Flax shives are a source of abundant biomass from renewable sources. They are considered to be environmentally benign and have a high-energy content for heating and generation of electricity, but only after being processed into pellets. Pelleting of the shives was done by using the single-pelleter and pilot-scale mill. The effect of grinding with screens of 2.4, 3.2, and 6.4 mm on unit density and durability was conducted with a completely randomized design using shives from Biofibre Industries Inc., Canora, SK. The central composite face-centered design with 3 levels of lower grade canola meal used as a binder (18, 21, and 24%), moisture content (8, 11, and 14% (w.b)), and hammer mill screen size (3.2, 4.8, and 6.4 mm) was used to determine the effects of these three factors on the properties of fuel pellets made from shives obtained from Biolin Research Inc., Saskatoon, SK. The initial moisture content of coarse flax shives from both sources was about 10.5% wet basis (w.b.). The moisture content of flax shive grinds ranged from 9.6 to 10.5% (w.b.) after grinding, using the smaller screens for the Biofibre material, while the moisture content ranged from 7.9 to 8.6% (w.b.) for shives from Biolin. Also, smaller screen size reduced the geometric mean particle size for shives from both sources. The use of the smaller hammer mill screen resulted in an increase in both bulk and particle density of shives. There was a decrease in coefficient of the internal friction of shives from 0.20 to 0.14 and an increase in a cohesion of shives from 2.18 to 3.83 kPa when the screen size decreased from 6.4 to 3.2 mm. The flax shives contained cellulose (53.27%), hemicelluloses (13.62%), and lignin (20.53%) at a moisture content of 7.9% (w.b). Specific heat capacity of flax shives changed from 1.5 to 2.7 kJ/ (kg °C) when the moisture content was increased from 8 to14% (w.b.) and temperature from 15 to 80°C. The shives had the combustion energy of 17.67 MJ/kg at a moisture content of 8.1% (w.b.).<p> The smallest screen size (2.4 mm) resulted in the highest unit density (1010 kg/m3) and the highest durability (88%) in the pellets produced by the single-pelleting equipment. The change in length of pellets produced by the pilot-scale mill increased as canola meal increased from 18 to 24% at the highest moisture content (%). The pellets were more stable at the highest moisture content when the lowest canola meal used. The addition of 18% canola meal and grinds from a screen size of 6.4 mm produced the highest unit density in the pellets at all moisture levels. The highest bulk density (682 kg/m3) was obtained from shive mixtures with 18% canola meal and a moisture content of 8%. The highest hardness and durability were found for the shive pellets that were produced with 18% canola meal at a moisture content of 14% (w.b). Pellets that were produced at a moisture content of 14% (w.b) resulted in the lowest percentage of moisture absorption. The inclusion of the canola meal in the shive mixture resulted in an increase in the combustion energy of the pellets because of the fat content in the binder. The two levels of canola meal for shive pellets had essentially the same level of emissions. However, there were significant differences between shive pellets and commercial wood pellets in the level of the emissions. Lower amounts of methane (1.29 ppm) and oxygen (164.3 ppt) were found for flax shive pellets than of methane (1.63 ppm) and oxygen (176.6 ppt) in commercial wood pellets.<p> In short, pelleting of flax shives into fuel pellets improved the handling characteristics, increased bulk density and energy content. Fuel pellets made from flax shives had less emission of methane and oxygen from combustion when compared to commercial wood pellets.

