Foamglass: from insulation material to sustainable agriculture
by Markus Haastert, Anne Kathrin Kuhlemann, Malte Plewa
Background: What is foamglass?
The construction business is an area of industry which the concept of sustainability has reached relatively late. Nowadays, however, the business of sustainable construction is booming. It is estimated that the profit generated from the green construction business will reach 245 billion US$ by 2016 in the USA alone. This is why new products which promise to make construction greener enter the market regularly. Today we look at one of these products in detail, namely foamglass.
For the production of foamglass, glass is powdered, enriched with carbon and heated up to 900 degrees Celsius, so that is starts to foam. The carbon reacts with the oxygen to carbon dioxide, which is responsible for the bubbles. After is has cooled down slowly, hard boards of foamglass are acquired. Instead of boards, one can also produce granulate by cooling down the hot material very quickly, so that it breaks into pieces.
The producers of foamglass promote that it can be produced to a large extent with recycled glass from landfills. Waste is transformed to value. Generally, glass is a material which can be molten over and over again to reuse it; however, this is very energy intensive.
Foamglass has several characteristics which make it an impressive insulation material. It does not absorb water, so that it cannot start to mold, and it dries up very quickly. Furthermore, it does not take up or release any compounds to the environment and does not react with chemicals; it is completely inert. Through its stability and resistance to influences from outside, the material does, in contrast to other materials, not lose its insulation capacity over time. The enclosed air particles make it a relatively well-suited insulation material. The heat resistance is impressive, the melting point lies at 650 degrees Celsius. Foamglass granulate is also resistant to very cold temperatures.
Also contaminated material, such as glass from television tubes or mercury containing bulbs can be used for foamglass production. During the melting process, heavy metals are separated from the glass and then delivered to metal processing plants1.
Despite these impressive characteristics, one has to examine the life-cycle of the product in detail to be able to make statement about its potential as a new green construction material.
Innovation: Insulation and construction with foamglass
Glass is produced from sand, limestone dolomite and feldspar; the production process is extremely energy intensive. The parent materials are heated up to 1600 degrees Celsius and molten. As the energy demand is that high, a study from the German Environmental Agency (UBA) considered it impossible, to produce glass in a sustainable way1. For the production of one kilogram of glass, an energy input of 14 Mega-Joule (MJ) are necessary. Each percent of recycled glass used in the process, reduces the energy consumption by about 0,25 percent. This means that with a recycling-glass content of 75%, as it is the target in foamglass products, one can save 19% of the energy needed. For insulation or construction purposes, aluminum boards are needed for stabilization. The energy input required for the production of a kilogram of aluminum is more than 120 MJ2. The primary energy demand of one cubic meter of foamglass lies between 750 and 1600 Kwh. If one compares the energy used to produce foamglass with the energy needed to produce other insulation materials, such as hemp, the statistics are not really favorable. Also the insulation characteristics of foamglass are not as good as some of its alternatives. Hemp used for insulation has a twice as high heat storing capacity (2300 J/KgK) than foamglass (1110 J/KgK).
The advantage of foamglass is that something which has been considered waste is brought back into the value chain. In Germany, every year about two million ton of glass are collected3. About 85% of this is recycled4. In the USA, however, the statistics look somewhat different; only 28% of the 11,6 tons of glass waste which are produced annually, is recycled5. The demand is therefore enormous. Unfortunately, the two glassfoam producers in the US are using only virgin material in the production process6.
Many airports are being insulated with foamglass, among them the airports of Doha, Dubai, Paris and Düsseldorf.
Potential: Sustainability and new areas of application
By now, foamglass is not only being used for insulation purposes but also as bearing material in the construction industry. Especially the in granulate form, foamglass is being increasingly used as a base material and in road construction. A study of Norwegian scientist has found out that foamglass-granulate is very well suited for road construction, as it can tolerate heavy weights, strong heat, moisture and cold. The study furthermore shows that the material can be used for the construction of airstrips7. There are already car park levels which are made from this material.
By now it is possible to replace concrete with foamglass. And this is where the actual green potential of the material lies. Instead of concrete, which is a very environmentally unfriendly product due to its high resource demand which often combined with a high quantity of steel, recycled glass can be used. Using foamglass as a material for walls, insulation becomes unnecessary which is often a major factor during construction works. For this, foamglass is combined with aluminum-frames which reduces the time needed for construction drastically. When not only concrete and steel, but also the insulation is replaced by foamglass and additionally a reduction of construction time is achieved, foamglass becomes economically interesting – which is important when is wants to compete with concrete and other materials. Sand resources are being protected and less steel is needed.
Concrete need 3-4MG energy per Kg during its production, steel about 80 MJ. Using an 80:20 mix, the energy demand is about the same as the one of foamglass in aluminum-frames (both from recycling). The foamglass parts can however be better recycled than concrete, which can only be reused as granulate.
For the construction industry, this product has a great potential. Its sustainability however depends on a few conditions. First of all, it is essential to use old glass in the production of foamglass. The production of virgin glass is very energy intensive and unnecessary as long as not 100% of the actually produced glass is recycled. Furthermore, the heat which used in the production process should stem from waste heat from industrial processes or from landfill gas. If it is possible to reuse the heat which develops as a result of decomposing activities in the landfill in a nearby foamglass factory, transportation distances and energy production can be reduced. At least, renewable energy should be used in the production process, as done by Europe’s biggest producer, Corning Europe NV8
Also the carbon dioxide which is produced on landfills can be used in the production process, in order to reduce the emissions of greenhouse gases. Furthermore it has to be ensured that the foamglass itself reenters the recycling process, once it has been disposed.
Foamglass has the ecological advantage that it is chemically completely inactive. Chemical pollution is often a big problem with insulation materials. Materials such as XPS are often treated with fire protection additives, so that they contain a large amount of toxic components when disposed. As foamglass is fireproof itself, no additives are needed.
Also outside of the construction area, foamglass is being used. Fine grained material is used as a substrate for plants in hydroponic installations. Furthermore, cleaning and polishing devices are made from it. “Sponges” made from foamglass can be used to clean hard surfaces, such as pools, kitchen devices or grills. It is also being sold as an alternative to sand paper1. Many other application areas will most probably follow in the near future, as the speed with which foamglass has entered the market is quite amazing.
The foamglass technology can contribute to transforming millions of tons of waste into a valuable product. However, it has to be made sure, that the process takes place sustainably. As a substitute for traditional construction materials, foamglass has a great potential, as it saves resources and is more stable than alternative materials. As it does not need chemical additives, it can also contribute to a healthier way of living.
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Photos: SXC, Koljern, Wikipedia