Today more than ever, politicians, engineers, researchers and citizens are actively seeking out ways to reduce our production of waste — everything from industrial byproducts, to old and outdated electronics, to human excrement.

It's no mean task, but it's one that is becoming increasingly possible, in light of recent advancements in fields ranging from chemistry to physics to microbiology. Let's explore some examples of how, by helping redefine what we regard as a resource, science is putting an end to waste. It seems only fitting, really, that we begin by examining the reinvention of the toilet.


Reinventing the Toilet

In a world where sanitation fixtures rule, the toilet is a perennial despot. With the exception of a few incremental tweaks relating to pipe and plumbing placement, the porcelain throne has remained largely unchanged for well over a century, and for good reason: it works. As explained by Rachel Swaby in Gizmodo's recent explainer on why toilets, after all these years, are still made of porcelain:

A toilet needs to do three things well, according to Brian Hedlund, Kohler's senior product manager for toilets. First, "It needs to be a flushing engine." Next, he says, "It needs to be water-proof, clean, and sanitary." Finally, explains Kohler's king of thrones, "it needs to be sturdy." Because people sit on it. Some of those people will be quite heavy. Porcelain, as it turns out, aces at all three of these requirements.

But here's the thing: eliminating our excrement, being sanitary, and bearing loads (snicker) is no longer enough; the time has come to ask even more of our toilets.

The fact of the matter is that toilets could be better, and people are pushing to see them revolutionized. Last year, Bill and Melinda Gates challenged 22 universities to come up with a toilet that not only works in parts of the world without sewers and running water, but also transforms waste into energy, nutrients, and even clean water. Since 2010, the Gates foundation alone has awarded upwards of 50 grants to "next-generation" sanitation projects.


So what are the alternatives? How do we improve upon one of the most enduring waste disposal designs of the modern era? One of the simplest (and oldest) methods, says Gretchen Vogel, in a perspective published in this week's issue of Science, is a composting toilet. In a composting toilet, bacteria are used to decompose waste, generating heat that eliminates harmful pathogens in a (surprisingly) odorless fashion. Despite their utility, however, composting toilets haven't really caught on (remember this — we'll come back to it in a second).

Other options include concepts like "Toilet 2.0," pictured here, which is designed to separate urine from feces to facilitate the recovery of nutrients and clean water.


"The bowl has two openings," reports Vogel, "one toward the front for urine and one toward the back for feces." She continues:

Separation has several advantages, says Tove Larsen of the aquatic research institute Eawag in Dübendorf, Switzerland. Urine contains fewer pathogens than feces and so needs less intensive treatment to disinfect it. Urine also contains most of the nitrogen and much of the phosphorus that could be used as fertilizers.


Reevaluating What We Regard as "Waste"

The quest for a better toilet — one that can actually generate nutrients and clean water — draws attention to what is arguably the most important theme in science's ongoing quest to make waste a thing of the past: "waste" that can be reused isn't really waste to begin with.


That might sound like an obvious deduction, but, historically, it's been a difficult one for humans to make. Sometimes this difficulty just boils down to psychological barriers; composting toilets — which are highly effective at putting human "waste" to use — have been around for decades, but have failed to really take off, due in no small part to the fact that many people find the idea of dealing with human excrement repulsive.


Even with the advent of technologies like Sweden's MullToa Waterless Composting Units — a remarkably sophisticated and, for lack of a better word, un-yucky take on the eco-friendly toilet — self-composting hasn't found a foothold. Logically, composting your own waste can make all the sense in the world; if you can't get over the fact that you're dealing with your own poo (and few people, it would seem, can), or live without the convenience of simply ditching it to the sewer system, you'll never see waste as anything but. (For a related perspective on how human psychology gets in the way of solutions to recycling waste water, see this incisive piece by Science Magazine's Greg Miller.)

Other limitations, however, are more practical in nature. Only recently, for instance, was crop waste identified as a viable starting material in the production of biofuels. This illustrates how thinking of waste as a resource just requires looking at it in a new light — like an even more creative form of dumpster diving.


Of course, sometimes there are technical or scientific hurdles that can prevent that light from being turned on in the first place. To that end, advances in chemistry and microbiology are helping people come up with new techniques for turning waste into resources — techniques that were once considered a) impossible, or b) impractical; that is, if they were ever considered at all.

"Recently developed microbial electrochemical technologies (METs) that use microorganisms to catalyze different electrochemical reactions, such as microbial fuel cells (MFCs) that generated electrical power, are promising approaches for" turning organic waste into pure energy, write environmental engineer Bruce Logan and microbial ecologist Korneel Rabaey in a review about how microorganisms will soon be used to generate everything from biofuels to valuable organic and inorganic chemicals.


A prototypical bioelectrochemical system, a.k.a. a microbial fuel cell (MFC), borrowed from Logan and Rabaey's article, illustrates the kinds of bioconversion reactions that are currently being explored. Write the authors: "Purple indicates reactions that do not directly result in current generation; green, reactions that can produce current; yellow, reactions that can occur spontaneously or can be accelerated by adding additional power; orange, power addition is required. The stoichiometry of the reactions is principally theoretical because many conversions lead to side products as well as biomass formation."

Many of these microbes are capable of producing electrical current (they're called "exoelectrogenic microorganisms," a description which somehow manages to out-awesome even the word "extremophile") by using waste biomass as a source of electrons, and are part of the burgeoning field of microbial electrochemical technologies.


According to Logan and Rabaey, organic sources of electrons "include simple molecules such as acetate, ethanol, glucose, and hydrogen gas; polymers such as polysaccharides, proteins, and cellulose;" and even "wastewaters from domestic, food processing, and animal sources." While there is still much to learn in the way of harnessing and directing the potential of these microbes, the commercial and industrial applications are boundless.

But reevaluating our conception of waste is important for reasons that extend beyond the spheres of production and manufacturing. Waste management is becoming a more and more pressing issue every year. The United States, alone, is estimated to produce on the order of 12 billion tons of waste annually. That number is growing, and while the U.S., being a developed nation, has a reasonably well-organized infrastructure in place for not only collecting waste, but looking into how it might be put to further use, such is not the case for many other regions of the world. In the years ahead, it will become increasingly important for countries — including the U.S. — to participate in the search for waste management methods that can make that which seems weathered and depleted new again.


As they say in England: "Where there's muck, there's brass." In the future, we'll look to science as the driving force behind this crucial conversion.

MFC diagram via Logan and Rabaey; Images via Shutterstock

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