The saying goes that “one man’s trash is another man’s treasure,” and as we speak, researchers around the globe are experimenting with taking this phrase literally. Right now, it’s possible to turn leftovers from brewing beer into batteries and to generate electricity from wastewater. There’s a lot of projects showing that practically no kind of waste is off-limits … including what our own bodies produce. I mean … there’s no shortage of waste, right? But there’s also no shortage of innovation for reusing it either. So, we’re not onto flying cars quite yet, but how close are we to Mr. Fusion? Let’s take a look at the top 5 craziest ideas for turning trash into treasure.

Waste is inevitable, but endless mountains of trash and constant pollution doesn’t need to be. Though a lot of us are used to tossing something as soon as it stops fulfilling its original purpose, or just not seeing value in waste in the first place, we’re in desperate need of a paradigm shift. You know the drill: there’s microplastics in every nook and cranny on the planet…and according to Our World in Data, when it comes to what we eat, about 6% of the world’s greenhouse gas emissions is caused by food lost on its journey to your plate, plus what’s ultimately left uneaten. That doesn’t include losses during production and harvesting! 1

This issue isn’t only a matter of maintaining our environment, either. By rethinking waste, we can reduce our dependence on raw materials, which means skirting supply chain issues. It’s all about creating a “circular economy.” When things are built to last, designed to be maintained for as long as possible, and easy to break down for repurposing, it also means higher quality products and saving money in the long run.2

The goal is to avoid the consequences that come with perpetual growth with finite supplies. And so far, scientists are working on solutions that are pretty wild — in more ways than one.

1: Human waste for fertilizer

We’ll start with what might be the most unlikely (and maybe a little stomach-churning) pitch: human waste fertilizer for food crops. Now, before you wrinkle your nose, keep in mind that turning crap into gold is already feasible, and if you don’t believe me, check out my previous video on processing poop into renewable energy In fact, we already use human waste in agriculture. That’s where about a fourth of the biosolids reused in the US end up after leaving wastewater treatment plants.3

What researchers have recently studied, though, is the effect of human waste on crops meant specifically for our consumption — in this case, the humble white cabbage. The practice of using human waste as fertilizer isn’t new. It was especially popular during the early 18th century in what is now Tokyo, Japan, and it’s making a big comeback. As a consequence of the rising cost of chemical fertilizers, sales of the alternative known as shimogoe have skyrocketed in the city of Tome, ballooning by 160% between March 2022 and March 2023.4

But why deal with this crap in the first place, besides the fact that it’s never in short supply? As it stands, finding alternatives to current approaches to fertilization is actually a necessity. Unfortunately, about 2.1% of global greenhouse gas emissions comes from heavy use of synthetic nitrogen on our crops.5 This not only comes from the production of the fertilizer, but also from its overuse.

We have a convenient, natural source of nitrogen and phosphorus to fall back on: ourselves. It might seem crude, but human urine can provide the nitrogen and potassium that plants need, while our feces has phosphorus and calcium to offer.6 Maybe I should have made this the #2 innovation on my list instead of #1.

With this in mind, a team of scientists representing Swiss and German research groups conducted an experiment using human waste as fertilizer between June and October 2019 at the Leibniz Institute of Vegetable and Ornamental Crops in Großbeeren, Germany.7 The study compared the effects of two nitrified urine fertilizers, or NUFs.8

So, did the human urine accomplish e-NUF to justify its use? Turns out that, to use the researcher’s words, “NUF alone appears to be a promising successful fertilizer substitute in horticultural food production.” The two NUF products, Aurin and C.R.OP., promoted the growth of cabbage yields at a rate similar to vinasse

2: Brewing up batteries

You’ll probably find this next innovation a bit more appetizing: beer turned into batteries. Like any other industrial activity, brewing beer results in waste, and an estimated 85% of that waste is composed of brewer’s spent grain, or BSG. What doesn’t make it into your frosty beverage can still be used. A lot of the time, its final destination is bags of animal feed.9 But what if we could convert this cheap draff into components for batteries?

