44. Recycled plastic sheets for greenhouses

In the past two decades, the use of polyethylene (plastic) films for greenhouses and for mulch has increased dramatically in the Third World. Between 1967 and 1987 in Jordan, for example, the use of plastics for greenhouses doubled every 2 years, then doubled every 3 or 4 years. Jordan began producing its own plastic films, but this entails importing plastic pellets to make the sheets. As well, the sheets are now causing a major environmental problem regarding their disposal: lasting only 1-1.5 years, they are then either discarded in neighbouring land or burned. Discarded plastic has been responsible for the deaths of cattle who have ingested it while grazing.

Researchers in Jordan have now developed a process to recycle used plastic sheets in the production of comparable quality, less expensive films for mulch and greenhouses. The new process will lower costs for farmers, decrease pollution from plastics, and reduce imports. As well, it has the potential to increase employment, both in production plants and in the collection of the waste plastic.

The process used is called coextrusion, which allows for the combining of layers of different materials to create a stronger and more resistant plastic. The new recycled plastic film is made up of two layers: a highly stable upper layer made from virgin plastic, and a bottom layer made from recycled plastic. In Jordan, used plastic sheets are readily available for recycling, reducing the need for imported plastic. It is estimated that a reduction of 20 to 50% in material costs occurs when using recycled plastic. The new sheets contain up to 50% recycled plastic, and have properties similar or better than virgin plastic films.

Prerequisites

Access to used greenhouse plastic films. The production plant requires a coextrusion machine, a fairly expensive item (US $240 000 to $400 000), 620 Kwh of electrical power, and 25 m of water to clean each tonne of used plastic. To save on water costs a closed system is recommended with a water recycling plant. The plant employs 10 people: two operators, two assistants and six labourers.

Potential users

There are plans to disseminate the technology to small and medium-sized plastic film producers in Jordan, Syria, Iraq, Turkey and Egypt. Currently the technology is being used in Jordan and Egypt, where it is being adapted to local materials and conditions. Researchers in Egypt are investigating as well the potential for using polyvinyl chloride (PVC) instead of polyethylene, which could reduce costs by as much as 45%.

Cost and availability

Raw materials (used films) cost about US $57 per tonne in Jordan. Total production costs for making regenerated plastic pellets from the used sheets is US $215 per tonne. Actual production of the two-layered recycled sheets runs from US $960 to $1150 per tonne for materials (depending on the thickness of the different layers), with production costs (covering salaries, water and electricity) at $500 per tonne. The coextrusion machine is the most expensive item, ranging from US $240 000 to $400 000.

Contact

Mr H. Khadra
Royal Scientific Society
PO Box 6945, Amman, Jordan
Tel.: 844802 or 844702; Telex: 21276 JO
RAMAH;
Cable: ERRAMAH

Professor M.R. Kamal
McGill University
3480 University Street
Montreal, Quebec, Canada H3A 2A7
Tel.: (514) 392-5432; Telex: 05-268510

Professor A. Yehia
Polymer Department
National Research Centre
Tahrir Street, Dokki, Cairo, Egypt
Tel.: 701 211; Telex: 94022 NAREC UN