Mehrdad Arshadi

Emission of Volatile Aldehydes and Ketones from Wood Pellets under Controlled Conditions

Different qualities of biofuel pellets were made from pine and spruce sawdust according to an industrial experimental design. The fatty/resin acid compositions were determined by gas chromatography-mass spectrometry for both newly produced pellets and those after 2 and 4 weeks of storage. The aldehydes/ketones compositions were determined by high performance liquid chromatography at 0, 2, and 4 weeks. The designs were analyzed for the response variables: total fatty/resin acids and total aldehydes/ketones. The design showed a strong correlation between the pine fraction in the pellets and the fatty/resin acid content but the influence decreased over storage time. The amount of fatty/resin acids decreased approximately 40% during 4 weeks. The influence of drying temperature on the aldehyde/ketone emission of fresh pellets was also shown. The amounts of emitted aldehydes/ketones generally decreased by 45% during storage as a consequence of fatty/resin acid oxidation. The matrices of individual concentrations were subjected to multivariate data analysis. This showed clustering of the different experimental runs and demonstrated the important mechanism of fatty/resin acid conversion.

Pre-treatment and extraction techniques for recovery of added value compounds from wastes throughout the agri-food chain

The enormous quantity of food wastes discarded annually forces a look into alternatives for this interesting feedstock. Thus, food bio-waste valorisation is one of the current imperatives of society. This review is the most comprehensive overview of currently existing technologies and processes in this field. It tackles classical and innovative physical, physico-chemical and chemical methods of food waste pre-treatment and extraction for the recovery of added value compounds and detection by modern technologies and is an outcome of the COST Action EUBIS, TD1203 Food Waste Valorisation for Sustainable Chemicals, Materials and Fuels.

Impact of supercritical extraction on solid fuel wood pellet properties and off-gassing during storage

Biofuel pellets derived from wood raw material are an important carbon neutral source of energy. Their storage and bulk transportation can lead to serious hazards as a result of off-gassing (CO, CO2, CH4 combined with serious oxygen (O2) depletion). Herein, supercritical carbon dioxide extraction (scCO2) has been demonstrated as an efficient tool in significantly reducing these emissions from wood pellets. 84% of the lipids and resin acids have been removed from the sawdust prior to pelletisation. Crucially, this work reports the first off-gassing measurements associated with lipid autoxidation in wood pellets post scCO2 extraction of the sawdust. These off-gassing processes were considerably reduced for scCO2-extracted sawdust pellets, when compared to pellets prepared from virgin untreated sawdust (reference pellets). Significant reductions in the levels of CO, CO2 and CH4 (85, 85, and 94% respectively) were observed. A slight reduction in O2 concentration (20% to 19.3%) was observed for the scCO2-pellets, while an 8% decrease (reduction in O2 concentration from 20% to 12%) was observed for the reference. The results support a connection between the amount of lipids/resin acids and intermediate products of autoxidation (i.e. 71% reduction in aldehydes) and the off-gassing of CO, CO2 and CH4. Finally, there was low impact on the production, durability, calorific values and density of scCO2 pellets compared to the reference pellets. This work demonstrated that scCO2 extraction is effective as a pre-treatment technology for wood based pelletised fuels, considerably reducing the risks associated with off-gassing and oxygen depletion, while also highlighting potential chemicals and biofuels which could be generated from extracts.

Supercritical fluid extraction (SFE) as an effective tool in reducing auto-oxidation of dried pine sawdust for power generation

Supercritical carbon dioxide was an ideal solvent for the extraction of fatty and resin acids from pine sawdust. This green extraction process significantly reduces the potential for uncontrolled auto-oxidation within this valuable fuel, thereby removing the risk of combustion during storage and processing. Experimental design was utilised to maximize the yield of the extractives. Within the experimental conditions investigated (74–250 bar and 40–60 °C), higher pressures and lower temperatures gave preferentially high extraction yields, with 97% of the fatty and resin acids in 2 h at 250 bar, 40 °C, 40 g min−1 and with 10% ethanol co-solvent. The calorific value of the pelletized sawdust was not significantly affected by the extraction process and the resulting extracts have demonstrated a significant potential for conversion to a biodiesel liquid fuel or higher value chemicals.

