TORREFACTION OR PYROLYSIS OF BIOMASS. PROSPECTS FOR UKRAINE
The article considers the processes of torrefaction and pyrolysis of biomass typical for Ukraine. The advantages of torrefied fuel and directions of its application are given. Technical problems that arise in industrial installations are separately considered (self-heating and self-ignition of the t...
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| author | Klyus , V. Chetveryk , H. Matviychyk , O. Senchyk , M. Masliukova , Z. |
| author_facet | Klyus , V. Chetveryk , H. Matviychyk , O. Senchyk , M. Masliukova , Z. |
| author_institution_txt_mv | [
{
"author": "V. Klyus ",
"institution": "Institute of Renewable Energy, NAS of Ukraine, Kyiv, Ukraine"
},
{
"author": "H. Chetveryk ",
"institution": "Institute of Renewable Energy, NAS of Ukraine, Kyiv, Ukraine"
},
{
"author": "O. Matviychyk ",
"institution": "General Energy Institute, NAS of Ukraine, Kyiv, Ukraine"
},
{
"author": "M. Senchyk ",
"institution": "Kyiv National University of Construction and Architecture, Kyiv, Ukraine"
},
{
"author": "Z. Masliukova ",
"institution": "Institute of Renewable Energy, NAS of Ukraine, Kyiv, Ukraine"
}
] |
| author_sort | Klyus , V. |
| baseUrl_str | https://ve.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-18T06:32:22Z |
| description | The article considers the processes of torrefaction and pyrolysis of biomass typical for Ukraine. The advantages of torrefied fuel and directions of its application are given. Technical problems that arise in industrial installations are separately considered (self-heating and self-ignition of the torrefied product, adsorption and condensation of liquid substances, the danger of self-ignition of torrefied gas). During the granulation of torrefied biomass, energy consumption increases 3 times compared to untreated biomass. Due to dry friction, abrasive wear of the matrix increases. The cost price of torrefied pellets is higher than that of fossil coal. Based on these considerations, it is assumed that torrefaction plants in Ukraine can be built with foreign equipment. The state of charcoal production in Ukraine has been analysed. A forecast has been made regarding further growth of its volumes. The production of biochar by the oxidative method for metallurgy and agriculture (biochar) is considered. Specific biochar rich in nutrients can be produced from granulated chicken manure and sewage sludge. A technological scheme for the continuous co-production of torrefied fuel and biochar has been developed. The use of oxidative pyrolysis reactors for creating cogeneration plants that produce both electrical and thermal energy from biomass has been considered. |
| doi_str_mv | 10.36296/1819-8058.2025.2(81).202-210 |
| first_indexed | 2025-07-17T11:40:05Z |
| format | Article |
| fulltext |
202
Відновлювана енергетика. № 2/2025 | Біоенергетика
UDC 620.952 https://doi.org/10.36296/1819-8058.2025.2(81).202-210
TORREFACTION OR PYROLYSIS OF BIOMASS. PROSPECTS FOR UKRAINE
Received Mar. 31, 2025; accepted Jun. 27, 2025
Available online Jun. 30, 2025
Klyus V. 1, Chetveryk H.2, Matviychyk O.3,
Senchyk M.4, Masliukova Z.5
Author for correspondence: Chetveryk Hennadii,
e-mail: biomassa@ukr.net
The article considers the processes of torrefaction and py-
rolysis of biomass typical for Ukraine. The advantages of
torrefied fuel and directions of its application are given.
Technical problems that arise in industrial installations are
separately considered (self-heating and self-ignition of the
torrefied product, adsorption and condensation of liquid
substances, the danger of self-ignition of torrefied gas).
During the granulation of torrefied biomass, energy con-
sumption increases 3 times compared to untreated bio-
mass. Due to dry friction, abrasive wear of the matrix in-
creases. The cost price of torrefied pellets is higher than that of fossil coal. Based on these considerations, it is
assumed that torrefaction plants in Ukraine can be built with foreign equipment. The state of charcoal production
in Ukraine has been analysed. A forecast has been made regarding further growth of its volumes. The production
of biochar by the oxidative method for metallurgy and agriculture (biochar) is considered. Specific biochar rich in
nutrients can be produced from granulated chicken manure and sewage sludge. A technological scheme for the
continuous co-production of torrefied fuel and biochar has been developed. The use of oxidative pyrolysis reactors
for creating cogeneration plants that produce both electrical and thermal energy from biomass has been consid-
ered.
Keywords: torrefaction, types of reactors, dry pyrolysis, oxidative pyrolysis, biochar.
ТОРРЕФІКАЦІЯ ЧИ ПІРОЛІЗ БІОМАСИ. ПЕРСПЕКТИВИ ДЛЯ УКРАЇНИ
Отримано 31 бер. 2025 р.; рекомендовано до публікації 27 черв. 2025 р.
Доступно онлайн 30 черв. 2025 р.
