Building Products from Fly Ash and CO2

Our friends at Materials Technology Ltd. have shared with me the following information about the significant progress they’re making to turn ash into useful materials using Supercritical CO2. Especially noteworthy is the fact that the CO2 is expected to come from the power plant flue gas, and thus represents significant sequestration of CO2 at the same time. Note the information presented on CO2 separation methods.

The original UFTO note about this work appeared on January 1, 1997 – available in the UFTO website database.

Here is the abstract of a paper they will present at the Green Chemistry Conf, Jun 30 – July 2 in Washington (conference details are attached below).


Roger Jones, President and CEO,
Materials Technology Ltd, 14525 Rim Rock Road, Reno, NV 89511;
Frank G. Baglin, Prof of Physical Chemistry, Univ of Nevada – Reno,
Bruce A. Salisbury, Plant Engineer, Four Corners Power Plant,
Arizona Public Service, P.O. Box 355, Fruitland, NM 87416.


Coal-fired electric power plant wastes, portland cement, calcium oxide and supercritical carbon dioxide (CO2) are feedstocks to make low-cost, superior roofing shingles, wallboard and other fiber-reinforced products. Flue-gas CO2, recovered using thermally-driven, gas-stripping techniques(1), is permanently bound into the products as carbonates, reducing atmospheric pollution and its contribution to global warming.

The purpose of this patented technology is to produce profitable building products and many other useful things using cemented “dusty” wastes treated with supercritical CO2 (2,3). Products are shaped from a paste made of quick lime, a small amount of portland cement, foamed fly ash and fiberglass reinforcement. Once hydrated, they are treated with supercritical CO2 (preferably recovered from flue gas) to react the hydroxide components, forming carbonates and water and reducing alkalinity to about neutral.

The process has four important advantages:

– Capital required is low (three-year plant and equipment payback).
– Parasitic energy loss to the power plant is low or non-existent.
– There is a sufficiently high value-added component in final products to offset the logistics costs of raw materials and finished goods.

Production of cementitious goods and gas separation technologies are well-settled. Practical gas-separation technologies can be subdivided into four broad categories (4):

Membrane separation followed by distillation
Membrane absorption
The appropriate technology depends upon feed stream composition and thermodynamics and upon required quantities of carbon dioxide. In our planned implementation, we will use propylene carbonate absorption. CO2 stripping will occur after sulfur and nitrogen scrubbing.

Forming fiber-reinforced cementitious products like wallboard and roof shingles is also settled technology. Presently, fiberglass reinforced cementitious products demand costly alkali-resistant or plastic-coated glass to prevent alkali-silica reaction. Supercritical carbonation technology allows use of low-cost e-glass instead.

With the exception of foaming agents, fiber reinforcement and portland cement, all raw materials are available on site. The lightweight building products (in this case, fiberglass reinforced roofing shingles and fiberglass reinforced wallboard) are made by cementing foamed fly ash (about 53,000 tons annually for this plant) with calcium oxide (quick lime) and a small amount of portland cement. Both products will be made on continuous lines. After cementing, the products are subjected to treatment with supercritical CO2, again, in a continuous process. The CO2 forms carbonates and carbonated zeolites and reduces the alkalinity of the product to about neutral (pH 7). This permits incorporation of low-cost e-glass fibers without fear of subsequent, harmful alkali-silica reaction. The reinforcement is in the form of both continuous and chopped fiber.

An analysis of the relative inputs to the prototype shingle compared with competing roofing products was made and the results appear in the chart at left (5).

Based on costs of raw materials and energy, our studies indicate that we will be able to sell these waste-based products at pricing points below those of the lowest-priced competing products.

These products are examples of practical, solid-waste-feedstock, chemically bonded ceramics. Many other products can be produced in a similar manner, sequestering large quantities of solid waste and CO2 while offsetting manufacture of products using more energy-intensive systems that increase atmospheric CO2. Examples of such systems include thermoplastics, metals, composites, ceramics and forest products.

As industrial infrastructure in the developed countries ages and requires replacement or renovation, it will be wise to consider supercritical CO2 treated chemically bonded ceramics to reduce energy, raw materials and atmospheric pollution. For developing countries, the benefits are even greater.

In a developing economy, the creation of new industrial infrastructure requires huge investments in transportation systems for feedstocks, raw materials and components. Investment is also required to develop primary, secondary and tertiary manufacturing capacity as well as power plants and facilities to dispose of all types of plant wastes at all levels. Supercritical CO2 chemically bonded ceramic technology reduces much of this investment. Wastes and CO2 simply replace most feedstocks. Ancillary benefits arise from reduction of capital and energy needed to harvest, mine, or otherwise produce raw materials and transport them and intermediate raw materials for secondary or tertiary manufacturing.

Supercritical CO2-treated chemically bonded ceramics rely upon proven, practical technology to produce valuable products from solid waste feedstocks. Capital requirements are lower than conventional production systems, particularly when considering cradle-to-grave economics. Parasitic energy loss to producers is essentially none. Profit margins are high, because most products can be produced with low-cost or no-cost feedstocks.


2 United States Patent 5,518,540 issued May 21, 1996, Cement Treated with High-pressure CO2

3 United States Patent 5,690,729 issued November 27, 1997, Cement Mixtures with Alkali-Intolerant Matter and Method for Making Same

4 21 unpublished papers on methodology for practical recovery of food-grade CO2 from power plant flue gases, Carnegie Mellon University, Professor W.T. Berg, Senior Design Project, March 6, 1996


The 2nd Annual Green Chemistry and Engineering Conference: Global Perspectives
June 30 – July 2, 1998
National Academy of Sciences, Washington, D.C.

The Conference is cosponsored by the American Chemical Society, Committee on Environmental Improvement, Division of Environmental Chemistry, Division of Industrial & Chemical Engineering, American Institute of Chemical Engineers, Chemical Manufacturers Association, Council for Chemical Research, National Institute of Standards and Technology, National Research Council, National Science Foundation, Engineering Directorat, the U.S. Department of Energy and the U.S. Environmental Protection Agency, Office of Pollution Prevention & Toxics and Office of Research and Development.

Details, registration form and complete program available at:

Contact Dianne Ruddy at the ACS for further information at
(202) 872-4402, or e-mail

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