The role of chemical formatting structures in biomass on the formation of dioxins and furans in soot deposits from the combustion of biomass

Lead Research Organisation: University of Leeds
Department Name: Chemical and Process Engineering

Abstract

It is estimated that ~350,000 tonnes/year of waste wood is used in UK domestic wood burning acquired via the 'grey' fuel market. Most of this waste wood is likely to be clean, however, a significant, yet unknown quantity, is likely to be contaminated. Combustion of contaminated wood has been shown to generate high levels of emissions of dioxins and furans. These dioxins and furans are also associated with the soot's and chars which deposit in the combustion flue gas system or open fire chimney. Such soot deposits contaminated with dioxins and furans represent substantial environmental and health risks. However, there is very little known about the formation of dioxins and furans in the soot deposits from waste wood combustion.
The aim of this present research proposal is to investigate the formation of dioxins and furans formed in the soot deposits from the combustion of biomass under the conditions simulating those of the flue duct conditions from domestic wood burning. The research will investigate how the different structure and surface chemistry of soot's produced from the main biomass components of cellulose, hemicellulose and lignin influence the formation of dioxins and furans under precursor and de novo formation conditions. In addition, soot produced from the combustion of a range of contaminated urban waste woods produced under various operational conditions will be investigated in terms of dioxin and furan formation. An integral study using model biomass aromatic and oxygenated model compounds will aid a mechanistic interpretation of the formation of dioxins and furans related to biomass components and biomass.
This research is timely and important in understanding the formation mechanisms of dioxins and furans in the soot deposits from biomass combustion. It also provides critical evidence for policy formulation, recommendations and risk assessments of the potential hazards to human health and the environment of the accumulation of PCDD/PCDF and PCBs in the domestic environment.
This is an ambitious proposal involving ultra-trace level organic micro-pollutants using advanced analytical techniques to fundamentally understand the important precursor and de novo reaction mechanisms which lead to the formation of dioxins and furans from biomass combustion

Planned Impact

This research will provide policy makers at Department for Environment, Food and Rural Affairs and the Department of Business, Energy and Industrial Strategy with key knowledge in relation to the emissions of dioxins and furans in relation to the combustion of contaminated wood by householders. This will enable key recommendations and risks assessment of the potential hazards to human health and the environment of the accumulation of dioxins and furans from wood burning in the domestic environment.
The UK Government "25 year Environment Plan" (2018; Chapter 4), declares that protecting the environment through a clean air strategy through reducing emissions, leading in environmental science are key priorities of the Plan. In addition, Goals and Targets of the 25 Year Plan focus on 'Managing exposure to Chemicals" in the environment and highlight Persistent Organic Pollutants (which include dioxins and furans) as a significant area of concern. Therefore the research proposed in this project directly addresses the concerns of the "25 year Environment Plan" (2018) through knowledge of the formation and control of dioxins and furans from the combustion of contaminated urban wood in the domestic environment.
There is approximately 1.6 million tonnes of wood are supplied to the domestic market each year. It is estimated that ~350,000 tonnes/year of this wood is waste wood acquired via the 'grey' fuel market. Most of this waste wood is likely to be clean, however, a significant, yet unknown quantity, is likely to be contaminated customers. Key knowledge from this research project will provide the evidence to enable the industry to clearly assess the risks associated with burning contaminated wood. In addition, knowledge of the toxicity of soot deposits from wood burning, particularly if contaminated wood has been used as fuel would provide this industrial sector with key knowledge in relation to cleaning and maintenance of wood combustion systems.

Publications

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Description Combustion of contaminated wood has been shown to generate high levels of emissions of dioxins and furans. They may also form in the soot deposits in the flue gas system of wood burning stoves or in chimney deposits from domestic fires. The aim of this present research proposal is to investigate the formation of dioxins and furans formed in the soot deposits from the combustion of biomass under the flue duct conditions simulating those of a typical domestic wood burning stove. The research will investigate how the different structure and surface chemistry of soot's produced from the main biomass components of cellulose, hemicellulose and lignin influence the formation of dioxins and furans under precursor and de novo formation conditions. In addition, soot produced from the combustion of a range of contaminated urban waste woods produced under various operational conditions will be investigated in terms of dioxin and furan formation. There are 210 chlorinated dioxins and furans and 209 polychlorinated biphenyls representing an enormous analytical challenge.
The grant is in an early stage. The analytical process is very complex; Extraction of dioxins and furans from the soot/char involves solvent extraction, the method is based on EPA Method 3545A. Clean-up of the samples from interferences is achieved using an automated Power-PrepTM Fluid Management System. Final analysis of dioxins and furans a Varian 450-GC attached to a Varian 320-MS triple quadrupole mass spectrometer. The analysis is calibrated throughout the sampling and analysis process using labelled isotope enriched dioxins and furans.
The methodology for the extraction and detailed analysis of dioxins and furans from soot and char deposits has been established. Trial combustion of waste wood in a wood burning domestic stove is underway.
Exploitation Route Final outcomes will be valuable to the wood burning stove industry
Sectors Energy,Environment