Клюс В. П. 1, Четверик Г. О.2, Матвійчук О. С.3,
Сенчук М. П.4, Маслюкова З. В.5
Автор для кореспонденції: Четверик Геннадій,
e-mail: biomassa@ukr.net
Розглянуто процеси торрефікації та піролізу біо-
маси, використовуваної в Україні. Наведено переваги
торрефікованого палива та сфери його застосу-
вання. Окремо розглянуті проблеми технічного хара-
ктеру, які виникають на промислових установках
(самонагрівання та самозаймання торрефікованого
продукту, адсорбція та конденсація рідких речовин,
небезпека самозаймання торр. газу). При грануляції
торрефікованої біомаси витрати енергії збільшу-
ються в 3 рази в порівнянні з необробленою
1 Cand. of Science (Tech.)
https://orcid.org/0000-0001-8536-3211
2 Cand. of Science (Tech.)
https://orcid.org/0000-0001-9398-1968
3 Cand. of Science (Tech.)
https://orcid.org/0009-0000-9004-0222
4 Cand. of Science (Tech.)
https://orcid.org/0000-0001-8968-7336
5 Researcher.
https://orcid.org/0000-0002-4180-7930
1, 2, 5 Institute of Renewable Energy, NAS of Ukraine,
Kyiv, Ukraine
3 General Energy Institute, NAS of Ukraine, Kyiv,
Ukraine
4 Kyiv National University of Construction and
Architecture, Kyiv, Ukraine
1канд. техн. наук.
https://orcid.org/0000-0001-8536-3211
2канд. техн. наук.
https://orcid.org/0000-0001-9398-1968
3канд. техн. наук.
https://orcid.org/0009-0000-9004-0222
4канд. техн. наук.
https://orcid.org/0000-0001-8968-7336
5наук. співроб.
https://orcid.org/0000-0002-4180-7930
1, 2, 5 Інститут відновлюваної енергетики НАН
України, м. Київ, Україна
3 Інститут загальної енергетики НАН України,
м. Київ, Україна
4 Київський національний університет
будівництва і архітектури, м. Київ, Україна
203
Відновлювана енергетика. № 2/2025 | Біоенергетика
біомасою. Внаслідок сухого тертя збільшується абразивне зношення матриці. Собівартість торрефі-
кованих пелет є вищою, ніж викопного вугілля. Передбачається, що в Україні установки торрефікації
можуть бути побудовані на закордонному обладнанні. Проаналізовано стан виробництва деревного
вугілля в Україні. Зроблено прогноз щодо подальшого нарощування його обсягів. Розглянуто виробниц-
тво біовугілля методом окиснювального піролізу для металургії та сільського господарства (біочар).
Специфічний біочар, насичений поживними речовинами, можна виробляти з гранульованого курячого
посліду та каналізаційного мулу. Розроблена технологічна схема безперервного сумісного виробництва
торрефікованого палива й біовугілля з рослинної біомаси. Розглянуто використання реакторів окисню-
вального піролізу для створення когенераційних установок з виробництва електричної й теплової ене-
ргії з біомаси.
Ключові слова: торрефікація, типи реакторів, сухий піроліз, окиснювальний піроліз, біочар.
Introduction
The search for new types of energy capable of replacing fos-
sil fuels with renewable sources has led to an increase in
both fundamental and applied research, primarily focused
on the potential for regenerating natural resources, as the
current energy system is based mainly on the use of fossil
fuels. Biomass plays a vital role, as it can be used to produce
solid fuel, combustible liquids, and biogas. Moreover, bio-
mass helps to offset the intermittency of solar and wind
power generation. Therefore, a backup form of energy pro-
duction is needed—one that can ensure continuity of en-
ergy supply when required. Biomass can be considered the
first energy source that humanity learned to utilise, initially
for combustion and later for producing charcoal (biochar).
In addition, biomass serves as a means of storing and accu-
mulating solar energy through the process of photosynthe-
sis. However, unlike fossil fuels, biomass has several disad-
vantages, such as low energy density, high moisture
content, low calorific value, expensive logistics, etc. These
drawbacks, however, can be reduced or eliminated through
the use of physical, biological, and thermochemical bio-
mass processing technologies.
This article examines thermochemical technologies for con-
verting biomass into a solid carbonaceous residue (biochar)
as the main product and combustible (pyrolysis) gas as a by-
product. The relevance of biochar production is driven by
the fact that the EU acquis restricts the use of fossil fuels by
the provisions of the Paris Climate Agreement and the ear-
lier Kyoto Protocol. At the same time, the use of biochar is
being encouraged at coal-fired thermal power plants and
boiler stations. In terms of fuel properties, biochar is com-
parable to fossil coal. It has a brittle structure, is easily
crushed and ground using existing power plant equipment
and can be used for flame combustion without the need to
reconstruct the heat supply system.
