title: Anaerobic digestion of post-hydrothermal liquefaction wastewater for improved energy efficiency of hydrothermal bioenergy processes.
abstract: Hydrothermal liquefaction (HTL) is a promising process for converting wet biomass and organic wastes into bio-crude oil. It also produces an aqueous product referred to as post-hydrothermal liquefaction wastewater (PHWW) containing up to 40% of the original feedstock carbon, which reduces the overall energy efficiency of the HTL process. This study investigated the feasibility of using anaerobic digestion (AD) to treat PHWW, with the aid of activated carbon. Results showed that successful AD occurred at relatively low concentrations of PHWW (≤ 6.7%), producing a biogas yield of 0.5 ml/mg CODremoved, and ∼53% energy recovery efficiency. Higher concentrations of PHWW (≥13.3%) had an inhibitory effect on the AD process, as indicated by delayed, slower, or no biogas production. Activated carbon was shown to effectively mitigate this inhibitory effect by enhancing biogas production and allowing digestion to proceed at higher PHWW concentrations (up to 33.3%), likely due to sequestering toxic organic compounds. The addition of activated carbon also increased the net energy recovery efficiency of AD with a relatively high concentration of PHWW (33.3%), taking into account the energy for producing activated carbon. These results suggest that AD is a feasible approach to treat PHWW, and to improve the energy efficiency of the HTL processes.
authors.affiliation: Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA E-mail: schidema@illinois.edu.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA E-mail: schidema@illinois.edu.
authors.forename: Lance
authors.initials: L
authors.lastname: Schideman
authors.affiliation: School of Environment, Tsinghua University, Beijing, 100084, China.
authors.forename: Mingxia
authors.initials: M
authors.lastname: Zheng
authors.affiliation: Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA E-mail: schidema@illinois.edu.
authors.forename: Ana
authors.initials: A
authors.lastname: Martin-Ryals
authors.affiliation: Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA E-mail: schidema@illinois.edu.
authors.forename: Peng
authors.initials: P
authors.lastname: Li
authors.affiliation: Laboratory of Environmental Biotechnology, Department of Food Engineering, University of Sao Paulo, Sao Paulo, 13635, Brazil.
authors.forename: Giovana
authors.initials: G
authors.lastname: Tommaso
authors.affiliation: Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA E-mail: schidema@illinois.edu.
authors.forename: Yuanhui
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000693:Anaerobiosis; D001421:Bacteria, Anaerobic / Q000378:metabolism*; D056804:Biofuels; D018533:Biomass; D002606:Charcoal / Q000378:metabolism; D005240:Feasibility Studies; D005658:Fungi / Q000378:metabolism; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D010578:Petroleum; D062065:Wastewater / Q000737:chemistry*; D018508:Water Purification / Q000379:methods* / Q000592:standards
chemical_list: D056804:Biofuels; D002606:Charcoal; D010578:Petroleum; D062065:Wastewater