Biodegradable materials in the construction industry

[edit] Introduction

A material that is biodegradable is one that can be broken down by living organisms, such as bacteria and fungi, without leaving any contaminating substances behind. A natural decay process, biodegradability results in compaction and liquefaction of materials. The nutrients released are eventually recycled into the environment by natural processes. Typical examples of biodegradable materials include leaves, food and sewage. Increasingly, biodegradable packaging materials are also available.

One side effect of this process can be the release into the atmosphere of the gas methane, which as a greenhouse gas can trap 100 times more heat than CO2.

[edit] Construction

The essence of biodegradability is not that these products break down – many other non-biodegradable products can also share this characteristic – but that the breakdown occurs without releasing toxins into the environment. This is of great significance to the demolition of buildings, which typically comprise a mix of potentially toxic materials.

The traditional building site or demolition site, is likely to produce an abundance of waste materials that are non-biodegradable and will end up in landfill (even if they are first reused or recycled). This includes most industrial materials such as plastics, glass and heavy metals, the disposal of which presents long-term problems for society. A study by Cardiff University found that 70–105 million tonnes of waste is created in the UK from demolishing buildings every year; only 20% of that is biodegradable.

Recent years have seen an increase in the availability of biodegradable materials and packaging, which may eventually help avoid accumulating mountains of potentially polluting waste.

Materials which are biodegradable include:

• Biodegradable paint – made from a mix of milk protein, lime and mineral pigments.
• Bamboo – used increasingly in recent years in loadbearing structures. It has also tested favourably as a replacement for reinforcing steel in concrete.
• Cork – a traditional material but is now seeing increased usage thanks to its aesthetics, fire resistance, acoustic insulation and the fact that it is extremely waterproof. It can be used internally and externally.
• Desert sand – contrary to common belief, normal sand of the type used in building is not in abundant supply and suffers heavy demand globally. Hitherto, desert sand has not been an option due to its fine, smooth grains which do not readily bind together. But it has been incorporated in a composite material called Finite developed at Imperial College, London. Claimed to be as strong as both concrete and ‘traditional housing bricks’, it is easy to reuse and biodegradable, has half the carbon footprint of concrete and can also be remoulded for multiple lifecycle uses.
• Hempcrete – a hemp-based bio-composite material that also combines lime, sand or pozzolans, it can be sprayed or formed into lightweight blocks that combine insulation and thermal mass. It does not have the strength of concrete but can be used as an infill to a structural frame. It has a claimed one-hour fire resistance.
• Linoleum (lino) – now coming back into fashion partly due to its eco-friendly attributes, linoleum’s constituent, natural materials of linseed oil, natural resin, ground cork dust, wood flour and powdered limestone result in a biodegradable floor covering that can be supplied in a variety of colours and textures.
• Soybean plastics – created from organic sources, however not all are biodegradable due to the addition of non-biodegradable polymers. However, some soybean plastics can be made to biodegrade. Their use at present is limited mostly to biodegradable packaging for consumer products but this is likely to increase as research intensifies.

[edit] Related articles on Designing Buildings Wiki

• BREEAM Recycled aggregates.
• Circular economy.
• Composting.
• Construction waste.
• Disposal.
• End of life potential.
• Environmental impact assessment EIA.
• Environmental plan for building design and construction.
• Managing packaging waste streams.
• Mean lean green.
• Pre-demolition audit.
• Recyclable construction materials.
• Reduce, reuse, recycle.
• Reused construction products.
• Site waste management plan.
• Site Waste Management Plans – A Necessary Burden.
• Sustainable materials.
• Waste and Resources Action Programme WRAP.
• Waste hierarchy.
• Waste management plan for England.