Pyrolysis of biomass—thermochemical decomposition of wood or organic waste at elevated temperatures and with minimal presence of oxygen—could be an 'interesting' option in a transition to replacing today's fossil oil with renewable alternatives, according to a Bio4Energy expert on the thermal conversion of biomass to fuels and chemicals. Thus far, however, lack of knowledge about the composition of the bio-oil obtained from pyrolysis of wood or woody waste has been a hindrance efficiently to design techniques for producing and using such bio-oil, to believe researchers in Bio4Energy at the SP Energy Technology Center (SP ETC) at Piteå, in Sweden.
After five years of research in Bio4Energy, and three new funding grants enabling the start of two research projects and the purchase of state-of-the-art instrumentation, that may be about to change.
Until recently, 'perhaps 50 per cent of the contents of the oil made by way of pyrolysis could be mapped by ordinary gas chromatography and other methods', said Magnus Marklund, CEO at the SP ETC, having just received the announcement of two research grants worth more than eight million Swedish kronor from the Swedish Energy Agency, plus support for highly advanced analytical equipment called GCxGC MS from the Kempe Foundations. GC is short for gas chromatography, which in this case is two dimensional, but in this new instrument it has been coupled with a technique called mass spectrometry.
'With the new funding from the Energy Agency for the research projects and for a state-of-the-art analytic instrument from Kempe we are going to complement, strengthen and inventory what is being done on an international top level.
'We want to know about various aspects of the [pyrolysis] oil depending on its application. We are going to need to know different things depending on whether it is going to be used as combustion fuel or be refined to transportation fuel and chemicals', Marklund added.
He said options for using pyrolysis oil as an alternative to fossil oil could include:
- Combustion of 'light' or 'heavy' fuel oil for heating purposes;
- Power production by means of using a gas turbine or;
- Upgrading to automotive fuels.
For the three options deeper knowledge on ash formation and particulate emissions and their mitigation were needed, neither of which had been thoroughly studied by scientists to date, said Marklund.
'We need to create this understanding so that then we can go back along the process chain and solve problems in order to optimise overall performance. These will mostly relate to the conversion process, but could also concern downstream environmental emissions, such as [the removal by scrubbing filters of] particulate matter', he said.
What are some cost-efficient solutions for using pyrolysis oil as a fossil oil replacement, in today's economic and societal context?
'There could be specific instances. One could place mobile pyrolysis units in the northern Swedish inlands and turn forestry residue into pyrolysis oil using simple techniques', according to Marklund. It was about using as much as possible of the raw material, include any char resulting from the combustion process and adapting to local conditions, he added;
'System boundaries for this kind of undertaking need to be drawn up but… in five-to-ten years we should be able to provide our national biorefineries with pyrolysis oil from wood.
'For the long term I have greater belief in [biomass] gasification, but this [gasification technology] will require larger changes in infrastructure', said Marklund, thus acknowledging that pyrolysis oil could be a more short-term bio-based product to go for in the transition to a society fuelled by renewable energy.
The two following projects were granted SP ETC by the Swedish Energy Agency:
- Ash Formation Processes during Production and Combustion of Pyrolysis Oil. Project leader: Henrik Wiinikka, SP ETC and Bio4Energy Thermochemical Platform.
The purpose of this project is to contribute to pyrolysis oil becoming a commercial fuel by studying the transmission of ash elements from raw material to fuel at the stage of production, according to the funding application. There will be a partial focus on issues impeding the proper functioning of equipment such as ash or tar formation inside the biomass reactor during the combustion process.
- Detailed Analysis and Characterisation of Fast Pyrolysis Oils. Project leader: Linda Sandström, SP ETC and the Bio4Energy Catalysis and Separation Platform.
This projects aims to analyse the contents of the pyrolysis oil to gain a more complete understanding of its composition and also, possibly, to recommend the best method for doing so.
The Kempe Foundation agreed to support the purchase and installation at the premises of the SP ETC of two-dimensional gas chromatography coupled with mass spectrometry.
The GC MS technology is a combination of two well-known analytical research techniques. In the current pyrolysis oil project, the two dimensional gas chromatograph will separate the components of the oil, while the mass spectrometer will provide information to facilitate the identification of each of its components.
In their application to the Kempe Foundations, the SP ETC researchers said: 'If our application for this instrument is granted, this… will further raise the level of the research of the institutions in northern Sweden and strengthen the reputation and power of attraction for the strategic research environment Bio4Energy as being world leading in biorefinery'.