Decarbonisation Technology - February 2024 Issue

Drying & compression for downstream usage

Drying & compression for downstream usage in Fis c her - Tropsch or gas to liquid process

Biomass

Biogas

Biomass

Syngas

Anaerobic digestor

Gasier

Figure 1 Anaerobic digestion

Figure 2 Gasification

combustion or further upgrading (Rosendahl, 2018), (Shahbeik, et al., 2024),(Almansa, et al., 2024) HTL technology is versatile in converting renewable biomass feedstocks, especially those in wet states, into biofuel (biocrude oil). Its ability to handle a wide range of biomass, including sludge, food waste, and certain plastic materials, makes it a promising pathway for biocrude oil production. A big advantage is that the process does not require drying of the feedstock, offering a pathway to convert typically underutilised or waste biomass into a valuable energy source. HTL is a thermal depolymerisation process that operates under moderate temperatures (typically 250-370°C) and high pressures (typically 10-25 MPa). thereby converting wet biomass into bio-oil. The crude-like oil produced through HTL has a high energy density with a lower heating value of 33-37 MJ/kg, containing 5-12 wt% oxygen and renewable chemicals. While HTL represents a sustainable method for managing biomass waste and producing renewable energy sources, it also presents challenges, such as the need for efficient disposal of complex aqueous byproducts that contain valuable chemicals (Almansa, et al., 2024). certain plastic materials, makes it a promising pathway for biocrude oil production ” “ Hydrothermal liquefaction’s ability to handle a wide range of biomass, including sludge, food waste, and

combustion or further upgrading. The removal of carbon increases the remaining hydrocarbon hydrogen content via thermal (pyrolysis) or catalytic (FCC) processes. Pyrolysis thermally decomposes the organic feed material, leaving a large portion as a residual solid (coke) and the remaining product as gas and liquid. The pyrolysis process typically requires temperatures of 450-600°C in an oxygen- depleted environment. Before pyrolysis, the biomass feedstock is prepared by drying in order to reduce moisture content, size reduction to improve the uniformity of heat transfer, and sometimes torrefaction to enhance the energy density of the biomass. The resulting pyrolysis oil (or bio-oil) is a dark, viscous liquid with a high oxygen content (about 35-40 wt%), which includes unique properties like non-volatility, corrosiveness, and immiscibility with fossil fuels (USDA, 2023). Its elemental composition is approximately 40-55 wt% carbon, 6-10 wt% hydrogen, 35-40 wt% oxygen, 0-3 wt% nitrogen, and less than 1 wt% sulphur, contributing to a lower heating value of 16-19 MJ/kg. The high oxygen content leads to thermal instability and a tendency for the oil to polymerise when exposed to air. Despite these challenges, pyrolysis oil is considered a promising renewable energy source and an alternative to fossil fuels, particularly in applications like chemical manufacturing, engines, turbines, and boilers. Biomass torrefaction is a mild form of pyrolysis at temperatures typically between 200 and 320°C in a low-oxygen atmosphere. Torrefaction changes the properties of biomass to provide a better fuel quality for combustion and gasification applications.  Hydrothermal liquefaction : HTL upgrades biomass to a product suitable for direct

 Pretreatment : The pretreatment of seed oils or animal fats is required to remove