After all, carbon is considered one of the best materials for supercapacitors, and activated carbon specifically is highly conductive, stable, and easy to come by. Scientists have investigated the practicality of using a lot of different biomasses as sources of activated carbon to keep material prices down, but BSG hasn’t really been in the spotlight…until now.10

BSG is advantageous as a medium because of how much of it we have on tap. Brewers in the European Union churned out about 6.8 billion tons of BSG in 2019, and 1.5 billion of that flowed out of Germany alone.10 Prost!

This abundance is what inspired a recent study by a team of chemists at Friedrich Schiller University Jena in Germany: a collaboration with Spanish researchers on engineering BSG into carbonaceous materials for energy storage. The scientists sourced the BSG from Papiermühle, a combination hotel, restaurant, and brewery in Jena.11 Once stocked with more than enough for drinks all around, they found that the boozy activated carbon stored an electric charge at almost double the amount of a similar device using commercial activated carbon. It was also comparably stable relative to other biomass-based types.10 That’s something to raise a glass to.

3: Bark for glue-free panels

Moving on comes a use for a different kind of grain. Within the timber industry, bark, which makes up roughly 10 to 20% of a tree, is for the most part cast off as a byproduct or simply trashed.12 By the time that timber reaches consumers, it’s common for manufactured wood products to use urea-formaldehyde resin as an adhesive. So, chances are that you’ve got the stuff of specimen jars within your cabinets or furniture. According to the Agency for Toxic Substances and Disease Registry, you can find formaldehyde in pretty much every home.13

The levels of formaldehyde inside a house do tend to decrease over time — usually within two years.13 That’s a long wait for a carcinogen to dissipate. What if we could cut down on waste and avoid the use of formaldehyde at the same time?

As described in a study published early this year, researchers at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany, have accomplished just that. The research team set out to take advantage of bark’s natural properties and managed to create planks out of it, no smelly glue required. The hot-pressing technique involved in the experiment was actually demonstrated all the way back in 1960, but this is the first time it’s been used to fuse bark together with minimal processing. The result? In the researcher’s words, “‘pure’ one-component products” that don’t need to be separated at the end of their lifetime.12

The pressing process also allows for bark panels to be molded into shapes without damaging them, providing curvature that would otherwise come from making additional cuts. As an added bonus, the roughness of the panels was found to be equivalent to sanded wood, meaning that you could get away with using them without the same sort of extensive treatment you’d have to apply to typical wood products. These features indicate that the bark panels would be easy to use for interior design, furniture, and packaging.1214 While there are still a few problems that are falling out of the woodwork, such as moisture absorption and swelling, pressed bark panels show some promise.

4: Agricultural waste for construction and car parts

If you’re planning on getting a new car in the future, I have good news and bad news. The bad news is that what we typically call “new car smell” stems from volatile organic compounds, or VOCs…and you don’t want to be breathing those in.15 The good news is that someday, our factory-fresh vehicles might naturally smell like lemon or pomegranate instead. How? With fruit-derived fascia!

That’s because car dashboard parts, car door trims, and a mold for the truss joints used in construction are all prototypes successfully created out of agricultural waste through the BARBARA project.

BARBARA stands for “Biopolymers with Advanced functionalities foR Building and Automotive paRts processed through Additive manufacturing.” I guess you could say food scraps aren’t the only mouthful here.1617 That’s really stretching it to get that acronym to work.

By the completion of this four-year public-private partnership with the EU, research teams in Spain, Italy, Germany, Belgium, and Sweden had worked together to synthesize eight new industrial materials for fused filament 3D printing. What makes these materials so special is that they’re made out of byproducts from crops like corn.181920

As part of the project, researchers partnered with the Italian automobile manufacturer Fiat to produce car parts out of odds and ends you’d otherwise throw onto your compost pile: lemon peel, almond shells, and pomegranate skins. And just like their origins, these biopolymers can have antimicrobial properties…and a fresh scent.16

At the end of your car’s life, it’s crushed and shredded. All that plastic from the dash, seats, and other panels, called “fluff,” is then separated from the recyclable metals and sent to the landfill. Theoretically, the BARBARA project’s materials would provide an alternative that’s recyclable, or at least biodegradable.

