Moving torrefaction towards market introduction – Technical improvements and economic-environmental assessment along the overall torrefaction supply chain through the SECTOR project

Abstract

The large-scale implementation of bioenergy demands solid biofuels which can be transported, stored and used efficiently. Torrefaction as a form of pyrolysis converts biomass into biofuels with according improved properties such as energy density, grindability and hydrophobicity. Several initiatives advanced this development. The first pilot-scale and demonstration plants displayed the maturity and potential of the technology.The European research project SECTOR intended to shorten the time-to-market. Within the project 158 Mg of biomass were torrefied through different technologies (rotary drum, toroidal reactor, moving bed). Their production led to process optimization of combined torrefaction-densification steps for various feedstocks through analysing changes in structure and composition. The torrefied pellets and briquettes were subjected to logistic tests (handling and storage) as well as to tests in small- and large-scale end-uses. This led to further improvement of the torrefied product meeting logistics/end-use requirements, e.g. durability, grindability, hydrophobicity, biodegradation and energy density. Durability exceeds now 95%.With these test results also international standards of advanced solid biofuels were initiated (ISO standards) as a prerequisite for global trade of torrefied material. Accompanying economic and environmental assessment identified a broad range of scenarios in which torrefied biomass perform better in these areas than traditional solid biofuels (e.g. white pellets), depending e.g. on feedstock, plant size, transport distances, integration of torrefaction in existing industries and end use. The implementation of industrial plants is the next step for the technology development. Different end user markets within and outside Europe can open opportunities here.

Full text

Research paper
Moving torrefaction towards market introduction eTechnical
improvements and economic-environmental assessment along the
overall torrefaction supply chain through the SECTOR project
Daniela Thr€
an
a
,
b
,
*
, Janet Witt
a
, Kay Schaubach
a
, Jaap Kiel
c
, Michiel Carbo
c
,J
€
org Maier
d
,
Collins Ndibe
d
, Jaap Koppejan
e
, Eija Alakangas
f
, Stefan Majer
a
, Fabian Schipfer
g
a
DBFZ Deutsches Biomasseforschungszentrum gGmbH, Torgauer Straße 116, 04347 Leipzig, Germany
b
UFZ HelmholtzeZentrum für Umweltforschung GmbH, Permoserstraße 15, 04318 Leipzig, Germany
c
ECN Energy Research Centre of the Netherlands, 1755 ZG Petten, The Netherlands
d
Universit€
at Stuttgart, Pfaffenwaldring 23, 70569 Stuttgart, Germany
e
Procede Biomass BV, Vlierstraat 111, 7544GG Enschede, The Netherlands
f
VTT Technical Research Centre of Finland Ltd., Koivurannantie 1, FI-40400 Jyv€
askyl€
a, Finland
g
Technische Universit€
at Wien, Gusshausstrasse 25/370-3, A-1040 Wien, Austria
article info
Article history:
Received 18 September 2015
Received in revised form
2 March 2016
Accepted 3 March 2016
Available online xxx
Keywords:
Torrefaction
Solid biofuel
Sustainability
Standardization
Densification
Market implementation
abstract
The large-scale implementation of bioenergy demands solid biofuels which can be transported, stored
and used efficiently. Torrefaction as a form of pyrolysis converts biomass into biofuels with according
improved properties such as energy density, grindability and hydrophobicity. Several initiatives
advanced this development. The first pilot-scale and demonstration plants displayed the maturity and
potential of the technology.
The European research project SECTOR intended to shorten the time-to-market. Within the project
158 Mg of biomass were torrefied through different technologies (rotary drum, toroidal reactor, moving
bed). Their production led to process optimization of combined torrefaction-densification steps for
various feedstocks through analysing changes in structure and composition. The torrefied pellets and
briquettes were subjected to logistic tests (handling and storage) as well as to tests in small- and large-
scale end-uses. This led to further improvement of the torrefied product meeting logistics/end-use re-
quirements, e.g. durability, grindability, hydrophobicity, biodegradation and energy density. Durability
exceeds now 95%.
With these test results also international standards of advanced solid biofuels were initiated (ISO
standards) as a prerequisite for global trade of torrefied material. Accompanying economic and envi-
ronmental assessment identified a broad range of scenarios in which torrefied biomass perform better in
these areas than traditional solid biofuels (e.g. white pellets), depending e.g. on feedstock, plant size,
transport distances, integration of torrefaction in existing industries and end use. The implementation of
industrial plants is the next step for the technology development. Different end user markets within and
outside Europe can open opportunities here.
©2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND
license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction
This paper is a condensed summary of final results from the
project SECTOR (Production of Solid Sustainable Energy Carriers
from Biomass by Means of Torrefaction), which was funded by the
European Union's Seventh Programme for research, technological
development and demonstration (GA no. 282826). The project
aimed at shortening the time to market of torrefaction technology
to provide high density bioenergy carriers, spanning the complete
value chain, which it achieved successfully.
Large scale implementation of bioenergy is expected to increase
[19], and high energy density commodities form the key to
*Corresponding author. DBFZ Deutsches Biomasseforschungszentrum gGmbH,
Torgauer Straße 116, 04347 Leipzig, Germany.
E-mail addresses: daniela.thraen@dbfz.de (D. Thr€
an), kiel@ecn.nl (J. Kiel), Joerg.
Maier@ifk.uni-stuttgart.de (J. Maier), JaapKoppejan@procede.nl (J. Koppejan), Eija.
Alakangas@vtt.fi(E. Alakangas), schipfer@eeg.tuwien.ac.at (F. Schipfer).
Contents lists available at ScienceDirect
Biomass and Bioenergy
journal homepage: http://www.elsevier.com/locate/biombioe
http://dx.doi.org/10.1016/j.biombioe.2016.03.004
0961-9534/©2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Biomass and Bioenergy xxx (2016) 1e17
Please cite this article in press as: D. Thr€
an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
environmental assessment along the overall torrefaction supply chain through the SECTOR project, Biomass and Bioenergy (2016), http://
dx.doi.org/10.1016/j.biombioe.2016.03.004

establish this. In Europe, adapted biomass fuels for co-firing in coal
power stations could significantly support the fulfilment of the
political targets ethe provision of 20% of the primary energy
consumption through renewable fuels until 2020, and 27% until
2030 ewith relatively minor technical adaptations and at accept-
able costs [2,10].
This requires bioenergy carriers that behave similarly to coal
during logistics, milling, combustion and gasification in order to
use the existing infrastructure. Crucial properties are the net calo-
rific value, required energy for milling, particle size distribution,
mill capacity and pneumatic feeding. Another short term applica-
tion is the use of bioenergy carriers in small and medium scale
boilers. Here, an optimal alignment between boilers and bioenergy
carriers regarding heating value, volatile matter and moisture, bulk
density and fuel pellet dimensions has to be established [3,4]. In the
long term, the use of bioenergy carriers to produce bio-chemicals
and bio-fuels via gasification routes is expected.
One approach to provide these bioenergy carriers is the torre-
faction of solid biomass, such as wood and herbaceous material
[4,11]. During torrefaction, as a form of mild pyrolysis, water and
part of the volatile matter are removed which results in a brittle and
to a certain degree hydrophobic intermediate. By combining tor-
refaction with pelletization or briquetting, solid biomass materials
can be converted into a high-energy-density commodity energy
carrier with additional advantageous fuel properties compared
with white wood pellets, such as improved grindability, higher
water resistance and good biological stability. These torrefied
biomass pellets can be provided in a constant, end-user specific
quality [1,5]. This indicates that logistics, handling and conversion
of torrefied biomass pellets may occur in a fashion that is more
comparable to fossil solid fuels such as coal. Additional value could
be created by reclaiming the volatile matter that is released during
torrefaction, as wood vinegar or resin substitute [6,12].
Technical development of this pre-treatment of solid biofuels
has been intensified during the last decade [7,8,13,14]. Technology
development and implementation is currently pushed with
different research and demonstration projects mostly in the Euro-
pean Union and North America (Fig. 1).
The main issues in torrefaction development at the start of the
project (2012) have been process control, heat integration, process
upscaling, ensuring product quality that allowed large scale
handling, outdoor storage and end use as well as flexible input
materials [15]. Torrefaction of non-woody biomass is an additional
relevant issue as large biomass potentials especially from residues
have been identified in several assessments [16,17]. Market
implementation and integration are further important subjects for
research.
The SECTOR project included these as major issues into its work
program. The overall objective was to produce torrefied biomass
pellets with properties similar to those of coal to enable its sub-
stitution without major adaptations of existing conversion in-
stallations. The project achieved continuous production ensuring
the required properties and proved the applicability of torrefied
material in major end uses.
The project included different torrefaction technologies, densi-
fication methods, logistic and storage testing, end use application in
small-, medium- and large-scale combustion and gasification units.
Furthermore assessments of the overall value chain were con-
ducted and several standards of fuel characterisation were pre-
pared. 21 partners from 9 countries contributed to this project.
More than 150 Mg of torrefied biomass have been produced from
12 different raw materials. These have been tested in about 30
different setups with respect to behaviour during logistics and end
use.
Two major framework conditions were set by analysing the
global and European biomass potential (most interesting in EU:
wood/wood residues (3.7 EJ a
1
) and straw (0.56e0.982 EJ a
1
) and
by identifying the end user needs (application specific values for
net calorific value, ash mass fraction, particle size distribution,
moisture and price) [18]. The optimization work within SECTOR is
based on these findings.
This paper will summarise the results in the different research
areas of the SECTOR project and conclude the market readiness of
torrefied solid biofuels. It will commence with the description of
the results from torrefaction and densification test performed in
the different facilities (chapter 2), followed by the results of the
logistic, storage (chapter 3) and end use application tests (chapter
4). Based on these results we provide an assessment of the fuel
quality, the environmental and economic aspects of torrefied
biomass in comparison to other solid fuels (untreated woody bio-
fuels and coal) and discuss proposals for appropriate fuel standards
and declarations, including sustainability requirements (chapter 5).
Finally, we discuss the market opportunities with regard to prom-
ising application fields (chapter 6) and conclude with suggested
market implementation strategies and the remaining research
demand (chapter 7).
2. Torrefaction and densification
The combination of biomass torrefaction and densification
potentially results in superior properties for the use of biomass in
many major end-use applications such as co-firing and co-
gasification in coal fired power plants. Torrefaction and densifica-
tion of biomass result in solid bioenergy carriers that display a high
extent of homogeneity in comparison with the corresponding un-
treated feedstock. This offers several advantages, amongst others: it
can be traded as a commodity, storage and handling does not need
to be dedicated to a specific feedstock, and milling and feeding
occurs in a steady manner. The combined optimization of torre-
faction and densification is necessary in pursuit of high-quality
solid bioenergy carriers.
During torrefaction, biomass is heated to temperatures between
250 and 350

