Solid culture amended with small amounts of raw coffee beans for the removal of petroleum hydrocarbon from weathered contaminated soil

Solid culture with small amounts of low-quality raw coffee beans was used for total petroleum hydrocarbon (TPH) removal from a weathered and polluted soil. Soil contaminated with 58 000 mg kg−1 of TPH was treated with soil:coffee bean ratios of 98:2, 96:4, 94:6, and 92:8, at a C:N:P ratio of 100:10:1, 20% humidity, and 28 °C, for periods of 15, 60, and 90 days. The highest TPH removal (63%) was obtained with a soil/bean ratio of 98:2 over 15 days, corresponding with the highest rates of microbial respiration and the greatest increases in bacterial and fungal counts to 9 lnCFU and 6 lnCFU, respectively. Scanning electron microscopy showed high fungal colonization of coffee beans, with Mucor sp., Aspergillus sp., Aspergillus niger., and Penicillium sp. growing on TPH as sole carbon source.