Hydrothermal liquefaction of biomass: Developments from batch to continuous process

Abstract

This review describes the recent results in hydrothermal liquefaction (HTL) of biomass in continuous-flow processing systems. Although much has been published about batch reactor tests of biomass HTL, there is only limited information yet available on continuous-flow tests, which can provide a more reasonable basis for process design and scale-up for commercialization. High-moisture biomass feedstocks are the most likely to be used in HTL. These materials are described and results of their processing are discussed. Engineered systems for HTL are described; however, they are of limited size and do not yet approach a demonstration scale of operation. With the results available, process models have been developed, and mass and energy balances determined. From these models, process costs have been calculated and provide some optimism as to the commercial likelihood of the technology.

Sources of Biomass Feedstock Variability and the Potential Impact on Biofuels Production

“…The harvest season can significantly impact moisture content of biomass resources. Moisture content generally decreases for late fall harvests, reducing required drying energy for pyrolysis or combustion processes but having little effect on hydrothermal liquefaction or fermentation processes [27,41]. Infield drying for 90 days decreases moisture content of pine trees, even in humid southern US climates, where reductions to 30 and 40 % moisture content have been reported for summer and winter conditions, respectively [8].…”

Biochemical evolution in response to intensive harvesting in algae: Evolution of quality and quantity

“…The production of algae in intensive land‐based culture systems is a relatively new approach with significant commercial potential and interest, particularly with regard to algal biochemistry. Algae have been proposed as substrates for a broad range of biofuels (Brennan & Owende, 2010; Elliott, Biller, Ross, Schmidt, & Jones, 2015; Mata, Martins, & Caetano, 2010; Rowbotham, Dyer, Greenwell, & Theodorou, 2012), and as a source of new bioproducts and animal feed (Gosch, Magnusson, Paul, & Nys, 2012; Jiménez‐Escrig, Gómez‐Ordóñez, & Rupérez, 2012; Li, Wijesekara, Li, & Kim, 2011; Pulz & Gross, 2004). A key concern here is the productivity of biochemical components (lipid, protein, carbohydrate) per unit area of cultivation—whether this productivity evolves in response to intensive harvesting remains unclear.…”

Perspectives on Resource Recovery from Bio-Based Production Processes: From Concept to Implementation

“…To this end, this work will focus on identifying promising separation technologies with the purpose of achieving resource recovery from bio-based production processes, as many economically lucrative raw materials are already present in these waste streams and can be recovered without the need for other conversion processes. In situations where raw materials need to be converted into a more economically lucrative form, other processes such as bio-conversion [11,12] or hydrothermal processing [13][14][15] can be applied. After establishing the economics of resource recovery and identifying the platform technologies, the techno-economic considerations that need to be considered when developing a resource recovery platform technology from a concept to an implementation are discussed in Section 4.…”

“…To our opinion, the overall TRL of the technologies surveyed in Section 4 is relatively high in comparison to other competing technologies such as bioconversion [11,12] and hydrothermal processing [13,15]. As such, from an industrial point of view, the resource recovery through extraction/separation can be a more established technology choice.…”