Gypsum recycling is the process of converting gypsum waste into recycled gypsum by producing this raw material that can replace virgin gypsum raw material in the manufacture of new products.
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Definition and type of waste gypsum
Gypsum waste consists primarily of waste from gypsum boards. Gypsum board is a wall or ceiling panel made of gypsum core with a layer of paper around it. Such boards are also referred to as plasterboards, drywall, wallboards and gyprocks. The major waste gypsum also in some countries consists of gypsum blocks and plaster, among others.
The three main types of gypsum waste based on their origin can be distinguished:
- Gypsum waste from manufacturing gypsum products.
- This waste, which appears on the industrial gypsum production site, comprises rejecting and non-spec materials produced during the manufacture of gypsum products. Recycling of this waste stream is usually part of the waste avoidance activity of the gypsum factory. Such waste is referred to as manufacturing gypsum or waste production and recycled gypsum obtained from recycling is known as "waste derived gypsum recycled production".
- Gypsum waste from new construction.
- The waste of gypsum from new construction activities is usually clean waste, and mainly consists of outer pieces of plasterboard (drywall, wallboard or gyprock) when the board has been cut to fit the dimensions of the wall or ceiling. The waste may be 15% of the gypsum material used on the site. Such waste is commonly referred to as new construction gypsum waste, and can be reduced by ordering boards "made for measuring", but in most markets less than 10% of all orders are "made to measure".
- Gypsum waste from demolition and reconstruction
- This trash appears when plasterboards already installed (drywall, wallboard or gyprock boards), which were usually installed several years ago, were brought out in connection with buildings that were demolished or renovated. For this reason some people refer to this waste as "old gypsum waste," whereas trade usually calls this waste "discharge waste". Unlike the two other types of gypsum waste described above, the type of waste gypsum from renovation, repair and destruction work is more likely to present certain levels of contamination, which can be nails, screws, wood, insulation, wall coverings, etc. In order for this waste to be recycled, equipment required to process the waste is capable of separating the contamination from the cast to arrive at pure recycled gypsum. New construction and discharge gypsum waste both occur after the gypsum product has left the plant site, and together these two types of waste are referred to as post consumer gypsum waste.
The recycled gypsum obtained from this is known as post-consumer recycled gypsum.
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Gypsum recycling process
Gypsum waste may be converted into recycled gypsum by treating gypsum waste in such a way that the contaminants are removed and the paper facing the plasterboard is separated from the gypsum core through mechanical processes including grinding and sieving in special equipment. Gypsum wastes such as gypsum and plaster beams need not be thrown away, as they are not made with paper from scratch. It's typical for gypsum recyclers to receive up to 3 percent contamination from other materials. Professional recyclers are able to handle gypsum waste with nails and screws, wall coverings, etc.
Why should gypsum waste be recycled?
The gypsum material consists of calcium sulfate dihydrate (CaSO4Ã, Â · 2H2O). Sulfate reducing bacteria convert sulfate into toxic hydrogen sulphide gas; they are killed by exposure to air, but the humid, stuffy, and carbon-filled environments in landfills are good habitat for them. So the cast is inserted into the landfill will decompose, releasing up to one quarter of the weight in hydrogen sulfide. In addition, methanogenic bacteria also thrive in such environments, and convert paper in plaster into methane gas which is a potent greenhouse gas.
Gypsum waste recycling also reduces the need for excavation and production of virgin gypsum raw materials.
Recycling a ton of plain gypsum will save 1,000 pounds of black alkali, 1 ton of lactic acid and 500 kwh of energy.
Recycling a metric ton of gypsum will save 28 kwh of energy and 4 pounds of aluminum.
Reasons for selecting closed-loop recycling
Gypsum is fully recycled and, as a consequence, gypsum waste is one of the few construction materials that allows closed cycle recycling.
The recycling of covered gypsum products involves the collection and processing of gypsum waste, and the recycled gypsum delivery obtained to gypsum product manufacturers. It is therefore important that recycled gypsum reach pre-determined quality suitable for the manufacture of new gypsum products. There are currently no European or American standards that determine the quality of recycled gypsum and the criteria vary from factory to factory.
By opting for closed cycle recycling, the producers' need to obtain virgin gypsum is reduced, thus contributing to promote a sustainable manufacturing process.
The most advanced plant, and mostly found in the Nordic countries of Europe, has replaced up to 30 percent virgin gypsum raw material with recycled gypsum.
Gypsum recycling in Europe
The recycling of gypsum in Europe was started by Danish company Gypsum Recycling International A/S in Denmark, in 2001. After several years, the recycling system received wastes from about 85 percent of all public civil recycling/leisure centers and recycling rates of 60 percent of all gypsum waste is achieved. This system has been exported to cover other European countries. Today also new recyclers have emerged and gypsum recycling systems have been introduced in more countries, such as Britain, France and Benelux, but the highest recycling rates for gypsum waste are still found in Denmark, Norway and Sweden. January 1, 2013, the European Life project "Gypsum to Gypsum" begins, with the overall goal of changing the waste dismantling market of gypsum to achieve higher gypsum waste recycling rates, thus helping to achieve resource-efficient economies. One of the drivers for this project is the target set by the European Union to achieve 70 percent of recycled construction and disassembly waste by 2020.
Gypsum recycling in North America
New West Gypsum Recycling began recycling wallboard waste in Canada in 1985. The recycled material is a mixture of pre-and post-consumer, wet and dry gypsum waste that is the source of raw materials for use in the manufacture of new drywall products. Gypsum Agri-cycle is one of the first companies to recycle drywall in the US. Gypsum Agri-cycle is another recycler of the new construction drywall in America located in Pennsylvania. Pennsylvania does not allow Gypsum Agri-cycles to recycle drywall demolition.
Zanker Recycling began recycling gypsum in sheetrock form in 1999. In the recycling process, materials such as wood, metal, and garbage are dumped in places where the dozer is used to destroy material.
USA Gypsum located in Denver, PA provides recycling cycle recycling and recycled gypsum recycling to higher-value gypsum products such as agricultural gypsum.
See also
- Recycling by product
- Henrik Lund-Nielsen
- International Gypsum Recycling
References
Source of the article : Wikipedia
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