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Scientists predict faeces recycling as part of an extreme economy

Imagine that you are dining on a ceramic plate and drinking water from a plastic cup while sitting in a brick house — a seemingly common scenario, except that your plate, cup, and home are made in part from recycled faeces.

Now imagine using your poop to propel a spaceship to Mars and shield it from cosmic radiation along the way.

In my next book, Flush: The Remarkable Science of an Improvable Treasure, I describe how the misunderstood by-product of our daily lives is a vastly underappreciated natural resource.

Poop has power: as a medicine, fertilizer, biomethane gas and reuse water, among other proven applications.

But this is just scratching the surface of our excremental potential; its biological, chemical and physical attributes have inspired even broader and more forward-looking brainstorming about what else we can create from our waste.

A hidden asset for space exploration

The extreme limits of space, in particular, have driven scientific innovation towards a more circular economy where nothing is wasted. That invention, in turn, depended on a universal truth: everyone has to go someday, even astronauts.

Among NASA’s poop-themed crowdsourcing challenges, a recent competition sought new design ideas for a lunar toilet, while another — the Waste to Base Materials Challenge: Sustainable Reprocessing in Space — asked the public to help debate how to repurpose space. garbage from both astronauts and bodily waste.

It’s all about self-sufficient flight: Steve Sepka, project manager for the Waste Compaction and Processing System at NASA’s Ames Research Center in California, said one goal is to create polymers from organic waste that can be used ​in propulsion systems for spaceflight — as well as planetary surface missions.

For a return flight from Mars, the space agency initially sought to produce fuel from red planet resources, Sepka wrote in an email. But NASA is now considering whether repurposing the crew’s own waste could help astronauts, well, take off.

As for protecting crew from dangerously high levels of radiation in outer space during an extended voyage, scientists have suggested that the density of molecules in wastewater could offer a solution.

A multi-purpose proposal by NASA called “Water Walls Architecture” envisions a space capsule lined with multiple water compartments, as well as sterile waste implanted as radiation shielding.

The primary ingredient in urine and faeces is water, and the hydrogen and oxygen atoms packed into the water provide a higher density of cosmic ray blocking nuclei than metals.

A water-based shield can work well to block radiation particles, said Peter Guida, a liaison biologist at NASA’s National Space Radiation Laboratory and a scientist at its host institution, Brookhaven National Laboratory in New York.

In space, every ounce of cargo – including heavy but necessary water – is precious. “If you have it anyway, can you use it for something?” he said. “In theory, it should work.”

a plastic proposal

Now try to reimagine wastewater treatment plants on Earth as multifunctional resource recovery facilities. As an alternative to plastics made from fossil fuels, for example, researchers are making strides in producing safe, biodegradable bioplastics from existing waste streams.

Creating bottles, containers and other planet-friendly bioplastics from what we left behind is still a work in progress, said Zeynep Cetecioglu Gurol, associate professor of industrial biotechnology at the KTH Royal Institute of Technology in Stockholm, Sweden.

Even so, developing an efficient and affordable method for recovering new waste water products can help offset the money, time and effort spent by treatment plants to meet pollution limits in wastewater. “I think it’s a win-win,” she said.

Many wastewater treatment plants are already using a microbe-dependent process called anaerobic digestion to create biomethane gas, a sustainable fuel alternative, from sewage.

Cetecioglu Gurol and other researchers have found that the organic compounds created during this biogas production process provide a good source of carbon for creating bioplastics. The objective now is to increase production efficiency. “We’re still in the early stages,” she said.

A type of bioplastic called polyhydroxybutyrate, or PHB, is naturally produced by some bacterial species as they feed on organic material. Tests suggest that PHB can replace a variety of petroleum-based plastics and that, unlike them, it biodegrades rapidly under normal environmental conditions.

A bacterial strain called Zobellella denitrificans ZD1 has attracted the attention of researchers like Kung-Hui Chu, professor of environment, water resources and coastal engineering at Texas A&M University.

Chu and his colleagues found that the strain, which normally lives in mangroves, can also thrive on glycerol (an industrial byproduct), wastewater and sewage sludge. Its ability to accumulate PHB when grown under a variety of conditions makes it a promising candidate for turning waste into bioplastics or other useful products such as fish feed.

A high load of bricks

Worldwide, treated sewage solids are still commonly burned or buried. But waste incineration creates ash that, while reduced to a fraction of the initial volume, is still often dumped in landfills. Here too, researchers are actively investigating how to convert the solids and ash into useful products.

These recycling processes can yield a ton of bricks. Engineers at the Royal Melbourne Institute of Technology in Australia focused on alleviating the environmental problem of digging up clayey soil for brick production, in part by exploring how to incorporate treated sewage solids, or biosolids, into burnt bricks. If making poop bricks seems like an unusual application, consider that animal dung has been used to build houses and produce pottery for centuries.

When fired for 10 hours at nearly 1,093°C, Melbourne residents’ clay bricks with varying amounts of treated biosolids were not as strong as traditional ones. But they were lighter and better insulators—and otherwise indistinguishable in appearance and odor.

A 2019 paper by civil engineer Abbas Mohajerani and colleagues at the institute suggested that bricks made with at least 15% biosolids could still meet engineering requirements while theoretically recycling the remaining millions of tons of poop.

A follow-up study by another group of researchers at the Melbourne institute suggested that raw biosolids, biochar (coal made from biosolids) and ash from incinerated sewage sludge could be used as cement replacement materials. Other UK researchers have suggested that sewage sludge ash could be re-used in a viable way in glass tiles and ceramics, with potential for wide applications in the construction industry.

The Museo Della Merda in Lombardy, Italy, in fact, once created terracotta tiles, flower pots and tableware from a mixture of cow pie and clay. It’s called Merdacota.

The yuck factor, of course, can be a bigger barrier to repurposed poop consumer products like bioplastic cups and ceramic plates. But the harsh environment of space and the growing challenges of extracting resources on our own planet are helping researchers source a source of raw materials that can aid exploration and increase investments in sanitation infrastructure, converting waste streams into revenue. Even better? This particular natural asset will never dry out.

Source: CNN Brasil

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