Composting of agricultural wastes for their use as container media: Simulation of the composting process

Separated cattle manure (SM) and grape marc (GM), and manure composts of these raw materials, were incubated in a composting simulator for 10 days. The effects of moisture content and addition of nitrogen on the rate of composting were measured in terms of oxygen consumption. Moisture content had a major effect on O₂ consumption. The higher the water content, the higher was O₂ consumption, which reached a maximum at 60-70% water content. Below 50% moisture, the microbial activity seemed to decline sharply. The O₂ consumption was extremely low for the manure composts and was unaffected by the moisture content. No effect was recorded when nitrogen was added to SM. However, the addition of 0·25% (w/w) nitrogen to GM at all moisture levels increased significantly the O₂ consumption, except for the mature compost. The most prominent effect of nitrogen addition was exhibited by GM that was composted at 60% moisture.