Humans have created 8 billion metric tons of plastic. More than half the plastic ever produced some 5 billion metric tons " lies smeared across the surface of the Earth. Chemists were creating "synthetic" plastics decades before the oil industry took off, from, among other materials, waste oat husks and vegetable oil. One of the tacks toward more sustainable plastics is to turn back to such biological sources. The ideal materials are not just biodegradable but also compostable " a narrower category that indicates the material can break down into organic components that are harmless to plants and animals. Compostability, unfortunately, is not easily achieved. The natural world already supplies promising polymers that are all compostable, says David Kaplan, a biomedical engineer at Tufts University. [Physicist Eleftheria] Roumeli, for example, has mined the promise of algal cells. They're small, and therefore easily manipulable; they contain large amounts of proteins, which are biological polymers, alongside other useful materials. She and her students took powdered algae and passed it through a hot presser. After several trials ... they found they could produce a material that was stronger than many commodity plastics. The material was also recyclable: It could be ground back to powder and pressed again. If it were to be carelessly tossed into the dirt, the material would break apart at the same rate as a banana peel.