MANUFACTURED GAS WASTE DISPOSAL
INVESTIGATIONS.
TWO CASE STUDIES IN IOWA
Suzanne Bangert, Environmental Engineer
Wisconsin Department of Natural Resources
Madison, Wisconsin 53707
Donald B. McDonald, Professor
Department of Civil and Environmental Engineering
University of Iowa
Iowa City, Iowa 52242
Stanley J. Prior, Jr., Consulting Geologist
West Branch, Iowa 52358
Samuel J. Tut hill. Vice President
Iowa Electric Light and Power Co.
Cedar Rapids, Iowa 52406
INTRODUCTION
Gas for heating and illumination was manufactured from coal in Iowa from the late nineteenth
century through early to mid 1950 when propane and natural gas became available. Two of Iowa
Electric Light and Power Co. (Iowa Electric) predecessor companies operated coal gasification plants
in Belle Plaine, Iowa, and Fairfield, Iowa, during this period (see Figure 1). Two gas manufacturing
processes were used at these plants. In the coal gas process, coal was heated in retorts and the gas
removed with exhauster fans. In the blue gas or water gas process, steam was passed over a bed of
incandescent coal or coke. To increase the BTU content of this gas, oil was added, resulting in
carbureted water gas. Before storage and distribution, the gas was passed through a series of purification steps to remove water, tar, sulfur, and other impurities. Plants operated with condensers, scrubbers, and iron oxide purifiers to complete the purification of the gas.1
Production of gas from coal resulted in the generation of two significant by-products, coal tar/tar
sludges and spent oxide from the purification steps. The quantity and the physical and chemical
characteristics of these by-products were determined by the type of manufacturing process used and
the type of coal used.2 Coal tar, or tar sludge, was removed from the gas in the scrubber, also known
as a wash box, the condenser, and the gas holders. The tar was separated from process water in
rectangular gravity separators and stored in brick-lined tar wells or earthen pits. If a market existed,
the coal tar was sold locally as a wood preservative for fence posts, for road treatment, as a herbicide,
or as a pesticide for application around chicken houses. In addition, the tar was often sold to
refineries for distillation into various organic fractions which could then be used to manufacture
roofing compounds or paint. The value of the coal tar residue was primarily the polynuclear aromatic
hydrocarbon (PAH) constituents (e.g., naphthalene, chrysene, pyrene) present in the tar. 2 Other
constituents in the coal tar included light aromatic hydrocarbons such as benzene and xylene, sulfur,
and metals (e.g., cadmium, copper, lead). Excess tar was disposed of on-site in the tar wells or pits.
Occasionally, the tar was discharged into nearby drainage ways.
Purifier or oxide box wastes consisted of spent iron oxide (wood chips treated with iron), sulfur
compounds, cyanides, and small quantities of coal tar. The spent oxides were often spread on the
ground near the purifier, aerated, and re-used. After the service life of the iron oxide material was
completed, the wastes were placed in earthen pits, low areas, or on the ground for final disposal.
Because of the ferrocyanides in this waste, the spent oxide typically exhibited a characteristic blue
color.
Other wastes generated during the coal gasification process included ash, clinkers, coke fines, and
various aqueous emulsions. These resulted from the operation of the boilers, the gas generators and