The aim of this study is to conduct a comparative analysis
of thermal biomass conversion methods—torrefaction and
pyrolysis—in order to assess their potential for application
in Ukraine. To achieve this goal, the following four objec-
tives must be addressed:
1. To analyse available state-of-the-art thermochemical
technologies for converting biomass into biochar;
2. To explore the feasibility of biomass torrefaction using
the method of oxidative pyrolysis;
3. To provide recommendations for biochar production in
Ukraine;
4. To develop a technology for the combined production
of biochar and torrefied biofuel.
Materials and Methods of Torrefaction
It is known that lignocellulosic biomass typically consists of
three main components: cellulose, hemicellulose, and lig-
nin. The chemical composition of dry woody and plant bio-
mass is approximately the same and consists of carbon
(50%), oxygen (42%), hydrogen (7%), and ash (1%). Studies
have shown that hemicellulose decomposes in the temper-
ature range of 210–320 °C, cellulose at 300–390 °C, and lig-
nin at 200–550 °C. When biomass is heated in the absence
of air or with limited oxygen access, chemical depolymeri-
sation of hemicellulose, cellulose, and lignin occurs, result-
ing in the formation of biochar with a high carbon content
of up to 92–95%, which is nearly pure carbon. This phenom-
enon was noticed by our ancestors, who began producing
biochar from wood by burning it in earth-covered piles.
However, biochar was not initially used as fuel but rather
as a soil amendment (biochar) to improve soil structure and
increase its fertility. Over 1,000 years ago, entire fields of
biochar-enriched soil (Terra Preta) appeared in the Amazon
Basin, and they have retained high fertility to this day [1].
Thus, the first use of biochar was likely agricultural. In those
ancient times, there also arose the need for smelting and
heat treatment of various metals. As a fuel, they used bio-
char made from wood. Over the centuries, the process of
biochar production was refined and developed into an in-
dustrial technology and became known as pyrolysis. Ac-
cording to the regulatory document [2], pyrolysis is an irre-
versible thermal decomposition process of fuel in the
absence of air. According to various sources, biomass pyrol-
ysis occurs within a temperature range of 200 °C to 900 °C
and lasts from several seconds to more than a day, depend-
ing on the size and moisture content of the raw material.
The process occurring at 200–320 °C is referred to as mild
pyrolysis (torrefaction or bertinisation). Currently, the term
"torrefaction" is the most commonly used.
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Відновлювана енергетика. № 2/2025 | Біоенергетика
Medium-temperature pyrolysis, also known as pyrolysis,
occurs at temperatures ranging from 300 to 600 °C and is a
widely used industrial process for producing charcoal for
energy applications. High-temperature pyrolysis, occurring
at 600–900 °C and sometimes up to 1,000 °C, enables the
production of biochar with a high sorption capacity.
Although torrefaction has been known for quite a long time
(over 100 years), the practical use of torrefied biomass has
historically been very limited. For example, firewood was
torrefied and then used to heat the homes of wealthy
households. In recent decades, interest in torrefaction has
grown—about 40 years ago—due to the restrictions on CO₂
emissions from fossil fuels. Biomass, as is well known, is a
CO₂-neutral fuel. Currently, plant-based biomass is
considered the primary feedstock for torrefaction, and its
availability is many times greater than that of woody raw
materials [3, 4]. This includes readily available materials
such as sunflower husks, buckwheat hulls, rice husks, and
screenings from grain elevators.
Another promising source is baled agricultural residues—
including straw from grain and rapeseed crops, baled corn,
sunflower and miscanthus stalks, and bedding manure—
amounting to millions of tons annually [3]. Thus, Ukraine
possesses sufficient plant biomass resources to establish in-
dustrial production of torrefied biofuel.
Fig. 1 shows the block diagram of the torrefaction process,
and Fig. 2 presents the technological scheme [5].
Fig. 1. The torrefaction flowchart
Fig. 2. The technological scheme of torrefaction
Types of torrefaction reactors. The main element of the
flow chart is the torrefaction reactor.
A rotary drum reactor is the most common type of contin-
uous reactor, where the feedstock can be heated either ex-
ternally—through the reactor wall—or directly within the
reactor using an inert (oxygen-free) gas stream.
Most often, the drum in which the biomass is transported
is heated from the outside, without direct contact between
the hot flue gas stream and the feedstock. Heat transfer oc-
curs through thermal conduction. The residence time of the
feedstock can be adjusted by controlling the rotation speed
of the drum.
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Відновлювана енергетика. № 2/2025 | Біоенергетика
Torrefaction reactor with a fluidised bed: Moist biomass is
placed on a grate, while hot inert gas is injected from below
through the biomass layer. At a sufficient gas velocity, the
biomass is lifted above the grate and behaves like a fluid.
This results in a uniform temperature distribution through-
out the biomass bed.
