Expert workshop on 

Biomass Combustion Generated Nanoparticles

Tuesday 14 June 2016

This workshop took place as part of the 20th Nanoparticles Conference

ETH, Zürich, Switzerland



Fireplaces and wood log stoves that burn wood in a suboptimal manner are an important source of particle emissions around the world. By phasing out polluting woodstoves and introducing better stoves, improving stove installations and educating stove users, large emission reductions can be achieved. Moreover, there is evidence that the health impacts of fine particles from well operated biomass combustion devices is much less harmful than that of suboptimally operated devices.As biomass heating consitutes an important option to contribute to renewable energy production in many countries, it is important to recognise the differences in environmental impacts and societal consequences for different types of combustion systems, and take appropriate policy measures.

This T32 organised expert workshop on biomass combustion generated particles took place on 14 June 2016 as integral part of the 20th Conference on Combustion Generated Nanaoparticles . See for more information and the other presentations offered at the conference.



The workshop showed that there is an enormous difference in the relevance of biomass combustion particles between well designed and operated stoves and boilers on the one hand, and inappropriately designed or used devices. While in a modern and automatically operated biomass boiler with state of the art flue gas cleaning, particle formation may be primarly in the form of inorganic components, which are then also almost fully captured in an electrostatic precitpitator or baghouse filter, older biomass stoves and boilers that do not avail of proper flue gas cleaning devices and are inappropriately used, may cause significant particle emissions with also greater toxicity.

All presentations of the workshop are available below.

An easily readible summary of the workshop, published by the Swiss Federal Office of Energy, is available in English and German.

Thomas Nussbaumer, Switzerland
Particulate Matter (PM) from biomass combustion: An overview on particle types and measures to reduce particle emissions

Jorma Jokiniemi, Finland
Chemical and physical properties of biomass combustion aerosols

Hans Hartmann, Germany
User and fuel impact on emissions of wood stoves

Christoph Schmidl, Austria
Real-life emission of automatically stoked biomass boilers

Morten Seljeskog, Norway
Variables affecting particulate emissions from residential wood combustion - simultaneous sampling on hot and ambient filter


Based on the results of the workshop, Task 32 released the following statement.

Biomass is used as a renewable energy carrier to substitute fossil fuels for heat and power production. Modern biomass boilers that comply with today’s emission limits and that are operated appropriately have typically a low environmental impact. Biomass can therefore be used in an environmentally friendly way, if the necessary requirements are met. There are, however, undesired situations which can lead to non-ideal conditions. This can potentially cause a high negative impact to the air quality with an increased contribution to volatile organic compounds (VOC) and inhalable particulate matter in the size range smaller than 10 micrometres (PM10) in the ambient air.

From the activities of various research groups represented in the International Energy Agency (IEA) Bioenergy Task 32 and at the ETH Conference on Combustion Generated Nanoparticles in June 2016 [1–5] it is concluded, that the following topics need to be supported to avoid a high impact of biomass combustion to ambient air quality:

  1. The operation of the combustion devices has a strong influence on the air pollutant emissions. This is true for all devices, however most relevant for manually operated boilers and stoves. One important issue is the use of an appropriate fuel with respect to fuel moisture, size, and ash content for the dedicated combustion device. Furthermore, an appropriate ignition is required. Investigations show that an “ignition from the top” is favourable for many conventional wood stoves. In addition, the amount of wood for one batch needs to be adjusted to the size of the combustion chamber. Finally, sufficient combustion air, although not exceeding a reasonable amount, needs to be supplied during the combustion phase.

  2. Standardisation of biomass fuels, combustion devices, type-tests, and measurement technologies can assist a target-oriented development to further improve the quality of biomass combustion applications and ensure a low impact on air quality. For the definition of new standards, test conditions which represent a real-life operation should be considered.

  3. Design guidelines and quality management for the planning and implementation of biomass combustion plants can assist an appropriate layout and dimensioning as a pre-condition for an ideal operation of the combustion and the flue gas cleaning. Furthermore, plant monitoring can assist an on-going optimisation of the operation mode and an adaptation on varying requirements and fuel parameters.

  4. An international exchange of experience between all stakeholders from research, industry, energy economics, and national authorities can assist this process. Nevertheless, the enforcement of regulations on energy standards and on air quality plays an important role and needs to be followed also on a national basis.


The above statement can be downloaded as a separate PDF document here