Convert waste CO2 and chicken feathers into fertiliser

Every year we ditch millions of tonnes of chicken feathers, and pump climate-altering carbon dioxide into the air. But combine the two in the right way and you can make an otherwise-scarce fertiliser.

More than 5 million tonnes of chicken feathers are produced globally every year. Most get thrown into landfill where they can sit for decades without breaking down. Changle Chen of the University of Science and Technology of China in Hefei, Anhui Province, and colleagues have found a use for them.

Heat chicken feathers to 600 °C for 3 hours in C02 and two useful substances form. One is ammonium bicarbonate, a fertiliser and food additive. But even better, warm this substance to 60 °C and it releases ammonia, an ingredient in urea, a superior fertiliser. Currently, 2 per cent of the world's energy is consumed making ammonia, using the energy-intensive Haber process. Chen says that getting urea from chicken feathers instead could save some of this energy.

The second product is carbon micro-spheres, which Chen found can make a water-resistant coating. Alternatively, adding a catalyst turns them into carbon nanotubes, which have been used in everything from solar cells to biosensors.

"Sequestering carbon as ammonium bicarbonate or as urea is quite a smart idea," says Walter Schmidt of the US Department of Agriculture in Beltsville, Maryland.

Chen's idea for chicken feathers has some competition. They can also be turned into plastic, or hydrogen fuel cells. Another group uses their complex structure to make composite materials like printed circuit boards and fashion materials. Breeders have even created featherless chickens, but these may suffer more and have not proved popular.