Microwave reactor. The microwave torrefaction reactor
uses high-frequency electromagnetic waves. These waves
create vibration of water molecules inside the biomass,
which leads to an increase in its temperature to a predeter-
mined value 6. The torrefaction process takes place in the
temperature range of 200–320 C, at which most of the
hemicellulose is destroyed while cellulose and lignin are
only partially. In the process of torrefaction, moisture evap-
orates, and volatile substances are formed – torrefaction
gas (torr. gas). At the same time, the mass of raw materials
is reduced by 20-30%, and 10% of the energy intensity of
raw materials is converted into torrefaction gas. As a result
of a significant decrease in the mass of raw materials, in
comparison with the loss of energy, the combustion heat of
the torrefied product increases by 10-15 % compared to the
initial raw material.
The main advantages of torrefied fuel [7]
The calorific value is 20-21.6 MJ/kg, hydrophobicity, less
volatile substances are released during combustion, and lo-
gistics costs are reduced when transporting torrefied pel-
lets with a high volumetric density of up to 750 kg/m3. Typ-
ically, torrefied fuel is mixed with fossil coal in coal
warehouses and then enters the fuel feeding system.
Parameters affecting the torrefaction process 8–13
Temperature and residence time. The residence time
mainly affects the decomposition of hemicellulose. The
characteristics of the final product are more influenced by
temperature than residence time. The rate of heating used
during the torrefaction process affects the secondary dehy-
dration reactions that determine the final distribution of
solid, liquid and gaseous products.
Raw material particle size. The discrepancy between the
particle size of the input raw material and the moisture con-
tent leads to variation in heat transfer and, as a result, un-
even heating. The smallest pieces will turn into charcoal,
while the larger pieces will not be fully baked.
Industrial development of torrefaction
The results of numerous studies on laboratory plants for
torrefaction of different types of biomass do not yet guar-
antee the capacity, continuity and reliability of torrefied bi-
omass production in pilot plants, and even more so in in-
dustrial ones. The main reason is the difficulty of scaling,
since many problems cannot be predicted, as they arise
when processes occur on a larger scale 14. According to
source 15 when torrefying Yunnan pine at a temperature
of 300 C, the yield of the solid phase was 46.27 % (wt), torr.
gas 33.62% (wt.), liquid fraction nearly 20% (wt.). The com-
position of torr. gas obtained by torrefaction of corn stalks
at a temperature of 300 C is as follows: hydrogen –
31.82%, CO – 19.97%, CO2 – 20.70%. Lower calorific value –
17.83 MJ/m3 16.
Torrefaction gases contain H2, CO, CO2, CH4 and a variety of
condensing components such as acetic acid, formic acid,
methanol, furfural, hydroxyacetone and water. They are
highly reactive and can quickly polymerise into bio-oils.
These bio-oils are adsorbed in the reactor on the surface of
torrefied biomass particles. After unloading and cooling,
the bio-oil particles condense and flow out of the storage
containers for the torrefied product.
A significant issue associated with torrefied products is the
phenomenon of self-heating and spontaneous combustion
[14]. For example, at an atmospheric air temperature of
+95 °C, torrefied material can begin to ignite and burn with-
out a visible flame. There have been documented cases of
self-heating and ignition of torrefied pellets stored in out-
door piles—even during rainy weather. To eliminate the
risk of spontaneous combustion, a two-stage torrefaction
technology for sunflower husks was proposed in [17]. This
method involves torrefaction in a hearth-type reactor at a
temperature of 250 °C, followed by cooling of the resulting
product using atomised water. The cooling process occurs
at a temperature above 120 °C. Upon contact with the hot
product, the water instantly turns into steam, as the latent
heat of vaporisation is exceeded. The water consumption
for cooling is about 0.3 L per kilogram of biomass. The pro-
posed torrefaction technology ensures rapid and reliable
cooling of the torrefied product while simultaneously sup-
pressing the exothermic processes that may occur in the
hot material, thereby increasing the fire safety of the torre-
faction process. The torrefied product does not require dry-
ing, as the water fully evaporates upon contact with the hot
material, and the resulting steam mixes with the torrefac-
tion gas and is expelled from the reactor.
The key problem observed during pelletising torrefied bio-
mass is high energy costs due to product friction. Compared
to pelleting of raw biomass, they increase almost 3 times,
from 50-60 kWh/t to 150 kWh/t. Also, the quality of tor-
refied pellets (strength, density, surface structure, mois-
ture resistance) turned out to be lower than expected.
The service life of the matrix when using torrefied material
is shorter because it is harder than raw biomass.
For the above and other reasons, many biomass torrefac-
tion projects have failed, as evidenced by various news sto-
ries on the Internet. There are no examples of torrefied pel-
lets being transported in open gondola cars. The cost of
torrefied pellets is still higher than that of coal.
Thus, in the world, biomass torrefaction is in the initial
stage of commercial implementation. For example, the
well-known Austrian company "Polytechnic" is building the
largest wood chip-based plant in Europe in Finland, with a
capacity of 60,000 tons. In the future, such plants, which
run on plant biomass, can be built in Ukraine, as is the case
with biogas plants that use foreign equipment.
