Workshop on aerosols from biomass combustion, Graz, Austria, March 2005

International seminar on 


Friday, March 18, 2005

Graz, Austria


Combustion of solid biomass offers the highest short-term
potential for significant CO2-reduction in energy production
of all renewable energy technologies in a cost-effectve manner.
Comprehensive R&D work carried out during the last decades has
already led to a state-of-the-art which allows a highly efficient
combustion of a wide range of solid biomass fuels at high plant
availabilities as well as low gaseous emissions.

However, several problems related to the formation of fine
particulates during combustion, so called aerosols, are still unsolved.
These problems affect both, the plant operation itself due to the
formation of deposits and ash mixtures with comparably low melting
temperatures as well as particulate emissions. Therefore, a
considerable number of research projects has been initiated to find
solutions for these technological problems. Aerosol immissions as well
as their impact on the human health are nowadays intensively
investigated and discussed.

Against this background and to present and discuss on-going
research, IEA Bioenergy, Task 32, “Biomass Combustion and Co-firing” in
co-operation with the Austrian Bioenergy Centre and the Graz University
of Technology have organised an international seminar “Aerosols in
Biomass Combustion”. The seminar presented, discussed and assessed the
actual state-of-science in this field and provided information about
non-technical issues especially related to legislative regulations,
aerosol immissions and health effects of fine particulate immissions.
Approximately 70 researchers, furnace and boiler manufacturers, filter
manufacturers as well as utilities, plant operators, energy agencies
and public authorities participated in the workshop.


One should clearly distinguish between old and new
biomass combustion devices. This is of special importance if small-scale
units are considered because new biomass furnaces achieve an almost
complete burn-out, which substantially reduces the amount of organic
aerosols formed.

Due to the fact that old small-scale biomass
combustion plants emit significantly larger amounts of aerosols (due to
incomplete combustion) than new systems, aerosol emissions from biomass
combustion could be substantially reduced by replacing old with new
automatically operated small-scale biomass combustion devices or at least
by improving the operation of old systems (e.g. by the installation of
storage tanks).

Inventories concerning aerosol emissions and
immissions need actual and secured data. New data con­cerning aerosol
emissions from biomass combustion (based on measurements per­formed
within ongoing R&D projects) should therefore be supplied for new as
well as old combustion devices as well as concerning the actual ratio
between old and new systems installed in a certain country. These data are
of great relevance in order to achieve correct calculations and
evaluations regarding the influence of aerosols from biomass combustion on
the overall emission and immission situation.

Regarding health effects of aerosols from
biomass combustion, first studies are ongoing but there is still a long
way to go in order to understand which influencing variables are of rele­vance
(e.g. particle size, chemical composition). Besides cell tests also
inhalation tests will be necessary to evaluate health effects properly.

First sets of release data, describing the
amount of aerosol forming species released to the gas phase during
combustion, are available for pulverised biomass fuels as well as for
grate com­bustion systems and will also be further investigated. These
data are of great relevance for aerosol formation as well as for
subsequent deposit formation modelling.

Aerosol formation models for biomass combustion
systems have already achieved a high level of development and will be
further improved within the next years. These models are of great
relevance to understand aerosol formation pathways as well as relevant
influencing variables.

Moreover, relevant investigations regarding the
influence of aerosols on deposit formation have been performed and have
shown that aerosols can strongly influence the ash melting behaviour of
deposits due to the formation of salt mixtures with low melting points.

New small-scale aerosol precipitation devices
are under development. Tests with prototypes have started but these
technologies are not yet commercially available.

Medium and large-scale biomass combustion plants
(nominal boiler capacity > 500 kWth) can precipitate
aerosols well if appro­priate filters are installed. An efficient aerosol
precipi­tation can be achieved by electrostatic precipitators as well as
by baghouse filters.



The proceedings of the
Aerosol Workshop have been published as a separate book (Volume 6) in
the Thermal Biomass Utilization book series of
BIOS Bioenergy Systeme
. Orders can be directly made through



Most of the presentations held at this workshop can be
downloaded below.




Welcome address

I. Obernberger, Graz University of Technology (A)

S. van Loo, IEA Bioenergy, Task 32 (NL)

E. Fercher, Austrian Bioenergy Centre (A)


Fly ash
and aerosol formation in biomass combustion processes – an introduction

I. Obernberger, Graz University of Technology (A)

Session 1: PM immissions and health
Chairman: S. van Loo, IEA Bioenergy Task 32 (NL)


international activities to abate European PM emissions

W. Winiwarter, ARC systems research (A)


imissions in Austria – 2000 to 2004

J. Schneider, Department of Air Quality Control


Coffee break


Health effects
of ambient aerosols

H. Hauck, Austrian Academy of Sciences (A)


relevance of aerosols from biomass combustion in comparison to diesel

N. Kippel, Verenum Zürich (CH)



SESSION 2:Aerosol formation and
behaviour in biomass combustion processes 
Chairman:C. Tullin, SP (S)


Release of aerosol forming species
during combustion in pulverised fuel systems

R. Korbee, ECN – Energy Research Centre of
the Netherlands (NL)


Release of aerosol forming species in
fixed-bed systems

Flemming Frandsen, Technical University of Denmark (DK)


Modelling of
aerosol formation

M. Joeller, Graz University of Technology (A)


Aerosol and
particle transport in furnaces

H.P. van Kemenade, Technical University Eindhoven


The influence
of aerosol particles on the melting behaviour of ash deposits in
biomass fired boilers

R. Backman, Umea University (S)


Coffee break

SESSION 3:Aerosol emissions and
emission control 
Chairman: I. Obernberger, Graz University of Technology (A)


analyses of aerosols formed during biomass combustion by SEM/EDX

S. Mitsche, Graz University of Technology (A)


Emissions from residential biofuel boilers and stoves

C. Tullin, Swedish National Testing and
Research Institute (S)


Fine particle
emissions from fluidised bed combustion of peat and wood

V. Linna, VTT Processes (FIN)


gas cleaning for small wood fired appliances – recent progress and
field test results

V. Schmatloch, Swiss Federal Institute for
Materials and Testing (CH)


precipitation in medium- and large-scale biomass combustion plants

BIOS Bioenergysysteme GmbH (A), M. Lixl, Scheuch GmbH (A)


Summary and Conclusions


This workshop was organised by Prof. Dr. Ingwald Obernberger
on behalf of


for Resource Efficient and Sustainable Systems

„Thermal Biomass Utilisation”

University of Technology

EU-Project SES6-CT-2003-502679 – BIOASH