Manufactured gas plant

Gas production

Two main processes were used to produce the gas. The older and simpler process was coal carbonization. In this process, coal was heated in closed retorts or beehive ovens. Inside these ovens, the coal was kept from burning by limiting its contact with outside air. Volatile constituents of the coal would be driven off as a gas, which was collected, cooled, and purified prior to being piped into the surrounding areas for use. The solid portion of the coal would become a black, granular material called coke. Coke was a valuable fuel for many industrial uses and for home heating, because it burned hotter and more cleanly than ordinary coal. Sometimes, the coke was the primary product, and the gas was a by-product, and the facility was called a coke plant.

As the gas manufacturing industry developed and expanded after the Civil War, a new process was introduced which produced a gas mixture that burned hotter and brighter. This process, carburetted water gas (CWG), was first introduced in the 1870s. By 1900, most MGPs in New York State were using this process. However, some MGPs in the state never made the conversion and continued as coal carbonization facilities for their entire lives.

A variety of water gas processes were developed, all of which involved a first step in which coke or coal was heated in a closed vessel or retort into which steam was injected. A chemical reaction took place which produced a flammable gas mixture of methane and carbon monoxide. Petroleum products were then sprayed into the hot gas mixture, creating another chemical reaction in which petroleum constituents were "cracked" to form methane, which increased the heating and lighting value of the gas.

Current use of MGP sites

Former MGP sites have found a variety of uses in the years since they ceased operations. Many are still owned by the utility companies and are used as electric substations, storage yards, truck garages, office buildings and major generating stations. Many also still contain gas regulating facilities, due to their access to the gas distribution system. Other uses range from abandoned industrial property, to commercial/retail uses, to schools and residences.

Potential problems

These sites often contain abandoned underground structures and pipes containing coal tar or other MGP residuals. Some of these waste materials (especially coal tars) may have migrated from existing/former structures and may be present in the subsurface. Impacts to surface water bodies and their sediments are also common since MGPs were typically located near a source of water.

It is not common to find MGP wastes exposed on the ground surface. Most of these plants have been closed for at least 50 years, and in some cases over 100 years. In many cases, subsequent redevelopment of the MGP sites has removed or covered wastes that were exposed at the surface.

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