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Unfortunately, domestic biomass torrefaction studies are
at the stage of laboratory installations.
For example, we conducted an experimental test into the
possibility of torrefying pellets by oxidative pyrolysis. To
conduct experimental research, a laboratory installation
was created, the scheme of which is shown in Fig. 3. The
unit operates under positive pressure (Fig. 3, a).
Thermocouples T1-T4 of type K are installed at the height of
the reactor to measure temperature. The thermocouples
were connected to a 4-position multimeter.
In the installation under vacuum (Fig. 3 b), there is no
gas meter 4. To cool the torr. gas to a temperature ac-
ceptable for the operation of the fan, the receiver 4 is
installed.
Fig. 3. The scheme of a laboratory installation for biofuel torrefaction
a) under air pressure; b) under vacuum
1 − reactor with thermal insulation; 2 − grate; 3 − cover; 4 − gas meter; 5 − valve; 6 − fan; 4 − receiver
Experimental studies on a pressurised air unit (Fig. 3, а).
Wood pellets with a diameter of 8 mm and a moisture con-
tent of 10% were loaded into the reactor. The weight of the
pellets was 900 g. The air supply fan 6 was turned on, and the
top layer of pellets was ignited using a gas burner. When the
temperature reached 450 °C on the thermocouple T1, the
burner was turned off. A combustion zone of torrefaction gas
was formed in the reactor, moving downward against the
flow of air supplied by the fan. The amount of air was regu-
lated by a damper and measured using a gas meter. At a tem-
perature of 450 °C, the process of oxidative pyrolysis of the
pellets occurred, resulting in the formation of biochar. By re-
ducing the air supply to the reactor, the temperature in the
combustion zone of torr. gas was gradually reduced to a
maximum torrefaction temperature of 320 С.
As the air supply was reduced, the combustion of the tor-
refaction gas gradually diminished, and smoke began to
emerge from the open top of the reactor. The temperature
recorded by thermocouple T1 dropped to 280–320 °C, and
the process came to a halt. When the air supply was in-
creased, the temperature at T1 rose again to 420–450 °C,
and the torrefaction gas burned smokelessly. Five test runs
of the system were conducted, which showed that torre-
faction does not occur at a temperature of 320 °C.
Experimental studies on a unit under vacuum (Fig. 3 b).
An advantage of this setup is its ability to operate in a con-
tinuous mode. The startup procedure is as follows: a layer
of red-hot pellets is placed onto the grate of the reactor.
The fan is then turned on, drawing air into the reactor
through its open top. 800 g of pellets with a diameter of
8 mm and a moisture content below 10% are loaded into
the reactor. A combustion zone of torrefaction gas forms
and moves upward against the incoming air stream. When
the temperature measured by thermocouple T4 reaches
450–500 °C, the air supply is reduced. With further reduc-
tion of the air flow, the temperature at T3 stabilises at
around 320 °C, as observed in previous tests. At this tem-
perature, smoke is emitted from the fan instead of torre-
faction gas. The temperature at T4 then begins to drop be-
low 320 °C, and the torrefaction process halts. To resume
the process, the damper is opened, drawing in more air into
the reactor. The process restarts at a temperature of 420–
470 °C, corresponding to low-temperature oxidative pyrol-
ysis.
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Відновлювана енергетика. № 2/2025 | Біоенергетика
It is assumed that at a torrefaction temperature of 320 °C
using the oxidative pyrolysis method, the torrefaction gas
contains a high proportion of nitrogen, carbon dioxide, and
water vapour (non-combustible components), and too few
combustible compounds (carbon monoxide, hydrogen, me-
thane). As a result, it cannot sustain combustion on its own.
Therefore, there is no internal heat source, and torrefac-
tion does not occur. Thus, torrefaction of biofuel is best
conducted using the dry pyrolysis method.
Charcoal production in Ukraine. Charcoal is produced by
dry pyrolysis (indirect heating of raw materials through the
retort wall). The amount of charcoal produced per capita is
extremely small, approx. 0.1 kg/year. In industrialised
countries, this figure is up to 20 kg/year, for example, in Ja-
pan. According to the portal of charcoal producers, 247
charcoal producers are registered in Ukraine.
Perechyn Timber Chemical Plant is the largest producer of
wood and coal products in Ukraine (up to 4,000 tons per
month). Coal production takes place in two vertical retorts.
All pyrolysis gases are burned in the waste heat boiler.
In addition to the official producers of charcoal, handicraft
production flourishes in Ukraine in all forest-rich regions –
from Sumy to Uzhhorod. The cycle of burning a batch of
coal is lengthy, while illegal producers often do not use
equipment that reduces harmful emissions, given its high
cost. Primitive charcoal production could turn Ukraine into
Haiti, where illegal charcoal production has led to an envi-
ronmental disaster yet has not enriched the inhabitants.