C in an oxygen depleted environment. In this tem-
perature range hemicellulose is the most reactive component
present in lignocellulosic biomass followed by lignin, while cellu-
lose is the most thermally stable [19]. Due to the fact that the
hemicellulose strength is severely weakened during torrefaction,
the torrefied biomass becomes brittle, which eases comminution
and subsequent densification into sustainable solid bioenergy car-
riers, such as pellets and briquettes. Upon moderate torrefaction
temperatures lignin is typically only slightly affected and can serve
as binder during the densification process. Therefore, different
performance parameters need to be considered that affect both the
pretreatment process (e.g. net energy efficiency and the resulting
production costs) as well as the product quality. The most impor-
tant product characteristics are the energy density (in order to
avoid de-rating of the power plants), grindability (to use the
existing mills also used for coal), mechanical durability (to prevent
loss of mass during transport and avoid dust formation), hydro-
phobicity and biological stability (required for storage) [4,9,11,20].
Therefore, also storage and end use application of the torrefied
biomass have been tested (see chapter 3 and 4).
Within SECTOR, about 12 different biomass feedstock have been
torrefied (e.g. pine, spruce, poplar, forest residues, bamboo, straw,
Paulownia), conditioned and densified at pilot- or demonstration
scale. The composition of a large number of torrefied materials that
are described in this paper can be found in the online Phyllis2
database [21]. This has resulted in further optimization of the tor-
refaction technologies under development by: 1. broadening the
feedstock range, 2. allowing the production of solid sustainable
D. Thr€
an et al. / Biomass and Bioenergy xxx (2016) 1e172
Please cite this article in press as: D. Thr€
an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
environmental assessment along the overall torrefaction supply chain through the SECTOR project, Biomass and Bioenergy (2016), http://
dx.doi.org/10.1016/j.biombioe.2016.03.004

energy carriers with properties that meet end use requirements for
transport, handling and conversion, and 3. the exchange of best
practices between different technology developers. Lab-, pilot- and
demonstration-scale torrefaction and densification facilities were
used to demonstrate that the optimization of the product quality
demands an integrated approach between torrefaction and densi-
fication. This approach has led to the development of dedicated
recipes for different feedstock, with this optimization of the prod-
uct quality being directed through elaborate mapping of the end
use requirements for torrefied bioenergy carriers. This paper will
mainly focus on the production, logistics and end use of torrefied
wood pellets.
2.1. Torrefaction
The tests in SECTOR covered different reactor technologies,
which are either under development or commercially available for
the torrefaction of biomass. These can be roughly divided in directly
heated technologies where torrefaction off-gases are directly con-
tacted to heat up biomass to the desired torrefaction temperature,
as well as indirectly heated technologies where an intermediate
medium or a physical separation is deployed to transfer heat from
combustion gases to the biomass. An overview of developers,
technologies and associated reactor designs is provided in Table 1.
Within the SECTOR project ECN, CENER, Umeå University and
Topell Energy collaborated to further optimize their torrefaction
technologies.
Prior to the torrefaction process most of the moisture is
removed through drying. During torrefaction, part of the volatile
matter is converted to gas. For woody biomass this typically results
in weight losses up to 30%, with approximately 10% of the initial
calorific value released through off-gases that also contain volatile
condensable components [23]. In most torrefaction technologies
under development these off-gases are combusted to provide the
energy required for drying as well as pre-heating of dried biomass
to torrefaction set point temperatures. The differences in net
thermal efficiency between different torrefaction technologies
under development in the SECTOR project were small when the
same feedstock was used. This is attributable to the heat integra-
tion; low-temperature heat is used for drying and flue gas losses are
minimized [24].
The product quality of the material is typically described by the
degree of torrefaction, which is defined as the anhydrous weight
loss observed during the torrefaction process. The torrefaction
temperature and residence time determine the degree of torre-
faction [25]. An increase of temperature and/or residence time will
result in an increase of the degree of torrefaction. It should be noted
that such an increase will also lead to increased mass losses
through biomass devolatilisation during torrefaction, and as such to
higher production costs associated with the increased feedstock
demand to maintain the same production capacity. Increased de-
grees of torrefaction tend to lead to higher net calorific values,
although the increased conversion of lignin may require the use of a
binder during downstream densification. Herbaceous streams
Fig. 1. Worldwide activities of biomass torrefaction facilities with different development status (the status “unknown”describes initiatives which have been active in the last years
but whose current status could not be verified; the lacking information policy indicates difficulties in operation, their dominance shows the recession in current torrefaction
developments).
D. Thr€
an et al. / Biomass and Bioenergy xxx (2016) 1e17 3
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an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
environmental assessment along the overall torrefaction supply chain through the SECTOR project, Biomass and Bioenergy (2016), http://
dx.doi.org/10.1016/j.biombioe.2016.03.004

generally display increased reactivity compared to woody biomass,
therefore relatively lower torrefaction operating temperatures
typically are used to prevent excessive mass losses during torre-
faction. The increased reactivity of herbaceous biomass in com-
parison with woody biomass is attributed to the relatively higher
volatile matter mass fraction possibly combined with some cata-
lytic activity of the higher inorganic mass fraction.
During most of the pilot-scale torrefaction trials in the SECTOR
project, elaborate product and off-gas characterization were con-
ducted. This facilitated the preparation of mass and energy bal-
ances for different feedstocks that were subsequently used in the
economic and sustainability evaluations; the use of data obtained
during large-scale continuous trials provides results that will
closely resemble commercial plant operation. Fig. 2 provides an
example of a mass and energy balance for the ECN technology
based on measurements during pilot-scale trials with pine chips. It
should be noted that given the moderate torrefaction temperature
of 270

C, the combustion of a small additional fraction of the
feedstock is required to provide the heat for drying and heating the
biomass up to the torrefaction set point temperature. The mass
yields and ultimate product composition during torrefaction of
biomass streams in the pilot facilities are typically homogenous and
predictable, with any deviations being compliant with analysis
acceptance repeatability criteria [26]. The ash mass fraction usually
remains unaffected during torrefaction, and therefore slightly in-
creases as a result of the decreasing volatile matter mass fraction.
The mass and energy balance indicates a slight decrease of the ash
mass fraction, which is attributed to the uncertainty during sam-
pling and analysis; minor deviations like these are commonly
observed at very low ash mass fractions. The electric energy used
for milling of the torrefied chips, pelleting and cooling of the pellets
has been included in the thermal energy balance, since it is
assumed that the electric energy is fully converted to heat through
friction. Water is used as lubricant and binder during pelletization,
roughly half of it evaporates during pelletization while the other
half ends up in the torrefied pine pellets. The equilibrium moisture
of torrefied biomass pellets typically ranges between 5 and 10%.
2.2. Densification
Densification experiments have been performed at lab-, pilot-
and demonstration-scale at DTI, CENER, ECN, Umeå University and
Topell. The main parameter for the densification quality is the
mechanical durability of the processed material under specific test
conditions in accordance with the existing standard for white wood
pellets EN 15210-1:2009 [27]. The durability of torrefied pellets
varies with regard to different feedstock and degree of torrefaction.
Torrefied hardwood species such as poplar, beech and willow
were relatively easy to pelletize, while torrefied softwood species
such as spruce and pine required significant optimization of
torrefaction and pelleting parameters to obtain high quality pellets.
Herbaceous biomass proved to be the most challenging species to
pelletize, although significant improvements were established in
time for pelleting of torrefied cereal straw, as can be seen in Table 2.
Upon increasing mechanical durability the appearance of the pel-
lets transforms from dull to shiny. For both softwood and herba-
ceous biomass, the optimized parameters involved the degree of
torrefaction, the moisture of feedstock, particle size of feedstock,
diameter/length ratio of the die and its rotational speed.
In general, an increased degree of torrefaction results in more
difficulties to establish inter-particle bonds that are required to
form high-quality pellets. This is attributable to the removal of
hydrogen bonding sites, depolymerisation and the destruction of
the fibrous structure (less entanglement). The addition of water or
steam acts as a plasticizer during pelleting through reduction of the
softening temperature of lignin. Furthermore it reduces friction and
improves bonding. A smaller particle size distribution of the tor-
refied feedstock improves the pellet density, with smaller particles
occupying the available voids in the bulk. It should be noted that
smaller particle size typically requires more energy for grinding,
while too small particles sizes do not build up friction in the
channels of the die. Pellets with the highest mechanical durability
were obtained with die channel diameters of 6 mm, while the
highest production capacities were established with die channel
diameters of 8 mm. Slight reductions of the die rotational speed
will positively affect the mechanical durability. Future improve-
ments should be directed to further reduce the energy consump-
tion of the pellet mills, which is directly proportional to wear and
associated maintenance intervals.
3. Logistics of torrefied material
The transport, handling and storage properties of torrefied and
densified biomass were assessed through small-scale storage and
outdoor stockpile tests with the aim to test the behaviour of tor-
refied material in real case conditions, e.g. in a real coal handling
line. Special focus was dedicated to the hydrophobicity and
explosivity as well as the biological degradation of the material
during storage and transport. The results of these tests were used to
proactively adjust the process conditions and recipes in the torre-
faction and densification processes to further optimize the product
quality.
3.1. Small-scale storage and handling tests
Numerous small-scale indoor and outdoor storage experiments
were conducted within the project, and these mainly serve to
mimic the behaviour of torrefied material at the surface of stock-
piles. The small-scale outdoor storage experiments largely confirm
the findings described in Paragraph 3.2, although covered outdoor
Table 1
Selected existing torrefaction reactor technologies and their developers (developers involved in the SECTOR project are marked in bold) [22]. Except for the plants of Solvay
Biomass Energy and Topell Energy, the plants are pilot and demo scale for R&D activities.
Reactor technology Technology developers &suppliers Production capacity (* in planning/commissioning)
Rotary drum Torr-Coal (NL) 4500 kg h
1
BioEndev (SE) 0.15 kg h
1
and 2100 kg h
1
*
CENER (ES) 100e400 kg h
1
Turbo dryer Wyssmont (US) 6000 kg h
1
Toroidal fluidised bed reactor Topell Technology (NL) 8000 kg h
1
, currently mothballed
Screw reactor Solvay Biomass Energy (US) (former New Biomass Energy LLC) 33,300 kg h
1
Moving bed reactor ECN (NL) Andritz/ECN (DK) 50e100 kg h
1
1000 kg h
1
Thermya/Areva (FR) 2500 kg h
1
Fluidised bed reactor River Basin Energy 1000 kg h
1
* (NL) and 6000 kg h
1
(US)
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an et al. / Biomass and Bioenergy xxx (2016) 1e174
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an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
environmental assessment along the overall torrefaction supply chain through the SECTOR project, Biomass and Bioenergy (2016), http://
dx.doi.org/10.1016/j.biombioe.2016.03.004

