New Process User Bacteria to Transform Waste Gases into Useful Chemicals

Advances in Industrial Energy-Efficiency Technologies

Prepared for:
U.S. Department of Energy
Office of Industrial Technologies
Washington, DC 20585

Produced by:
National Renewable Energy Laboratory
Golden, Colorado 80401-3393

In conjunction with:
Energetics, Inc.
Columbia, Maryland 21046

DOE/CH10093-138
DE92001230
August 1992

Waste gas from carbon black production represents "lost energy" and creates pollution

More than 5 million tons of waste gases are discharged into our environment each year as by-products of the manufacture of carbon black, a material used to make rubber products (such as tires, shoe heels, and mechanical goods), printing inks, and pigments. These waste gases contain carbon dioxide (CO2), carbon monoxide (CO), and hydrogen (H2) and represent both lost energy and chemical feedstocks. At the same time, discharging these gases into the atmosphere contributes to environmental pollution on both a local and global scale. Unfortunately, conventional methods of waste gas recovery and separation are expensive and impractical with current methods of carbon black production.

Biological conversion of carbon black waste gas yields acetic acid and reduces emissions

Using bacteria to convert such as waste gases into usable chemicals for sale to other industries is not as far-fetched as it sounds. Recent advances in biotechnology have led to the development of "designer" micro-organisms capable of promoting chemical reactions for a variety of applications. In fact, scientists sponsored by the U.S. Department of Energy (DOE) have developed a biological process for utilizing waste gases from the carbon black process. The biological conversion of these gases into commercial products would save both the energy and the feedstocks that go into the conventional production of these products and would reduce emissions of the gases into the atmosphere.

In a cooperative project with DOE, Engineering Resources, Inc., is developing and testing a biological process for converting the waste gases into acetic acid. The process can operate at the atmospheric temperature and pressure of the carbon black waste gas stream and can selectively utilize the gas components to produce acetic acid. The technology should also be applicable to waste gases from the production of coke (used to make steel) and other industries as well.

In 1991, the first year of the project, researchers selected the most promising microorganisms for the process and conducted chemical studies with them in the laboratory. One of these, an anaerobic bacterium, has emerged as the favorite because it has the fastest rates of acetic acid production and is compatible with the chemicals needed to separate out the acid. Experiments to optimize the performance of the bacterium have resulted in waste gas conversion rates much faster than researchers had ever hoped to achieve.

Photo: Research is continuing with the bench-scale system and will lead to larger scale field tests in the next few years. [provided in source document]

Bioconversion of Waste Gases to Acetic Acid

Major uses of the acetic acid will include plastics and de-icers

More than 1.5 million tons of acetic acid are produced in this country annually, with the plastics industry representing the major consumer. Acetic acid is also a major component of a new road deicer; the market for this material could expand rapidly if cheaper acetic acid becomes available. Conventionally, acetic acid is made from petro-chemicals and is relatively expensive, with a current market price of about $0.36 per pound. The price of biologically produced acetic acid is expected to be substantially less because the process uses industrial wastes as the feedstock and requires much less energy for its operation.

Initial application of the new technology will be aimed at the carbon black industry. With a biological conversion system, the average carbon black plant would produce up to 55,000 tons per year of acetic acid, replacing an equal amount of chemically produced acid. The biological system would require 14,000 Btu per pound, compared to 57,000 Btu per pound for the conventional method. Therefore, replacement of all current acetic acid production would result in a savings of as much as 4.9 trillion Btu per year per plant, or a total of 100 trillion-150 trillion Btu (equivalent to 580 million-870 million barrels of oil) annually for the 30 carbon black plants currently operating in the United States. The subsequent application of the new process to coke-producing plants and other industrial processes could yield even more savings.

In addition to saving energy, this new technology can reduce the emission of harmful waste gases in two ways - through recovery and use of the waste gases from carbon black (and eventually coke) production, and from the reduced energy requirements of acetic acid production via the biological process, which in turn reduces the use of fossil fuels. By 2010, the total national reduction in waste gases from the new technology is predicted to be 10 million-20 million annually.

A preliminary design and conservative economic analysis has shown a return on investment of approximately 1 year for the installation of a biological acetic acid facility at a typical carbon black plant. However, this analysis was based on slower conversion rates than have already been achieved in the laboratory, indicating that the economics of the technology may be even better than expected.

Future efforts will focus on demonstrating the new process

Over the next several years, Engineering Resources, Inc., will conduct both bench-scale and full-scale demonstrations of the biological conversion process. The full-scale demonstration will take place on-site at a commercial carbon black facility, utilizing the actual by-product stream. Industry representatives have been impressed by the potential of this technology, and an industrial cost-sharing partner has already been selected for the full-scale tests. Several engineering companies have also expressed interest to providing expertise for the design and scale-up of the technology. The final phase of the project will involve operation of the system continuously for several months to determine the viability of the bacterial cultures under actual conditions.

This series of experiments should lead to the development of a sound technology that can be readily commercialized.

For More Information:

Industrial Waste Reduction Program
CE-222
Office of Industrial Technologies
U.S. Department of Energy
1000 Independence Ave., SW
Washington, DC 20585

(202) 586-6750


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Last Updated: February 13, 1996