5: Microbial fuel cells for processing vegetable oil wastewater

While we’ve still got food on the brain, let’s wrap up with our last advancement…in vegetable oil.
This one is the most technical of the bunch, so I’ll keep the explanation high-level. Processing vegetable oil generates literal tons of wastewater — about 8 million tons a year during the production of the olive variety, for example. All these fluids full of grease and fat would wreak havoc on the environment if let loose as-is, so they need extensive treatment to prevent ill effects on wildlife and on humans. As you might imagine, this requires a lot of energy. But we need our cooking oil, and in the face of increasing demand, scientists have been tinkering with opportunities to multitask by producing renewable energy during wastewater treatment.21

One possible path is the use of microbial fuel cells (or MFC). With bacteria as a catalyst, MFCs can convert the chemical energy stored in wastewater goop into electricity.22 Under normal conditions, microbes free electrons as they break down organic matter, then surrender them to oxygen molecules. Within an MFC, microbes grow atop an anode in a sealed-off chamber free of oxygen, which leads them to send their electrons to the cathode on the other side, creating current.23

As a concept, these bacterial batteries have been around for a long time, with some of the earliest research published in 1911.24 Despite this, industrial applications of MFCs had yet to exist a full century later.25 However, we’ve seen a renewed interest in the subject. Several companies have now developed tech that can integrate MFCs into multiple kinds of systems, from biosensors in agriculture to life support in space.26

But as you might expect, MFCs produce tiny amounts of power, so scale has been one of the major challenges plaguing their adoption outside the lab.272322 Fortunately, their performance is continuing to improve. Last December, a team of researchers based in Iran achieved a new milestone by modifying the electrodes within MFCs for vegetable oil wastewater treatment. The team developed an anode catalyst that enhances the power of the fuel cells and also verified that powdered activated carbon sourced from bamboo is a cost-effective alternative to platinum.2822 Expensive materials have previously hobbled MFCs’ usefulness in treating wastewater, so while this particular development might not sound as exciting as pouring a bottle of canola oil into your gas tank, it’s a promising step in the right direction.22

So, would you drive a citrus-scented car with a dash made from upcycled lemon peels? Or charge up your future phone battery made from beer waste?

  1. Food waste is responsible for 6% of global greenhouse gas emissions ↩︎
  2. Circular economy: definition, importance and benefits ↩︎
  3. Basic Information about Biosolids ↩︎
  4. As prices soar, Japan returns to human waste fertilizer ↩︎
  5. Greenhouse gas emissions from global production and use of nitrogen synthetic fertilisers in agriculture ↩︎
  6. Our toilets can yield excellent alternatives for widespread polluting fertilizers ↩︎
  7. Recycling fertilizers from human excreta exhibit high nitrogen fertilizer value and result in low uptake of pharmaceutical compounds ↩︎
  8. Vinasse ↩︎
  9. Brewer’s spent grain: a valuable feedstock for industrial applications ↩︎
  10. Brewery waste derived activated carbon for high performance electrochemical capacitors and lithium-ion capacitors ↩︎
  11. Chemists create carbon materials for energy storage device from brewery waste ↩︎
  12. Adhesives free bark panels: An alternative application for a waste material ↩︎
  13. Formaldehyde in Your Home: What you need to know ↩︎
  14. Rethinking a waste product of the timber processing industry ↩︎
  15. That new-car smell may be a sign of exposure to a host of hazardous chemicals ↩︎
  16. Lemon peel, flax fibres hold keys to eco-friendly car parts ↩︎
  17. About | Barbara Project ↩︎
  18. Yesterday BARBARA project closed with a Conference broadcasted live from AITIIP ↩︎
  20. Final video Barbara Project ↩︎
  21. Utilization of wastewater from edible oil industry, turning waste into valuable products: A review ↩︎
  22. Turning vegetable oil industry waste into power: Electrode modification improves wastewater treatment ↩︎
  23. Electrifying Wastewater: Using Microbial Fuel Cells to Generate Electricity ↩︎
  24. Electrical effects accompanying the decomposition of organic compounds ↩︎
  25. Microbial Fuel Cell ↩︎
  26. Recent Microbial Fuel Cell Applications and Developments ↩︎
  27. Engineer deploys research on ‘mud batteries’ for powering sustainable agriculture ↩︎
  28. Treatment of vegetable oil industry wastewater and bioelectricity generation using microbial fuel cell via modification and surface area expansion of electrodes ↩︎

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