Organic emissions with focus on terpenes, from biomass drying and storage were investigated by Solid Phase Microextraction (SPME) and GC-FID and GC-MS. The remaining terpenes in the biomass (Spruce and pine wood chips) after drying were dependant on the drying temperature and drying medium used. The drying medium used was steam or hot air; the drying temperatures used were 140degreeC, 170degreeC and 200degreeC. Steam drying at 170degreeC left more of the terpenes remaining in the wood chips, not emitting them into the drying medium. The terpenes emitted from storage of forest residues and bark and wood chips increased up to three-four or four-five months of storage, and then dropped down to approximately the same low level as the first month. The leachate taken from the forest residue pile contained 27µg PAH per liter. The SPME response for a monoterpene (a-terpene) at different temperatures, amounts and humidities was quantified. The highest concentration calibrated was 250 ppm and the lowest 9.4 ppm. There is a better linear agreement at higher temperatures (70degreeC and 100degreeC) than lower temperatures (below 40degreeC). Organic emissions from biofuel combustion were measured at three medium sized (~ 1MW) biomass fired moving grate boilers fired with different fuels: dry wood fuel, forest residues and pellets. The PAH emissions varied by almost three orders of magnitude between the three boilers tested, 2.8-2500 microgram/m3. It was difficult to identify any general parameters correlating to the PAH emissions. The variation in PAH emission is most probably a result of boiler design and tuning of the combustion conditions. When comparing the contribution to self-heating from different wood materials by means of isothermal calorimetry with different metals added and stored at different temperatures, the differences were quite large. Some of the samples released as much as 600mW/kg, whereas others did not contribute at all to the self-heating. The storage temperature, at which the samples released the most heat, was 50C. There was a peak in heat release for most of the samples after 10-30 days. Stepwise increase in temperature did not favour the heat release in the sample Dry Mix; the heat released was even lower than when it was directly put in the different storage temperatures. When metal is added, there is an increase in heat release, the reference sample without metal released 200mW/kg compared to 600mW when copper was added.

<p>Bioenergi är en stor industri i Sverige och står för en betydande del av energiomsättningen. Bioenergi i form av flis förvaras runt om i landet på hög i väntan på förbränning. Då högarna läggs upp startar olika processer som värmer upp stacken, ofta till temperaturer på 50°C under det första dygnet. En vanlig ansats i litteraturen är att denna temperaturstegring beror på aerob nedbrytning. Arbetet ämnar undersöka om denna uppvärmning endast beror av mikrobiella aktiviteter. Hypotesen prövas genom kalorimetriska mätningar av effekt från prover av flis och simulering av första dygnets temperaturutveckling i ett program som programmeras under arbetes gång.</p><p>I modellen så betraktas för enkelhets skulle flisstacken som en avlång figur med rektangulärt tvärsnitt. Figuren delas sedan in i lämpligt stora beräkningsceller. Problemet löses genom att iterativt räkna fram ett strömningsfält. Strömningsfältet och effekterna som räknas ut hålls sedan konstanta under ett tidssteg, 5-15min. Den magasinerade värmeenergin används sedan för att räkna fram en ny temperatur som så ger ett nytt strömningsfält och nya effekter. I modellen användes enbart explicita metoder eftersom de är snabbare och mycket enklare att programmera.</p><p>Ett flertal experiment i kalorimeter genomfördes med olika prover av flis och torv. Prover med barkflis gav högst utslag. Den högsta effekten som uppmättes var 2,16W/kg TS. Då effekter av denna storleksordning användes som inre effektgenerering i programmet gav detta inte en temperatur ökning motsvarande sådana som uppmätts i verkligheten. Detta tyder på att mer än aerob nedbrytning krävs för att ge en temperatur på över 50°C.</p> / <p>Bioenergy is a major industry in Sweden and accounts for a significant part of the energy production. Bioenergy in the form of wood chips is stored in piles across the country awaiting combustion. When the piles are acumulated, various processes that heat the stack begin, often to temperatures of 50 °C during the first day. A common approach in the literature is that this temperature rise is due to the aerobic decomposition. This paper will investigate whether the microbial activity is the fundamental cause for warming. The hypothesis is tested by calorimetric measurements of power from the samples of wood chips and simulation of the first day's temperature development in a programme that was desinated.</p><p>For simplicity the model considers an oblong wood chip pile with rectangular cross-section. The pile is then subdivided into appropriately sized calculation cells. The problem is solved by calculating a flow field iteratively. The flow field and the effects that are calculated is then static during one time step for approximately 5-15 minutes. The produced heat energy is then used to calculate a new temperature, which renders a new flow field and new powers. The model uses only explicit methods because they are faster and much easier to programme.</p><p>Several calorimetric experiments were carried out with various samples of wood chips and peat. Samples of bark chips achieved the highest result. The highest power measured was 2.16 W / kg DM. When the effects of this magnitude were used as internal power source in the programme the temperature did not increase corresponding to those measured in reality. This suggests that more than aerobic decomposition is needed to reach a temperature above 50°C.</p>

