Co-pyrolysis of oil-contaminated shoreline sediment with harmful macroalgae: Synergistic resource recovery and techno-economic analysis

The cleanup of oil-contaminated shoreline sediment (OCSS) and species due to nearshore oil spills has been a challenge. This study investigated the co-pyrolysis treatment of OCSS and Enteromorpha prolifera (EP) for synergistic resource recovery. The effects of co-pyrolysis treatment at different OCSS:EP ratios and temperature on the removal of petroleum hydrocarbons and resource recovery were investigated, and the co-pyrolysis products were characterized to explore the synergistic mechanism. The concentrations of petroleum hydrocarbons in the pyrolysis solids were significantly lower than the relevant soil pollution standard when the treatment temperature was > 400 ℃. The product yield results show that co-pyrolysis at low temperatures (350–400 ℃) had a significant synergistic effect on the pyrolysis oil yield. The optimal pyrolysis oil yield of 22.68 % was achieved at OCSS:EP = 1:1 (OE11) and 400 ℃, increased by 5.19 % compared with the theoretical value. Kinetic analysis shows that the co-pyrolysis lowered the optimal reaction temperature from 450°C to 400°C. The product characterization results indicate that the oxygenated compounds (aldehydes, ketones, phenols) and C/H ratio of the OE11 pyrolysis oil were significantly reduced, leading to an increased higher heating value of 31.14 MJ/kg. The probabilistic techno-economic analysis shows that the co-pyrolysis treatment had a 90.4 % probability of obtaining a positive net present value (NPV), with an average value of 22,756,047 CNY over 10 years, whereas conventional landfilling treatments resulted in negative NPVs. This study presents a sustainable resource recovery approach for the co-treatment of oil-contaminated sediments and species in shoreline cleanup.