Monitoring Chemical Changes for Stored Sawdust from Pine and Spruce Using Gas Chromatography-Mass Spectrometry and Visible-Near Infrared Spectroscopy:

Fuel pellets that are very often made of sawdust represent a renewable energy source for heat production and there is a growing interest in these products in a large part of the world. Raw material production in the sawmills and use of sawdust in the pellet mills are out of phase during a large part of the year and for reasons of logistics there is a need for storage of large quantities of the raw material. Long-term storage changes the sawdust and, therefore, processing parameters have to be adapted, making some knowledge of storage time or maturity necessary. An experiment on the industrial storage of pine and spruce sawdust was carried out over a period of 16 weeks. Samples were taken out every week and all samples were analysed by visible-near infrared (vis-NIR) spectroscopy, while some samples were analysed by GC/MS for their composition of fatty- and resin acids. The resulting data were subjected to multivariate data analysis. GC/MS data showed the difference between pine and spruce sawdust and the influence of maturity. This maturity effect could be associated with the decrease in fatty- and resin acids due to auto-oxidative reactions. The first six weeks of storage had no influence on the concentration of fatty- and resin acids. Most of the changes in the amount of fatty- and resin acids occurred in the fresh pine sawdust during weeks six to 12. Since the spruce sawdust had less initial amounts of fatty- and resin acids, the changes were less in absolute terms but the fractional changes were similar to pine. During weeks 13 to 17 the fatty- and resin acids content had stabilised and changes were marginal. Multivariate analysis of the vis-NIR data showed a major effect due to maturity associated with a colour change and also weaker effects of fatty- and resin acid differences. PLS regression was used to predict the storage time with RMSEP values between 10 and 15 days. However, since weather conditions, precipitation and seasonal variation, have a very strong influence on the rate of maturing of sawdust it will be necessary to monitor the stored sawdust to determine the degree of maturity. Because of the large flow rate human eye assessment should be replaced by frequent vis-NIR measurements. The vis-NIR spectra allow prediction of storage time and therefore maturity.

Effects of microwave drying on biomass fatty acid composition and fuel pellet quality.

Abstract Drying of biomass for fuel pellet production is a time- and energy-consuming process. The objective of this study was to investigate not only whether microwave drying could be an alternative drying method but also whether the microwave treatment brings beneficial chemical properties into the biomass feedstock in terms of, for example, fatty acid composition and, further, whether this could be advantageous in the production of wood pellets. Microwave drying tests were conducted using fresh sawdust from pinewood as a biomass model. In these tests sawdust was dried from weight-based moisture content 0.47 to final moisture contents in the interval 0.08–0.14. The chemical composition, pellet-making and mechanical properties of the pellets were then investigated. It was shown that 0.5 kg sawdust could be dried within 40 min of microwave exposure. The effects of microwave treatment on the fatty and resin acid composition indicated that some changes occurred, but the total amounts were not significantly different from those in oven-dried samples. However, the microwave treatment of sawdust significantly improved pellet density and pellet strength. These results indicate new possibilities to alter fatty and resin acid composition and to improve particle bonding within fuel pellets.

Lipophilic extractives in different tree fractions and forestry assortments of Pinus sylvestris due for thinning or final cutting

ABSTRACT The objectives were to determine the content and composition of lipophilic extractives, particularly fatty and resin acids, in three Scots pine trees from each of two stands in northern Sweden, one that was due for thinning and one due for final cutting. Extractives content of branches, needles, barks, stem discs from branch whorls, and sapwood and heartwood samples from various heights was measured. Fractions had very different concentrations and distributions of extractives due to differences in the composition of tissues. The needles had the highest total extractive concentration (around 150 kg/ton d.w.), followed by the branches, bark, timber from the final cut stand, and then the pulpwood and timber from the thinning stand. The final cut stand generally provided higher yields of extractives in assortments per hectare than the thinning stand; the difference was five-fold for timber, three-fold for whole trees, two-fold for branches, needles and bark and similar for pulpwood. This information on the content and composition of extractives in different tissues, and the dependence of these quantities on tree age could be used together with information on conventional stand data such as tree numbers and dimensions to guide the selection and management of feedstocks for biorefineries.