Making packaging greener – biodegradable plastics
Glossary
biodegradable. Able to be broken down into simpler substances by the activities of living organisms and therefore unlikely to persist in the environment.
composting. Breaking down aerobically plant and animal material using microorganisms. For successful composting there must be sufficient water and air to allow the microoganisms to break down the material.
Material derived from the aerobic breakdown of plant or animal material by microorganisms.
culture. To grow microorganisms such as bacteria and fungi in a laboratory under controlled conditions.
decomposer organism. An organism, usually a bacterium or a fungus, that breaks down organic material into simple chemical components, thereby returning nutrients to the physical environment.
gene. The basic unit of inheritance. A gene is a segment of DNA that specifies the structure of a protein or an RNA molecule. (Nova)
greenhouse gas. A gas that is transparent to incoming solar radiation and absorbs some of the longer wavelength infrared radiation (heat) that the Earth radiates back. The result is that some of the heat given off by the planet accumulates, making the surface and the lower atmosphere warmer. For more information see The greenhouse effect (CSIRO Atmospheric Research, Australia).
monomer. A molecule that can join with other molecules to form a large molecule called a polymer. A monomer is the smallest repeating unit in a polymer chain.
photosynthesis. The biochemical process in which green plants (and some microorganisms) use energy from light to synthesise carbohydrates from carbon dioxide and water. Photosynthesis can be shown as:
CO2 + H2O + energy→ [CH2O] + O2
polyhydroxyalkanoate (PHA). A biodegradable polymer produced by bacteria that has the qualities of plastic. At one extreme, PHAs share properties with polypropylene, and at the other end of the range, they are similar to natural rubber. For more information see Material: PHAs – polyhydroxyalkanoates (Design inSite, Denmark).
polylactide (PLA). A biodegradable polymer derived from lactic acid. Because this polymer is broken down in our bodies, it has biomedical applications (eg, sutures). For more information see Material: PLA – polyactide (Design inSite, Denmark).
polymer. Polymers are large molecules that are made up of many units (monomers) linked together in a chain. There are naturally occurring polymers (eg, starch and DNA) and synthetic polymers (eg, nylon and silicone). More information can be found at The basics – polymer definition and properties (Plastic Resource, USA), Introduction to polymers (Case Western Reserve University, USA) and History of polymers and plastics for teachers (Hands On Plastics, American Plastics Council).
tuber. A thickened short underground stem or branch formed by some plants (eg, potatoes) as a food storage organ. Each of the 'eyes' on a potato are buds that can grow into new roots and shoots.
Page updated August 2006.