Biocontained Carcass Composting for Control of Infectious Disease Outbreak in Livestock

The video shows an Example of a study that was conducted at the Lethbridge Research Center that was sponsored by the CRTI program of the federal government, as well as by Alberta Agriculture. The objective of the project is to look at cotton posting as a method of carcass disposal during an infectious disease outbreak in a beef cattle population. This technique was previously used by Dr.Lloyd Spencer of the CFIA, to control the bird flu outbreak that occurred in the Fraser Valley a couple of years ago.

The objective of the project is basically to effectively control the infectious agent and prevent it from spreading to any other surrounding cattle populations. In order to achieve this, you have to have a very rapid response in terms of developing a method of disposal and having it ready and operational hopefully within a 24 hour period. And that's why in the design of this particular experiment, we use locally available materials for the entire composting process, which could be readily re purchased from local farm suppliers, enabling us to construct the structures within a 24 Hour period.

The Outer frame of the structure was based on using simply barley straw as a structure. We put small straw veils in the bottom of the structure just in case there was any seep, each from the overall composting process, and that those small bales would act to absorb any of that liquid. We then use large square bales as the outer walls of the structure.

So our objective was to look at whether or not we could use a similar model, only scale it up to a much larger size to deal with the large body size of full-sized feedlot cattle. The level of containment that we employed in this study was much higher than what would be in a typical composting process. We used the large straw bales in order to contain the entire composting pile within a structured framework.

We collected manure from a the Lepar research center feedlot, and we pre-prepared it by running it through a manure spreader in order to aerate it so that it was heating new ones. Now, this is basically the first time this has been attempted under such a large scale and without such a high level of containment. And one of the concerns we had with regard to when we first tried this was whether or not we would get a significant amount of liquid coming off of the composting process.

So we deliberately placed a drain system, the composting pile, as a means of attempting to collect any liquid that may be produced during the composting process. We use standard silage plastic. This is the same plastic that's available that feedlots used for covering their silage pits.

The idea of the plastic is the, is to include it in order to get a a very high level of security. So basically everything in the composting pile is retained within the plastic barrier. We put a layer of barley straw down in the bottom of the composting structure as an absorbent, and also to help facilitate the composting process.

In addition, we placed temperature transmitters within the compost itself. Now these transmitters continuously record temperature throughout the entire composting process, and then we recover those transmitters at the end of the composting process and download the temperature data from the entire duration of composting. Now, one of the disadvantages of using the plastic is that there's a high likelihood that it'll restrict the flow of oxygen into the composting pile.

Here we used simple drainage tile or drainage pipe that you would typically use in house construction, and we placed these tubes every 16 feet or so throughout the entire composting structure. And the idea of this was to ensure that air was moving down into the composting pile in order for the composting to be an aerobic process and not an anaerobic process where oxygen is excluded and you end up basically making the same process as silage. And we didn't want that to happen.

We wanted oxygen to enter the structure to maximize the degradation of the carcasses. These cattle were obtained from local feedlots in which the cattle died primarily of pneumonia, which is from natural causes. We did not slaughter these animals or kill them for the study itself.

Now, these tubes that we placed in just depended upon passive aeration, which is just the air normally moving through the pipe from the surrounding atmosphere. We didn't use fans or anything like that because again, in the event of a infectious disease outbreak, you wouldn't want to be blowing the infectious agent outta the composting structure and into the surrounding area. Now, in the case of a normal outbreak, you wouldn't implement the degree of detail that we have here, but because this is an experiment, we use these what we call baker retrieval pyramids as a method of implanting samples into the compost and then extracting them at later dates.

For further study, we had model microbes, both bacteria and viruses that we placed in these small white bags and then placed them in the triangle and then put them into the composting structure. The idea there is we wanna make sure that the composting process is killing microbes so that the infectious agent is destroyed during the composting process. We also put additional substrate ends such as tissue, brain tissue, and keratin, which is the protein that makes up hooves and horns.

Keratin is very resistant to digestion, and we wanted to see whether or not if we could get a breakdown of this very resistant protein during the composting process, if we did see significant breakdown, we'd have a good indication that the carcasses would also be completely degraded as well. We pack the pyramids with manure because you wanna make sure that the environment within the pyramid itself is very similar to that of the rest of the surrounding manure. During the composting process, There's only three bags bring back.

