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Independent Professional: Experienced educator and management consultant for engineering educational institutions, researcher, trainer, technical consultant on sustainable technologies, related to cement manufacturing and characterisation, using industrial and agricultural wastes in cement and concrete, durability of concrete and fuel cell power.

Tuesday, December 30, 2008

Sustainable housing

Sustainable housing

Dr J D Bapat

Combined vegetable and plastic waste to make low-cost, sustainable housing

In the poverty-stricken countryside of Paraguay, a landlocked country in the heart of South America, an innovative social activist has found a new use for an old vegetable. Elsa Zaldívar, whose longstanding commitment to helping the poor while protecting the environment has won her deep respect in her native land, has found a way to mix loofah – a cucumber-like vegetable that is dried to yield a scratchy sponge for use as abrasive skin scrubber – with other vegetable matter like husks from corn and caranday palm trees, along with recycled plastic, to form strong, lightweight panels. These can be used to create furniture and construct houses, insulating them from temperature and noise. About 300,000 Paraguayan families do not have adequate housing. Her work shows how making a simple change can transform people's lives.

She persuaded local women in Caaguazú to consider loofah as a means of generating income. When harvested before it completely ripens, loofah can be eaten. The women organized themselves in a cooperative and sold loofah sponges, produced from ripened loofah, as cosmetic products. They used loofah to manufacture mats, slippers, insoles and a variety of other products that were exported to markets as far away as Europe.

Zaldívar was awarded an Ashoka Fellowship in 2001 to continue her efforts to empower rural women to make products from loofah products and to set up a micro-enterprise.

Even with the women's efforts to grow the high-standard vegetables, roughly one-third of the loofahs they cultivated were of inferior quality and could not be exported. Nearly 30 per cent of the sponge material destined for the finished products was trimmed off during manufacture. Determined to find a means to recycle and market for the loofah waste, Zaldívar teamed up with Pedro Padrós, an industrial engineer, to search for a way to recycle the waste vegetable material to construct inexpensive panels for walls and roofing for building houses. She had realized that if the first step to improving the lives of the poor was increasing their income, the next was to help them find decent housing, which would dramatically raise their living standards. The initial efforts to mix loofah with different types of glues did not produce the desired result, mainly because of the high costs involved.

Then Padrós got the idea of using plastic waste with the loofah. He invented a machine that melted a mixture of three types of waste plastic and combined the resulting liquid with loofah and other vegetable fibres, such as cotton netting and chopped corn husks. After hundreds of trials, the results began to produce a working product. With the help from Paraguay's environment ministry, Base ECTA (a non-profit organization headed by Zaldívar) obtained a grant from the Inter-American Development Bank to construct the prototype of a machine to produce the panels.

Combining a melting unit, mixer, extruder and cutting unit, the machine can produce – in an hour – a half-metre-wide panel 120 metres long. Depending on the exact mix of plastics and fibres, as well as the thickness of the panel, the composite can have varying amounts of flexibility, weight and insulating qualities, making it adaptable to a variety of construction needs. Colouring can be included in the panel's plastic mix at the time of fabrication, so there is no need to paint the walls after construction, saving homeowners time and money. The panels with greater strength can be produced by using a honeycomb or earthen filler, as well as vegetable matter, to create a sandwich of two panels.

The composite panels are easier to handle than lumber or brick, and much better than conventional materials in an earthquake or other natural catastrophe. Combined with special metal connectors, it will bend but not break, in an earthquake .If a house collapses, human lives are likely to survive as the walls are lighter in weight than conventional materials. Using the panels will help spare the nation's forests. The fibers that are completely renewable and lumber can be spared. That's very important in Paraguay as the original forests have been reduced to less than ten per cent of Paraguay's territory.

As Padrós has refined the design of the panels, improvements have brought the cost down. The panels initially costing about US$ 6 per square metre to produce, have already dropped to less than half that figure, making it competitive with existing construction materials, such as wood. Zaldívar predicts the price will continue to fall as experiments continue. She is also involved in discussions with several companies interested in using the panels commercially, but her main aim is to make the construction material available at low cost to those who need them most.

Zaldívar believes rural families should be able to build their own simple house in just three to four days, supplementing the panels with other locally obtained materials such as bamboo and adobe. Even urban residents, who often have access to subsidized credit and other government assistance, will be able to use the panels in constructing decent housing.

The project's success derives from the unique combination of Padrós' engineering skills with Zaldívar's genius in creating an integrated system of cultivation, recycling the waste, production and distribution. In addition to the loofah producers, Zaldívar is working with recyclers in urban areas in order to guarantee a flow of appropriate plastic and with groups of women to provide the tonnes of corn and palm husks, for example, that will be needed – all materials that would otherwise end up as waste thrown in landfills.

Padrós says the panels are designed so that they will not generate any waste – should they wear out or break, they can be ground up and recycled into new panels. The process could be repeated several times until the composite becomes too rich in vegetable fibers, but Padrós says the mixture can then be used as a high-energy fuel. That means the recycled plastics used in the initial mix must be carefully selected to insure that they can be burned without producing toxic fumes.

As Zaldívar and Padrós finish testing the improved panel-making machine, the Rolex Award will finance a promotion centre near Asunción and the construction of three model houses where the panels' versatility will be displayed for both urban and rural audiences, as well as funding the production of a video that will be used to describe the project to people interested in using similar sustainable techniques in other countries.

Contact address:

Ms Elsa Zaldívar
Defensores del Chaco
350 San Lorenzo 2140

Tel: + 595 21 580 239