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The average person generates around a pound of poop each day. So, what happens to it? It depends on where you live. In places with flushing toilets, your waste travels through pipes to large treatment plants, which clean the water and manage the remaining waste, often by incinerating or landfilling it. In areas without flushing systems, people use cesspits and outhouses to collect the sludge, which eventually has to be disposed of.
Excrement is a known carrier of disease, which is why we work hard to get rid of it quickly. However, scientists and engineers are revealing that we’ve been underestimating the value of our waste. When recycled properly, this inexpensive, renewable, and abundant resource produced by all 7 billion people can be used to grow crops, cook meals, fuel vehicles, and generate power. Here are some of the latest technologies that are already recycling human waste—and may soon include yours.
1. Preparing Your Meal Using Waste
Nairobi, Kenya’s capital, is so densely packed that there’s no room for even the simplest of toilets, including outdoor latrines. Yet, people still need to relieve themselves. As a result, many residents use plastic bags to dispose of their waste, tossing them along roadsides where they pile up, scatter, and float away during heavy rains. This phenomenon is known as 'Kenya’s flying toilets.'
At the same time, Kenya faces a severe deforestation issue. Since wood is the primary source of energy for many, people chop down trees and turn them into charcoal, which is used for everything from cooking to drying tea leaves for the country’s tea industry.
A startup called Sanivation is tackling both issues by turning waste into a resource. They provide low-income households with portable toilets that collect waste in hygienic containers. A team collects this waste and takes it to a repurposing facility. Human waste contains lignin—a complex organic polymer found in plant cell walls. When heated, lignin turns waste into a sticky substance. By adding burnable fibers, like sawdust or agricultural waste, the mixture becomes fuel briquettes. Sanivation’s founder, Emily Woods, reports massive demand from factories. 'We are only limited by how much we can produce,' she says, noting that in their fourth month of selling 'poop logs,' they sold 50 tons.
2. Creating a Sewage Smoothie for Healthier Plants
Turning manually collected feces into fuel may not find a large market in the Western world, but there are alternative ways to reuse our waste. Ajay Singh, a scientist at the University of Waterloo in Ontario, noticed many large trucks hauling human waste around his city. These trucks usually transport sewage to be dewatered and purified before being returned to nature. However, the remaining biosolids create a problem. They are often sent to landfills or incinerated, contributing to greenhouse gas emissions. In some areas, they are stored in 'lagoons'—large cesspits covered with PVC.
Biosolids are a controversial byproduct in the sewage industry. They're unwanted because they’re too thick, sticky, and foul-smelling to handle like liquid waste. However, they are packed with valuable nutrients, such as nitrogen and phosphorus, which make them excellent for fertilizing soil.
Singh and a colleague came up with a way to transform biosolids into a 'sewage smoothie.' They designed a large industrial blender that processes the biosolids into a consistency similar to a milkshake. (They initially tested the idea with a regular kitchen blender, but please don’t try this at home!) This high-speed blender uses a razor-sharp blade that spins fast enough to break down bacterial cells in the sludge, solving two problems at once: killing pathogens and creating a smooth mixture that can be pumped into trucks and injected into farmland soil. Their company, Lystek, produces a bio-fertilizer mix called LysteGro—a nutrient-packed food for plants.
3. Microbial Creatures Turn Poop into Methane
Biodigesters at DC Water transform poop into a fertilizer called Bloom. | BloomDC Water, the wastewater plant in the U.S. capital, uses a kitchen-inspired method to recycle poop—not in a blender, but in a massive pressure cooker. The plant operates 24 giant pressure cookers, which simmer the city's waste at 320°F and six times the usual atmospheric pressure for 30 minutes. This process kills all pathogens, and the remaining 'sewage stew' is transferred into enormous concrete tanks called biodigesters. There, microbes break down the sludge, producing methane, which is captured and burned to generate electricity for the plant.
Before microbial digestion, DC Water produced 1,100 tons of biosolids daily. Now, thanks to the microbes, that number has dropped to around 450 tons per day, with the difference converted into gas for green energy. The leftover carbon is returned to the earth in the form of black, gooey compost, which is dewatered, dried, and packaged as an organic fertilizer called Bloom. Bloom is available for anyone—from farmers to gardeners. Christopher Peot, DC Water’s director of resource recovery, emphasizes the importance of not wasting waste: 'There’s no such thing as waste, only wasted resources.'
4. Providing Fertilizer for Growing Your Own Crops
While a massive pressure cooker might be too expensive for most households, smaller, more affordable biodigesters exist. Israeli company HomeBiogas produces personal digesters that break down food waste in a similar way. These digesters can also be paired with pump toilets, which use manual pumps to flush and require much less water. The digesters, shaped somewhat like camels resting on the ground, are filled with special microbes that decompose biomass and turn it into methane. This methane travels through a hose to power stoves or hot-water heaters. Meanwhile, a brown, goopy liquid collects in a bucket, providing a powerful fertilizer.
For countries where energy costs are high, HomeBiogas digesters (priced around $600-$700) can save money, according to one of the company's founders, Yair Teller. In the United States, where energy is relatively inexpensive, these digesters could serve as a source of affordable organic fertilizer. Additionally, they could benefit off-the-grid communities no matter where they are located. Imagine being able to grow your food and cook it with your own waste!
5. Technology That Turns Poop into Petroleum
Beyond powering kitchen stoves, waste can fuel nearly anything, including vehicles. The Metro Vancouver wastewater plant in British Columbia is testing a groundbreaking technology that turns sewage into crude oil. Developed by the Pacific Northwest National Laboratories (PNNL), a research facility of the United States Department of Energy, the technology’s key feature is a shiny, silver serpentine pipe. Sludge is loaded into this pipe, where it is heated to 660°F and subjected to 200 times the typical atmospheric pressure.
These extreme conditions, known as hydrothermal liquefaction (HTL) in scientific circles, replicate the processes that created oil and gas deep beneath the oceans over millions of years. Under such intense heat and pressure, the sludge doesn't cook in the traditional sense; instead, its long organic molecules break apart into shorter, smaller carbon compounds, which form oil and gas. While nature takes millions of years to achieve this, the PNNL technology does it in just 15 minutes. In simple terms, you input stinky black goo and get stinky black goo in return, but the difference is that the output holds significant economic value.
While it still requires refinement like any crude oil, says Paul Kadota, Metro Vancouver’s program manager, this process not only aids in sewage disposal but also decreases the need to extract oil from the earth, which remains crucial as we still rely on fossil fuels. The project is currently in its pilot phase, but if successful, Vancouver residents could soon be powering their vehicles with the remnants of yesterday’s meals.
