Environmental Impacts of Cattle Manure Composting

Abstract

Measurement of the losses of nutrients during composting is needed to understand the composting process, to implement methods of nutrient conservation and highlight potential environmental impacts. Cattle manure was aerobically composted under ambient conditions to evaluate composting as a method of manure handling. Composting was conducted using 3-4-tonne heaps of fresh cattle manure in 5 x 5-m concrete bunkers. Temperatures inside the manure heaps were -monitored during the composting process. Total mass and nitrogen losses such as ammonia volatilisation, nitrous oxide emission and leaching were measured. Differences in temperature between composting treatments were small. Temperature in the composting manure piles reached in excess of 70 degreesC and remained above 55 degreesC for up to 70 days. Total mass loss ranged from 23% for the unturned static treatment to 67% of the initial mass for the indoor treatment turned three times. Nitrogen losses from the manure heaps ranged from 8 to 68% of the initial total manure N content. Leaching losses accounted for between 0 and 1.5% of the initial total manure N content. Gaseous N losses, primarily as NH3, accounted for between 7 and 67% of the initial manure N content. The decision on whether to compost cattle manure needs to consider all of the issues, and not just nutrient losses. Some of the issues to consider are the effects of temperature on weed seeds and pathogens, the supply of plant nutrient following land spreading and the quantity and friability of the end product