Decontamination of Natural Animal Bedding in Containment Facilities

Why Natural Bedding?

In containment facilities, there are a variety of different biowaste streams that have to be treated before they can leave the facility to be disposed of – anything which may have come into contact with infectious material (liquids, solids, sharps, glassware, gloves and masks, etc).  For facilities who study animals, this also means bedding.

The animals are more comfortable, safe and calm in an environment with natural bedding, and thus the research is less influenced by the animals’ living conditions. Less stress leads to a more authentic research conclusion.  It is for those reasons that some regulators have incorporated natural bedding as a requirement for animal research facilities.

Why Is Animal Bedding Such a Challenging Waste Stream?

There are many factors which make it difficult to treat animal bedding.  Here are just a few of the various aspects of bedding that make it more challenging than other waste streams:

• Types: straw, wood chips, wood shavings all with their own densities and properties.
• Soil Loading: can contain urine, feces, feed particles, animal hair, etc.
• Volume: can be very large volume, but low weight.
• Containers: often bagged or placed in bins.
• Mixed Loads: bedding may contain other materials such as gloves, wipes, towels after cleaning.

What Are Current Treatment Efforts?

Facilities have to consider whether they would prefer to treat directly through the containment barrier, versus removing from containment and treating externally (if allowed to do so).  Possibilities include gaseous or vapor treatment, autoclave, or incineration, but none are ideal for this type of waste:

Gaseous & Vapor Treatment: Utilizing gas or vapor sounds easy enough, but there is no way to assure penetration through the entirety of the load.  If the bedding is in a bag or plastic container, the gas or vapor will not penetrate.  You simply cannot apply this technology in these cases.

Incineration: Incinerators within containment include a double-door design which is undesirable at best, and in most cases the incinerator is outside of containment, requiring the transport of hazardous materials to the unit.  Additionally, incinerators are highly inefficient for bedding, considering they will fill up quickly but have a low overall mass – each cycle will under-utilize the incinerator, wasting energy in the process.

Autoclaves: Autoclave capacity may be consumed quickly by the volume of bedding materials.  There are concerns with load densities, varying soil loadings, and penetration of bags and containers.  Validation becomes difficult if not impossible.

What is Our Proposed Solution?

Hybrid Shredding Autoclave (BSLXstream™): with a hybrid shred autoclave, the bedding, storage containers and any other waste particles are placed in the system, shredded, and then steam sterilized at 138 °C, 3.5 bars pressure.  This process solves many of the challenges listed above.  The shredding process solves the volume and density problem, reducing the material into smaller, accessible particles, reducing volume by up to 80%, ready for steam sterilization.  The shredding process also solves the challenges with containers by shredding them, exposing the material inside.  Once shredded, the steam sterilization process begins, with treatment to an 8 log reduction of Gb Stearothermophilus.

The hybrid shred autoclave can be installed in multiple configurations, with loading outside containment, or loading through the containment floor, with a bio-seal (similarly to how our digester systems are installed).

Here’s the step-by-step treatment process in action:

1. Loading of waste through the top opening.
2. Shredding starts as soon as the lid is closed, sealed and locked.  Heavy-duty shredder features automatic reverse rotation to prevent jamming.
3. Heating is achieved through steam, raising the temperature to 300°F at 51 psi.
4. Sterilization achieved by maintaining pressure and heat for 10 minutes (adjustable time/temp to meet material density).  Achieves microbial inactivation of 10⁶ – 10⁸ reduction.
5. Cooling through the flash tank lowers temperature and pressure to prepare for system opening.
6. Draining of condensate and cooling water into the sanitary drain.
7. Unloading of the sterilized waste into a waste tote, while liquid can be sent to an Effluent Decontamination System (EDS)

Sample Bedding Testing:

In our sample test runs, straw was gathered into blue collection bins and bags, loaded into the system, and processed altogether.  The shredder was able to break-up everything, including the bins and straw, for steam sterilization to take place.

Upon completion of the cycle, the waste is discharged through the bottom of the system, for disposal as regular municipal waste.

How do We Validate Efficacy?

Detailed Temperature Mapping: In order to demonstrate that all parts of the system reach the appropriate treatment temperature, a temperature mapping plan was developed and implemented.  The base machine includes two fixed temperature sensors that are monitored during a normal operation.  For this test, 10 additional temperature sensors were installed in the machine in various places.

The temperature data was recorded by the PLC every minute and logged into a datasheet.  The temperature points were then graphed together.  Even though some of the temperature sensors start at significantly different levels, they quickly converge during the heating cycle and are easily maintained above 138 °C set-point during the sterilization cycle.  During this test, there were approximately 10 different runs completed with differing cycle programs.

Biological Indicator Validation & Data Logging: The efficacy tests of the system has been evaluated by various organizations such as:

• Pasteur Institute (ISO/IEC 17025 International Standard Accredited Laboratory – Accreditation No. 1-2215) WNWN International, and many others

Tests were conducted using various microorganisms such as Bacillus Stearothermophilis, Bacillus Subtilis Spores and others.  Samples were taken at critical points and times in the cycle with different waste compositions.  Effluent water and air emissions were tested as well and were found to be within the regulatory guidelines.

Conclusion: BXLXstream™

The hybrid shred autoclave addresses many of the challenges of treating animal bedding, with pre-shred allowing for varying solids loading, plastics and other objects to be treated in one cycle.  It can be designed for loading within contained spaces with a bio-seal.  The system uses a validatable process, and has been temperature mapped to ensure sterilization temperature is achieved and maintained.  For animal bedding, there is no better solution to address all these pain points.

Our BIOXstream™ and BSLXstream™ hybrid shred autoclaves offer solutions for biopaharmaceutical manufacturing, or high containment applications.  If you are interested or if you have questions about these systems, please contact us for more details.