The development of a safe and effective alternative for the processing of condemned material at abattoirs.

Project Title :

Development of a cost effective, pathogen free and environmentally friendly treatment / recycling method for condemned meat products and specific risk material at abattoirs.

Introduction

Condemned material is continuously produced by abattoirs and can considered to be an environmental and bio-hazardous pollutant unless properly treated. There currently exist numerous ways to dispose of condemned material.

Traditional methods include:

• Rendering plants
• Incineration
• Composting
• Anaerobic fermentation
• Burying

This document will focus on the development and operational requirements of an acceptable system for the processing / treatment of condemned material, related meat products and SRM that is proven to be effective, not only in safely and reliably processing the condemned material, but also to accomplish this in a cost effective and environmentally sound manner.

Background Information

Traditional composting systems

Definition of Composting and Compost : The controlled biological decomposition of organic solid waste under aerobic conditions that results in a humus-like compost or compost like material. Compost can therefore be defined as the aerobically decomposed remnants of organic matter

Generally speaking, condemned meat composting is often done in a similar manner to mortality composting, and as such usually ends up in a windrow or a mortality composting bin. The standard procedure for mortality composting is to bed the meat on a layer of carbonaceous material and then covered with chicken manure in alternate layers. The bin or windrow is then capped with a layer of compost that acts as an insulator and smell inhibitor. The windrow is turned every six weeks and the process usually takes around 12 to 16 weeks to completely break down the meat/mortality and render it down to a compost-like product.

The main problems associated with most outdoor composting systems are that they are not as environmentally friendly as one would ideally like to see. Examples of this are leachate affecting groundwater, bad smells hanging around the composting sites, fly and rodent problems, scavengers digging up rotting meat and so on.

Indoor composting is somewhat friendlier to the environment and tends to address a large number of the issues as identified above. The biggest obstacle to indoor composting is usually the price tag associated with setting up the required infrastructure. Indoor composting mostly rely on artificial aeration of the substrate and this is normally accomplished by either placing aeration pipes under floor or by placing the compost on a grid elevated from the main floor, forming a pressurized cavity and forcing air through the compost by means of strong high pressure fans. Compost manipulation is typically achieved through large hydraulic machines and expensive conveyor systems to move product from one position to the next.

A brief overview of the composting process specific to animal by-products.

Composting is done in various phases, and the process is typically determined by the raw materials that are being used as well as the desired end product after composting. Generally speaking the composting process can be divided into two primary categories - active composting and the curing phase. Any other process would be a sub-process of these two phases.

The active composting phase is primarily thermophylic with temperatures exceeding 45 degrees C, whereas the curing phase occurs in the mesophylic range with temperatures gradually reducing to between 20 and 30 degrees C. The curing stage of composting does not really benefit from active management by the compost maker, and is usually accomplished by leaving the compost in large static piles for a period of between six and sixteen weeks (depending on the maturity of the compost after the active phase) with one or two turns incorporated during this period. There are several definitions for compost maturity, but in the interest of keeping this document as straightforward as possible they will be excluded for the time being.

The traditional approach to composting meat waste has been to cover the meat with a combination of carbonaceous materials and chicken manure in alternate layers. This process is nothing more than burying above ground, and as can be expected, smell is a major factor whenever the compost is disturbed. The traditional approach also does not really accomplish any significant pathogen reduction as the composting process itself is not homogenous enough as far as temperature, pH and moisture distribution go.

Specific Reference to the processes investigated and trials conducted using condemned material

We conducted the following trials with condemned material to test the effectiveness of the various composting methods on these specific products

1. Standard & Adapted Mortality Bin
2. Passive Windrow
3. Active Windrow
4. Static Pile
5. Aerated Static Pile
6. In-Vessel Passive Aeration
7. In-Vessel Active Aeration
8. Indoor Shelf Composting

Observations made and Lessons Learned:

1. During both the indoor and outdoor processes we were surprised by the sheer volume of fat that accumulated below the compost. The fat all but destroyed our temporary aeration pipes and totally clogged up all the aeration netting. Had it been a permanent installation, we would have been forced to dig up the pipes and entirely rethink the methodology. The additional costs that would have been incurred in order to provide a fat free aeration environment would be prohibitive and for this reason the system is not the one of choice.


