Waste Not, Want Not

Meet the communities forging the way to a trash-free future, by reshaping unwanted by-products into valuable resources

- Hayley Bennett

IN BLOOM

The contents of your toilet is precious – to algae,anyway. Human waste is packed with phosphorus and nitrogen, nutrients that algae needs to grow. Researchers have developed bioreactors, like this machinery designed by ClearAS in Missoula, USA, that exploit the way that algae grows rapidly when exposed to human waste. The system is packed with algae that extracts nutrients from wastewater, therefore cleaning the water to ensure it meets industry standards. The algae is then used to make materials for bioplastics and bioenergy. A full-scale system is up and running at South Davis sewers in Utah, treating 18 million litres of water daily.

SET IN STONE

Geothermal power plants, which use heat from the Earth’s core to generate energy, may provide a steady stream of electricity, but they’re not entirely clean. They produce some emissions – mostly CO2 released when hot water is pumped up from carbonate-containing rocks.

However, at this well (one of over 100 at the Hellisheiði power plant in Iceland) CO2 can be returned to the rocks by adding it to water that is reinjected back into the ground after energy production. Scientists once thought this ‘remineralisation’ process took hundreds of years, but a 2016 study showed it is rapid – working within a year or two to lock the CO2 away. Iceland’s CO2 emissions from geothermal energy are low, but remineralisation keeps the environmental impact to an absolute minimum.

GREENHOUSE ON FIRE