Sustainability

Manufactured gas plants leave waste behind

Editor’s Note: “Sustainability” is a column granted to the Student Sustainability Task Force by the Editorial Board to discuss issues of sustainability on the Rensselaer campus and around the nation.

Manufactured gas plants? Why would we need to manufacture gas? Don’t we use natural gas? It actually wasn’t until the 1940s through the 1950s that we transitioned to the use of natural gas. Prior to that time we had to find ways to create gas for lighting, cooking, and heating.

How do you manufacture gas? Well, one technique is to heat coal with little exposure to new air. This process is known as coal carbonization, the byproduct of which is coke—the solid left from the coal, which burns hotter and cleaner. Back when these plants were still operating, some chose to focus on the production of coke and considered gas to be the byproduct.

While coal carbonization began just prior to the Civil War, a newer technique called carbureted water gas came about not too long after the end of the war. This technique involved heating coke or coal, adding steam to produce a methane-carbon monoxide mixture, and then adding petroleum products, which then broke down, producing additional methane. The gas mixture that resulted burned hotter and brighter than the gas produced by coal carbonization.

So what became of the manufactured gas plants during the transition to natural gas? The utility companies that owned these plants altered the use of these spaces for electric substations, storage yards, truck garages, office buildings, and major generating stations. Although the last manufactured gas plant in New York State ended production in 1972, the remaining waste has left its mark, keeping this old practice in our minds. Of the 300 MGPs that previously existed in New York State, 194 are scheduled for remediation.

While coke was a byproduct of early MGPs that was easily dealt with, other byproducts such as coal tars (also known as tar sands) have proved more difficult. Coal tars were often used for sale or reuse, but when formed as tar-water emulsions (mixtures), complete separation was difficult. The dirty water that resulted was discharged to nearby bodies of water. Because coal tar is heavier than water, the remnants in this discharge would sink to the bottom, causing contamination to the sediments.

At MGPs, underground tanks were typically used for the storage of coal tar. When MGPs were taken down and redone to serve a new purpose, many of these storage tanks were left untouched, still containing coal tars. Why does this matter? Because coal tar is not always as thick as the tar used for roads, but is rather an oily liquid. Being a liquid, it has the ability to leak out of the storage tanks and into the ground, contaminating both the sediment and the groundwater in the area. Unfortunately, the groundwater serves as a form of transportation for the coal tars, spreading the contaminant and dirtying well water in the area as it moves.

Over the years there has been a growing understanding of how our waste should be disposed of. History has helped us to reach this understanding. With remediation underway, and greater techniques and technology to help us move forward, we have a cleaner future to look forward to.