Fig. 2. Mass and energy balance of the ECN moving bed technology for pine chips.
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an et al. / Biomass and Bioenergy xxx (2016) 1e17 5
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an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
environmental assessment along the overall torrefaction supply chain through the SECTOR project, Biomass and Bioenergy (2016), http://
dx.doi.org/10.1016/j.biombioe.2016.03.004

storage did not result in any degradation of the torrefied wood
pellets unlike the observations for white wood pellets. Fig. 3 dis-
plays the results of the dry matter losses that were obtained during
storage trials of pellet samples in the climate chamber at ECN. The
samples were stored for 20 days at a temperature of 22

C and a
relative humidity of 95%, resembling a typical humid summer
morning in the Southeast of the USA. The results imply that white
wood pellets are much more prone to biological degradation while
torrefied biomass pellets are much more resistant to biological
activity, thereby reducing the risk of self-heating.
Torrefied biomass pellets and the corresponding raw biomass
chips were pulverized using a cutter mill, and the obtained dust
samples were used to determine the Minimum Ignition Energy
(MIE) in accordance with the standard EN13821:2002. These tests
demonstrated that pulverized torrefied spruce pellets and raw
spruce chips were the most sensitive to ignite for the dust fraction
below 63
m
m, as displayed in Fig. 4. This figure also shows that the
MIE of torrefied wood pellets appears to be related to the material
that is used as feedstock, and that torrefaction does not increase the
explosivity of biomass. Consequently, existing explosion mitigation
systems could be used to mitigate any risks during milling of tor-
refied biomass pellets.
3.2. Outdoor stockpile tests
Three outdoor stockpile tests were conducted within the
SECTOR project, during these tests torrefied pellets displayed
increased water resistance compared to white wood pellets. White
wood pellets are well-known to swell and disintegrate upon the
slightest exposure to rain, to the extent that discharging of trans-
port ships will cease at the first drop of rain. During the first weeks
of the testing, the surface layer of approximately 15 cm
Table 2
Optimization of mechanical durability of torrefied pine and straw pellets at CENER in the ring-die pellet mill.
Date Durability in % Pine Date Durability in % Straw
October 2012
Torrefied at 290

C
88.8 February 2013
Torrefied at 270

C
84.2
January 2013
Torrefied at 290

C
92.3 September 2013
Torrefied at 270

C
94.3
June 2013
Torrefied at 290

C
94.7 October 2013
Torrefied at 270

C
96.6
November 2013
Torrefied at 290

C
95.7 November 2013
Torrefied at 270

C
97.6
Fig. 3. Climate chamber biological degradation tests with torrefied wood pellets, torrefaction temperature displayed in C[28].
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dx.doi.org/10.1016/j.biombioe.2016.03.004

demonstrated large increases in moisture and corresponding de-
creases in mechanical durability of the torrefied pellets. At a depth
of approximately 15 cm from the surface a layer of fines was formed
during all tests, which proved rather impenetrable both for mois-
ture seepage into the pile, as well as for sampling probes. The latter
was exemplified by stockpile tests conducted at Topell, two cubic
piles of 1 m
3
or 700 kg were stored for a period of one and two
months, and subsequently excavated and analysed by layers of
10 cm [29].
For the large quantities of material needed by power plants, the
degraded surface layer would be a small fraction of the total de-
livery. It is therefore possible to envisage a situation where degra-
dation of this portion of the fuel could be acceptable in return for
the greater logistical flexibility of being able to establish temporary
(e.g. 1 month) stocks outside and to allow discharge and movement
of biomass materials in more inclement weather conditions. The
excavation of the stockpile may however need to take place in a
different manner than with coal, i.e. the entire height of the
stockpile should be scooped up at once to prevent the formation of
a subsequent surface layer that could be affected again. It may be
possible to extend storage periods through the use of sheeting or
simple covers to prevent direct rain exposure ethese systems
would be lower in costs than the fully enclosed storage required for
white wood pellets.
The results of the outdoor storage tests conducted by EON are
summarized in Fig. 5. Two stockpiles of approximately 4 Mg each
were erected on a surface area of 2 2 m and a height of roughly
1.5 m, one with a flat surface and one with a peak surface. The
middle sample was obtained 40 cm below the surface. The figure
provides the mechanical durability of torrefied spruce pellets dur-
ing the first 70 days of outdoor uncovered storage. The mechanical
durability of torrefied spruce pellets inside the pile stays more or
less intact while the pellets on the surface display a reduced me-
chanical durability, in analogy with the other outdoor storage tests.
The sampling occurred at set intervals during a time frame of one
year, thus involving varying weather conditions. The observed
fluctuations in the mechanical durability of the pellets sampled
from the surface of the pile are the direct result of rainfall in case of
lower durability and dry periods in case of higher durability.
White wood pellets require to be shielded from the ambient
atmosphere during the entire value chain, while torrefied wood
pellets display improved storage and handling behaviour. The
outdoor stockpile tests revealed that the tested torrefied pellets
appeared to be unsuitable to be stored outdoors uncovered for long
durations, i.e. during one year. During this timeframe, the moisture
in the piles increased gradually, hence lowering the net calorific
value of the material and potentially reducing the plant efficiency.
However, storage periods of a few weeks up to a month are deemed
feasible. It should be noted that the pellets used were produced
prior to the optimization work in torrefaction and densification,
and therefore it may prove more robust and allow storage periods
to be extended.
4. Torrefied biomass applications
The various implications of introducing torrefied biomass in
existing pulverized coal-fired boilers and gasifiers were investi-
gated in close collaboration with power producers within the
SECTOR project [30]. An inventory of potential issues that could
affect the integrity of representative coal-fired boilers and gasifiers
when introducing torrefied biomass was made. The impacts on
milling and feeding, burners, combustion behaviour, process-ash/
slag behaviour, reactivity, gas composition and emissions were
investigated and are presented here.
Experimental investigations covered a range of torrefied
biomass fuels sourced from clean woody biomass, forestry residues
and agro-residues, while tests were performed in facilities ranging
from lab scale to industrial scale. The experimental work was also
supported by CFD simulation for prediction of continuous full scale
applications. This section identifies operational aspects that would
need to be adapted when handling torrefied biomass, while also
proffering the properties of torrefied biomass that would need
further improvement.
4.1. Co-milling coal and torrefied biomass pellets in a roller mill
Co-milling of bituminous coal and torrefied wood pellets was
demonstrated in a bowl (vertical roller) mill at medium load
Fig. 4. Minimum Ignition Energy (MIE) of dust samples obtained from pellets and chips (corresponding original material) through a cutter mill (fraction below 63
m
m and dried at
75 C), torrefaction temperature displayed in C[28].
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(400 kg h
1
) for torrefied biomass shares of up to 32%. The mill was
calibrated with bituminous El Cerrejon coal (from Colombia,
moisture of 11.7%) by means of fineness analogous to power plant
requirements (Fig. 7). Pelletized torrefied spruce (torrefied at
285