2. The bin systems produced the same results as far as fat goes, with the additional problem of an extremely bad smelling liquid constantly leaching out of the bin in rather unexpectedly large volumes. The smell and unsanitary liquid were just too much of an issue to make this a viable proposition without again investing in an effluent disinfectant system. The system did perform relatively well as a long term microbial tissue digestor alternative as it proved to be reasonably effective in dealing with certain types of bone matter provided that enough time was allowed.


3. The indoor shelf system worked surprisingly well but several serious drawbacks were observed that discounted this system’s value as a safe alternative. The process created a very uncomfortable and smelly working environment due to steam, high VOC concentrations and high levels of NH3 in the atmosphere. In addition, the warm and humid conditions created a perfect breeding ground for any number of micro-organisms that may or may not be harmful to humans and as such required extraordinary levels of protective clothing that proved all but impossible to work in. This system will require a lot of further development to make it a viable proposition.


4. Windrows and static piles in any shape or form, produced no surprises. They were really smelly, slow and uneven in composting the waste and required substantial labor inputs on a daily basis. Maggots stripped the sawdust cap within 12 hours exposing the rotting meat to the environment. Leaching of all sorts of unholy liquids again became an issue. Whilst windrows are great for compost curing purposes, we prefer not to use them for anything else for the reasons as stated above.


5. Odour will always remain an issue when composting rotten meat, regardless of the composting or aeration system employed. It is best summarized by the comment made by a visitor during a tour of the compost trials “ …just because it doesn’t stink to high heaven does not necessarily imply that it smells good – this batch of compost is merely less offensive than the previous one…”

All the systems as tested above required one additional step to ensure safety. The compost, once fully mature would have to be extensively and aggressively pasteurized at very high temperatures in a separate building that provided an environment where adequate pathogen reduction could be accomplished with a high degree of certainty. Apart from the huge capital investment that would be required to fully implement this system, it would also double on operational costs such as labor and require duel sets of equipment.

An additional and very serious concern was that bone matter, which typically are considered SRM, would prove very difficult to fully process to a pathogen free state using composting alone as a means of disposal.

BSE / Mad Cow Disease - It is a well known fact that prions and their infectiousness are not affected by any of the traditional processes except incineration at 850-1000 Celsius with a minimum exposure period of not less than two seconds. Most importantly, no amount of upgrading would enable this (or any other) composting system to accomplish prion elimination as it is simply not designed, nor can it be designed to provide an environment that can accomplish this critically important aspect with any degree of certainty.

Design Criteria Of A Suitable Alternative.

Based on all the observations above, it became obvious that unless we could develop a process that would eliminate or address all of the issues above, composting as a stand-alone disposal method for meat, condemned material and SRM cannot be considered a safe alternative, and would ultimately not satisfy the stringent legal and best practice frameworks that are in place for these types of products.

Any acceptable alternative solution would have to satisfy the following criteria:

1. Provide an effective means of disposing of tissue and bone matter
2. Be Environmentally Friendly
3. Comply with Occupational Health and Safety requirements.
4. Produce an end product which is both useful and pathogen free.
5. Must be cost effective to both the operator and the client.
6. Consistently provide reliable, verifiable and reproducible results.
7. Is not extremely capital or land intensive
8. Offer guaranteed levels of pathogen destruction.
9. Must have the ability to be integrated into any abattoir and form an integral part of their waste disposal activities without requiring changes to infrastructure or product/process flow.
10. Must have the flexibility to deal with variable tissue loads according to variable production throughputs

Project Result

We developed a proprietary MAAHP system that not only met all the specified criteria, but in most instances far exceeded them. We feel confident that the proprietary MAAHP system will satisfy all the relevant industry role players and that, given time, the MAAHP system will emerge as the preferred and superior alternative for disposal of condemned meat waste and SRM throughout Southern Africa.

Client Comments

For further information regarding this process or our performance on this project, please contact Mark Tecklenburg at Nelspruit Abattoir. Tel (+27) 013-753 3700/39.

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