LESS COMMONLY USED TECHNOLOGIES

No full-scale plant is operating in the United States. Until one is constructed, a consistent set of data to use in documenting energy, environmental releases, and costs will be lacking. That need might be partly met by data on plants that are operating in other countries, if they were available. The 1,000 ton per day San Diego facility will be valuable in providing information to evaluate the economics, energy balance and emissions.

Cofiring RDF with Coal for Power Production

Barriers to Widespread Use

The most significant barriers to wider use of cofiring as an MSW management strategy include:

• Finding utilities with coal fired boilers that they can afford to derate, and that are willing to overcome the engineering concerns about performance and reliability
• Providing incentives to induce those utilities to take the institutional and public exposure risks associated with the change.

Among the major technical problems are those of compatibility between specific coals and RDF mixtures; the influence of these combinations on ash slagging and fire box performance must be considered separately for each coal and RDF mixture used. Continued study of long-term performance and possible needs for operational modifications will be important in determining the future for cofiring installations.

The emissions from cofiring may also differ from those of coal-only plants; the possible effects of those differences are a technical, as well as a regulatory, concern.

Emissions

Direct comparisons between the emissions from cofiring and those from coal-only installations are impossible at present because no data are available on:

• Air emissions arising from a coal unit that was converted to cofiring
• Air emissions from the few operating units that alternately fire coal and RDF
• Effects, if any, of cofiring on the composition and amounts of waste water.

An important need is documentation for full-scale operating plants in the United States. Until such plants exist, actual operating data on energy requirements, environmental releases, costs, and product properties for gasification/pyrolysis on a basis consistent with those of other MSW technologies will not be available. That need might be partly met by data on plants that are operating in other countries, if they were available. However, current data on the few large plants in Japan and France are missing, and very little is known about the new plant under construction in Italy.

NOTES:
(1) Expert panels convened by the U.S. Department of Energy (DOE) have also identified research needs for each technology; in contrast with the observations in this report, the recommendations of those panels are at a detailed scientific and engineering level.

11. REFERENCES

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