C, moisture of about 8%) was added stepwise while the
throughput was kept constant.
During co-milling experiments, power consumption rises (for
13.5%e58.5% mass fraction of torrefied biomass) as inhomogeneity
of feedstocks increase (Fig. 6). With the further increase in torrefied
biomass share (58.5%e100%), energy consumption decreases again
slightly (see Fig. 6) probably due to a more homogeneous feedstock
as well as a decrease in the classifier speed by about 25%.
The torrefied biomass “parent”size represents original particle
size of materials before been pressed into pellets. Part of the goals
of the test was to evaluate whether the particles within the pellets
were reduced in size in addition to the obvious disintegration of the
pellets. For 100% torrefied biomass, due to the classifier speed
reduction by 25% (in order to prevent filling up of the mill), the
pellets are disintegrated back to their original particle sizes (before
pelletization) with minimal degree of fractionation (Fig. 7). Co-
milling improves this degree of fractionation substantially in
addition to the pellet disintegration. The mill can handle white
pellets also but the conditions (i.e. classifier speed, gas flows etc.)
would have to be adapted with higher derating.
The particle size distribution of raw (parent) feed into the mill
(torrefied biomass pellets and bituminous El Cerrejon coal) is also
shown in Fig. 7.
During torrefaction, the hemi-cellulose fraction which is
responsible for the fibrous nature of biomass is degraded, thereby
improving its grindability [31e33]. The results demonstrate that
co-milling would produce a finer product size distribution rather
than dedicated milling (Fig. 7). Finally, pulverized raw wood par-
ticles are very heterogeneous and needle shaped. The shape of the
torrefied wood is closer to coal than raw wood and this favours
conveyance in conventional coal pneumatic feeding systems.
4.2. Co-firing in pulverized coal boilers
4.2.1. Emission behaviour and ash characteristics at 500 kW pilot
scale
The key combustion related issues were investigated in single-
burner pilot scale facilities (500 kW) at University of Stuttgart
(Germany) [34]. Based on experimental data generated by com-
busting SECTOR torrefied material, the following conclusions were
drawn:
The co-fired flames as well as torrefied biomass flames were
more elongated compared to coal flames which were shorter
and more intense. The coarser torrefied biomass particles would
require longer heat-up times and subsequently combustion [34].
Burn-out was however not negatively affected at the furnace
outlet.
Replacing coal with biomass or torrefied biomass leads to lower
NO
x
and SO
2
emissions. During 50% un-staged combustion of
torrefied wood and coal, a 10% reduction of NO
X
emissions was
measured compared to coal, while NO
X
emissions during tor-
refied wood un-staged combustion represents a 71% reduction
of the NO
X
levels measured for coal combustion (Fig. 8). Air
Staging will further reduce the NO
X
during 50% co-firing with
torrefied biomass by another 59% and for torrefied wood com-
bustion by another 20%. For coal, air staging is already estab-
lished as an effective measure for NO
X
reduction.
Sulphur from the coal reduces the formation of KCl from
biomass in deposits through the preferable formation of po-
tassium sulphate. This was confirmed by measured HCl in the
Fig. 5. Mechanical durability of torrefied spruce pellets torrefied at 285 C as function of time/location in peak top and flat top stockpiles during outdoor tests at EON [29].
Fig. 6. Graph shows the average grinding energy for the various settings in a bowl mil
(with vertical rollers). 0% represents pure coal, while 100% represents pure torrefied
spruce pellets torrefied at 285 C.
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flue gas in the case of co-firing, whereas KCl containing deposits
with low ash melting points were found in the case of com-
bustion of torrefied wood [34]. Similarly, coal containing
aluminosilicate ashes also reduce the formation of low melting
alkali silicates and consequently the slagging tendency [34].
4.2.2. Co-firing in pulverized coal boilers: CFD assessment of full
scale application
CFD analyses were carried out on two anonymous but repre-
sentative full scale pulverized coal-fired plants in preparation for a
larger-scale industrial test campaign with the SECTOR torrefied
material at end of 2015 in Finland. Both plants were front wall fired,
and equipped with swirl burners burning hard coal.
Combustion of torrefied material will reduce the amount of
inorganics in the overall fly-ash, simply because the torrefied fuel
(just as the original raw biomass) contains significantly less amount
of ash than coal (0.4%e5% on a dry mass basis, compared to 5%e20%
for coals) [35]. If the same particle size distribution is used for
torrefied biomass co-combustion as for coal combustion, a reduced
mass of unburned carbon ends up in the fly ash. However this does
not necessary imply that the Loss on Ignition (LOI) in the fly ash also
decreases, since the fuel also contains significantly less ash. Coarser
particles size of torrefied biomass lead to a higher amount of un-
burned carbon in the fly ash. More fuel gas is produced when
burning torrefied material causing the combustion reaction to
extend higher up in the combustion chamber as displayed in Fig. 9.
When coal is completely replaced by torrefied biomass, the flame
size can increase up to about 25%. The torrefied biomass flame will
also start more quickly and grow backwards towards the burner.
The results of co-firing tests demonstrate that this is feasible
without significant adaptations. Blending (torrefied) woody
biomass with coal lowers SO
X
emissions mainly as a result of
dilution [36].NO
X
emissions have a more complex dependency on
the nitrogen mass fraction. Other factors such as furnace and
burner configurations also impact the final NO
X
emissions. Due to
the lower nitrogen mass fractions in torrefied biomass, it is also
possible to reach lower NO
X
emissions. Recent research indicates
that through the torrefaction process, a significant amount of
chlorine (up to 90%) can be removed from the original biomass [37].
This would imply that chlorine related corrosion impacts can be
significantly reduced through the torrefaction process. There may
be impacts on power plant integrity such as superheater corrosion,
ash deposition, ESP or SCR performance, etc. It is anticipated that
Fig. 7. Cumulative mass distribution with respect to particle size determined by sieve analysis before and after co-milling in a roller mill (400 kg h
1
). Parent size of coal simply
implies raw coal sizes, while for torrefied pellets, parent size represents original particle size of material before been pressed into pellets.
Fig. 8. Impact of air staging at primary lambda
l
1 0.9 and 0.75. NOx emissions during El Cerrejon coal and torrefied spruce (co)firing in down-fired 500 kW pilot scale plant.
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an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
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dx.doi.org/10.1016/j.biombioe.2016.03.004

these effects are similar for torrefied biomass and raw biomass, as
the inorganic composition of the fuel is not negatively affected
during torrefaction.
4.3. Co-gasification in entrained flow reactors: evaluation of
feasibility
The feasibility of operating the various systems with different
torrefied materials compared to their standard reference fuels was
evaluated. The co-gasification of torrefied biomass and coal were
carried out at different facilities up to 240 MW.
Transport, handling, unloading, milling and feeding did not
result in any major issues in any of the facilities. Available infra-
structure for conventional operation was utilized. To reduce the risk
of powder explosions, a dedicated (water spray) dust suppression
system was installed in the full-scale plant. Gasification perfor-
mance and efficiencies attained for torrefied materials were
generally reported to be improved or approximately in the same
range as for the reference wood. Gasification plant efficiency, i.e.
the ratio between available energy in the cooled syngas and the
thermal energy in the corresponding fuel after taking the power
consumption of the mill into account was also improved by torre-
faction because of the reduced milling energies. Products of
incomplete gasification were found to remain in typically the same
or somewhat lower levels as for the reference fuels. For the most
severely torrefied biomass, significantly reduced methane mass
fraction in the syngas was reported [38e40].
4.4. Torrefied biomass use in small-to-medium scale pellet boilers
Torrefied wood pellets have the potential to provide at least the
same or even a higher combustion efficiency as is achievable with
wood pellets. This is based on combustion technology screening of
torrefied wood pellets in state-of-the-art pellet heating systems
such as understoker, grate and overfed boilers up to 50 kW of
thermal output [41]. The air ratio and air staging as well as the
control settings may need some adaptations and this depends on
the specific boiler technology applied. The higher fixed carbon mass
fractions in torrefied fuels however lead to increased need for
burnout time, making adaptations necessary. The level of pollutant
emissions is largely similar to that of wood pellets, given that
similar wood resources are used. This was observed for CO, VOCs,
NO
x
and PM emissions. Due to the higher expected fuel bed tem-
peratures of torrefied fuels, fine particle emissions may increase
and a higher share of slag formed. Measures to inhibit slagging are
therefore of major relevance.
4.5. Utilization of torrefaction condensates
The quality and utilization potential of condensates can be
affected by temperature ranges. Separation of compounds from the
mixture may prove difficult and possibly not so economical.
However, the total condensates formed at 280

C could be utilized
as biodegradable pesticides to replace synthetic ones. The con-
densates obtained at the higher temperature phase may have po-
tential in wood protection or as a binder in pelletization of torrefied
products. Due to the low heat transfer in the slow pyrolysis reactor,
the reactor may not be representative of all torrefaction plants [12].
At a pilot scale torrefaction plant (ECN), tens of kilograms of birch
torrefaction condensates at different torrefaction temperatures
using the slowly moving bed pilot reactor was produced, and suc-
cessfully demonstrated for partial substitution of resins used in
plywood production [42].
5. Assessment of fuel properties and environmental
economic performance
This chapter presents final results of the SECTOR-project ac-
cording to the fuel characterisation and its standardization status,
the climate implications by pellet use and trade as well as economic
considerations regarding the application of torrefied fuel in mono-
or co-firing plants. Torrefied biomass is intended to substitute fossil
fuels. Therefore in all subchapters of the assessment comparisons
to fossil fuels can be made.
Fig. 9. Simulated fuel gas mass fraction during combustion of: left: 100% hard coal, middle: 50% hard coal/50% torrefied biomass, right: 100% torrefied biomass.
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dx.doi.org/10.1016/j.biombioe.2016.03.004

