A Mortality Composting How-To

( Jennifer Shike, Farm Journal's PORK )

As pig farmers fine-tune their biosecurity plans in the face of increased foreign animal disease (FAD) pressure, many are turning to composting to handle daily mortality. Not only is it the most environmentally friendly method of waste disposal, but it’s also a system that can handle spikes of input, says Chandler Cummins of Advanced Composting Technologies.

“Mortality is a lot of work,” Cummins says. “Things happen and some days are tough – you lose hogs. This system allows you to handle those spikes.”      

Composting is a natural biological process where microbes break down organic material. According to Cummins, the key to great composting is to give microbes what they need, when they need it, in the right proportions and let them do the work. 

“Creating the perfect environment is key,” Cummins says. “Composting requires proper conditions to occur rapidly, minimize odor issues and maximize biosecurity. It’s all about controlling the nutrient balance (mix or diet), water content, aeration and temperature.”

Cummins shares a step-by-step guide to composting utilizing a compost mixer.

Step 1
1.    Develop your recipe and add ingredients to compost mixer. Combine 1,000 lb. of carbon source (sawdust, corn stover, soybean trash) + 1,500 lb. of mortality + 500 lb. 2nd-stage compost to the mixer. This is the most important step because this is where the microbe’s diet is formulated, Cummins says. 

Step 2
2.    Grind mixture for 25 minutes. The mixer grinds and blends the ingredients down to a more uniform size. This homogenous mix (also) captures the liquid from the animal, allowing you to perfect the diet and water content, which speeds up the composting process and allows more surface area for the microbes to do their work. The goal is to achieve 45% to 50% moisture content, Cummins says.

Step 3
3.    Prepare the aerated composting bin first by turning on the compressor and then adding a 12-inch layer of carbon filter such as sawdust. 

4.    Load composting bin utilizing forced aeration system. Enhancing basic composting with forced aeration mechanically moves oxygen-rich air up through the composting pile, evenly and at pre-determined intervals to create optimum aerobic conditions. Bacteria, fungi and other microorganisms will break down organic materials to a stable mixture called compost while consuming oxygen and releasing heat, water, and carbon dioxide. Then, cover with a 2”-3” layer of sawdust to keep fly population down.

Step 5
5.    Compost for 10-20 days. Check temperature regularly to make sure temperatures stay above 140 degrees Fahrenheit for optimal pathogen kill. All disease-causing organisms face three adversaries when composted: heat, toxicity caused by products of decomposition and microbial antagonism. Composting with forced aeration can produce consistently higher temperatures than the typical static pile, Cummins says. This process typically gets the temperature above 150 degrees Fahrenheit.

Step 6
6.    Unload, mix and reload. 

Step 7
7.    Compost for 10-20 days. Continue to check temperature regularly to make sure compost stays above 140 degrees. Heat generated in the composting process inactivates disease-causing organisms and serves as the performance indicator of microbial activity within the composting pile. High temperatures will translate into higher microbial activity, reduced retention time in each bin and pathogen kill. 

Step 8
8.    Store and cure. Composting reduces the volume of the parent materials (by about 10% to 15%) and kills any fecal, coliform, salmonella and e-coli that cause the pathogens that may be present if the process is controlled properly.

9.    Apply to land at agronomic rates. The finished compost resembles humus and is used as a bio-secure, stable soil fertilizer that is N20 P24 K16 plant-available in its first year. Cummins said great compost results in a quality fertilizer. 


More on Composting:

Mortality Composting: Making Happy Microbes