Enhancing the composting process by using lactic acid bacilli for the hygienic disposal of dead fish

Fish producers in Iraq currently facing large and growing problems, represented by the difficulty of getting rid of large numbers of dead fish as a result of mass phenomenon mortality since 2018. As their treatment and disposal have become very cumbersome and costly, and leaving it to wild animals and natural forces is unacceptable, so most of them resort to the composting method because it is a simple, easy, and inexpensive process and benefits outputs, but it takes a long time.

The study aimed to compare two different composting methods for the disposal of dead fish, one of them includes the use of lactic acid bacilli (LAB) to improve composting efficiency.

Sawdust, hay, one-inch perforated plastic tubes, plastic covers, and dead fish were used to make four equal composting piles, two of them were treated with LAB, and others were left to compost naturally, the composted content was daily tested physically for color, odors, pH estimation, and LAB count.

The results showed that there are significant differences between normal-composed and LAB-treated groups in duration and efficiency, the total threshold limits of temperature, pH, and LAB count were 60°C ± 8°C, 6.7 ± 0.04, and 10.8 × 10⁶ ± 1.96 CFU/g, respectively, in normal composting groups, while they were 70°C ± 2.8°C, 4.26 ± 0.01, and 23.2 × 10⁶ ± 1.34 CFU/g, respectively, with total decomposition and disintegration of fish carcasses through 31 days in effective microorganisms treated groups.

We concluded that the use of LAB in composted materials led to a quick and efficient composting process in terms of heat, pH, LAB count, total disintegration speed, and the ability of biosafety.