MUMBAI, India — On average, humans produce 640 billion pounds (240 billion kilograms) of feces and approximately 3.5 billion gallons (1.98 billion liters) of urine. Each year, this is more than 213 times the weight of the Empire State Building and enough urine to fill up 1400 Olympic-sized pools. While this is an astonishing amount of human waste, it can be used in a gainful and environmentally friendly manner.
Human feces and urine contain enough nutrients and other elements that can be used resourcefully. However, the waste is relayed into a sewage plant where the useful components of the waste are polluted and made unusable. The traditional method of treating sewage rarely involves the retention of bacterial and viral contaminants. Instead, it typically turns the waste into a sludge that is of no use.
Data from the World Bank estimates that by 2050 humans will have to produce 50% more food to feed a global population of nine billion, which would be fairly difficult considering that climate change will reduce harvests by 25%. According to the U.N., while 80% of our wastewater is discharged into the environment without treatment, safe drinking water remains inaccessible for 2.1 billion people across the globe. Upcycling human waste to water can be a revolutionary solution to food and water scarcity around the world.
Human Feces as a Source of Water
The Omniprocessor is a compact water treatment plant created by Janicki Bioenergy, a small family-run business in Seattle. The Omniprocessor, unlike the traditional sewage plant, is a combination of an incinerator, a water filtration system and a steam power plant.
The raw waste is separated into dry solids and water vapor by boiling it to 100 degrees Celcius. The dry solids are burned in the incinerator, which generates high-pressure steam. The steam passes through a generator to produce electricity, which powers the plant in a self-sufficient manner. The electricity that remains unused in the process is distributed elsewhere. Next, the steam is condensed into water and purified several times, converting it into drinkable water.
The highly advanced processors generate 11,000 liters of good quality water that is safe for human consumption. Additionally, ash containing nitrogen and phosphorous is a by-product of the process that can be used as a fertilizer.
Human Feces as a Source of Food
A team of researchers from Penn State University, led by Christopher House, a professor of geosciences, published an article on food production through human waste. Human waste is processed via anaerobic digestion, followed by the methanotrophic growth of Methylococcus capsulatus to produce a protein and lipid-rich biomass that can be directly consumed or used to produce other high-protein food sources such as fish.
Beyond yogurt and other fermented foods, consuming microbes is not considered a suitable or realistic solution. However, according to Peter Ruhdal Jensen, a researcher at the Danish National Food Institute, “microbes can produce high-quality proteins for food applications, and they are highly competitive.” Moreover, if the microbial biomass is too bland a food, House suggests using it “more as a protein supplement than as a main food staple.”
Urine as a Source of Water
Despite these technological progresses, the direct reuse of urine, colloquially known as “toilet to tap,” is still a far-out reality, even after successful tests in certain countries. However, progress is being made with NASA installing a filter and distillation system on the International Space Station, which converts astronauts’ urine and sweats into drinkable water. According to NASA, the same system is being used in regions that are hit by catastrophes.
A group of scientists from the University of Ghent, Belgium, designed a solar-powered machine that separates urine into drinking water and salt minerals that can be used in fertilizers. The machine uses membrane distillation to recover 75% of the water and 95% of ammonia from urine. In 2016, the same group of researchers collected 1,000 liters of urine at a music and theatre festival in central Ghent to make Belgian beer. In areas lacking basic facilities or an electrical network, this unit may provide a realistic solution to water scarcity.
Currently, a direct “toilet to tap” system is implemented solely in the capital of Namibia, which is one of the driest countries in Africa. Singapore’s NEWater scheme provides high-quality recycled wastewater, which is mainly used for purposes unrelated to human use but is expected to become a vital source of drinking water.
Urine as a Source of Food
Unlike human feces, urine cannot be used as a direct source of nutrition. However, urine is a rich source of nitrogen, phosphorous and potassium. These nutrients promote plant growth and are also found commonly in industrial fertilizers. These components are in a form that is ideal for plant consumption. For example, nitrogen is present in food in the form of complex organic molecules. Nevertheless, our digestive system breaks down these molecules into basic minerals, which are perfect for plants to use. Hence, the diluted version of urine can be smeared onto crops to promote growth and a more rewarding yield.
Although it might take some time to fully implement these treatments and for people to accept these techniques worldwide, there is no doubt that human waste offers a solution to the food and water scarcity issue. As more research and attention are given to reusing human waste, water scarcity and food shortages might become stories of the past.
– Prathamesh Mantri