Recyclet Limited collect plasterboard and gypsum based wastes to be processed in their recycling facility.

The waste material is processed into a gypsum powder that can then be used as a raw material by plasterboard manufacturers or be utilised in mushroom composting, soil stabilisation and growing media. There are process engineering issues that dictate that only a percentage of this recycled material can be used in these applications and therefore Recyclet Ltd were keen to identify other suitable applications where the recycled gypsum can be utilised.

ETCIC were commissioned by Recyclet to conduct an investigation into the possibility of using recycled gypsum in the manufacture of cement, as the company are keen to try and establish a route for their recycled gypsum into this market.

Gypsum is used as one of the raw materials in the manufacture of cement with approximately 5% gypsum / anhydrite being added to the cement clinker to retard the setting time of the cement. The cement industry in the UK uses approximately 0.6 million tonnes per year of gypsum and this figure is set to rise to 0.68 million tonnes by 2010. Natural Gypsum / anhydrite is the preferred material for cement manufacture, although synthetic gypsum is also used, despite its higher moisture content making it slightly more difficult to handle.

The other main uses of gypsum in the UK are in plaster and plasterboard manufacture and changes in building regulations which require improved sound and thermal insulation are leading to increased use of gypsum in these areas.

Demand for gypsum is primarily driven by activity in the construction sector and the projected trend for this industry looks set to be an increase in construction activity. This increase in activity will lead to an increase in demand for gypsum. This may lead to an increase in cost if the demand begins to outweigh supply.

The amount of natural gypsum that has been extracted in the UK has steadily decreased over the last decade. Currently the majority of gypsum used in the construction industry is synthetic gypsum (desulphogypsum) produced from flue gas de-sulphurisation in coal fired power stations. The gypsum industry does not view desulphogypsum as being a long term source as the future of coal fired power stations is uncertain and it is possible that they will begin to be de-commissioned from 10 years time onwards. If this occurs it will further exacerbate the demand on gypsum supplies and may lead to further price increases. Increasing freight costs are also impacting on the import of gypsum, making it less viable to import low value raw materials.

Therefore by using recycled gypsum in the cement making process, cement manufacturers would be guaranteeing their supply and keeping the associated costs down.

The Cement Industry is regulated by the Environment Agency and has to adhere to the Integrated Pollution Prevention and Control Directive (IPPC). This legislation imposes a number of requirements on industry to control emissions to land, air and water and to manage the use of raw materials and waste. The British Cement Industry has worked closely with the Environment Agency to produce a sector plan which defines the key environmental performance indicators against which their performance can be measured.

Cement manufacturers would therefore benefit from using recycled gypsum in the cement making process as it would help them to meet their targets against the following performance indicators:

• Reduce consumption of natural resources per tonne of cement manufactured;
• Optimise the sustainable use of wastes from other industries or sources;
• Promote product stewardship and wider supply chain benefits.

Trials and Use of Recycled Gypsum in Cement

A wrap funded project was conducted in 2007 to look at cementitious mixes using recycled gypsum. The project partners were Lafarge Cement, Coventry University and Skanska UK Ltd. The conclusion of the project was that recycled gypsum could be effectively used in the manufacture of cement to produce low to medium strength concrete mixes for use in road foundations.

Castle Cement are currently using recycled gypsum (Brand name Cemset) produced by Minerals Resource Management (MRM) and Mid UK in their cement manufacturing facilities.

A number of cement manufacturers in the USA are also using recycled gypsum in their cement manufacturing operations as an alternative to virgin material.

Advantages of Using Recycled Gypsum in Cement Manufacture

• The source of recycled gypsum is close to Cemex Cement’s South Ferriby manufacturing facility, therefore reducing the amount of transport required. This will help to reduce associated costs and also reduce the emissions to air from haulage operations;
• Guaranteed source of gypsum for use in the cement manufacturing process;
• The recycled gypsum can be processed by Recyclet to meet the customer specifications;
• Cost of recycled gypsum should be highly competitive with that of virgin gypsum, especially if the demand for the virgin gypsum begins to outweigh supply and the material has to be imported;
• Use of recycled gypsum will assist cement manufacturers to comply with performance indicators such as reduction in the consumption of natural resources and optimising the use of waste materials from other industries or sources.

The research carried out by ETCIC showed that it is feasible to use the recycled gypsum product in the manufacture of cement and there is therefore an opportunity for Recyclet to enter into this market and take advantage of an additional outlet for their product.

The subsequent report has allowed Recyclet to approach a major cement manufacturer to begin discussions on the possibility of supplying recycled gypsum into their cement manufacturing processes.