Characteristics and Volume of Effluent Produced by Livestock Vessels

Summary

Meat and Livestock Australia commissioned Landline Consulting to determine the characteristics and volume of effluent produced by livestock vessels and make comparisons with effluent from passenger ships. This basic information is required for the International Maritime Organisation’s (IMO’s) Marine Protection Committee meeting in March/April 2004.

Effluent from livestock vessels, depending on number of stock carried, contains considerably greater amounts of organic matter (BOD5), nitrogen (N), phosphorus (P) and potassium (K) than passenger ships. This is particularly the case for large vessels carrying in the order of 10,000 cattle and 50,000 sheep or goats. However, for a standardised ship with 1,000 head the following daily effluent production is predicted:

• Cattle, 500-700 kg BOD5, 30-45 kg N, 35-40 kg P and 60-90 kg K;

• Sheep, 36-54 kg BOD5, 6.5-9.5 kg N, 2.6-3.9 kg P and 9.6-14.4 kg K; • Goats, 30-48 kg BOD5, 5.5-10.0 N, 2.8-4.4 kg P and 7.8-12.4 kg K; and

• Humans, 50-75 kg BOD5, 9-14 kg N, 1.8-2.7 kg P and 2.8-4.2 kg K.

Currently the effluent from livestock ships discharges raw into the sea, though the discharge practices vary between cattle ships (continuous discharge on the outward voyage) and sheep/goat ships (continuous discharge during part or all of the return journey). For passenger ships there is a significant trend towards short-term storage of effluent, treatment and discharge.

An understanding of the nature and composition of effluent from livestock and passenger vessels will allow an informed debate on the impacts of effluent disposal from livestock vessels. However, it is strongly recommended that the impact of effluent discharge on marine water quality should be assessed within the mixing zone behind the vessel, and not simply on the composition of the effluent.