All of the material was weighed into the bags prior to being placed in the pyramid, or the numbers of microbes were counted before they were placed in the pyramid. We're just gonna give them, now, in this case, at each of the pyramids, we also put in temperature measurements so that we actually measure the temperature at the site of each individual pyramid. Within the composting pile, we put or placed over 20 of these pyramids into the composting pile at two depths, one which was about half a meter down into the pile itself, and one that was a meter down in the area of where the carcasses were placed.

Now, under normal conditions, most these model bacteria wouldn't cause serious disease in people, but under normal conditions, when you are dealing with an infectious outbreak, you'll notice that the employees are wearing gloves and protective suits, but under an infectious disease outbreak, they would also have masks on special boots. The level of protective wear would be much higher if you were dealing with a real disease outbreak. Once we'd introduced the carcasses, we put about 16 animals in each of these composting structures.

We would then take the manure and cover them using that heated manure, and you can see the amount of steam coming off of that indicating that the manure is already heating. Prior to its introduction into the composting pile, we placed the manure, filled the structure up completely, so now the carcasses themselves are about a meter and a half below the surface of the manure. You see here.

We then put in additional aeration vents in the top of the pile, again, wanting to assure that we have an aerobic composting process. Should we jump to the next space in Fred? Because that's, We also use these vents to measure the types of greenhouse gases that were being emitted.

During the composting process, everything was tightly sealed to ensure that in the case, if it were, if there were truly an infectious agent in the pile, that it would have a very low likelihood of escape. And you can see how we've placed tires on the top, which basically restricts access by birds or carry on feeders to the pile as a whole, ensuring that the infectious agent isn't transferred to other potential carriers. Those wires that you see are what we use to broadcast the temperature at the site of the pyramid out from the pyramid to a computer that we have outside of the composting structure, we monitor temperature at over 48 different sites within each composting pile to get an idea of the spatial variation in the efficiency of the composting process, the tubes were used to measure oxygen at various depths within the composting pile.

As mentioned earlier, it's very critical that the oxygen Penetrate into the pile. Now, because of the degree of detail that we're using here in terms of the placement of those pyramids, the time that it took us to build these structures was much longer than it would be under a normal condition. You wouldn't be placing the pyramids or taking the degree of caution that we are here in terms of making sure we don't damage any of our experimental instruments that we've placed in the pile at various times.

Then during the composting process, we went into the structure and we would pull the triangles outta the structure from those depths of one to half a meter below the surface of the manure, and then measure whether or not the microbes had survived during the composting process and the amount of tissue that had been degraded during composting and the chains and the strength of the triangle enabled us to just pull that right up through the compost itself and retrieve our samples. Now at this point, under normal situations, if you were dealing with a truly infectious outbreak, the temperatures within the composting pile, because we can monitor them outside, we know they've already reached temperatures of 70 degrees Celsius at temperatures of above about 55 degrees Celsius. Most infectious agents are killed, and when we did the measurements on the microbes and the viruses that we did plant the model organisms that we did place in the pile, the viruses were killed within a week and the microbes were killed Within two weeks.

Now, this is us opening the pile Up after the completion of the composting process. This has gone on for a period of about 150 days. The temperature was above 70 degrees in regions of the pile for periods longer than 70 days.

The temperature tended to be higher at the top of the pile than it was at the bottom, but all regions of the pile exceeded 55 degrees Celsius. Now that we're emptying out the composting pile, if it was truly an infectious disease outbreak, the infectious agent would've essentially been killed as a result of the composting process. During this procedure, as we're removing the material, we're also recovering the transmitters, the temperature transmitters that have been in the pile for the entire time, and we will take those out and and load them into a computer to measure what the temperature was over the entire composting process at the site of the animal as well.

We did find that there was some evidence of still remaining bones and tissue, but the animals certainly were no longer recognizable. After the composting process, the sizes of the tissue were relatively small, all much less than than a kilo or or 500 grams. After dismantling of the composting structure, we turned the material and put it into outside windrows, at which point any remaining tissue would be degraded during the secondary composting process.

The critical factor is, is that at the point of that final opening, the infectious agent would've already been killed as a result of the high temperatures that were achieved during the prolonged composting process and the brain tissue. About 98%of that was degraded within the first two months of the composting process.