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Waste Not, Want Not


Are Americans Ready for New Sanitation Technology?


Two million dollars: That’s one response Alison Wood received in a survey of homeowners who were asked how much their town would have to offer for them to install a composting toilet in their home. “They couldn’t pay me enough,” said another. But short of every town forking over $2 million in incentives to each resident, what does it take to change someone’s mind? An assistant professor of environmental engineering, Wood says that’s a big, messy question, but the answer has to do with the way that people interact with technology—or, more specifically, the disconnects between technologies and what people need from them. 

Wood conducted a case study of Cape Cod, where many communities rely on septic systems, a common solution in low-density neighborhoods because of their relative low cost to install. But these aging systems release wastewater directly into the environment with relatively little treatment, and while nitrogen is necessary for plant and animal life, too much of it can cause eutrophication. When that happens, an oversupply of nutrients in the water causes the growth of algae, which uses up the oxygen supply in the water that would otherwise support fish. Coastal waters around the lower Cape are now experiencing the effects of nitrogen pollution, in part because of the area’s reliance on aging septic systems. As a result, the EPA mandated that the communities make improvements—which smells like an opportunity to Wood, who joined the Olin faculty this fall.

She similarly studied Pittsburgh, a city that went through the trouble and expense of installing a combined sewer system for its high-density population. But when a big storm blusters through town and the sewers overflow, sewage is released directly into the local water body. The result is downstream environmental impacts somewhat similar to Cape Cod’s septic problem, but a very different population profile, Wood says.

“Both of these systems—septic and sewer—have various problems associated with them,” Wood says. Sewer infrastructure is designed for a lifespan of 50 years, but many of our systems have been in place for much longer than that, she says. “Replacing them is extremely expensive and disruptive, so rather than letting our infrastructure crumble or just blindly replacing it, I think now is a great time to say: Let’s see if there’s a better way. My hope is that this moment in time is an opportunity,” Wood says.

The Cape Cod communities considered a variety of solutions, from septic systems with more advanced on-site treatment systems, to more middleground technologies, such as an anaerobic digester. “At the far end of the spectrum are options like composting toilets and urine diversion toilets, which are becoming more popular. At least in research,” Wood clarifies. “I’m not sure they’re popular in [household] installations.”

Quite the contrary, at least so far. From an environmental perspective, these technologies offer huge value propositions, such as reducing water usage and wastewater treatment, and when you consider the cost picture the way a municipality would, the results are quite clear: “Doing the cost calculations the way they would, using certain kinds of interest rates based on market rates and based on very specific calculations of trade-offs over time, then we find that composting and urine-diversion toilets look like a great option,” Wood says.

Human beings are exponentially more complex than a balance sheet, of course. In her research on incentives, Wood found that the results are highly situational, with significant differences between Cape Cod and Pittsburgh due to their population differences, existing infrastructure, and income levels, among other factors. As an example: “People with lower household incomes require higher incentives in order to be convinced [to install a composting toilet], because money now matters more to them than money in the future,” she says. 

Financial considerations are among the reasons that people aren’t ready to adopt these technologies, but cultural and societal influences exert a strong force, as well, she says. “Part of what we want to do is step back and think about what is the bigger problem we need to solve: Is it to design a better toilet, or to redesign the whole sanitation system,” she says. “What we really need is to have mechanical engineers, civil engineers, electrical engineers working with sociologists and economists and psychologists. Because these problems touch on every aspect of human life.”

And that’s one of the lessons Wood hopes to reinforce with her students at Olin: to always remember the humans at the center of this engineering problem.