Environmental professionals are often confused about what can and cannot be done with inorganic acids that have already been used in some process. Many would be shocked to learn that YES, YOU CAN USE THESE PRODUCTS IN FERTILIZER MANUFACTURING, as well as for other land applications and for other beneficial reuse applications. Some will ask “how can this be?”, yet the answer is really fairly easy.
In EPA’s restrictions regarding “use constituting disposal” [40 CFR 261.2 (c) (1) (A)], the agency is specifically seeking to protect the land, including the nation’s supply of clean drinking water. The “land ban” as it is sometimes called, is intended to protect our surface water and aquifers from pollutants. Land application of many waste products have proven beneficial for farming and other agricultural processes. For example, cow and chicken manures are wastes that are often applied to the land as fertilizers. Altiras has used pond dredging materials for various industrial development land applications . Chemical fertilizers, often made using sulfuric acid, nitric acid, and phosphoric acid have long been used for agricultural purposes (i.e., applied to the land). Normally these products are made using virgin acids. Such use does NOT violate the intent of the restriction, and therefore is acceptable. Furthermore, acids already used in another process CAN still be used in the manufacture of fertilizers or other materials normally applied to the land, so long as they do not have other toxics along for the ride.
So why is sulfuric acid, for example, that was already used in another process any different? This is where we have to pay close attention, because the key to legal reuse has to do with whatever else is in the acid. Toxic constituents make all the difference in viable beneficial reuse. Sometimes metals, such as lead or arsenic or mercury may be present and sometimes toxic organic constituents may be present. For example, if the levels of any such contaminants are above RCRA limits, then use of the sulfuric acid to manufacture fertilizer would potentially release those contaminants onto the land and into our precious drinking water supply. This would obviously not be acceptable. In fact, even having toxic constituents below RCRA limits, but well above the levels of prime products could potentially lead to accumulation on the land or in the water supply and should be avoided.
A recent case of the EPA vs. Air Products scared many manufacturers away from beneficial use of their used acids for fertilizer manufacturing and any other land applications, primarily because the violations were not understood by other manufacturers. The problem for Air Products, who settled the case without admitted any wrongdoing, was that a toxic chemical (dinitrotoluene or DNT) was “along for the ride”.
Careful evaluation of the ultimate disposition of each of the potentially hazardous constituents should be made to ensure risks are no different for use of the previously used acid versus prime acid.