Rotary Drum Composting of Poultry Mortalities

Rotary Drum (or In-Vessel) Composting

• Reduce odor and disease-causing organisms.
• Eliminate the leaching threat and potential for soil and water contamination.
• Remove animal decomposition from the public eye.
• Enhance biosecurity by enclosing material and removing the scavenger threat.
• Produce finished compost material that has value as a soil amendment.

• Adequate moisture content (40 to 60 percent).
• Oxygen (>5 percent).
• Proper carbon-to-nitrogen (C:N) ratio (25-35:1 seems to work best).
• Enough carbon source or bulking agent (shavings, recycled compost, used litter, etc.).
• Correct amount of mortality (do not overload the unit, thereby upsetting the C:N ratio and decreasing the porosity).
• The porosity (or amount of air space within the material) affects the availability of oxygen, temperature, microbial activity, composting time, and the bulkiness and density of the material. It appears the porosity of compost material should be at least 35 percent to facilitate good air distribution and maintain optimum microbial growth. Moisture levels in excess of 60 percent should be avoided because moisture fills up the air spaces within the material, increasing the bulkiness and density of the material and retarding aerobic activity, which reduces the temperature and increases the composting time. In addition, too much moisture can result in the material becoming anaerobic, which increases the likelihood of excess odor generation.

Rotary Composter on the MSU Poultry Research Farm

We use pine shavings as a carbon source (Figure 4). Initially, we tried using chicken litter, but our commercial houses have not been totally cleaned out in several years, and the carbon content of our litter is too low to act as a good carbon source. Therefore, we could not achieve the results we wanted. We do reuse a portion of the discharged compost back through the unit, and that seems to work fine if the moisture content is adequate. Manufacturer literature indicates that you can reuse up to 50 percent of the compost exiting the unit. We have a small unit, which consists of two 11-foot drums, 5 feet in diameter, connected to each other. Our unit turns once or twice each day (starting at 6 a.m.), depending on the size of chickens we have on the farm. The grower programs start times and number of turns using the control box on the side of the unit (Figures 5 and 6), and these values can be changed at any time as conditions warrant. The unit turns very slowly, and one complete turn takes approximately 15 minutes and will discharge about half of a 30-gallon trash barrel of material. Two turns will take about 30 minutes and produce a full 30-gallon trash barrel of material.

It is fairly easy to observe if the material being discharged is too wet, too dry, or just about right (Figure 10). In our case, material that is too wet is usually very dark and may contain excess moisture. Material that is too dry is often very light. Having material that is too wet seems to be more of a problem for us than material that is too dry. Clumps in the compost are another indicator that there is too much moisture in the mixture (Figure 11). As with all composting, there is a learning curve associated with properly managing a rotary composter, and you must continually adjust the level of shavings or carbon source you add to the composter as the chickens grow. However, the longer you do it, the better you become at determining what the unit needs. For example, while a 1:1 ratio of carbon source to mortality may work fine for young chicks, market-age birds may require a 4:1 ratio or more. You must add enough carbon source to account for all the water that is in the birds or the material will become too wet. Market-age birds have a lot more water in them than baby chicks; therefore, market-age birds will require a lot more shavings than baby chicks to soak up this additional moisture. It is important to recognize that surface area, particle size, and physical properties of the waste material will affect:

• Rate at which composting occurs.
• Types and numbers of microorganisms present.
• Level of biological activity present within the compost material.

The composting process does allow you to make a mistake and then correct your error. If you mess it up, you can fix it. Very few people have the material too dry. Almost everyone who has problems ends up with the material being too wet to generate sufficient heat. However, adding extra bulking material or carbon source will help dry out the material, and, once it dries out enough, the process will start working correctly. In most cases, the problems are similar for both static bin/alleyway and rotary drum composters. Most growers tend to use too much mortality and not enough dry carbon source to account for all the water in the birds. Once the material gets too wet, it becomes dense and heavy and loses its porosity. When that happens, the material converts from an aerobic to an anaerobic state. Anaerobic conditions yield more odors and flies and lower temperatures. The lower temperatures slow the decomposition process, which can lead to serious problems, such as mortalities being discharged from a rotary composter or remaining in a bin, alleyway, or windrow when the material is turned. Again, composting requires that you follow a recipe. If you don’t follow the recipe, bad things can happen.

You must have access to electricity to power the motor that turns the unit and the one that powers the blower. The 1 horsepower motor that turns the unit requires a 220-volt outlet. The unit has a low cost of operation and requires minimal electrical energy usage because the unit turns only a few times each day. The unit is not designed to load mortalities or carbon source with a front-end loader bucket on a tractor. The loading door on the unit is narrower than the width of most front-end loader buckets.

In Mississippi, the NRCS does have a cost-share scenario for in-vessel rotary drum composting. This scenario has a payment rate of $121 per pound of dead birds per day. The composter has to be placed on concrete and must have a roof covering the structure. The objective of the cost-share program is to provide service to as many producers as possible. Therefore, NRCS has a cost cap on all composting scenarios of $22,950 as of this writing. While the cap may create a problem for many producers, it does allow NRCS to assist multiple producers instead of only a few who may require large funding amounts. Cost-share rates are the same throughout the state, regardless of the number of poultry farms in any particular area. 

Similar to bin/alleyway composters or incinerators, rotary drum composters in Mississippi must be permitted by the Mississippi Board of Animal Health (MBAH). The MBAH regulates all dead bird disposal methods in Mississippi. If you are considering a rotary drum composter, contact the MBAH at (601) 832-3351 for assistance with determining the composter size you will need based on your farm size, as well as help with the necessary paperwork.

Summary

Composting is the preferred method of dealing with mortality losses on most commercial poultry farms across the country. Composting offers numerous benefits over other disposal methods, and the final end product is a valuable soil amendment. Rotary drum composters are the newest addition to the composting family. They offer several advantages over static bin or alleyway composting, including reducing odor, eliminating the threat of leaching that would result in soil and water contamination, removing animal decomposition from public view, and enhancing biosecurity by removing the scavenger threat and keeping mortality disposal contained or enclosed. Flies are not an issue if the material stays hot enough (130–150°F) to kill fly eggs and larvae. Lower temperatures may mean flies will be more of a problem. Composting requires that you follow a recipe, which is just as true for rotary drum composters as it is for static bin or alleyway composters. Given the proper conditions, rotary drum composters work well and are a sound alternative to static bin or alleyway composters for dealing with daily mortality losses on commercial poultry farms.

This article was originally published by the Mississippi State University Extension Service, Publication 3012 (POD-11-19).