochar, similar to charcoal made from plants and other organic materials. Biochar is a valuable, safe-to-handle product that can serve as an agricultural amendment or be made into a char-fuel briquette with similar heating efficiency to commercial charcoal. This household toilet prototype is being redesigned into a system that can serve multiple houses in a community setting. Turning waste into valuable productThis need for better sanitation technologies has spawned a wave of innovations in toilet technologies, driven by the private sector, public sector, and foundations.Solutions making headway range from adapting and improving on the current paradigm of pit latrines to development of novel devices and approaches.Businesses such as Sanergy profit from providing clean toilet services and the collection and recovery of fecal waste. They provide the toilets, keep them clean, haul the fecal waste, treat and then reclaim the waste resources for reuse in agriculture. Using a franchise approach, their waste haulers safely compost large volumes of fecal sludge to make and sell valuable fertilizer. The Sanergy model can reach deep into informal settlements by using human labor to access and haul waste in areas which trucks cannot access.Another social enterprise, Sanivation, has a similar collection model to Sanergy but turns fecal waste into a fuel through a briquetting process. Their approach is to install low-infrastructure mobile toilets that can be deployed in urban communities and refugee camp settings. After collection, the waste is treated using solar energy. This solar-dried waste is then combined with a binder and made into fuel briquettes that can be sold as a replacement for wood, coal, and other sources.