Hydrocarbon removal in oil-contaminated soil using in-vessel composting with yard waste and rumen waste

This study aimed to determine hydrocarbon removal in oil-contaminated soil using composting with an amendment of yard waste and rumen waste. Hydrocarbon-contaminated soil samples from a public oil-mining field in Wonocolo District, Bojonegoro, Indonesia, were composted with yard waste (Y), rumen waste (R), and mixed YR in varied compositions. Manual agitation was applied every 3 days for air supply and homogenization. The experiment was conducted in two replicates in reactors of 3.5 L capacity for 80 days. Moisture was kept within the range of 50-60%. Measurements of temperature, pH, and moisture content were done every 3 days, whereas total Kjeldahl nitrogen (TKN), nitrite, nitrate, total bacterial count, organic carbon, and hydrocarbon concentration were measured every 20 days. The results showed that the highest hydrocarbon removal efficiency (45.26%) was observed in the reactor containing 50% contaminated soil amended with mixed YR. The second- and third-highest hydrocarbon removal efficiencies of 42.11 and 38.33% occurred in contaminated soil reactors to which 50% w/w R and Y were added, respectively. The hydrocarbon removal in these reactors followed first-order kinetics with a rate constant range of 0.006-0.007 day^-1. In order to meet the quality standard limit for oil-contaminated soil, the estimated composting time was 135-181 days.