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THERMOCHEMICAL CONVERSION OF MARINE WASTE
BIOMASS TOWARDS RENEWABLE FUELS AND CHEMICALS
Frederik Ronsse, 26 nov ‘21, Songdo, GUGC
DEPARTMENT OF GREEN CHEMISTRY AND TECHNOLOGY
RESEARCH GROUP - THERMOCHEMICAL CONVERSION OF BIOMASS
MARINE WASTE BIOMASS & THERMOCHEMICAL CONVERSION
3
Thermochemical conversion
• High T
• Optionally high P
• Dry or wet conditions
Marine microalgae
Residues from cultivation
Macroalgae (seaweeds)
Residues from cultivation
Algal blooms
Biological conversionThermochemical
conversion
Feedstock type Wet biomass Dry biomass (mostly)
Selectivity High Low
Degree of conversion Moderate to low High
Reaction conditions <70°C, 1 atm 100-1200°C, 0 - 250 atm
Conversion speed Slow: minutes to hours Fast: seconds to minutes
Materials
Fuels
Chemicals
Energy
PYROLYSIS: INTRODUCTION
4
BiomassLiquid
(bio-oil)
Solid
fraction
GasHeat
Principle of pyrolysis
• Decomposition of biomass by heating in an oxygen-free or oxygen-deficient environment.
• Only useful for dry biomasses
• Always results in 3 product fractions: non-condensable gases, condensable vapors (result in bio-oil or
pyrolysis oil) and char(→biochar)
• Product distribution can be controlled based on process conditions – different process types to be
distinguished:Type Temp
(°C)Vapor
residence time
Heat source Char yield (wt.%)
Liquid yield(wt.%)
Gas yield(wt.%)
Slow pyrolysis 300-500 5-30 min external/internal 35 % 30 % 35 %
Fast pyrolysis 500-600 1 s external 12 % 75 % 13 %
Torrefaction (partial
pyrolysis)
< 300 minutes external 80 % 5 % 15 %
Gasification > 750 10-20 s internal (oxygen addition)
10 % 5 % 85 %
HYDROTHERMAL CONVERSION: INTRODUCTION
5
Principle of hydrothermal conversion
• Hot, compressed water has remarkably different physicochemical properties (i.e. Kw, e, r) compared to at
ambient T, P
• At T > 374°C and P > 22.1 MPa: No distinction between the vapor and liquid phase: a single, new phase
emerges, the so-called supercritical fluid (SCW)
Sub critical
Near critical
Supercritical
Source: Dahmen, 2015
HYDROTHERMAL CONVERSION: INTRODUCTION
6
Principle of hydrothermal conversion
• Different conversion processes can be distinguished at different T, P yielding different product slates
• Ideal for the conversion of wet feedstock (→marine waste feedstocks), no drying necessary
POTENTIAL USE OF THERMOCHEMICAL CONVERSION PRODUCTS
7
Benefits of thermochemical conversion products: flexibility of applications
Transportation fuelsChemicals
Biomass
Whole fractions (i.e. sugars, phenols)
Single compounds
Bio-oil Char
+
Heat & power
Biochar
Pyrolysis
Functional carbon materials
Gasification UpgradingExtraction BoilerTurbine,
diesel engineSolid fuel
Adsorptive medium
Catalyst support
Electrode materials
Reductans
HTC
HTL
Biomass Biomass
8
BIO-OIL / BIOCRUDE
10
• When used in soils (aggregated) maximum yield improvements of 20 to 120%
Potential mechanisms
• Increasing the soil organic matter
• Form a protective habitat for soil micro-organisms
• Increase of soil porosity (thus increasing soil water retention and soil aeration)
• Increase soil’s cation exchange capacity (reduces leaching of nutrients and fertilizer)
• pH-correction (on average +1 pH unit)
• N-fixation an interaction in N-cycle
• Absorption of herbicides, heavy metal and other plant-toxic compounds
BIOCHAR
11
• In soil: biochar is highly recalcitrant (long
lifetime in soil)
• Slow mineralization both biotic and abiotic)
of biochar in soil: C-mineralization rate at
least one order of magnitude lower than
parent biomass (to half-life of > 1000 yr)
• Biochar is mainly composed out of C. That
carbon was originally taken up by plants
from the atmosphere.
