Masters Thesis

Pyrolysis of Agricultural Waste Plastic into Diesel and Evaluation of the Carbonaceous Byproduct as a Soil Amendment

High density polyethylene[HDPE] from used drip irrigation tubing was thermochemically broken down through pyrolysis at 500 °C for 20 minutes in the presence of a clinoptilolite zeolite catalyst to produce pyrolysis oil and a carbonaceous byproduct. The pyrolysis oil produced had a melting point of 50 °C, a boiling point of 80 °C, and a flash point of 89 °F. The melting point is higher than that of diesel fuel and the boiling point and flash point are lower than that of diesel fuel. The high melting point necessitates preheating before use as a fuel and prevents the pyrolysis oil from being a direct substitute for diesel fuel. The carbonaceous byproduct, when used as a soil amendment, increased soil water holding capacity and microbial respiration but had not effect on cation exchange capacity. Two-percent by weight of carbonaceous byproduct reduced soil hydraulic conductivity and increased nitrate leaching but lower treatment levels did not affect soil hydraulic conductivity or nitrate leaching. Amended soil had a slightly increased pH compared to the control. The properties of the pyrolysis oil can potentially be improved by using a different catalyst or increasing the pyrolysis reaction time from 20 minutes to several hours. The carbonaceous byproduct can be used as an effective soil amendment that improves several important soil characteristics.

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