Pyrolysis is a thermal process that converts biosolids into biochar (a soil amendment), py-oil and py-gas, which can be energy sources. The objectives of this research were to determine the product yield of dried biosolids during pyrolysis and the energy requirements of pyrolysis. Bench-scale experiments revealed that temperature increases up to 500 °C substantially decreased the fraction of biochar and increased the fraction of py-oil. Py-gas yield increased above 500 °C. The energy required for pyrolysis was approximately 5-fold less than the energy required to dry biosolids (depending on biosolids moisture content), indicating that, if a utility already uses energy to dry biosolids, then pyrolysis does not require a substantial amount of energy. However, if a utility produces wet biosolids, then implementing pyrolysis may be costly because of the energy required to dry the biosolids. The energy content of py-gas and py-oil was always greater than the energy required for pyrolysis.

Biosolids handling is an energy intensive and expensive process. Thus, the use of beneficial endproducts is strongly desired to reduce costs. Pyrolysis, the thermal decomposition of organic matter under anaerobic conditions, has potential to be a beneficial biosolids handling process. Pyrolysis results in biochar that can be used as a fertilizer, pyrolysis oil (py-oil), and pyrolysisgas (py-gas), which can be used to fuel the pyrolysis process. Two objectives of this work were to determine i) the impact of temperature on product yields and gas energy content and ii) the enthalpy of pyrolysis of biosolids from bench-scale experiments and modeling. Increased temperatures resulted in decreased char yields, but py-oil content did not increase after 500°C. The increase in temperature resulted in higher permanent gas yields, and higher energy content in the py-gas.