Why it’s not the last straw for Lush
Lush has embarked on its first straw bale construction project in a bid to slash carbon emissions in the built environment, as Maxine Perella finds out
Lush has recently completed build work on what it claims is a European first – an industrial straw bale cold room for its fresh creams, shower gels and skincare products. The sustainability win lies in embodied carbon savings; the sequestered carbon in the straw, wood and clay used has a far lower global warming impact than a conventional cold room made from steel, uPVC and expanded foam.
Lush’s green manufacturing co-ordinator Nick Read oversaw the construction phase, which took around three weeks, and says the rationale behind the project simply grew out of a “good idea” which stuck. Both Read and Lush’s head of green development Ruth Andrade had some experience of straw building and realised the value in utilising this material.
“Straw is a very unused waste product,” says Read. “When you look at the insulation value of straw, you can get the same performance from it compared to traditional materials, and it’s cheaper too. It can also be composted at end-of-life. We wanted to reduce our carbon impact in our manufacturing operations going forward and it was the right material to use.”
Sourcing a good straw builder was no problem – both Read and Andrade knew of Bee Rowan, who has 13 years’ experience in straw construction work. The company chose to use English straw for lower carbon impact which was sourced from a farm in Milton Keynes. Hand tools and traditional techniques were employed throughout the build, including a sharpening horse to sharpen the wooden hazel pins that hold the bales together.
Other materials used included clay, which was leftover and recycled from a previous project Rowan was involved in, and eco-paints. The thermacell cooling system however was sourced from Germany as it had to meet building regulation specifications, and there were no suitable solutions in the UK.
The wall thickness of the room was determined by the width of the bales while the fabric of the external walls comprises 90% recycled newspaper and 10% recycled gypsum. The end-of-life reuse and recovery potential of every material was an important consideration for the company – once construction was finished, only 133.8kg of waste was sent to landfill at a total cost of £11.50.
“We sifted through all our waste streams by hand to separate them out and find a use for them where possible,” Read explains. Wood waste, for instance, totalled 1,257kg of which 140kg was used to feed the company’s biomass boilers, 209kg was stored for future use, and the remainder sent to an organic recycler. There were also ten 1-tonne bags of leftover straw and leftover clay which Bee Rowan took to her next straw build.
Project cost stayed within the allocated £36,000 budget and only went over timescale by a few days due to it being the first of its type. Being load-bearing brought some additional complications, mainly from a fire regulation perspective.
“Because there isn’t a fire regulations test for load-bearing straw in the UK, it couldn’t be given a fire risk rating,” Read explains. “As a result we are probably going to carry out the fire risk test ourselves – by doing that, we also give something back to the straw building community as we will have shared our knowledge and it enables us to carry that through to future developments.”
While the straw bale building isn’t expected to bring any additional energy usage savings compared to a conventional unit, its global warming potential is a lot lower. The embodied energy value of straw is 0.24 MJ/kg compared to rolled aluminium (155 MJ/kg), plastic uPVC film (69.4 MJ/kg), polyurethane rigid foam (101.5 MJ/kg), steel plate (25.1 MJ/kg) and steel beams (20.1 MJ/kg).
According to Andrade, if you compared an ordinary building with 150mm of polyisocyanurate to Lush’s one built with 500mm straw walls, “very rough back of envelope calculations” would reveal the former to have 310 times more embodied energy than the latter.
And in terms of carbon savings during the building phase – just comparing the insulation element – Andrade reckons the straw bale materials are saving nearly 25 tonnes of emissions on the walls alone. She also points out that straw has a negative global warming potential as it sequesters carbon from the air.
While straw does present challenges to builders because it’s not a standardised product – its size, density and humidity are all dependent on how it gets baled and stored, for Lush the sustainability advantages of using the material far outweighed these concerns.
“If you were to create a standard for how good a building could be in terms of recyclability, you couldn’t do much better than this,” Read maintains, adding that the company also benefited from a R&D tax credit for the project due to its novel nature.
Plans are now afoot to build an entire new manufacturing facility from straw – Lush’s mission is to make it “the greenest factory in Europe, perhaps in the world” according to Read. The company has already identified a site, subject to planning permission, which it hopes will be up and running within the next three to four years.
Maxine Perella is editor of edieWaste
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