Composting of a heavy oil refinery sludge

Preliminary experiments using a range of bulking agents, moisture contents, nutrients, cosubstrates and inocula were undertaken to determine suitable ingredients for the successful composting of a heavy oil refinery sludge. The best ingredients were then chosen for a detailed study of the CO 2 evolution rate and Total Petroleum Hydrocarbon (TPH) reduction versus time during the composting process. The initial TPH content of the refinery sludge was found to be 30% (mainly C 15 ‐C 30 ), two thirds of which were saturates and aromatics that were thought to be biodegradable. The results show a significantly higher TPH reduction using Solv‐II (55% reduction) as a bulking agent/nutrient source compared to heat‐treated peat moss and barley straw (both at 30% reduction). The CO 2 evolution was high with Solv‐II and barley straw indicating the presence of high microbial activities in those composters.