Understanding Sulfuric Acid Waste and Beneficial Reuse
Environmental professionals are often confused about what can and cannot be done with sulfuric acid waste and other inorganic acids that have already been used in a process. Many would be surprised to learn that you can reuse sulfuric acid waste in fertilizer manufacturing, other land applications, and beneficial reuse processes. But how is this possible? The answer is simpler than it seems.
EPA Regulations on “Use Constituting Disposal”
According to the EPA’s restrictions on “use constituting disposal” [40 CFR 261.2 (c) (1) (A)], the agency aims to protect land and clean drinking water supplies. This regulation, often called the “land ban,” safeguards our surface water and aquifers from pollutants. However, land application of waste products can benefit agricultural processes. For example, cow and chicken manure, though waste, is often used as fertilizer. Similarly, chemical fertilizers made with sulfuric acid, nitric acid, and phosphoric acid have long supported agricultural use.
Typically, these fertilizers are produced using virgin acids, which is acceptable and doesn’t violate the EPA’s intent. Sulfuric acid waste can be reused in fertilizer manufacturing if they don’t carry additional toxic contaminants.
What Makes Sulfuric Acid Waste Different?
So, why is sulfuric acid waste any different once it has been used? The key to legal reuse lies in the other substances present within the acid. The presence of toxic constituents significantly impacts whether beneficial reuse is viable. Contaminants like lead, arsenic, or mercury, if present in levels above RCRA limits, can make sulfuric acid waste unsuitable for reuse in fertilizer production. This could release hazardous substances into the land or water supply, posing significant risks.
Even if toxic constituents are below RCRA limits but above the levels found in prime products, there is potential for harmful accumulation on land or water sources. This is why proper evaluation is crucial before considering it for reuse.
The Case of EPA vs. Air Products
The EPA vs. Air Products case discouraged many manufacturers from reusing their used acids for fertilizer manufacturing or any land applications. In this instance, a toxic chemical (dinitrotoluene or DNT) was “along for the ride,” leading to violations. Although Air Products settled without admitting wrongdoing, the case highlighted the importance of understanding the risks involved.
Ensuring Safe Use of Sulfuric Acid Waste
To safely reuse sulfuric acid waste, a careful assessment of potential hazardous constituents is essential. This ensures the risks associated with using the previously used acid are no greater than using prime acid, protecting both the environment and human health.