5.1. Characterisation of torrefied fuels
Torrefied biomass can be an opportunity to increase flexibility of
the fuel supply and improve the conversionperformance of existing
biomass systems in medium and small scale applications. Each fuel
is characterised by specific fuel properties which will be typically
defined in a product standard. For market implementation reasons
(e.g. requirements on handling, transport and storage), consumer
acceptance (e.g. to order defined fuel qualities) as well as for con-
version plant developers (e.g. input material, the fuel particle size)
it is important to know the characterising fuel parameters.
Fuel Properties.InTable 3 selected chemical and mechanical-
ephysical product properties of torrefied wood pellets were
compared to existing solid biofuels and coal. Through the torre-
faction process, the material becomes a dry biogenic material,
which is stable, brittle and water resistant. The lower moisture of
torrefied material by contrast with conventional wood chips/pellets
results from the release of a higher amount of volatile matters
(decomposition of hemicellulose, cellulose and lignin). Therefore,
the torrefied material is also characterised by a higher energy
density as well as a reduced biological degradation in storage and
thus favourable for long distance transport. Furthermore, this re-
sults in cost advantages for transport and storage of the torrefied
material compacted in form of pellets or briquettes (see chapter 3).
However, depending on the biomass raw material and the tor-
refaction process conditions (see chapter 2) the favourable mini-
mised biological activity and water resistant features vary slightly
and can differ in stability over time. Therefore, an additional fuel
parameter was described in SECTOR to define the water resistance
or hydrophobicity of a torrefied material in form of the term “water
absorption”[33,43].
The homogenous quality of torrefied fuel and the similarity of
selected fuel parameters of torrefied wood with coal (e. g. moisture
, energy density) offer optimal conditions for the use in co-firing
coal-power plants in order to substitute fossil fuels (Table 3). To
describe the adopted fibrous biomass structure of the torrefied
material, which eases the processing in existing mills of coal power
plants, a new fuel characterisation parameter has been defined as
“grindability”in SECTOR [12].
However, more analysis work and end use application tests have
to be done with torrefied material of non-woody biomass to set
limits for its application in different end use pathways and to favour
its market entrance as well.
Product Standardization. On the initiative of SECTOR project
partners, the International Organisation for Standardization (ISO)
Technical Committee 238 (ISO/TC 238) has started to draft an in-
ternational product standard for torrefied pellets and briquettes
made from woody and non-woody (herbaceous, fruit and aquatic)
biomass in February 2013 [35,36]. The standard development is
focused on “Graded thermally treated and densified biomass fuels”
for industrial and non-industrial use and will be published as ISO
17225-8 as well as in Europe as EN ISO 17225-8. Thermal treatment
includes processes such as torrefaction, steam treatment (explosion
pulping), hydrothermal carbonization and charring, which all
represent different exposure to heat, oxygen, steam and water.
After the discussion and adaption of first standard drafts within the
committee and by involving the International Biomass Torrefaction
Council (IBTC) its publication is foreseen by the end of the year
2016.
The highest quality classes (TW1a and TW2b) for thermally
treated woody pellets and briquettes are recommended for non-
industrial use (residential and other small-scale applications).
Also other TW classes for woody biomass TW2a, TW3a and TW3b
were drafted. Additional classes (TA1, TA2 and TA3) were developed
for non-woody biomass. These classes are suitable only for indus-
trial use or small-scale boilers specially designed for non-woody
biomass. In the coming draft international standard (DIS) woody
biomass classes are divided into two tables based on net calorific
value on dry basis. The threshold value in the current version is
21 MJ kg
1
on dry basis. If the net calorific value on dry basis is
higher than 21 MJ kg
1
, it is proposed to mark classes by TW1a,
TW2a and TW3a and if it is lower, then they are marked by TW1b,
TW2b and TW3b. Moisture (M, % of mass) and fines (F, particles less
than 3.15 mm) should be stated at the point of delivery. Table 4 lists
the normative (mandatory) properties for thermally treated
densified biomass fuels. In all classification tables, ash melting
behaviour is informative (voluntary) and it is recommended to
state all characteristic temperatures shrinkage starting tempera-
ture (SST), deformation temperature (DT), hemisphere temperature
(HT) and flow temperature (FT) in oxidising conditions.
Within the SECTOR project, two international Round-Robin-
Tests (interlaboratory tests performed independently several
times) were conducted to prove the application of existing chem-
ical and physical test methods for torrefied material. The existing
Table 3
Comparison of selected properties of torrefied material with wood chips, pellets and coal [34,44], adapted according to ISO 06/2015 (moisture/heating value/bulk density); the
related parameter definition is also given in Table 4.
Wood chips Wood pellets Torrefied wood pellets Coal
Moisture (%) 30e55 7e10 1e10 10e15
Net calorific value (Q, MJ kg
1
) as received 7e12 15e17 17e24 23e28
Volatile matter (VM) (%, mass, dry basis) 70e84 75e84 55e80 15e30
Fixed carbon (C
f
) (%, mass, dry basis) 16e25 16e25 22e35 50e55
Bulk density (BD) (t m

