Share thisToday’s biocontainment community is evolving at record pace with expanding science and rapid discovery of new diseases. In the past few years, this increase in research has challenged the waste treatment industry to play a major role in development of new technology.
This new waste treatment industry, once limited to landfill and incineration, has expanded with microwave sterilization, rendering, and alkaline hydrolysis treatment methods. Not only are each of these technologies viable for consideration, but there are also multiple providers of each technology. One of the issues, given the expansion of technology and providers, is adequate testing and validation.
Over the next few months, a group of seasoned industry members, including a microbiologist, mechanical engineers and biosafety officers, will share some insight into the alkaline hydrolysis technology, which in today’s market is referred to as the “tissue digester” or “caustic digester.” This series of articles will provide a clear history of the technology and share a better understanding of the costs associated with the operation, design consideration, and compliance issues for each of these waste treatment technologies.
Considering the basic facts and developing an understanding of the each these solid waste treatment systems and how each works in the biocontainment market is critical. It also provides insight as to why more caustic digesters are being used to treat animal carcasses. Some critical elements might be inadequate coverage of local municipality issues, public perception, and guideline compliancy requirements. However, before discussion of today’s market, a review of the history of alkaline hydrolysis is appropriate.
The History of Alkaline Hydrolysis
In 1888, Amos Herbert was granted U.S. Patent 394,982 for alkaline hydrolysis. His patent summarized reads, “My invention relates to the treatment of bones and animal waste and the horns, hoofs, skins, cartilages, and meat of animals,” “If the bones be treated with from 5 to 10 per cent of their weight of caustic potash or its equivalent, the…matter of the bone is dissolved... especially if heated to or above boiling point.”
The similarity between Herbert’s patent and today’s caustic digesters is the “specified” mixture of the percent of caustic to carcass weight. A comparison between the 1888 patent and today’s mixture of caustic is the addition of caustic to achieve a pH 13. This aggressive pH, which breaks up the tissues in today’s digesters, is typically achieved with the addition of sodium or potassium hydroxide—measured to 7 ½ percent the weight of the animal carcass—at an elevated temperature.
In addition, the science of alkaline hydrolysis is identified in the U.S. Federal Register (44 FR 53460, September 13, 1979) under the Environmental Protection Agency, 40 CFR, Part 257 – Criteria for Classification of Solid Waste Disposal Facilities and Practices. Appendix II to Part 257 states:
A. Processes to Significantly Reduce Pathogens… “Lime Stabilization: Sufficient lime is added to produce a pHof 12 after 2 hours of contact.”
B. Processes to Further Reduce Pathogens… “Heat Treatment: Liquid sludge is heated to temperatures of 180 °C for 30 minutes.”
One important aspect about the Federal Register is it relates to a term often used in this industry, “reduce.” For instance, the biological testing protocol requires a pathogen death rate of a 6 log reduction.
So what is the significance? This technology actually dates back over 122 years as a documented method of treating carcasses as well as an acceptable method in the sterilization process. Other than being cased in a shiny stainless steel vessel, there is prior art which identifies the process.