Passive aeration composting of chicken litter: Effects of aeration pipe orientation and perforation size on losses of compost elements

A passive aeration composting study was undertaken to investigate the effects of aeration pipe orientation (PO) and perforation size (PS) on some physico-chemical properties of chicken litter (chicken manure + sawdust) during composting. The experimental set up was a two-factor completely randomised block design with two pipe orientations: horizontal (Ho) and vertical (Ve), and three perforation sizes: 15, 25 and 35 mm diameter. The properties monitored during composting were pile temperature, moisture content (MC), pH, electrical conductivity (EC), total carbon (CT), total nitrogen (NT) and total phosphorus (PT). Moisture level in the piles was periodically replenished to 60% for efficient microbial activities. The results of the study showed that optimum composting conditions (thermophilic temperatures and sanitation requirements) were attained in all the piles. During composting, both PO and PS significantly affected pile temperature, moisture level, pH, CT loss and PT gain. EC was only affected by PO while NT was affected by PS. Neither PO nor PS had a significant effect on the C:N ratio. A vertical pipe was effective for uniform air distribution, hence, uniform composting rate within the composting pile. The final values showed that PO of Ve and PS of 35 mm diameter resulted in the least loss in NT. The PO of Ho was as effective as Ve in the conservation of CT and PT. Similarly, the three PSs were equally effective in the conservation of CT and PT. In conclusion, the combined effects of PO and PS showed that treatments Ve35 and Ve15 were the most effective in minimizing NT loss.