GYPSUM BOARD

Carbon Impact of Gypsum Board

Gypsum board (sometimes referred to as plasterboard or drywall) is a commonly used building finish material for walls, ceilings, and partitions, in part due to its inherent fire resistance. About 2 billion m2 (25  billion ft2) of gypsum board is manufactured annually1 using about 23 million tonnes (25 million tons) of crude and synthetic gypsum2. The gypsum used in gypsum board comes from both natural (mined) and synthetic sources. Synthetic, or Flue Gas Desulphurization (FGD) gypsum, is a by-product of coal-fired power plants3. 

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Gypsum board is an energy intensive product to manufacture. According to an Industry Average EPD, every 93 board meters (1,000 board feet) of drywall produced requires about 5,048 MJ of non-renewable primary energy (electricity and natural gas usage)4. 

There is a significant amount of gypsum board waste disposal &#; it is estimated that 300,000 tonnes (330,700 tons) per year of gypsum board waste from new construction alone are generated as a result of over-ordering, incorrect specification, damage, and off-cuts during construction3. While gypsum board is easy to recycle, finding recycling facilities for gypsum board can be difficult. 

The paper exteriors and gypsum cores of gypsum board can be made from high percentages of recycled material, but this results in limited to no energy savings because it must go through the manufacturing process again. 

Some manufacturers are reducing carbon emissions from gypsum board by reducing the amount of water used in the mix and hence the amount of heat, and associated emissions, needed to dry the mix. This results in a lightweight product that also cuts down on transportation emissions. 

Specifying lightweight gypsum board products and eliminating waste material are the most impactful ways to reduce the carbon footprint of gypsum board. 

Don&#;t count on the demise of gypsum wallboard anytime soon. The transformation of gypsum wallboard manufacturing from a traditional smokestack industry to a 21st century sustainable manufacturing powerhouse is already well underway. Recent developments in alternative energy technology promise to accelerate this conversion, creating thousands of new jobs along the way. Low cost solar thermal technology is the next evolutionary step towards the goal of producing low cost drywall from 100-percent recycled materials with zero carbon footprint.

Manufacturing gypsum wallboard takes millions of BTUs of heat to produce every 1,000 square feet of drywall. Normally, the required heat is produced by burning natural gas. This made perfect sense when natural gas was low cost and there were no restrictions or costs for emissions.

Many gypsum wallboard plants in operation today were designed and put in service decades ago when natural gas prices were below $2 per million BTUs (MMBTUs). However, the average price paid by industrial users in the United States over the last 12 months is more than $7.60 per MMBTU and there were several months when prices exceeded $12 per MMBTU.

The American Clean Energy & Security Act (aka the &#;Waxman-Markey bill&#;), which passed the U.S. House of Representatives in June, included provisions to cap carbon emissions that could significantly increase the cost of burning natural gas, and hence increase the cost of drywall manufacturing. If the bill passes, the drywall industry could experience energy price increases.

The industry has responded to these changes by improving the efficiency of its manufacturing processes to reduce the amount of natural gas required in drywall manufacturing. Techniques already in use include recovering and recycling waste heat and using additives to reduce the amount of water required to make the gypsum slurry. This in turn requires less gas to be burned to dry the boards.

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However, improved efficiency alone is not enough to counteract the increase in natural gas prices and the potential impact of Waxman-Markey on the cost of drywall production. A more fundamental change, already in use in several drywall plants, is the use of so called co-generation or &#;co-gen&#; facilities. The idea behind co-gen is to use waste heat from gas turbines used in electricity generation for drywall manufacturing purposes.

The same gas turbines ordinarily used to produce electricity for the grid are also used in co-gen units. In electricity generation plants the 1,000 degrees Fahrenheit exhaust gas from these turbines is normally just vented to the atmosphere. In a co-gen plant this waste heat powers the drywall manufacturing process resulting in significant cost reductions.

One typical configuration is the collocation of an electricity generating gas turbine close to a drywall plant so that it can sell the waste heat to the drywall plant. Another common set-up is for the drywall company to own a small gas turbine generator that can provide its own electrical power needs and the required heat for the manufacturing process at the same time. In this case it is not uncommon for the drywall company to sell unused electricity to the grid.

Currently, only a small percentage of drywall plants have co-gen facilities installed but the number is growing. As energy prices rise and carbon emissions costs increase, we can expect to see many more co-gen facilities come online over the next few years.

Although co-gen and the use of more efficient manufacturing techniques reduce the costs and emissions, they still require large volumes of natural gas. As a result they are only part of the solution. Further reductions in the cost and carbon footprint of drywall manufacturing will require the use of renewable energy to provide some or all of the heat required.

The most promising renewable energy source for drywall manufacture is solar thermal heat. Normally, when we think of solar power we think of the solar cells on rooftops or calculators that turn sunlight directly into electricity. Solar thermal systems, on the other hand, convert sunlight directly into heat. Conceptually, the process is very simple. Mirrors focus sunlight onto pipes containing oil that heats up to over 750 degrees Fahrenheit. This hot oil can then be used for anything from powering steam turbines to manufacturing drywall.

Solar thermal process heat is good for large-scale industrial heat applications. It has reliably powered large-scale electricity generation for decades. Older solar thermal power plants are more costly than their natural gas counterparts, which have restricted their use to locations with government mandates for renewable energy.

But how times have changed. The latest generation of solar thermal technology providers can now deliver industrial process heat at lower costs than burning natural gas. These systems can be used to directly replace natural gas in powering a drywall plant directly or powering a co-genturbine combined with a drywall plant. Since every BTU of solar heat displaces a BTU of heat produced by burning natural gas, energy costs drop, whether the energy goes directly to the drywall plant or through a co-gen facility.

Solar-powered drywall plants are both cleaner and lower cost to operate than gas fired plants. Depending on the location of the plant, more than 80 percent of the heat required for a drywall plant can be provided by solar thermal power, so the cost savings can be significant.

Market demand for a low carbon footprint product thus can be served without changing the chemistry or manufacturing process of today&#;s drywall products, and without need for retraining installers and builders. Today&#;s dependable gypsum product, manufactured with near-zero fuel burn, can lead a green revolution without risk to designers, builders, or customers.

Existing plants can be retrofitted with solar thermal systems, and new plants can be designed from the ground up to use the technology.

The stimulus bill, ARRA, provides a substantial discount-a Federal grant for 30 percent of the entire cost of the installed solar system-for installations which begin construction before the end of . W&C

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