Bio plastic

Eco-friendly bio-plastics made from plants cause environmental problems, according to a recent study.

The substitute for conventional oil-based plastic can increase emissions of greenhouse gases on landfill sites as some need high temperatures to decompose and others cannot be recycled, the study said. Many of the bio-plastics are also contributing to the global food crisis by taking over large areas of land previously used to grow crops for human consumption. Bio-plastics are made from maize, sugarcane, wheat and other crops, it added.

The industry, which used words such as ''sustainable'', ''bio degradable'', ''compost able'' and ''recyclable'' to describe its products, claimed bio-plastics could save carbon up to 30-80 per cent compared with conventional oil-based plastics and can extend the shelf-life of food.

Some of the biggest supermarkets and food companies were using a corn-based packaging made with polylactic acid (Pla), which looks identical to conventional polyethylene terephthalate (Pet) plastic.

The product has been used to package organic foods, salads, snacks, desserts, fruits and vegetables and bottles mineral water as well.

While Pla was said to offer more disposal options, it has been found that it would barely break down on landfill sites, and could only be composted in the handful of anaerobic digesters which exist in Britain, but which do not take any packaging.

These new generations of biodegradable plastics ends up on landfill sites, where they degrade without oxygen, releasing methane, a greenhouse gas 23 times more powerful than carbon dioxide.
''A significant percentage leaks to the atmosphere,'' the Guardian quoted him as saying.

''Just because its biodegradable does not mean it's good. If it goes to landfill it breaks down to methane. Only a percentage is captured,'' said Peter Skelton of Wrap, the UK government-funded Waste and Resources Action Programmed.

Some environmentalists said the terminology confused the public.

''The consumer is baffled,'' a Wrap briefing paper said. ''It considers these products degradable but ... they will not degrade effectively in (the closed environment of) a landfill site,'' it added.

Insects use.......

Some insects that live above and below the ground communicate with each other by using plants as "green telephone lines", a new study has found.

Subterranean insects issue chemical warning signals via the leaves of the plant. This way, insects above the ground are alerted that the plant is already "occupied", according to the study by scientists.

This messaging enables spatially-separated insects to avoid each other, so that they do not unintentionally compete for the same plant, Science Daily reported.

In recent years it has been discovered that different types of above-ground insects develop slowly if they feed on plants that also have subterranean residents and vice versa.

It seems that a mechanism has developed via natural selection that enables the subterranean and above-ground insects to detect each other. This avoids unnecessary competition.

Using these "telephone lines", subterranean insects can also communicate with a third party, namely the natural enemy of caterpillars.

Parasitic wasps lay their eggs inside above-ground insects. The wasps also benefit from the volatile signals emitted by the leaves, as these reveal where they can find a good host for their eggs.

The communication between subterranean and above-ground insects has only been studied in a few systems. It is still not clear how widespread is this phenomenon.