What if we could tap a daily waste product for energy? Making power out of pee is nearing practical application - it's a effective and hygienic option for sustainably managing waste.
Whether we like it or not, urine is an essential part of our daily lives - and so is electricity. And scientists have been researching for decades how both can be reconciled.
In 2014, scientists from a Bristol robotics laboratory were able to charge a mobile phone with urine.
And now, a recent study has moved a step closer toward using urine as source of energy, by reducing the price and speeding up the process.
But what about implementation of urine as a power source - how far is it from becoming a common fuel for our daily lives? And how do you get power from pee, anyway?
Recycling 1 trillion liters of waste
Urine - along with other human waste - has found many purposes throughout history, from medicine to agriculture. This is not surprising considering that the average person produces between 800 and 2,000 milliliters of urine per day.
If multiplied by the global population, that amounts to 1.4 trillion liters of urine per day - which mostly ends up going down the drain.
This huge amount of waste requires proper management, which is costly - and energy-intensive. "Waste treatment accounts for a large portion of daily energy demand," said Mirella Di Lorenzo, co-author of the recent study.
"We want to use waste as a source of energy rather than something that requires energy to be treated," Di Lorenzo told DW.
Taking the best from the waste
Converting urine to electricity involves harnessing the energy of bacteria. Removing oxygen from the environment causes the bacteria that break down the urine to generate electrons instead of carbon dioxide and water.
Electrochemical devices called microbial fuel cells turn the charge from the liquid into electricity - extremely efficiently.
Though effective, until now microbial fuel cells had been too expensive and the power generated too low.
These are the two main challenges that Di Lorenzo and her team seem now to have overcame. The new miniature microbial fuel cells are much smaller, using cloth and titanium wire instead of platinum, and can scale up the generation of power through a protein found in egg white.
"The amount of energy produced is still very low," said Di Lorenzo. "But we are not far from practical applications." The team is confident that soon, our waste can give energy back to our daily lives.
Di Lorenzo is aware that urine will likely not generate as much energy as solar or wind power - which has aroused criticism of the project. But since the waste is generated anyway, she believes the balance between input and output is beneficial.
"Urine is not intended as an alternative to other renewable energies," Di Lorenzo explained. "But more as a complement."
Urine, which has been used for years to analyze our health, now may have a new function for our living
The use of urine as energy could involve smart toilets, prepared to channel the waste from our homes directly to a treatment center - avoiding potential hygiene problems.
Whether urine can be transformed into energy on a large scale is uncertain; whether people will accept their home being powered by their own waste is even more uncertain. But in the meantime, researchers are keen to keep working on the concept.
"People seem quite enthusiastic about the idea," Di Lorenzo said. "As long as we don't ask them to carry their urine with them," she quipped.