Metal conveyor belts are less environmentally taxing: While virtually no manufacturing operation is without a carbon footprint, plastic is far more taxing on the environment to produce. Plastics are made from petroleum, which isn't exactly the poster child for sustainability. While the production of metal does result in pollutants, the sector has made strides in recent years. http://www.metallicconveyorbelts.com/metal-converyor-belts/balanced-weave-belts.html