• → Biomass growth + pyrolysis + biochar soil
amendment is a carbon negative process.0 0.1 0.2 0.3 0.4 0.5 0.7 0.8 0.9
O/C Atomic ratio
100
101
102
103
104
105
106
107
108
Ha
lf lif
e (
ye
ars
)
t½ > 1000 years 100 years< t½ < 1000 years t½ < 100 years
Reduction volatile C compounds
Increase of fixed-C
BIOCHAR
12
BIOCHAR
• Biochar in electrical energy storage
In: IEA (2009)
• Electric double layer capacitor
• Electrode material requirements:
• High specific surface area
• High meso/microporosity to support ion diffusion
• Micropore diameter > ion diameter
• High electrical conductivity
• Hydrophilic surface
Activated biochars
• Na-ion batteries
• Anode material requirements:
• Low meso/microporosity: ion flux
is much lower than in
supercapacitors
• No microporosity: Li-ions
intercalate between graphene
sheets in graphite
• For Na: ultramicroporosity, Na
ions can’t intercalate in graphite
(dNa+ > dLi+)
High temperature biochars
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• 1. High water content → hydrothermal processes
• 2. High heteroatom content (N, S and O), high ash content
• Lopez Bareiro et al. 2016: 8 microalgae strains processed through HTL at 375°C
• Upgrading through HDO to remove N, S and O (400 ºC, 4 h, 20 wt % catalyst: Pt/Al2O3 and HZSM-5)
CHALLENGES IN USING MARINE BIOMASS
Species Yield N C H O S
Scenedesmus obliquus 50.6 6.3 73.2 8.9 8.1 0.3
Phaeodactylum tricornutum 54.3 5.8 73.4 9.1 7.8 1.0
Nannocholoropsis gaditana 54.3 5.2 74.7 9.9 8.5 0.4
Scenedesmus almeriensis 58.1 6.1 74.3 9.1 8.4 0.4
Tetraselmis suecica 45.6 6.1 74.0 9.0 7.7 0.9
Chlorella vulgaris 55.3 7.1 72.5 8.7 8.6 0.5
Porphyridium purpureum 47.1 6.8 73.9 8.2 8.7 0.7
Dunaliella tertiolecta 55.3 6.2 72.0 8.8 9.9 0.3
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• 1. High water content → hydrothermal processes
• 2. High heteroatom content (N and O), high ash content
CHALLENGES IN USING MARINE BIOMASS
Scenedesmus almeriensis
C H N S O* HHV H/C O/C
Biocrude oil 74.3 9.2 5.7 0.8 10.0 36.1 1.486 0.101
Uncatalysed dry 82.3 10.4 4.8 <0.1 2.4 41.1 1.516 0.022
wet 80.6 10.0 4.9 0.1 4.4 39.8 1.489 0.041
Pt/Al2O3 dry 82.7 11.0 4.2 0.2 1.9 41.9 1.596 0.017
wet 80.1 10.1 4.7 0.2 4.9 39.7 1.513 0.046
HZSM-5 dry 81.8 10.3 5.0 0.1 2.8 40.7 1.511 0.026
wet 83.2 10.3 3.5 0.1 2.9 41.1 1.486 0.026
Nannochloropsis gaditana
C H N S O* HHV H/C O/C
Biocrude oil 74.4 10.1 4.8 0.5 10.2 37.1 1.629 0.103
Uncatalysed dry 83.6 11.3 2.1 0.2 2.8 42.3 1.622 0.025
wet 81.4 10.9 2.3 0.1 5.3 40.8 1.607 0.049
Pt/Al2O3 dry 84.2 11.7 2.4 <0.1 1.6 43.2 1.667 0.014
wet 82.0 11.2 2.8 <0.1 3.9 41.6 1.639 0.036
HZSM-5 dry 83.7 11.2 2.4 0.1 2.6 42.3 1.606 0.023
wet 82.4 11.0 2.5 <0.1 4.0 41.5 1.602 0.036
16
• 1. High water content → hydrothermal processes
• 2. High heteroatom content (N and O), high ash content
• 3. How to integrate in biorefineries for maximum value creation ?
CHALLENGES IN USING MARINE BIOMASS
Water
Biomass
Produc-
tion
Light
C source
Nutrients
Harvesting
Water and nutrients recycle
Valuableco-products(e.g. lipids,
amino acids)
CO2 richgas
Solid residue
BIOCRUDE OIL
Fractionation HTL
FUELS
Frederik RonsseProf. dr. ir.
DEPARTMENT OF GREEN CHEMISTRY AND TECHNOLOGY
T +32 9 264 62 00
www.ugent.be