3
) 0.20e0.30 0.55e0.65 0.55e0.80 0.80e0.85
Energy density (E) (GJ m

3
) 1.4e3.6 8e11 12e19 18e24
Hygroscopic properties Hydrophilic hydrophilic moderately hydrophobic hydrophobic
Biological degradation Fast fast Slow none
Milling requirements Special special standard (feedstock-specific) standard
Product consistency Limited high high high
©Kay Schaubach/DBFZ ©Thomas Siepmann/pixelio.de ©Kay Schaubach/DBFZ ©Gabi Sch€
onemann/pixelio.de
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test methods were originally developed for the characterisation of
solid biomass. These Round Robin tests demonstrated that
numerous established methods could be adopted for the determi-
nation of specific property parameters (e. g. determination of
heating value, major and minor elements). Additionally, new fuel
property parameters were analysed and the development of new
test methods started within SECTOR (e. g. for grindability, hydro-
phobicity/water absorption) [35,36]. The project also collected
property data for fuel specification standard development.
5.2. GHG-emissions of torrefied pellets supply and application
Solid biofuels are often considered as energy carriers with
potentially low life-cycle greenhouse-gas (GHG) emissions. Hence,
anticipated GHG-mitigation effects from the use of these energy
carriers are the strongest rationale for their promotion. Considering
the limited resource base, torrefaction is discussed as a promising
approach to decrease the costs of logistics while increasing local
biomass availability due to long distance transports.
The GHG-mitigation effects from the use of various (torrefied)
biomass value chains have been investigated comprehensively
within the SECTOR project [7]. This assessment has been conducted
considering the actual data and project results on the mass and
energy flows for the torrefaction technology, which have been
compiled during the project. This allows for a detailed assessment
based on primary data which would not be possible with infor-
mation from available publications. Based on these mass and en-
ergy balances, GHG-emissions have been calculated using the LCA
methodology according to ISO 14040:2006 and ISO14044:2006
standards.
Fig. 10 shows the GHG-emissions per MJ of supplied pellets for
three feedstocks straw, logging residues and willow (short rotation
coppice) and four locations (Spain, USA, Tanzania, Canada). As ex-
pected the results showed that, due to the higher energy density,
the transportation of the torrefied pellets leads to lower energy
specific GHG-emissions compared to the transportation of con-
ventional pellets (e.g. CO
2
-Eq. of 11.5 g MJ
1
Canadian straw white
pellet distribution compared to a CO
2
-Eq. of 9g MJ
1
for torrefied
Canadian straw pellets).
Other major impact factors that have been identified during the
assessment are the type of energy carrier (e.g. biomass or natural
gas) used during the processes of torrefaction/densification as well
as the emission factor of the local electricity supply. Together with
the different distribution scenarios this explains the main differ-
ences between the results of the various locations. In general, the
production and use of pellets from residues resulted in lower
emissions compared to the use of plantation wood.
To counterbalance the GHG-emissions from the supply of (tor-
refied) pellets from different origins, the avoided GHG-emissions
from the replacement of fossil fuels have been investigated for
various end use markets [46]. The results are summarized in
Table 5.
The results show a GHG-mitigation potential of the pathways
investigated for co-firing between 72% and 87%. Due to the slightly
lower upstream emissions, the results for the application of torre-
fied pellets show slightly lower overall GHG emissions compared to
the heat production based on conventional pellets.
Another possible application where torrefied biomass could find
a direct outlet is for small scale natural gas fired boilers. The results
in Table 5 indicate that this yields a GHG mitigation potential be-
tween 58% and 79%. This is lower than the use of the pellets in co-
firing applications due to the lower CO
2
emission factor of natural
gas. In case a carbon intensive fuel is replaced (e.g. coal briquettes),
the figures favour small scale heat over biomass co-firing.
5.3. Economic aspects
The economic aspects of producing and using biomass torre-
faction pellets have been evaluated against those of wood pellets
[6,24] (see: Table 6). The energy and mass balances based supply
chain costs calculations from Ref. [24] were implemented in the
BioChainS tool (Biomass-to-end-use Chain Simulation tool) to
simulate a higher variety of supply chains. The tool enables the
comparison of supply chains varying multiple factors.
For the production of torrefied pellets, a base case was assumed
of a medium scale stand-alone torrefaction plant in Europe of
Table 4
Selected normative properties to be specified for ISO 17225-8 draft international standard [5,45]. Note: this is a proposal of working group 2 of ISO/TC 238 for DIS version, and
values can be changed in the final draft international standard (FDIS), which will be discussed in April 2016. The standard foresees the use of weight percentage (w-%) as unit
which is not used in this paper.
Property, standard for
analysis
Unit Remarks
Raw material, ISO 17225-
1:2014
To be stated from ISO 17225-1:2014/Table 1, Woody biomass. ISO 17225-8 list approved raw materials more detailed
for each classes
Diameter, D and Length L
,
ISO 17829
mm Diameter classes for TW1a
a
, TW1b and TW2a, TW2b, TW3a and TW3b from 6 to 25 mm for pellets.
Less length classes for TW 1a. TW1b and TW2a, TW2b, maximum length 40 mm for TW1 classes, and maximum length
for TW2 and TW3 classes is 50 mm depending on the diameter of pellet.
For briquettes actual diameter and length or width is stated depending on shape of briquettes.
Moisture, M
c
, ISO 18134-1,
ISO 18134-2
%
b
Moisture on wet basis is 8% or 10% depending on traded form (pellet or briquette) and raw material and class
Ash, A
c
, ISO 18122 % (dry mass) From A1.2 to A10 depending on classes and raw material. Lowest class for TW1a and TW1b.
Mechanical durability, DU
c
,
ISO 17831-1
% (mass as received) From DU95.5 to DU95.0 depending on classes. Highest class for TW1a and TW1b.
Fines, F
c
, ISO 18846
(<3.15 mm)
% (mass as received) From F1 (1%) to F6 (6%) depending on classes and raw material. Lowest class for TW1a and TW1b.
Additives % (dry mass) Maximum 4% for TW1a and TW1b classes. Type and amount to be stated
Net calorific value, Q
c
, ISO
18125
MJ kg
1
or kWh kg
1
as received
From Q16.0 to Q21.0 depending on classes, technology and raw material
Bulk density, BD
c
, ISO
17828
kg m
3
From BD550 to BD700 depending on classes, technology and raw material. Lowest class for pellets, which are
thermally treated after pelleting.
a
TW is symbol for the quality classes of thermally treated woody biomass.
b
in ISO 17225 standards, unit w-% for weight percentage is used
c
Symbols D, L, M, A, DU, F, Q and BD are designations of properties stated in ISO 17225-1:2014 and ISO 17225-8 (under preparation) standards. After symbol the threshold
value is marked, e.g. M10 (moisture 10%).
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72,800 Mg a
1
, with production costs of 43 VMWh
1
. A significant
fraction are fuel costs at 18e25 VMWh
1
. A larger production plant
located in North America (500,000 Mg a
1
) and fed with cheaper
biomass feedstock (15 VMWh
1
) lowers the production costs to 29
VMWh
1
. All cases presented below are based on 800 0 annual
operating hours and a capital charge factor of 0.1175 (10% interest
during 20 years).
The simulation of the supply chains illustrated decisive factors
for production costs: (1) the combination of feedstock yield,
availability and accessibility and (2) the production plant size.
Fig. 10. GHG-emissions from the supply of torrefied pellets from different feedstock types and locations compared to white pellets [46].
Table 5
GHG-emissions reduction compared to conventional fuel, and from the use of conventional and torrefied pellets from different supply chains per MJ of product (derived from
Ref. [46]).
Application
a
Conventional pellets Torrefied biomass
Co-firing with hard coal CO
2
-Eq. of 0.06e0.08 kg MJ
1
(electric output) 72e80% reduction CO
2
-Eq. of 0.03e0.06 kg MJ
1
(electric output) 80e87% reduction
Replacing natural gas in 15 kW
boiler
CO
2
-Eq. of 0.22e0.31 kg MJ
1
(thermal output) 58e70% reduction CO
2
-Eq. of 0.15e0.21 kg MJ
1
(thermal output) 71e79% reduction
Production and combustion of
methanol
CO
2
-Eq. of 1.25e2.01 kg MJ
1
(electric output) 5e42% reduction CO
2
-Eq. of 0.95e1.55 kg MJ
1
(electric output) 28e55% reduction
a
The reference levels for the three applications are: 1: hard coal: CO
2
-Eq. of 0.3 kg MJ
1
(electric output); nat. gas: CO
2
-Eq. of 0.07 kg MJ
1
(thermal output); MeOH: CO
2
-Eq.
of 2.15 kg MJ
1
.
Table 6
Production costs of torrefied wood pellets for stand-alone plants and integrated in new/existing plants [24].
Case Stand-alone torr. plant
nordic region
Stand-alone torr. plant
nordic region
Stand-alone torr.
plant SE USA
New sawmill and torr.
plant integrated
Existing sawmill and
new torr. plant
Existing pulp mill and
new torr. plant
Output capacity in t a
1
72,800 500,000 500,000 231,600 101,100 407,200
Fixed operating costs in
MVa
1
3.99 8.70 8.70 5.39 3.47 6.71
Variable operating costs in
MVa
1
9.87 74.56 57.66 31.73 14.00 58.5
Annualized capital costs in
MVa
1
5.44 20.95 21.23 11.68 6.84 17.34
Total costs in MVa
1
19.30 104.2 87.58 48.80 24.31 82.54
Production costs in Va
1
265 208 175 211 240 203
Production costs in V
MWh
1
43 34 29 34 38 33
Market price of wood
pellets in VMWh
1
30 30 30 30 30 30
Price compared to base
case in %
100 79 66 79 91 76
Price compared to market
price in %
145 114 96 115 126 111
D. Thr€
an et al. / Biomass and Bioenergy xxx (2016) 1e17 13
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an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
environmental assessment along the overall torrefaction supply chain through the SECTOR project, Biomass and Bioenergy (2016), http://
dx.doi.org/10.1016/j.biombioe.2016.03.004

Higher heating values resp. energy density lower the costs after
production through reduced mass/volume in transport, thus
increasing competitiveness to white pellets.
Integration into an existing CHP plant does not reduce the costs
substantially, but integration in other operations (sawmills, pulp
and paper mills) however does (5e24% compared to base case
[24]). This is mostly due to the larger possible production capacities
and lower feedstock costs (e.g. excess forest residue).
The purchase power for torrefied wood pellets over white wood
pellets was determined in this context. All additional costs for
biomass co-firing excluding fuel costs were calculated for both 10%
and 30% co-firing on energy basis. This was done for a 400 MW
(electric output) power plant in the Netherlands with 6,000 annual
operating hours. A loan interest level of 6% was assumed (65% of the
capital), a company tax level of 25% and a demanded return on
equity of 12% (35% of the capital). This results in a project interest
rate of 6.9%; at an economic lifetime of 10 years this results in an
annuity of 14%. The results are displayed in Fig. 11.
The total annual costs excluding fuels are higher for white wood
pellets than for torrefied wood pellets, particularly at an increased
co-firing share of 30%. This fact can be translated to a maximum
excess price that could be paid for torrefied wood pellets to achieve
equal annual electricity production costs. The results in Table 7
imply that at a co-firing share of 30%, the large-scale stand-alone
plants and some of the integrated concepts could produce pellets at
price levels that would be economically competitive to use for
utilities instead of white wood pellets. The significantly lower in-
vestment costs also offer flexibility when incentives for co-firing
are subject to fluctuation [48].
6. Market opportunities
As described in the preceding chapters, the torrefaction tech-
nology has improved significantly during the last years and is now
commercially available for woody biomass. Non-woody biomass
torrefaction has been investigated and improved as well but still
needs further development for market readiness. Research
activities now aim mostly at optimizing, e.g. technology, the overall
value chain, standardization, trade registration and legal permis-
sions [50,51].
This development is embedded in a growing bioenergy carrier
market worldwide [1,9]. The European Union considers bioenergy
as an integral part of the low carbon economy [52] and has set
ambitious goals for the share of renewable fuels in the primary
energy consumption (20% for 2020 and 27% for 2030) [10], which
should support the further development and implementation of
torrefaction technology [2].
The primary market for torrefied material has been seen by
many producers in co-firing as one third of power supply is ex-
pected to be from large power producers [2,24]. In Europe (EU 28)
alone, 285 Tg of hard coal and 421 Tg of lignite were consumed in
2014 [26,53]. An average co-firing share would result in a European
market of ca. 70 Tg per year. Nevertheless, market conditions (e.g.
CO
2
, needed amounts) and chosen lock-in solutions from potential
co-firing customers (e.g. that have already invested to accommo-
date white pellet) require a careful policy approach to support
market introduction but also the commitment of producers and
other stakeholders. Important factors here are the CO
2
emissions
and possible savings, as well as the economic aspects for different
end-user markets.
Regarding the development and implementation one can
distinguish three focus areas for business development (Fig. 12). A
main driver for business development comes from the end user
markets, as end users can create a market pull for the technology.
The end user markets are categorised in “torrfuel production”
(torrfuel: torrefied fuel), which includes the sales to intermediaries
and users. As described above, small and medium scale appliances
are now considered alongside co-firing. A strategic consideration is
the geographical location of producers and end users. Production
and end-use in Europe can strengthen the internal energy security
and present business opportunities for biomass surplus regions.
The beneficial long distance transport properties of torrefied fuels
allow the import into Europe from biomass surplus regions
worldwide, potentially reducing CO
2
emissions and increasing
Fig. 11. Annual cost of co-firing white wood pellets and torrefied wood pellets at 10% and 30% co-firing share excluding fuel costs [47,26].
D. Thr€
an et al. / Biomass and Bioenergy xxx (2016) 1e1714
Please cite this article in press as: D. Thr€
an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
environmental assessment along the overall torrefaction supply chain through the SECTOR project, Biomass and Bioenergy (2016), http://
dx.doi.org/10.1016/j.biombioe.2016.03.004

