Review of Studies on Joint Recovery of Macroalgae and Marine Debris by Hydrothermal Liquefaction

Abstract

At the moment, macroalgae blooms in sea waters, the rotting of which causes greenhouse gas emissions and contributes to the formation of a negative ecological and economic situation in coastal zones, which has become a serious problem. Fuel production through hydrothermal liquefaction (HTL) of macroalgae and marine debris is a promising solution to this ecological problem. The article provides an overview of studies on producing fuel from macroalgae and an assessment of the possibility of their joint recovery with marine debris. The optimal process conditions and their technological efficiency were evaluated. The article shows the feasibility of using heterogeneous catalysis and co-solvent to increase the yield of bio-oil and improve its quality. An assessment of the possibility of joint processing of waste macroalgae and marine debris showed the inexpediency of this direction. The high degree of drift macroalgae contamination also raises the question of the appropriateness of the preliminary extraction of other valuable components for nutrition use, such as fats, proteins, carbohydrates, and their derivatives.

Feasibility of Old Bark and Wood Waste Recycling

“…Dry gasification of BWW is used to generate heat and electricity, as well as for the synthesis of gas [40]. The problem with all traditional thermal processing methods is that they are difficult to apply to the processing of BWW previously accumulated in the bark dump, because the waste is characterized by high humidity (up to 60%) [14,44].…”

“…Hydrothermal liquefaction (HTL) is a wet-biomass processing method that produces liquid synthetic oil [18,35,44]. The process is designed to treat pulp with a maximum dry matter concentration of 20% [50].…”

“…The process is designed to treat pulp with a maximum dry matter concentration of 20% [50]. The efficiency of the process is largely affected by the pH value; thus, with a decrease in pH, the yield of char increases significantly, and the yield of liquid fuel decreases [44,51]. The yield of synthetic oil for various types of wood is 10-30% [52][53][54].…”

“…HTL-oil is viscous and, unlike pyrolysis oil, has a low oxygen content and a higher calorific value [36]. The gas and water phases, as well as HTL-char [44], are the byproducts of the HTL process.…”

“…The general advantage of hydrothermal methods is their applicability to wet biomass, because water does not interfere with the process, but participates by acting as a donor of hydrogen ions and, in some cases, as a polar solvent [44]. Although HTC is the simplest and most easily implemented method, the resulting hydrochar is not widely sold.…”