Apart from oceans, soil, rocks and trees, human and animal urine can also absorb carbon dioxide (CO2) and help reduce pollution, says a Spanish researcher.
Absorbing CO2 and other greenhouse gases in cities would require millions of tonnes of some naturally occurring substance. Urine is produced in large quantities and is close to the pollution hubs of large cities.
"For every molecule of urea in urine, one mole (a unit to measure the quantity of a substance) of ammonium bicarbonate is produced along with one mole of ammonia that could be used to absorb one mole of atmospheric CO2," said study author Manuel Jimenez Aguilar, the Journal of Hazardous Materials reports.
After absorbing CO2, another unit of ammonium bicarbonate is produced, which is in use in China as a nitrogen fertilizer for the last 30 years.