Biodegradable and Non-Biodegradable Substances Essay Example

non-toxic polymers with physicochemical thermo-sensitivity as a matrix for drug delivering. One research group at the University of Utah at Salt Lake City in 1997, for instance, synthesized an injectable polymer that forms a non-toxic biodegradable hydro gel that acts as a sustained-release matrix for drugs. Transgenic plants expressing microbial genes whose products are degradative enzymes may constitute a potential solution in the emoval of explosive residues from water and soils.

A group of University of Cambridge and University of Edinburgh scientists in the United Kingdom developed transgenic tobacco plants that express an enzyme (pentaerythritol tetranitrate reductase) that degrades nitrate ester and nitro aromatic explosive residues in contaminated soils. Another environmental problem is the huge amounts of highly stable and non-biodegradable hydrocarbon compounds that are discarded in landfills, and are known as polyacrylates.

Polyacrylates are utilized as absorbent gels in disposable diapers, and feminine hygiene absorbents, as well as added to detergents as dispersants, and are discharged through sewage into underwater sheets, rivers, and lakes. A biodegradable substitute, however, known as polyaspartate, already exists, and is presently utilized in farming and oil drilling. Polyaspartate polymers are degradable by bacteria because the molecular backbone is constituted by chains of amino acids; whereas polyacrylates have backbones made of hydrocarbon compounds.

The main challenge in the adoption of biodegradable substances as a replacement for existing hazardous chemicals and technologies is cost effectiveness. Only large-scale production of environmental friendly compounds can decrease costs. Public education and consumer awareness may be a crucial factor in the progress and consolidation of "green" technologies in the near future. The substances which cannot be broken down to harmless or non-poisonous

substances by the action of micro-organisms are called non-biodegradable substances.

These substances do not undergo rotting or take a very long time for rotting. For example, polythene bags, plastics, glass, aluminum, iron nails and DDT. Due to their decomposition problem, it is very difficult to get rid of these non-biodegradable substances. Their burning causes lots of pollution. Quite often stray animals eat these substances and die. Sometimes these non-biodegradable substances could be harmful for our health. Non-biodegradable material is inorganic or man-made matter that will not decompose. Any material that is non-biodegradable does not decay or breakdown into simpler forms of matter.

This means that when disposed of by us, nature cannot reuse these materials to fuel the cycle of life and it will remain as pollution in the environment. It also means, all the resources and energy used to make the material in the first place, are trapped within the waste. Because nature cannot breakdown the material; the matter and energy cannot be reclaimed and reused by the environment to generate more organic matter and energy. Relying on non-biodegradable materials and ingredients is an unsustainable and polluting practice. It traps resources and energy that cannot be re-claimed in materials that cannot be broken down.

Resulting in masses of polluting substances and rubbish that cannot every truly be digested by the planet. Fortunately we are able to recycle some non-biodegradable waste. Meaning the materials can be reused to make new products and materials. This saves natural resources and reduces the impact of the vast amounts of inorganic waste ending up as landfill and pollution throughout the world. In the natural world, many

substances can be broken down by living organisms (mainly fungi and bacteria).

Breakdown of these biodegradable materials (such as food and sewage) keeps them part of the biogeochemical system and thus makes them harmless. These products release nutrients, which are then recycled by ecosystems. Many substances (particularly plastics) that are described by manufacturers as ‘biodegradable’ are not, or they cause various pollution problems as they break down. Non-biodegradable substances (such as glass, heavy metals and most types of plastics) cannot be broken down by living organisms. As a result, they cannot be recycled by natural processes within the biogeochemical system and have to be dealt with in other ways.