energy security by diversifying the energy carrier base. As soon as
torrefaction of technically more demanding feedstock is available,
torrefaction can aid with the energetic and material use of these. A
third option within torrefied fuel production is the provision and
use of torrefied fuels outside of Europe. This does not improve the
energy sector in Europe directly but presents the opportunity for
technology providers to establish or extend their business, thus
stabilising their operation which in turn is beneficial for the tor-
refaction sector within Europe.
Directly connected to this scheme is the business area “torre-
faction technology”, where technology providers sublicense or sell
technology. Thus, the technology provider is not necessarily the
operator of a torrefaction plant but different stakeholders fulfil
these different market roles.
Diversifying the end user markets (appliance and location) and
utilizing technology as an additional product can be complemented
by a third business area: “production of chemicals or biomaterials”,
which is a possibility of utilising by-products to improve the overall
torrefaction process efficiency [54]. The latest research has shown
the potential of torrefaction gas condensate to be processed into
different materials not connected to energy provision, such as
biodegradable pesticides and phenols for wood protection sub-
stances (see chapter 4.5). These options are far from market ready
but might add to profitable business in the future for torrefaction
plant operators and also support the establishment of more sus-
tainable economies.
7. Conclusions
The SECTOR project focused on the further development and
optimization of torrefaction-based technologies for the production
of solid bioenergy carriers up to pilot-plant scale and beyond,
including the whole process chain from torrefaction to end use
application. Additional assessments of different sustainability di-
mensions, technical standardization needs and market introduc-
tion strategies identified the current chances and obstacles of this
new technology comprehensively. The generated data can also
support future research on torrefaction of biomass. The now ach-
ieved quality parameters of the torrefied material have been further
specified and are in preparation for standardization.
While different torrefaction and densification technologies were
applied to different biomass feedstock successfully, the further
optimization of the processes and concepts can only be effectuated
for specific concepts. The challenge is to proceed from demon-
stration to industrial scale. Market implementation strategies can
act as a navigator for the next steps for the implementation of in-
dustrial plants. Different end user markets can open opportunities
here:
(1) Co-firing in EU countries: For co-firing price parity with coal
is essential to enable commercial market introduction of
torrefied biomass. The relatively low CO
2
price is however a
major hurdle for the business case. Although the EU tries to
increase the market price of CO
2
by ‘backloading’EU emis-
sion allowances for CO
2
, the actual effect is still limited for
the time being. It is essential that EU member countries
continue their efforts on establishing substantial CO
2
market
prices. In the absence of price parity with coal, it is important
that countries launch additional co-firing support schemes
to enable co-firing or 100% conversion, which could lead to
Table 7
Purchase power of torrefied wood pellets vs. white wood pellets at equal annual costs [49].
unit 10% co-firing 30% co-firing
Excess costs of white wood pellets over torrefied wood pellets MVy
1
1.86 10.31
Amount of biomass of pellets used PJ 2.16 6.48
Price difference VGJ
1
(VMWh
1
) 0.86 (3.10) 1.59 (5.72)
Case 1: price difference at higher rate of return (12% /15%) VGJ
1
(VMWh
1
) 1.08 (3.89) 2.02 (7.27)
Case 2: price difference at reduction of economic lifetime from 10 to 5 years VGJ
1
(VMWh
1
) 1.24 (4.46) 2.34 (8.42)
Fig. 12. Torrefaction business areas.
D. Thr€
an et al. / Biomass and Bioenergy xxx (2016) 1e17 15
Please cite this article in press as: D. Thr€
an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
environmental assessment along the overall torrefaction supply chain through the SECTOR project, Biomass and Bioenergy (2016), http://
dx.doi.org/10.1016/j.biombioe.2016.03.004

significant growth in the next couple of years. Recent ex-
amples of such countries are UK, Netherlands, and Belgium.
(2) Co-firing outside Europe: In case coal based power producers
have already made investments to enable large scale use of
white wood pellets, it could be too late to make use of the
potential cost savings of torrefied pellets. For countries and
regions where interest in biomass co-firing has only recently
started (e.g. in Asia, South Africa), torrefied biomass could
provide an option to leapfrog technology without the need to
invest in significant modifications of existing plants. The
same is true for power plants in Europe that consider co-
firing, but have not yet invested.
(3) Additional market for security of financing: Securing the
financing for investment is another hurdle. Compared to the
fuel requirements of a pulverised coal fired power plant, the
volume of torrefied fuels that can be offered from any of the
existing torrefaction companies to a single power plant is
relatively small, which makes end users hesitant to absorb
torrefied fuels and sign long term offtake contracts. This
makes it again difficult for an investor to obtain finances to
establish a torrefaction plant. Governments could help in
securing financing of such plants by arranging non-recourse
financing. A local heat market or a relatively small market for
use in higher value applications (e.g. chemicals or trans-
portation fuels after gasification) could help in this way to get
rid of the chicken and egg problem. In this case both the
torrefaction facility and the end user need to be established
at the same time, to enable an optimal business case.
Parallel to end-user market development, the further develop-
ment of the resource base needs specific attention. Due to the fact
that almost half of the costs for torrefaction processes come from
feedstock, it is important to research possibilities for reduction of
the raw material costs by developing sustainable and cost-efficient
supply chains for biomass. Appropriate product standards and the
consideration of sustainability standards are essential to facilitate
trade as well as the production of suitable end use appliances that
are optimized for torrefied biomass.
So, for successful market implementation not only technical
improvements but also various conducive policies are required to
support the application of torrefied biomass for power supply, the
heat sector and in industries, keeping in mind the differentiation in
qualities and prices required.
Acknowledgement
The authors would like to thank the EU for the financial support
from the Seventh Programme for research, technological develop-
ment and demonstration under grant agreement no 282826 and
Virginie Bellmann (DBFZ) for her support in organising and
reviewing the paper.
References
[1] M. Cremers, J. Koppejan, J. Middelkamp, J. Witkamp, S. Sokhansanj, S. Melin, et
al., Status overview of torrefaction technologies. A review of the commerci-
alisation status of biomass torrefaction, in: IEA Bioenergy, 2015.
[2] M. Deutmeyer, D. Bradley, B. Hektor, J.R. Hess, L. Nikolaisen, J. Tumuluru, et al.,
Possible effect of torrefaction on biomass trade, in: IEA Bioenergy, 2012.
[3] M. Rudolfsson, W. Stelte, T.A. Lestander, Process optimization of combined
biomass torrefaction and pelletization for fuel pellet production eA para-
metric study, Appl. Energy 140 (2015) 378e384, http://dx.doi.org/10.1016/
j.apenergy.2014.11.041.
[4] A. Janssen, M. Carbo, D. Schneider, A. Pollex, W. Stelte, J. Gil, et al., Report on
Requirements of End Users on Densified and Torrefied Materials, SECTOR
Deliverable D4.1, 2013.
[5] E. Alakangas, Graded Thermally and Densified Biomass Fuels: Development of
the ISO 17225e8 Standard, SECTOR Deliverable D8.3, 2015.
[6] F. Schipfer, K. Bienert, L. Kranzl, S. Majer, E. Nebel, Deployment Scenarios and
Socio-economic Assessment of Torrefied Biomass Chains Part 2, SECTOR
Deliverable D9.5, 2015.
[7] S. Majer, M. Gawor, E. Nebel, LCA of Torrefied Biomass Chains in Comparison
to Reference Pathways, SECTOR Deliverable D9.6, 2015.
[8] J. Koppejan, K. Schaubach, J. Witt, D. Thr€
an, Torrefaction Technology and
Strategy Report, SECTOR Deliverable D10.2, 2015.
[9] M. Junginger, C.S. Goh, A. Faaij (Eds.), International Bioenergy Trade, vol. 17,
Springer, Dordrecht, 2014. Netherlands.
[10] European Commission, 2030 Energy Strategy, Energy (2015). https://ec.
europa.eu/energy/en/topics/energy-strategy/2030-energy-strategy [accessed
30.07.15].
[11] M.J. Prins, K.J. Ptasinski, F.J.J.G. Janssen, Torrefaction of wood, Part 2. Analysis
of products, J. Anal. Appl. Pyrolysis 77 (2006) 35e40, http://dx.doi.org/
10.1016/j.jaap.2006.01.001.
[12] L. Fagern€
as, E. Kuoppala, V. Arpiainen, Composition, Utilization and Economic
Assessment of Torrefaction Condensates, Energy Fuels 29 (5) (2015)
3134e3142, http://dx.doi.org/10.1021/acs.energyfuels.5b00004.
[13] M.J.C. van der Stelt, H. Gerhauser, J.H.A. Kiel, K.J. Ptasinski, Biomass upgrading
by torrefaction for the production of biofuels: A review, Biomass Bioenergy 35
(9) (2011) 3748e3762, http://dx.doi.org/10.1016/j.biombioe.2011.06.023.
[14] J. Tumuluru, S. Sokhansanj, J.R. Hess, C.T. Wright, R.D. Boardman, A Review on
Biomass Torrefaction Process and Product Properties for Energy Applications,
Ind. Biotechnol. 7 (5) (2011) 384e491, http://dx.doi.org/10.1089/
ind.2011.7.384.
[15] J. Koppejan, S. Sokhansanj, S. Melin, S. Madrali, Status overview of torrefaction
technologies. Final Report, in: Enschede: IEA Bioenergy, 2012.
[16] D. Thr€
an, T. Seidenberger, J. Zeddies, R. Offermann, Global biomass potentials
dResources, drivers and scenario results, Energy Sustain Dev. 14 (3) (2010)
200e205, http://dx.doi.org/10.1016/j.esd.2010.07.004.
[17] C. Weiser, V. Zeller, F. Reinicke, B. Wagner, S. Majer, A. Vetter, et al., Integrated
assessment of sustainable cereal straw potential and different straw-based
energy applications in Germany, Appl. Energy 114 (2014) 749e762, http://
dx.doi.org/10.1016/j.apenergy.2013.07.016.
[18] E. Alakangas, M. Flyktman, Quality Demands from Producers and End Users,
SECTOR Deliverable D2.4, 2013.
[19] K. Werner, L. Pommer, M. Brostr€
om, Thermal decomposition of hemi-
celluloses, J. Anal. Appl. Pyrolysis 110 (2014) 130e137, http://dx.doi.org/
10.1016/j.jaap.2014.08.013.
[20] C. Medic, M. Darr, A. Shah, B. Potter, J. Zimmermann, Effects of torrefaction
process parameters on biomass feedstock upgrading, Fuel 91 (1) (2012)
147e154, http://dx.doi.org/10.1016/j.fuel.2011.07.019.
[21] ECN Phyllis2 Database for biomass waste 2016. ECN Phyllis2 n.d. https://
www.ecn.nl/phyllis2/[accessed on 20.01.16].
[22] DBFZ. DBFZ torrefaction plant database 2015. [accessed on 15.09.15].
[23] P.C.A. Bergman, A.R. Boersma, R.W.R. Zwart, J.H.A. Kiel, Torrefaction for
Biomass Co-firing in Existing Coal-fired Power Stations “BIOCOAL.”, Petten,
The Netherlands, 2005, pp. 05e013.
[24] C. Wilen, V. Arpiainen, Report on Optimisation Opportunities by Integrating
Torrefaction into Existing Industries, SECTOR Deliverable D3.2, 2014.
[25] C. G€
obl, U. Wolfesberger-Schwabl, Report on Test Methods and Properties of
Torrefied Biomass, SECTOR Deliverable D8.5, 2015.
[26] J. Witt, K. Schaubach, M. Ristola, V. Bellmann, D. Thr€
an, Final Report Based on
Conference Proceedings of Final Project Conference, SECTOR Deliverable D1.3,
2015.
[27] BS EN 15210-1: 2009 British Standards Institution, Solid Biofuels. Determi-
nation of Mechanical Durability of Pellets and Briquettes, British Standards
Institution, London, 2009.
[28] M. Carbo, P. Abelha, M.K. Cieplik, C. Mour~
ao, Fuel (Pre-)processing, Pre-
treatment and Storage for Co-firing Biomass and Coal, Fuel Flex. Energy
Gener., Woodhead Publishing, Sawston, United Kingdom, 2015.
[29] S. Weatherstone, N. Simonsson, G. Karlsson, N. Padban, A. Adell i Arnuelos,
P. Abelha, et al., Final Report on Bulk Tests in Existing Storage and Handling
Facilities, SECTOR Deliverable D6.7, 2015.
[30] EU FP7 Innovation Project, SECTOR n.d. http://www.sector-project.eu
[accessed on 15.07.15].
[31] M. Phanphanich, S. Mani, Impact of torrefaction on the grindability and fuel
characteristics of forest biomass, Bioresour. Technol. 102 (2) (2011)
1246e1253, http://dx.doi.org/10.1016/j.biortech.2010.08.028.
[32] T.G. Bridgeman, J.M. Jones, A. Williams, D.J. Waldron, An investigation of the
grindability of two torrefied energy crops, Fuel 89 (12) (2010) 3911e3918,
http://dx.doi.org/10.1016/j.fuel.2010.06.043.
[33] V. Repellin, A. Govina, M. Rolland, R. Guyonet, Energy requirement for fine
grinding of torrefied wood, Biomass Bioenergy 34 (7) (2010) 923e930, http://
dx.doi.org/10.1016/j.biombioe.2010.01.039.
[34] C. Ndibe, S. Grathwohl, M. Paneru, J. Maier, G. Scheffknecht, Emissions
reduction and deposits characteristics during cofiring of high shares of tor-
refied biomass in a 500kW pulverized coal furnace, Fuel 156 (2015) 177e189,
http://dx.doi.org/10.1016/j.fuel.2015.04.017.
[35] C. Ndibe, J. Maier, G. Scheffknecht, Combustion, cofiring and emissions char-
acteristics of torrefied biomass in a drop tube reactor, Biomass Bioenergy 79
(2015) 105e115, http://dx.doi.org/10.1016/j.biombioe.2015.05.010.
[36] H. Spliethoff, K.R. Hein, Effect of co-combustion of biomass on emissions in
pulverized fuel furnaces, Fuel Process Technol. 54 (1e3) (1998) 189e205,
http://dx.doi.org/10.1016/S0378-3820(97)00069-6.
D. Thr€
an et al. / Biomass and Bioenergy xxx (2016) 1e1716
Please cite this article in press as: D. Thr€
an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
environmental assessment along the overall torrefaction supply chain through the SECTOR project, Biomass and Bioenergy (2016), http://
dx.doi.org/10.1016/j.biombioe.2016.03.004

