Ecodesigners embrace materials derived from renewable sources. And why wouldn’t they? These materials can displace those normally extracted from otherwise finite resources. Warren McLaren has a look at eight materials created from annual or bi-annual agricultural by-products for building.
Flax flooring
Flax is a remarkable plant, accounting for why we’ve been cultivating it since before 3,000 BC. The first part of its scientific name, Linum usitatissimum, hints at its double life (the latter Latin term meaning ‘most useful’.) Flax plants can produce the durable fibre known as linen, but it is pressing the seeds that give us linseed oil, one of the key ingredients in the production of the original resilient flooring — linoleum. Linoleum ruled the roost of the durable hard floor covering market for nearly 100 years after it was patented in 1960, before being nudged out by the cheaper (and more toxic) polyvinyl chloride (PVC). One of linoleum’s great strength was its longevity — well laid floors can endure 20 to 40 years of hard wear. But ‘lino’ is not flax’s only trick in the architectural game. It is also the base ingredient in traditional wood putty, together with a little chalk.
Soy insulation
The not so humble soy bean, like hemp, seems to be able to metamorphose into just about anything. One of its more recent transformations has been as building insulation, both as spray-on foam and as batts. Insulation providers in the US offering spray-on foam soy trumpet the product as being free of formaldehyde and other off-gassing volatile organic compounds. One supplier suggests that 450 grams of the base matter used to create the product sequesters 1 kg of carbon dioxide. Apparently soy foams can expand up to 120 fold to completely fill cavities and create a leak-resistant thermal seal. And although not 100 per cent biodegradable, soy-based foam is said to have the highest content (bio or renewable material) of any foam-based insulation. Soy is not, however, totally benign, with over half of world soy bean production of genetically modified origin and vast tracts of South American rainforest being felled to expand cultivation.
Banana veener
When bananas — a massive herb plant — are harvested, the tall stem which produced the fruit becomes permanently non-productive. They are normally cut out to allow other suck stems to grow from the same root base and produce a fresh trunk and subsequent fruit. Following more than a decade of development, Papyrus Australia, an Adelaide-based company, last year opened the world’s first commercial factory and can now take the waste banana ‘tree’ trunks and convert them into a range of building materials, including veneers and fibreboards. The waterless and minimal chemical manufacturing of the fire retardant and water resistant banana product, known as Beleaf, is undertaken on-farm in Queensland’s Walkamin. Beleaf was officially launched as a wall panel veneer at the Monaco Boat Show in September 2009. European businesses are also eyeing off Beleaf for use in furniture, tongue and groove flooring and acoustic tiles.
Macadamia tableware
Australia produces around 29,000 tonnes of raw macadamia nuts annually. Such harvesting generates a heap of waste product from the unwanted shells. The macadamia nut only grows natively along a 600 km ribbon of the Australian east coast. Macadamia husks are also processed into landscaping mulch and used in agricultural waste to energy power plants. Designer Marc Harrison and architect Paul Fairweather established the company Husque back in 2003 to craft products from discarded macadamia nut shells. Husque grind up the shell of the nut and mix it with an unspecified polymer to create a range of tableware products, with the inner surfaces polished with polyester. The completed products are provided with a final sheen from hand rubbing with macadamia oil. The macadamia nut is said to make up 80 per cent of the finished Husque vessels. The guys have plans to expand beyond bowls, vases and platters into what they term ‘architectural products’.
Rice blocks and straw
The Ricegrowers Association of Australia says we produce around 1.3 million tonnes of rice each year. Yet for very hectare of rice grown, some 7 tonne of stalk stubble is created, a ‘waste’ which is subsequently burnt. The Australasian Strawbale Building Association (Ausbale) calculate that NSW rice farmers alone “burn over 600,000 tonnes of rice straw, releasing 30,000 tonnes of carbon dioxide and 2,000 tonnes of particulate directly into the atmosphere”. Ausbale figures this waste could instead be used to construct the walls of around one third of all new homes in Australia annually. Ortech already use some of the waste for its formaldehyde-free Durra wall panel system, which contain one twelfth the embodied energy of a comparable plasterboard/timber stud wall. Ampan have been working on a rice straw particle board as well, but it’s not yet been commercialised. In the US, Oryzatech has developed a rice-straw based building block which resembles a Lego block for giants. Testing suggests it has three times the insulation value of a standard insulated stud wall.
Sugary bitumen
According to Ecopave Australia, the world currently consumes around 2 billion tonnes of asphalt and 200 million tonnes of bitumen binder every year to make roads and pavements. The global expansion in mobility sees an ever increasing use of crude oil not only for the production of petroleum fuels, but also to produce the bitumen on which our transport travels. Ecopave claims to have developed a world-first non-petroleum based bitumen asphalt and binder. After 20 years of development, GEO320 is an asphalt substitute derived from agricultural by-products, in particular, the molasses that results from sugar production. Unlike petroleum-based bitumen, which needs to be kept heated to remain liquid, this bio-bitumen can be stored as a dry granulated product until required on-site. It is said to offer 50 per cent higher durability, and in a coloured formation, absorbs 50 per cent less heat than oil-derived bitumen.
Wheat acoustics
Like rice, the harvesting of wheat grain leaves behind a vast amount of agricultural by-product in the form of wheat straw. It too can be used to make strawbales for thermally efficient wall construction. However, it has also found a home in the realm of acoustic panel insulation. The Solomit product compresses wheat stubble stalks into ceiling panels that maintain their shape due to being stitched together with galvanised wire. It is like a thick industrial version of a tatami mat, with the gold wheaten colour exposed as the building's ceilings. Many building products arrive from overseas production plants with all the attendant carbon emissions, but Solomit is sourced from Australian farms and fabricated locally. The original Solomit panels were fixed to a steel house frame and concrete rendered on the exterior with plaster interiors. Such walls were considered, in their day (the 1940s), to be 20 per cent cheaper than brick and stronger than timber.
Hemp houses
In the spring of 2008, the NSW government finally joined most other Australian states by allowing farmers to legally cultivate low THC hemp crops for fibre and oil production. Farmers from Bunbury, WA, to QLD are finding they can grow industrial hemp from seed to harvest in less than 120 days. Although hemp processing plants are thin on the ground in Australia, landscape designers can at least specify hemp mulch. In Europe, however, complete hemp building construction is in full flight. Taking up on an idea developed in France, English and Irish builders are embracing hempcrete (aka isochanvre), an insulative material made from the pithy centre of hemp stalks, with just a ninth of the weight of cement concrete. So enthused by the potential of this building medium, participants from 17 countries attended the 1st International Hemp Building Symposium held in Ireland last year.
