Gypsum is wonderful stuff. It occurs in nature widely, but can also be synthesised. It is endlessly recyclable. It is fire-resistant and fairly durable. It can be moulded into intricate forms that will then endure for centuries (plaster has been used in buildings for practical and artistic purposes in civilisations from the ancient Egyptians onwards). Although gypsum has an ‘Achilles heel’ - it does not perform very well in the presence of water or moisture - this weakness can be modified with the addition of waxes, silicones or other water-proofing chemicals. Gypsum can be processed at relatively low temperatures (particularly when compared to high-temperature processes like cement clinkerisation at 1450°C). Due to its recyclability, low embodied energy, low embodied CO2 and its relatively low cost, gypsum is very widely used in a variety of industries for its chemical, mineralogical and physical-mechanical properties. In many applications, it has no economic or practical substitute.
So, it’s clear that we cannot do without the wonder-mineral that is gypsum. It keeps us safe from fire, can help in keeping us warm or cool as part of an insulation system, and is used to create concrete - the crux materials that forms our man-made world. The supply of gypsum is critical to modern life. Is that supply secure?
The first, crucial thing to realise is that in nature, gypsum is a sedimentary mineral, formed from calcium- and sulphur-rich waters subject to strong evaporation, for instance an inland sea or lagoon. The most soluble salts will precipitate out first from a concentrated brine, followed eventually by less and less soluble species, including gypsum, which is a hydrous (water-containing) calcium sulphate mineral. Depending on the circumstances of the original water body (regularly re-connected to the seas or long-isolated), the resultant deposit may be interleaved with salt, with shale, or with limestone. Gypsum deposits can form thin layers or very thick layers, and may also have varying degrees of impurities, usually in the form of tiny clay mineral particles. Gypsum layers or strata have formed over the entirety of geological time (perhaps even since water formed on the surface of the planet around 4.6bn years ago) and are still forming in some areas of our planet today.
The primary deposits of natural gypsum occur in Baja California, Mexico; in Pernambuco state, Brazil; in Nova Scotia, Canada; in Spain, Germany, France and the UK; in Oman and Thailand, and in Iran, China and Australia, as well as in other locations around the world. The thickness, purity and depth of the gypsum layer will determine whether it is mined using surface mining, open-cast, or deep mining. Transport costs - and closeness to a navigable waterway - are also crucial in deciding the economic viability of a deposit.
Access to and the possibility of exploitation of gypsum deposits is variable worldwide, and has reduced somewhat in Europe following ever-more stringent environmental regulations. However, the industry contends that it can exist side-by-side with well-protected nature areas such as Natura 2000 sites.
At the same time as supplies of natural gypsum are becoming harder to access in some areas, environmental regulations (and basic economics) are forcing the closure of many coal-fired power stations in Europe and north America, taking their flue gas desulphurisation (FGD) gypsum with them. A number of gypsum wallboard plants in Europe and America that were built next to FGD gypsum-producing power stations will become veritable ‘orphans’ when their ‘parent’ plants close in the next few years. If they are lucky, they are located on substantial waterways that will allow them to import their raw materials.
Other environmental directives - as well as hard economics - are also driving the rise of gypsum recycling. I have been shocked, when visiting my local dump (or ‘Community Recycling Centre’ as they prefer it to be called), to see large signs proclaiming that ‘Gypsum wallboard is BANNED from this site.’ The anaerobic breakdown of gypsum in the presence of biodegradable waste can lead to the formation of poisonous hydrogen sulphide gas - which can kill with a single lung full. So, there is a supply of pre-used gypsum, and as detailed above, an increasing demand for alternative sources of gypsum. After an initial tentative recycling technology research and development phase, the logistics and infrastructure of gypsum recycling is really gaining momentum (in Europe and in North America) and could provide millions of tonnes of raw materials to industrial users of gypsum in the coming years.
All of these topics will be addressed at the inaugural GypSupply Conference and Exhibition, which will take place in Brussels on 13 - 14 March 2018 . The event (www.Gyp-Supply.com) will look specifically at issues of gypsum supply, gypsum shipping, synthetic gypsum supply trends and at the latest research and trends in gypsum recycling. It promises to be very interesting!