[37] T. Keipi, H. Tolvanen, L. Kokko, R. Raiko, The effect of torrefaction on the
chlorine content and heating value of eight woody biomass samples, Biomass
Bioenergy 66 (2014) 232e239, http://dx.doi.org/10.1016/
j.biombioe.2014.02.015.
[38] F. Weiland, M. Nordwaeger, I. Olofsson, H. Wiinikka, Entrained flow gasifi-
cation of torrefied wood residues, Fuel Process Technol. 125 (2014) 51e58,
http://dx.doi.org/10.1016/j.fuproc.2014.03.026.
[39] M. Risberg, O.G.
€
Ohrman, B.R. Gebart, P.T. Nilsson, A. Gudmundsson, M. Sanati,
Influence from fuel type on the performance of an air-blown cyclone gasifier,
Fuel 116 (2014) 751e759, http://dx.doi.org/10.1016/j.fuel.2013.08.008.
[40] N. Padban, First Experiences from Large Scale Co- Gasification Tests with
Refined Biomass Fuels, Intern. Torrefaction Workshop CEBC, Graz, 2014.
[41] F. Biedermann, T. Brunner, C. Mandl, I. Obernberger, W. Kanzian, S. Feldmeier,
et al., Executive Summary, SECTOR Deliverable D7.3 and D7.4, 2014.
[42] DBFZ. SECTOR, Publishable Summary, Reporting Period 2. Leipzig, 2014.
Available at: http://cordis.europa.eu/result/rcn/149543_de.html [accessed on
15.07.15].
[43] C. G€
obl, K. J€
org, U. Wolfesberger-Schwabl, Round Robin Report II eValidation
of New Test Methods, SECTOR Deliverable D8.4, 2015.
[44] J. Kiel, Torrefaction eProcess and Product Quality Optimisation, in: Intern.
Conference eBiomass to Bioenergy, 2013 (Munich).
[45] ISO/CD 17225-8 Solid biofuels dFuel specifications and classes dPart 8:
Graded thermally treated and densified biomass fuels (ISO/TC 238/WG 2
N20005) 2015.
[46] S. Majer, E. Nebel, M. Gawor, F. Schipfer, L. Kranzl, M. Meyer, J. Priess,
T. Chand, Executive Summary of WP9 Results, SECTOR Deliverable D9.8, 2015.
[47] V. Arpiainen, E. Alakangas, P. Kroon, M. Carbo, Report on Optimisation Po-
tential towards the Quality of the Solid Energy Carriers, 2015.
[48] M. Carbo, S. Majer, F. Schipfer, SECTOR Specials: Value Chains, Economics and
Sustainability; BioBoost and SECTOR Policy Workshop, 2015. Available at:
https://sector-project.eu/fileadmin/downloads/workshop/2-5_SECTOR_
Specials_Michiel_Stefan_FINAL.pdf [accessed 15.01.16].
[49] M. Carbo, P.M.R. Abelha, M.K. Cieplik, P. Kroon, C. Mour~
ao, J.H.A. Kiel, Handling
and storage of torrefied biomass pellets, World Biomass Power Mark. (2015)
(Amsterdam).
[50] M. Wild, Torrefied Biomass: the Perfect CO
2
Neutral Coal Substitute Is
Maturing, VGB PowerTech, 2015, pp. 72e75.
[51] D. Thraen, Exemplary Results of the SECTOR-project, ISO Meeting, York, 2015.
[52] P. Verhoef, Bioenergy in the European Context, BioBoost and SECTOR Policy
Workshop, Brussels, 2015. Available at: https://sector-project.eu/fileadmin/
downloads/workshop/Bioenergy_in_EUropean_context_final.pdf [accessed
15.01.16].
[53] Coal consumption statistics - Eurostat Statistics Explained. Available at: http://
ec.europa.eu/eurostat/statistics-explained/index.php/Coal_consumption_
statistics [accessed 31.07.15].
[54] J.J. Chew, V. Doshi, Recent advances in biomass pretreatment eTorrefaction
fundamentals and technology Review, Renew. Sustain Energy Rev. 15 (8)
(2011) 4212e4222, http://dx.doi.org/10.1016/j.rser.2011.09.017.
D. Thr€
an et al. / Biomass and Bioenergy xxx (2016) 1e17 17
Please cite this article in press as: D. Thr€
an, et al., Moving torrefaction towards market introduction eTechnical improvements and economic-
environmental assessment along the overall torrefaction supply chain through the SECTOR project, Biomass and Bioenergy (2016), http://
dx.doi.org/10.1016/j.biombioe.2016.03.004