Citylab says that most roads in the Netherlands are paved with a porous and water permeable blacktop. Compared to more run-of-the-mill types of asphalt, it requires higher volumes of bitumen, which binds together the stones and sand that make up the asphalt. Cellulose is added to thicken the mixture and prevent the bitumen from dripping off the aggregate during processing, transporting, and paving.

Meanwhile, the Dutch flush about 180,000 tons of toilet paper annually. That paper ends up at wastewater treatment plants where it’s filtered out, dried and incinerated. The incineration process produces large amounts of CO2 and destroys resources found in wastewater like cellulose.

Now that cellulose is being re-used instead. IT is extracted from waste streams and made back into a raw material to be used in asphalt. The paper fibers are sifted out of the wastewater by an industrial sieve before proceeding through a series of machines to be cleaned, sterilized, bleached, and dried, resulting in a fluffy, grayish material. Officials say you can’t even tell it was once used in toilet paper.