There is a great demand for charcoal worldwide, so most of
its producers focus on exporting it due to its high price and
low requirements for its quality. Overseas, this product is
mainly used as raw materials for further processing.
According to the State Customs Service, in 2023, Ukraine
exported 122 thousand tons of charcoal and imported 957
tons.
The most important for biochar consumers are its mechan-
ical strength, electrical resistance, calorific value and poros-
ity. Table 1 shows the tentative composition of charcoal.
Table 1. Elemental composition of charcoal
Pyrolysis
temperature, С
Output,
%
Content of elements, %
С Н О
100 100 47.4 6.5 46.1
200 92.6 58.4 6.1 36.5
400 39.2 76.1 4.9 19.0
600 28.6 93.8 2.6 3.6
800 26.7 95.7 1.0 3.3
Further increases in charcoal production are predicted,
both by expanding the operating enterprises and construct-
ing new ones.
Biochar production by the oxidative pyrolysis method. By
dry pyrolysis technology, only one product is manufactured
— charcoal. The pyrolysis gas generated during the process
is used to meet the system’s own technological needs. To
improve the energy efficiency of the process, a method
known as oxidative pyrolysis was proposed nearly 40 years
ago. This method yields two products: biochar and pyrolysis
gas. The term biochar refers to charcoal made from woody
or plant-based biomass. In addition to the term oxidative
pyrolysis, the literature also uses the term partial gasifica-
tion [18, 19]. This technology is based on the effect of a “re-
verse thermal wave” in the fuel bed. The fundamental dif-
ference between oxidative pyrolysis and dry pyrolysis is
that in oxidative pyrolysis, the fuel is evenly heated inside
the reactor with limited air access, due to the combustion
of part of the pyrolysis gas. The optimal particle size for bio-
fuel in oxidative pyrolysis is 10–40 mm (such as wood chips,
pellets, and briquettes), and the optimal moisture content
is up to 20%.
For the first time in Ukraine, the technology of oxidative py-
rolysis was studied at the National Metallurgical Academy
(Dnipro-based) by a research team led by Dr. Tech. Sci.
Hubynskyi M.V. [20]. The processing of sunflower husks
and walnut shells into biochar was investigated as a raw
material to produce high-calorific fuel briquettes. Cur-
rently, research is being conducted to develop methods for
using carbon materials derived from plant biomass in met-
allurgical processes. This will help reduce the metallurgy
sector's dependence on fossil fuels. The production cost of
biomass-based coke will be lower than that of fossil coal
coke. The cheapest types of biofuel are sunflower husks
and cereal straw.
At the Institute of Gas of NAS of Ukraine, under the super-
vision of Ph.D. in Technical Sciences Pianyh K.Y., cogenera-
tion units for the production of electric and thermal energy
from biomass are being developed based on oxidative py-
rolysis technology. For instance, the Institute is testing an
industrial unit powered by wood pellets with an electrical
capacity of 25 kW. Due to improvements in technology, the
tar content has been reduced to 0.1 g/m³ of pyrolysis gas.
Such gas is fully suitable for use in gas-piston engines. An-
other product of biomass thermal processing—biochar—is
used to produce fuel briquettes using a roller press. The
unit operates in batch mode; therefore, to ensure continu-
ous electricity generation, several pyrolysis reactors are re-
quired [19]. Based on the developments of the Institute of
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Відновлювана енергетика. № 2/2025 | Біоенергетика
Gas, the company “Biosmartex” in Rivne offers cogenera-
tion units with a capacity of 4,000 kW (electric) and 3,900
kW (thermal). Fuel consumption is 3,000 kg/h, and the bio-
char yield is 20% [21].
At the Institute of Renewable Energy of the National Acad-
emy of Sciences of Ukraine, under the supervision of Ph.D.
in Technical Sciences Klyus S.V., a technology was devel-
oped for producing organic fertilisers from large-scale
waste, namely poultry litter and sewage sludge [22]. Poul-
try litter is classified as Class IV hazardous waste. According
to Article 246 of the Tax Code of Ukraine (as amended July
1, 2019), the rate for waste disposal is set at 5 UAH/ton.
Poultry farms that can utilize poultry litter by any method
or sell it directly to consumers are exempt from taxation. In
Ukraine, the volume of poultry litter amounts to approxi-
mately 5 million tons per year (about 10% of the European
figure).
To facilitate the successful utilisation of bedding-based
poultry litter, some poultry farms install pelletising lines.
The pellets have a diameter of 8–10 mm and a moisture
content of up to 30%. Due to their unpleasant odour, the
pellets are packaged in sealed bags. We conducted a test
processing of these pellets using the oxidative pyrolysis
method. At a temperature of 400–600 °C, carbonised bio-
char (an organic fertiliser) is obtained, with a nutrient con-
tent comparable to simple superphosphate. Additionally,
thermal processing of pellets made from sewage sludge
from the Bortnychi Aeration Station in Kyiv was carried out
on a pilot-industrial unit. The carbonised sludge also con-
tains nutrients and can be used as fertiliser [22].
