Comment on “Pyrolysis of dried wastewater biosolids can be energy positive”

Zitomer, Daniel; Liu, Zhongzhe

doi:10.1002/wer.1148

Cited by 2 publications

(3 citation statements)

References 11 publications

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“…It is notable that a positive/negative net energy balance for these processes does not consider the drying process. The initiating drying process is a complete endothermic step for the vaporisation of the water content in biomass/waste requiring a substantial amount of energy, such as 3.4 MJ/kg in typical dryers with non-unity efficiency [60].…”

Section: Energy Consumptionmentioning

confidence: 99%

“…Typically, a low heating value of the non-condensable fraction has made it more suitable for heating the unit [67]. For sewage sludge, McNamara et al (2019) found the energy content of pyrolytic gas and oil to be always sufficient for the pyrolysis process using the theoretical heat capacities of the constituents [60]. In another study of sewage sludge pyrolysis [68], the available theoretical heat of combustion for domestic sewage sludge was determined as 825 kJ/kg.…”

Section: Energy Consumptionmentioning

confidence: 99%

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Managing Non-Sewered Human Waste Using Thermochemical Waste Treatment Technologies: A Review

et al. 2021

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The utilisation of micro-scale thermal treatment technologies for non-sewered applications has been emerging as a prominent route for the safe treatment and disposal of high water content hazardous feedstock. This study provides a comprehensive review of the technological concepts practiced up to date in commercial/pilot and small scales for various types of solid fuels. The respective challenges are critically described and discussed to aid in the selection of promising technology for on-site sanitary applications. Furthermore, the challenges observed with the nominated (pyrolysis) technology are discussed in detail and addressed. This study suggests rapid energy recovery from by-products primarily made up of the highest yield of syngas with a desirable calorific value. The optimum operating ranges are discussed to ensure a reliable thermal conversion of sludge materials considering the application constraints and technology drawbacks. However, further studies are needed to investigate the uncertainties regarding emissions, energy consumption and overall associated costs.

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Section: Energy Consumptionmentioning

confidence: 99%

Section: Energy Consumptionmentioning

confidence: 99%

Managing Non-Sewered Human Waste Using Thermochemical Waste Treatment Technologies: A Review

et al. 2021

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“…However, for the water resource reclamation industry, energy is not the only parameter of concern related to sustainability. Public health, pathogen reduction, and pollutant removal must also be considered while meeting energy demands (McNamara et al, 2019). Biosolids pyrolysis could realize these benefits simultaneously.…”

Section: What We Know About Biosolids Pyrolysismentioning

confidence: 99%

Pyrolysis—A tool in the wastewater solids handling portfolio, not a silver bullet: Benefits, drawbacks, and future directions

Liu

Tong

Santha³

et al. 2023

Water Environment Research

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Pyrolysis is the process whereby carbonaceous materials, such as biosolids, are heated between 400°C and 900°C in the absence of oxygen. Three main products are generated: a solid product called biochar, a py‐liquid that consists of aqueous phase and non‐aqueous phase liquid, and py‐gas. The biochar holds value as a beneficial soil amendment and sequesters carbon. The py‐liquid is potentially hazardous and needs to be dealt with (including potentially reducing it on‐site via catalysis or thermal oxidation). Py‐gas can be used on‐site for energy recovery. Pyrolysis has gained recent interest due to concern over per‐ and polyfluoroalkyl substances (PFAS) in biosolids. Although pyrolysis can remove PFAS from biosolids, it has been shown to produce PFAS that reside in py‐liquid, and the fate in py‐gas remains a knowledge gap. More research is needed to help close the PFAS and fluorine mass balance through pyrolysis influent and effluent products because pyrolysis alone does not destroy all PFAS. The moisture content of biosolids substantially affects the energy balance for pyrolysis. Utilities that already produce a dried biosolids product are in a better position to install pyrolysis. Pyrolysis has both defined benefits (solids reduction, PFAS removal from biosolids, and biochar production) as well as remaining questions (the fate of PFAS in py‐gas and py‐liquid, mass balance on nutrients, and py‐liquid handling options) that will be answered through more pilot and full‐scale demonstrations. Regulations and local policies (such as carbon sequestration credits) could affect pyrolysis implementation. Pyrolysis should be considered as an option in the biosolids stabilization toolbox with application being based on individual circumstances of a utility (e.g., energy, moisture content of biosolids, PFAS). Practitioner Points Pyrolysis has known benefits but limited full‐scale operational data. Pyrolysis removes PFAS from biochar, but PFAS fate in gas phase is unknown. Moisture content of influent feed solids affects energy balance of pyrolysis. Policy on PFAS, carbon sequestration, or renewable energy could impact pyrolysis.

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Comment on “Pyrolysis of dried wastewater biosolids can be energy positive”

Cited by 2 publications

References 11 publications

Managing Non-Sewered Human Waste Using Thermochemical Waste Treatment Technologies: A Review

Managing Non-Sewered Human Waste Using Thermochemical Waste Treatment Technologies: A Review

Pyrolysis—A tool in the wastewater solids handling portfolio, not a silver bullet: Benefits, drawbacks, and future directions

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