A leaf that falls from a tree takes just one year to be absorbed into the soil, but a plastic bag survives for a century. Plastic bags in landfill sites make it difficult for organic refuse to biodegrade. For example, food scraps discarded in a closed plastic bag take 30-70 years to break down. In Greece, about 60,000 tons of plastic material are produced every year, corresponding to 1 billion disposable bags used in supermarkets and department stores. According to the relevant law of 2001, plastic bags should be collected, recycled and made use of. This week the City of Athens announced it would begin a drive in March to remove plastic bags from shops and replace them with bags made from materials that are less harmful to the environment. Athens is now a member of the C40 cities, which aim to coordinate efforts by cities across the world to tackle global warming and climate change. In recent years, research has resulted in a biodegradable material which, to be designated as such in accordance with the definition of the relevant EU directive, must break down in about as much time as natural materials. Research into these materials began in the 1980s and today there are several options available in Greece. So far there has been no agreement within the scientific community regarding the complete effectiveness of biodegradable bags and there are reservations as to whether they leave traces in the environment that are not visible to the naked eye and could therefore be dangerous. Those that are regarded as completely biodegradable are the ones made of primary materials such as starch. Even then, there is some dispute over the use of fertilizers and large quantities of water used to grow the materials and to process them. Some of these options are: * Mater-Bi, based on corn starch, a prize-winning invention of the Italian firm Novamont. Non-genetically modified, the BioBags biodegrade within 3-8 weeks in any environment containing bacteria. Available at the Ecozoi cooperative (tel 26610.492-92), Plastemboriki (tel 23106.31294), Ecofamily (tel 210.429.3520) and selected organic food stores. * Potato starch. Made from non-edible potato species that break down within six months at the most when buried. Their decomposition produces carbon dioxide, water and biomass, resulting in an organic fertilizer suitable for organic cultivation. At La Melusine (tel 210.898.1563). *Photo-biodegradable, or oxy-degradable plastics are made with new technologies in which polyethylene breaks down due to the addition of a small quantity of oxy-degradable additive in the presence of sunlight, so the bags have to be stored in the dark at temperatures below 30 Celsius (86 Fahrenheit). At La Melusine. This article first appeared in the January issue of Kathimerini supplement ECO.