Thus, carbonised waste—poultry litter and sewage
sludge—can be considered a specific type of biochar en-
riched with nutrients. The discussed applications of oxida-
tive pyrolysis technology for biomass show good potential
for industrial implementation in Ukraine.
Development of a technology for the combined production
of biochar and torrefied biofuel.
The gas produced during oxidative pyrolysis has a low calo-
rific value. Therefore, it is often burned as production
waste. To enable the beneficial use of pyrolysis gas, a basic
scheme has been developed for a continuous-operation
unit for the combined production of biochar and torrefied
biofuel (Fig. 4).
Fig. 4. The Scheme of installation of continuous operation
1 − oxidative pyrolysis reactor; 2 − gateway shutter; 3 – collection of biochar; 4 – smokehole;
5 – combustion chamber; 6 – auger torrefier; 7 – engine
209
Відновлювана енергетика. № 2/2025 | Біоенергетика
The unit operates as follows. First, biochar is loaded into
the oxidative pyrolysis reactor (1), with the upper layer be-
ing ignited. Then, the lock valve (2) is switched off, allowing
part of the biochar from reactor (1) to enter the collector
(3), while fresh biofuel in the form of pellets, wood chips,
or briquettes is fed into reactor (1) to replace it. Due to the
vacuum created by the exhaust fan (4), air is drawn into the
reactor (1), initiating the oxidative pyrolysis process. The
discharge of biochar and the feeding of biofuel into reactor
(1) are then synchronised. [23].
The pyrolysis gas generated in reactor 1 flows into the com-
bustion chamber (5), where it is burned with air. The result-
ing flue gases are directed into the jacket of the screw tor-
refier (6), heating it to the required temperature (max
320 °C). Finely dispersed biomass (pellets, wood chips,
grain cleaning waste, etc.) is fed into the body of the torre-
fier through a conveyor system and a lock valve. This bio-
mass is heated, torrefied, and transported by the screw to
the discharge hatch. Torrefaction gas, which contains no ni-
trogen, is formed inside the torrefier. After appropriate pu-
rification, this gas can be used as boiler fuel. The flue gas
from the jacket of torrefier 6 is released into the atmos-
phere. By combining the oxidative pyrolysis reactor and the
screw torrefier in a single technological scheme, the follow-
ing products are obtained: biochar, torrefied biofuel, and
torrefaction gas. The overall energy efficiency is increased
by utilising the pyrolysis gas to heat the torrefier.
Conclusions
Biomass torrefaction is presented as a process capable of
improving the combustion properties of biomass. However,
this technology is still in the early stages of industrial imple-
mentation in developed countries. It is anticipated that tor-
refaction units in Ukraine could be built using imported
equipment, as in the case with biogas installations.
Based on the results of experimental studies, the torrefac-
tion of wood pellets using the method of oxidative pyrolysis
has shown that the process is physically impossible, even at
the highest torrefaction temperature of 320 °C. The torre-
faction gas does not contain a sufficient amount of combus-
tible components to sustain combustion, causing the torre-
faction process to stop.
A promising direction for Ukraine is the use of oxidative py-
rolysis of biomass to produce biochar from plant waste, poul-
try litter, and sewage sludge. In particular, biochar can be
used in metallurgy, while agricultural biochar can be applied
in farming. At the Institute of Gas of NAS of Ukraine, cogen-
eration units for generating electric and thermal energy have
been developed based on oxidative pyrolysis reactors.
An energy-efficient technological scheme is proposed that
combines the operation of an oxidative pyrolysis reactor for
biochar production and a screw-type torrefier for the pro-
duction of torrefied biofuel. The knowledge and experience
accumulated by Ukrainian scientists and engineers are al-
ready being implemented in demonstration projects and
are expected to be scaled up for industrial use.