Flax shives are a source of abundant biomass from renewable sources. They are considered to be environmentally benign and have a high-energy content for heating and generation of electricity, but only after being processed into pellets. Pelleting of the shives was done by using the single-pelleter and pilot-scale mill. The effect of grinding with screens of 2.4, 3.2, and 6.4 mm on unit density and durability was conducted with a completely randomized design using shives from Biofibre Industries Inc., Canora, SK. The central composite face-centered design with 3 levels of lower grade canola meal used as a binder (18, 21, and 24%), moisture content (8, 11, and 14% (w.b)), and hammer mill screen size (3.2, 4.8, and 6.4 mm) was used to determine the effects of these three factors on the properties of fuel pellets made from shives obtained from Biolin Research Inc., Saskatoon, SK. The initial moisture content of coarse flax shives from both sources was about 10.5% wet basis (w.b.). The moisture content of flax shive grinds ranged from 9.6 to 10.5% (w.b.) after grinding, using the smaller screens for the Biofibre material, while the moisture content ranged from 7.9 to 8.6% (w.b.) for shives from Biolin. Also, smaller screen size reduced the geometric mean particle size for shives from both sources. The use of the smaller hammer mill screen resulted in an increase in both bulk and particle density of shives. There was a decrease in coefficient of the internal friction of shives from 0.20 to 0.14 and an increase in a cohesion of shives from 2.18 to 3.83 kPa when the screen size decreased from 6.4 to 3.2 mm. The flax shives contained cellulose (53.27%), hemicelluloses (13.62%), and lignin (20.53%) at a moisture content of 7.9% (w.b). Specific heat capacity of flax shives changed from 1.5 to 2.7 kJ/ (kg °C) when the moisture content was increased from 8 to14% (w.b.) and temperature from 15 to 80°C. The shives had the combustion energy of 17.67 MJ/kg at a moisture content of 8.1% (w.b.).<p> The smallest screen size (2.4 mm) resulted in the highest unit density (1010 kg/m3) and the highest durability (88%) in the pellets produced by the single-pelleting equipment. The change in length of pellets produced by the pilot-scale mill increased as canola meal increased from 18 to 24% at the highest moisture content (%). The pellets were more stable at the highest moisture content when the lowest canola meal used. The addition of 18% canola meal and grinds from a screen size of 6.4 mm produced the highest unit density in the pellets at all moisture levels. The highest bulk density (682 kg/m3) was obtained from shive mixtures with 18% canola meal and a moisture content of 8%. The highest hardness and durability were found for the shive pellets that were produced with 18% canola meal at a moisture content of 14% (w.b). Pellets that were produced at a moisture content of 14% (w.b) resulted in the lowest percentage of moisture absorption. The inclusion of the canola meal in the shive mixture resulted in an increase in the combustion energy of the pellets because of the fat content in the binder. The two levels of canola meal for shive pellets had essentially the same level of emissions. However, there were significant differences between shive pellets and commercial wood pellets in the level of the emissions. Lower amounts of methane (1.29 ppm) and oxygen (164.3 ppt) were found for flax shive pellets than of methane (1.63 ppm) and oxygen (176.6 ppt) in commercial wood pellets.<p> In short, pelleting of flax shives into fuel pellets improved the handling characteristics, increased bulk density and energy content. Fuel pellets made from flax shives had less emission of methane and oxygen from combustion when compared to commercial wood pellets.

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Bioenergy is one of many contributors to reducing the use of fossil fuels in order to mitigate climate change by decreasing CO2-emissions, and the potential for biofuels are large. The wood fuel pellets are a refined biofuel made of sawdust, which is dried and compressed to achieve improved fuel and transportation properties. In 2007 the amount of wood fuel pellets used for heating purposes in Sweden was 1715000 tons. The aims of this work was: to examine the moisture content and emission of monoterpenes during the drying and pelletising steps of the pellets production (Paper I); to investigate how the recirculation of drying gases affects the energy efficiency of rotary dryers and how the energy efficiency is related to the capacity of the dryer. (Paper II); to analyse the causes of the problems encountered by household end-users of pellets and investigate whether an improved pellet quality standard could reduce these problems (Paper III); to investigate how the energy consumption of the pelletising machine and chosen pellet quality parameters were affected using an increased amount of rapeseed cake in wood fuel pellets (Paper IV); and to identify gaps of knowledge about wood fuel pellet technology and needs for further research on quality, environmental and health aspects throughout the wood fuel pellet chain, from sawdust to heat. (Paper V).

<p>One of the great challenges facing society is to convert theglobal energy system to a sustainable process. Currently, 80%of the world´s energy is supplied through the combustionof fossil fuels. Not only are the fossil resources limited, theutilisation also increases the level of greenhouse gases in theatmosphere. The convertion to a sustainable energy system isproblematic since the technology needed to exploit mostnon-fossil energy sources is not yet fully developed, e.g.solar energy. Biofuel is an available renewable energy sourcewhich is already widely used in many countries. If an effectiveswitch-over from fossil fuels to biofuels is to be realised,biofuels must be viewed as a limited resource. Consequently, itis important that the handling, upgrading and utilisationprocesses involving biofuels are efficient so that itspotential can be fully exploited.</p><p>This thesis considers efficient biofuel utilisation andupgrading within the sawmill industry. The goal has been toanalyse not only the technical opportunities for energy savingsin the sawmill industry, but also to analyse the costeffectiveness and environmental impact of studied measures. Theheat demand of the sawmill industry is almost completelycovered by its own by-products; primarily bark, sawdust andwood chips. The increased demand and improved economic value ofwoody biofuels on the market is thus an incentive for thesawmill industry to place more focus on energy issues. Thesawmill industry also has a more or less constant heat loadover the year, which is a beneficial factor for integrationwith district heating networks, biofuel upgrading plants andcombined heat and power plants.</p><p>The conclusion of the study is that a variety of energyproducts such as heat, unrefined biofuel, pellets andelectricity can be efficiently produced in the sawmill industryand sold for profit to external customers. The payback periodsfor the proposed investments are moderate and both theemissions of volatile organic compounds and global CO2 aredecreased. Should the proposed measures be fully implemented atSwedish sawmills, about 2.8 TWh of biofuel could be savedannually, 0.5 TWh of waste heat could be sold as districtheating and 0.8 TWh of green electricity could be produced.Language: English</p><p><b>Keywords:</b>Sawmill industry, energy efficiency, heatrecovery, integration, biofuel, upgrading, district heating,fuel pellets, CHP, VOC, CO2</p>