Techno-economic evaluation of carbon capture via physical absorption from HTL gas phase derived from woody biomass and sewage sludge

Abstract

• Carbon capture from the HTL gas phase is modeled based on physical absorption. • Pre-combustion CO 2 capture has potential to facilitate H 2 recovery from HTL gas. • CO 2 with purity between 90 and 98 mol % is obtained at a cost of 40–53 EUR/tonne. • Higher CO 2 purity of 98–99 mol % can be achieved at a cost of 57–77 EUR/tonne. Due to its capability to produce negative CO 2 emissions, bioenergy in combination with carbon capture and storage (BECCS) has been identified as a key technology to limit global warming and to support the energy transition in pursue of the climate targets of this century. Among different bioenergy applications, advanced liquid biofuels produced through the hydrothermal liquefaction (HTL) of waste biomass have gained interest as promising drop-in alternatives to fossil fuels. However, there is lack of studies in literature that evaluate the potential of HTL as negative emission technology in the context of BECCS and present detailed process design of such an implementation for different types of biomass. In this paper, we perform carbon capture modeling based on state-of-art experimental data on HTL of waste lignocellulosic and urban biomasses by means of physical absorption via the Selexol™ process. The process model is utilized for developing a techno-economic analysis that highlights key parameters to optimize CO 2 capture cost efficiency. The results indicate that the purity of the CO 2 product fulfils the requirements for geological storage in all cases studied, and is on-spec for pipeline transportation when the composition of C 2+ hydrocarbons and H 2 S in the HTL gas are kept below 4 and 1 mol % respectively, or by the implementation of two absorption steps. For the standard process evaluated, the estimated cost of the captured CO 2 is between 40 and 53 EUR/tonne, which is in the range of the carbon price expected within this decade in the EU emission trading system, given the announced cap reductions until 2030 and the targets set by the European Green Deal.