They present substantial problems in waste management. Non-biodegradable substances can last for a very long time in our environment. They are very harmful. As they do not decompose, they pose a threat to the flora and fauna of a place. We need to find ways to dispose of non- biodegradable substances without harming the environment. The search for a biodegradable substitute for plastic polymers, for instance, is of high environmental relevance, since plastic waste (bags, toys, plastic films, packing material, etc. ) is a major problem in garbage isposal and its recycling process is not pollution-free. In the 1980s, research of polyhydroxybutyrate, a biodegradable thermoplastic derived from bacterial metabolism was started and then stalled due to the high costs involved in fermentation and extraction. Starch is another trend of research in the endeavor to solve this problem, and starch-foamed packing material is currently in use in many countries, as well as molded starch golf tees. However, physical and chemical properties of starch polymers have

so far prevented its use for other industrial purposes in replacement of plastic.

Some scientists suggest that polyhydroxybutyrate research should now be increased to benefit from new biotechnologies, such as the development of transgenic corn, with has the ability to synthesize great amounts of the compound. This corn may one day provide a cost-effective biodegradable raw material to a new biodegradable plastics industry. It is important to distinguish between the different types of biodegradable plastic, as their costs and uses are very different. The two main types are oxo-biodegradable and hydro-biodegradable.

In both cases degradation begins with a chemical process (oxidation and hydrolysis respectively), followed by a biological process. Both types emit CO2 as they degrade, but hydro-biodegradable can also emit methane. Both types are compostable, but only oxo-biodegradable can be economically recycled. Hydro-biodegradable is much more expensive than oxo-biodegradable. This new technology produces plastic which degrades by a process of OXO-degradation.

The technology is based on a very small amount of pro-degradant additive being introduced into the manufacturing process, thereby changing the behaviour of the plastic. Degradation begins when the programmed service life is over (as controlled by the additive formulation) and the product is no longer required. There is little or no additional cost involved in products made with this technology, which can be made with the same machinery and workforce as conventional plastic products.

The plastic does not just fragment, but will be consumed by bacteria and fungi after the additive has reduced the molecular structure to a level, which permits living microorganisms access to the carbon and hydrogen. It is therefore “biodegradable. ” This process continues until

the material has biodegraded to nothing more than CO2, water, and humus, and it does not leave fragments of petro-polymers in the soil. Oxo-biodegradable plastic passes all the usual ecotoxicity tests, including seed germination, plant growth and organism survival (daphnia, earthworms) tests carried out in accordance with ON S 2200 and ON S 2300 national standards.

The length of time it takes for oxo-biodegradable products to degrade can be ‘programmed’ at the time of manufacture and can be as little as a few months or as much as a few years. They are protected from degradation by special antioxidants until ready for use, and storage-life will be extended if the products are kept in cool, dark conditions. Unlike PVC, the polymers from which oxo-biodegradable plastics are made do not contain organo-chlorine. Nor do oxo-biodegradable polymers contain PCBs, nor do they emit methane or nitrous oxide even under anaerobic conditions.

Hydro-biodegradation is initiated by hydrolysis. Some plastics in this category have a high starch content and it is sometimes said that this justifies the claim that they are made from renewable resources. However, many of them contain up to 50% of synthetic plastic derived from oil, and others (e. g. some aliphatic polyesters) are entirely based on oil-derived intermediates. Genetically-modified crops may also have been used in the manufacture of hydro-biodegradable plastics.

Hydro-biodegradable plastics are not genuinely “renewable” because the process of making them from crops is itself a significant user of fossil-fuel energy and a producer therefore of greenhouse gases. Fossil fuels are burned in the autoclaves used to ferment and polymerise material synthesised from biochemically produced intermediates (e. g. polylactic acid

from carbohydrates etc); and by the agricultural machinery and road vehicles employed; also by the manufacture and transport of fertilisers and pesticides. They are sometimes described as made from “non-food” crops, but are in fact usually made from food crops.

A disproportionate amount of land would be required to produce sufficient raw material to replace conventional plastic products, and a huge amount of water, which is in such short supply in so many parts of the world. Residues from some native starches can be seriously toxic; bitter cassava for example (tapioca) has a high level of hydro-cyanic glucoside present, which has to be removed by careful washing. During growth the plant is toxic to wildlife. Cassava is exhaustive of potash. Thus, these are the new types of plastics and the research.