Techno-Economic Analysis of the Production of Liquid Biofuels from Sewage Sludge via Hydrothermal Liquefaction

Abstract

This work addresses the process and economic performance of the production of gasoline and diesel range fuels from urban sewage sludge. The overall production route involves direct conversion of the sewage sludge to an intermediate oil phase, so-called biocrude, via hydrothermal liquefaction at near-critical water conditions and further upgrading of the biocrude based on conventional refinery processes. The overall mass and energy yields of combined naphtha and middle distillate from sewage sludge on dry basis are approximately 19 and 60%, where the naphtha fraction represents about 45% of the total, with a minimum fuel selling price ranging between 2.4 and 0.8 €/liter assuming full investment in both the biocrude production and upgrading plant with sewage sludge feed capacities in the range of 3 to 30 dry-ton/day. If existing equipment at refinery can be used for upgrading of the biocrude, the minimum fuel selling price can be reduced by approximately 7%.

Comparative Techno-Economic and Life Cycle Analyses of Synthetic ‘Drop-In’ Fuel Production from UK Wet Biomass

“…The price range of fuel from the grey hydrogen centralised scenarios of £14.76 -£31.5 per GJ (£0.47 -1.00 per GLE) agrees with the prices of £15.39 -29.1 per GJ (2021 prices) published by the Royal Society [77] and Jiang et al [78], which used grey hydrogen for HTL of forest residues and SS. Also, the results of this study agree with Alamo et al [79] drop-in fuel prices for SS HTL of £18.48 -30.10 per GJ over similar plant scales (100 -400 tons/day). The prices of fuel from SS for this study using grey hydrogen centralised scenarios are in the range of £17.20 -23.92 per GJ.…”

“…However, these studies and many others in the literature do not consider the impact of using blue or green hydrogen in drop-in fuel production. Royal Society [77], Jiang et al [78] and Alamo et al [79] did not present a cost breakdown in their analysis but our study suggests that the fuel prices can increase by up to £5.40 per GJ when switching the hydrogen source from grey to green hydrogen. Additionally, the prices of drop-in fuel production via HTL are competitive with fossil diesel of £28.58 per GJ, based on 2021 wholesale prices of diesel published by RAC [76].…”

“…The prices of fuel from SS for this study using grey hydrogen centralised scenarios are in the range of £17.20 -23.92 per GJ. Analyses by Jiang et al [78] and Alamo et al [79] also assumed negative feedstock prices for SS like the assumptions used here. However, these studies and many others in the literature do not consider the impact of using blue or green hydrogen in drop-in fuel production.…”

A comprehensive review on sewage sludge as sustainable feedstock for bioenergy production

“…Globally, there is an urgent need for improvements in environmentally friendly sewage sludge treatment and recovery of valuable products. Currently, the industrial waste management for SS involves the generation of biogas by anaerobic digestion, power, and heat generation through thermal energy conversion, as well as cement manufacture using combined combustion inside kilns (Del Alamo et al., 2022; Periyasamy, Kavitha, et al., 2022).…”

“…The utilization of advanced biofuels has been incorporated into a bigger global strategy to cut the transport sector's releases of greenhouse gases (Del Alamo et al., 2022). For heavy‐duty transportation industries, such as marine, aircraft, and lengthy route transportation, in which it is impractical to use any other forms of renewable energy, such as electricity or H 2.…”