Bamboo offers green building solution

Prof. Dirk E. Hebel is seen with bamboo in its stages from raw stalk to fibre which is the moulded in various shapes to create bamboo-fibre-reinforced concrete.

In the martial arts movie Crouching Tiger, Hidden Dragon, the characters of actors Chow Yun Fat and Zhang Ziyi spar atop a swaying stand of bamboo, but the towering plants never break.

Now, researchers from the Future Cities Laboratory, a collaboration between Singapore and the Swiss Federal Institute of Technology in Zurich (ETH Zurich), hope to harness the flexibility and strength of bamboo fibres to replace steel rebar used in reinforced concrete.

As Singapore goes through a construction boom, it is paying more attention to greening the construction process - from studying the use of bamboo to reinforce concrete, to calculating the carbon footprint of buildings. Recently, the Building and Construction Authority (BCA) made "green and gracious builder" certification a requirement for public construction projects from 2017.

The construction and manufacturing industries produce about 5 per cent of the nation's greenhouse gas emissions, said Associate Professor Evelyn Teo of the National University of Singapore's Building Department, who studies sustainable construction.

Dr Chew Soon Hoe, a civil engineering researcher and council member of the Institution of Engineers Singapore (IES), said there are several ways to shrink this carbon footprint: Use less material, use material made with less energy, use greener energy in construction processes, and recycle material better at the end of its lifespan.

This is where the bamboo project, led by Assistant Professor Dirk Hebel of the Future Cities Laboratory, fits in. Even with the energy involved in splitting bamboo pieces down to fibres and compressing them with heat and adhesives, the carbon footprint of bamboo fibre is "a fraction" that of steel, Prof Hebel said.

"Bamboo stores carbon as it grows, so we could, so to speak, store the carbon in our buildings instead of releasing huge amounts in the steel industry," he explained.

And it grows in most of the developing countries that could use it most, he added.

His team is testing different "recipes" for making stronger bamboo-fibre bars, and hopes to commercialise them within three years.

Meanwhile, Prof Teo is working out the carbon footprint of various construction materials, starting with cement. For example, the carbon footprint of cement from a factory in Taiwan - one of Singapore's largest suppliers - is about 0.42kg of carbon dioxide for every kilogram of cement. (By comparison, a round-trip flight to Kuala Lumpur emits about 60kg of CO2 per person.)

"Collecting this information will be informative and will act as the first step on the path to carbon management," Prof Teo said in a proposal. That will help the industry make better decisions about its environmental impact, she added.

In Singapore, typically 20 per cent of a building's energy use over its lifetime is actually embodied in the building materials, the BCA said, while 80 per cent comes from its usage and operations such as air-conditioning.

Companies are also getting in on the act. When it built its new factory in Boon Lay, packaging firm Greenpac calculated the carbon footprint of the entire process with the Singapore Institute of Manufacturing Technology, or SIMTech.

SIMTech found that materials and the transport of materials, especially imported ones, contributed most to the building's carbon footprint. Utilities, worker transport and on-site equipment also bumped up its energy use.

"Reduction of one's carbon footprint has a broad impact beyond climate change," said Dr Song Bin, director of SIMTech's Sustainable Manufacturing Centre.

"It drives down energy consumption from fossil fuels, encourages the use of renewable energy as well as the use of materials which are made with less energy from fossil fuels, and promotes efforts to reduce waste and increase reuse and recycling. All these would also result in cost reduction and improved operations."

What about at the end of a building's lifespan?

Currently, steel-reinforced concrete has to be broken up and the steel removed with magnets to recycle both steel and concrete, said the IES' Dr Chew.

But at NUS' Civil Engineering Department, Associate Professor Gary Ong is working on ways to dismantle buildings more easily or better adapt them for other uses. For example, he is designing building joints that hold up to repeated dismantling and reuse.

Already, Singapore recycles nearly all of its construction waste, using crushed materials in non-structural applications like roads.

And in the BCA's Green Mark assessments, developers are given points for using cement made with industrial by-products, or using concrete made with recycled construction material instead of rock or sand.

While these measures may come at a cost, Dr Chew said, it is a small cost; a large Green Mark Platinum building might cost 3 per cent to 5 per cent more than an ordinary one, but this can be recouped in energy savings over a building's lifespan.

"We have no choice," he said. "We have to do it for the benefit of the next generation."

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