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|
| id | veorgua-article-541 |
| institution | Vidnovluvana energetika |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-19T01:16:12Z |
| publishDate | 2025 |
| publisher | Institute of Renewable Energy National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | veorgua/a1/f0f29995f07fd11f7d2719cbfb3491a1.pdf |
| spelling | veorgua-article-5412026-07-18T06:32:22Z TORREFACTION OR PYROLYSIS OF BIOMASS. PROSPECTS FOR UKRAINE ТОРРЕФІКАЦІЯ ЧИ ПІРОЛІЗ БІОМАСИ. ПЕРСПЕКТИВИ ДЛЯ УКРАЇНИ Klyus , V. Chetveryk , H. Matviychyk , O. Senchyk , M. Masliukova , Z. torrefaction, types of reactors, dry pyrolysis, oxidative pyrolysis, biochar. торрефікація, типи реакторів, сухий піроліз, окиснювальний піроліз, біочар. The article considers the processes of torrefaction and pyrolysis of biomass typical for Ukraine. The advantages of torrefied fuel and directions of its application are given. Technical problems that arise in industrial installations are separately considered (self-heating and self-ignition of the torrefied product, adsorption and condensation of liquid substances, the danger of self-ignition of torrefied gas). During the granulation of torrefied biomass, energy consumption increases 3 times compared to untreated biomass. Due to dry friction, abrasive wear of the matrix increases. The cost price of torrefied pellets is higher than that of fossil coal. Based on these considerations, it is assumed that torrefaction plants in Ukraine can be built with foreign equipment. The state of charcoal production in Ukraine has been analysed. A forecast has been made regarding further growth of its volumes. The production of biochar by the oxidative method for metallurgy and agriculture (biochar) is considered. Specific biochar rich in nutrients can be produced from granulated chicken manure and sewage sludge. A technological scheme for the continuous co-production of torrefied fuel and biochar has been developed. The use of oxidative pyrolysis reactors for creating cogeneration plants that produce both electrical and thermal energy from biomass has been considered. Розглянуто процеси торрефікації та піролізу біомаси, використовуваної в Україні. Наведено переваги торрефікованого палива та сфери його застосування. Окремо розглянуті проблеми технічного характеру, які виникають на промислових установках (самонагрівання та самозаймання торрефікованого продукту, адсорбція та конденсація рідких речовин, небезпека самозаймання торр. газу). При грануляції торрефікованої біомаси витрати енергії збільшуються в 3 рази в порівнянні з необробленою біомасою. Внаслідок сухого тертя збільшується абразивне зношення матриці. Собівартість торрефікованих пелет є вищою, ніж викопного вугілля. Передбачається, що в Україні установки торрефікації можуть бути побудовані на закордонному обладнанні. Проаналізовано стан виробництва деревного вугілля в Україні. Зроблено прогноз щодо подальшого нарощування його обсягів. Розглянуто виробництво біовугілля методом окиснювального піролізу для металургії та сільського господарства (біочар). Специфічний біочар, насичений поживними речовинами, можна виробляти з гранульованого курячого посліду та каналізаційного мулу. Розроблена технологічна схема безперервного сумісного виробництва торрефікованого палива й біовугілля з рослинної біомаси. Розглянуто використання реакторів окиснювального піролізу для створення когенераційних установок з виробництва електричної й теплової енергії з біомаси. Institute of Renewable Energy National Academy of Sciences of Ukraine 2025-06-30 Article Article application/pdf https://ve.org.ua/index.php/journal/article/view/541 10.36296/1819-8058.2025.2(81).202-210 Vidnovluvana energetika ; No. 2(81) (2025): Scientific and applied Journal renewable energy ; 202-210 Возобновляемая энергетика; ##issue.no## 2(81) (2025): Scientific and applied Journal renewable energy ; 202-210 Відновлювана енергетика; № 2(81) (2025): Науково-прикладний журнал Відновлювана енергетика; 202-210 2664-8172 1819-8058 10.36296/1819-8058.2025.2(81) en https://ve.org.ua/index.php/journal/article/view/541/449 Copyright (c) 2025 V. Klyus , H. Chetveryk , O. Matviychyk , M. Senchyk , Z. Masliukova https://creativecommons.org/licenses/by-nc-nd/4.0 |
| spellingShingle | torrefaction types of reactors dry pyrolysis oxidative pyrolysis biochar. Klyus , V. Chetveryk , H. Matviychyk , O. Senchyk , M. Masliukova , Z. TORREFACTION OR PYROLYSIS OF BIOMASS. PROSPECTS FOR UKRAINE |
| title | TORREFACTION OR PYROLYSIS OF BIOMASS. PROSPECTS FOR UKRAINE |
| title_alt | ТОРРЕФІКАЦІЯ ЧИ ПІРОЛІЗ БІОМАСИ. ПЕРСПЕКТИВИ ДЛЯ УКРАЇНИ |
| title_full | TORREFACTION OR PYROLYSIS OF BIOMASS. PROSPECTS FOR UKRAINE |
| title_fullStr | TORREFACTION OR PYROLYSIS OF BIOMASS. PROSPECTS FOR UKRAINE |
| title_full_unstemmed | TORREFACTION OR PYROLYSIS OF BIOMASS. PROSPECTS FOR UKRAINE |
| title_short | TORREFACTION OR PYROLYSIS OF BIOMASS. PROSPECTS FOR UKRAINE |
| title_sort | torrefaction or pyrolysis of biomass. prospects for ukraine |
| topic | torrefaction types of reactors dry pyrolysis oxidative pyrolysis biochar. |
| topic_facet | torrefaction types of reactors dry pyrolysis oxidative pyrolysis biochar. торрефікація типи реакторів сухий піроліз окиснювальний піроліз біочар. |
| url | https://ve.org.ua/index.php/journal/article/view/541 |
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