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Coal Combustion By-Products (CCBs)

What are the barriers to utilization?

  • TECHNICAL
    • lack of standards and new applications

  • ECONOMIC
    • transporation costs are such that CCBs cannot be transported beyond 50 miles of the power plant

  • REGULATORY
    • designation of CCBs as solid wastes, lack of government incentives, lack of knowledge among users

Technical

Lack of standards:   Before most materials can be used in manufacturing or construction, they must meet specific standards established by the industries using them. Many of these standards have been established through years of experience and are in place to ensure that consistent products are produced. While CCB's are certainly not new materials, using them to replace older, more established materials presents a barrier - since few standards have been established allowing their use. Unless utilization standards are developed, many industries will continue to be reluctant to consider using CCBs.

New Applications:   While CCB utilization continues to increase, we are simply producing more of these by-products than the existing applications can consume. As the need for coal-based electrical generation continues to grow, ever increasing amounts of CCBs will be produced, making the gap between production and utilization even larger. There is both a tremendous need and opportunity to develop new uses for CCBs, taking advantage of the unique physical and chemical properties of these by-products.

Decreasing Ash Quality:   Combustion practice is often changed by utilities to meet more stringent emission regulations. While this certainly improves air quality, the consequence is reduction in ash quality. A common example is conversion to low-NOx burners, which effectively reduces NOx emissions, but also increases the amount of unburned carbon in the ash, often to a level where the ash cannot be used. Another example is carbon injection for mercury removal. The result is lower mercury emissions, but large quantities of additional solid waste, since the ash is rendered unusable. The net result for both of these examples is that cleaner emissions produce more solid waste.

Prescriptive Standards:   When concrete is used in a construction project, the project engineer typically specifies its composition and method of construction. These "prescriptive" specifications are often too conservative and can preclude or restrict the use of supplementary cementitious materials (SCMs) such as fly ash. The ready mix concrete industry has established the P2P (prescriptive to performance) Initiative to encourage performance-based specifications that define the functional requirements of the concrete rather than its composition. The performance-based specifications provide more flexibility for the producer to use fly ash (and other SCMs) in the concrete to maximize durability. For more information, visit the National Ready Mix Concrete Association.

Economic

Transportation Costs:   As transportation costs increase, the distance that any material can be economically shipped is reduced. This is particularly a problem for CCBs since electric utilities are frequently located in locations remote from manufacturing and population centers. Since many utilities are located along navigable waterways, one solution is take advantage of cheaper barge transport, but this requires large volume applications. Another solution is to generate higher value CCB products. Since their value is higher, the distance they can be economically transported will be greater.

Traditional Uses:   Traditional uses such as agriculture and construction have the potential to use larger volumes of CCBs, however, the value is quite low. One of the reasons is that the agriculture and construction industries have become accustomed to low prices that do not always reflect the benefit CCBs provide. An excellent example is using fly ash in concrete. If the ash is within quality specifications, it will be sold for a certain price. If it is of superior quality, it will be sold for essentially the same price. Little or no price consideration is given to the outstanding long-term benefits the high-quality ash will provide. This deficiency can be addressed by developing specifications that are based on performance, not on composition. If a high-quality fly ash can provide exceptional durability to concrete, allowing it to last for 50 years instead of 20 years, it should be worth more. The current pricing system is based solely on whether an ash meets minimal specifications or not. A performance-based system has worked well in Europe, but is currently not used in the U.S.

Regulatory

Government Incentives:   Unlike many countries, the U.S. does not provide incentives for CCB utilization. One of the primary reasons that CCB utilization is so high in Europe is that many countries impose taxes or fees on CCBs that are landfilled. It is less costly for the utilities to subsidize usage and transportation than to pay these fees. This is particularly the case where limited land is available. The government can provide more encouragement by offering tax incentives or other forms of credit for using, rather than disposing of, CCBs.

Lack of Knowledge:   The perception that CCBs are hazardous and detrimental to the environment is simply not accurate. There is a long history of using CCBs responsibly in many applications. Understanding any potential hazardous risks is a prerequisite for using any material or product. Well established scientific procedures are in place to ensure that potential hazards are avoided. Ignoring these procedures and basing opinions on unsubstantiated claims or prejudice is detrimental to the overall benefit that can result.