There's been so much in the news lately about bad plastics -- including right here in this column -- that I thought I should write about a potentially good thing happening with them.Bioplastics, plant-based biodegradable plastics, are gradually replacing plastics made from petroleum. They comprise only a small portion of the plastics, but as soaring prices and politics make petroleum an expensive and controversial raw material, bioplastics are an increasingly attractive alternative. The Guardian reported recently that the sector is growing by 20% to 30% a year. Major players include NatureWorks, owned by Cargill and Japanese company Teijin Ltd.; Mirel, a joint venture between Archer Daniels Midland ( ADM) and biotech firm Metabolix ( MBLX); Cereplast; Italian firm Novamont and Australia's Plantic Technologies, which has a marketing agreement in the U.S. with Dupont ( DD). The Biodegradable Products Institute has a list of others. The plastic fibers these companies manufacture are indistinguishable from conventional plastics. Chances are good that you've already bought products containing or packaged in bioplastic -- without even knowing it. Toyota ( TM) has used it to make components for the Prius and Raum. Novamont's bioplastic is a component in Goodyear ( GT) Tires. Sony ( SNE) puts bioplastic in its Walkman. Target ( TGT) uses it for its gift cards. The brand that seems to have the most reach so far, Natureworks, has seen its plastic used to pack fresh veggies, salad greens and cut fruit sold at Wal-Mart ( WMT) and Kroger ( KR), in packaging for Green Mountain Coffee Roaster ( GMCR) coffees, and in sheets sold at Target and J.C. Penney ( JCP).