This Degree Project has been done at Växjö University, department of bioenergy technology and discusses the released thermal power in wood pellets. The purpose of the project is to investigate if two new types of wood biofuels (pellets) are more or less reactive than the pellets previously investigated at Växjö University. To measure the released thermal power, an isothermal calorimeter with eight channels has been used. To see how the microbial activity is influenced, the pellets have been stored under various conditions with focus on temperature and metal.

Bioenergi är en stor industri i Sverige och står för en betydande del av energiomsättningen. Bioenergi i form av flis förvaras runt om i landet på hög i väntan på förbränning. Då högarna läggs upp startar olika processer som värmer upp stacken, ofta till temperaturer på 50°C under det första dygnet. En vanlig ansats i litteraturen är att denna temperaturstegring beror på aerob nedbrytning. Arbetet ämnar undersöka om denna uppvärmning endast beror av mikrobiella aktiviteter. Hypotesen prövas genom kalorimetriska mätningar av effekt från prover av flis och simulering av första dygnets temperaturutveckling i ett program som programmeras under arbetes gång. I modellen så betraktas för enkelhets skulle flisstacken som en avlång figur med rektangulärt tvärsnitt. Figuren delas sedan in i lämpligt stora beräkningsceller. Problemet löses genom att iterativt räkna fram ett strömningsfält. Strömningsfältet och effekterna som räknas ut hålls sedan konstanta under ett tidssteg, 5-15min. Den magasinerade värmeenergin används sedan för att räkna fram en ny temperatur som så ger ett nytt strömningsfält och nya effekter. I modellen användes enbart explicita metoder eftersom de är snabbare och mycket enklare att programmera. Ett flertal experiment i kalorimeter genomfördes med olika prover av flis och torv. Prover med barkflis gav högst utslag. Den högsta effekten som uppmättes var 2,16W/kg TS. Då effekter av denna storleksordning användes som inre effektgenerering i programmet gav detta inte en temperatur ökning motsvarande sådana som uppmätts i verkligheten. Detta tyder på att mer än aerob nedbrytning krävs för att ge en temperatur på över 50°C. / Bioenergy is a major industry in Sweden and accounts for a significant part of the energy production. Bioenergy in the form of wood chips is stored in piles across the country awaiting combustion. When the piles are acumulated, various processes that heat the stack begin, often to temperatures of 50 °C during the first day. A common approach in the literature is that this temperature rise is due to the aerobic decomposition. This paper will investigate whether the microbial activity is the fundamental cause for warming. The hypothesis is tested by calorimetric measurements of power from the samples of wood chips and simulation of the first day's temperature development in a programme that was desinated. For simplicity the model considers an oblong wood chip pile with rectangular cross-section. The pile is then subdivided into appropriately sized calculation cells. The problem is solved by calculating a flow field iteratively. The flow field and the effects that are calculated is then static during one time step for approximately 5-15 minutes. The produced heat energy is then used to calculate a new temperature, which renders a new flow field and new powers. The model uses only explicit methods because they are faster and much easier to programme. Several calorimetric experiments were carried out with various samples of wood chips and peat. Samples of bark chips achieved the highest result. The highest power measured was 2.16 W / kg DM. When the effects of this magnitude were used as internal power source in the programme the temperature did not increase corresponding to those measured in reality. This suggests that more than aerobic decomposition is needed to reach a temperature above 50°C.

<p>This Degree Project has been done at Växjö University, department of bioenergy technology and discusses the released thermal power in wood pellets. The purpose of the project is to investigate if two new types of wood biofuels (pellets) are more or less reactive than the pellets previously investigated at Växjö University. To measure the released thermal power, an isothermal calorimeter with eight channels has been used. To see how the microbial activity is influenced, the pellets have been stored under various conditions with focus on temperature and metal.</p>

Storage of biomass is often associated with problems such as heat development, drymatter losses and reduction of fuel quality. The rise in temperature can potentiallycause a risk of self-ignition in the fuel storage. Moreover, emissions from storage pilescan cause health problems in the surrounding. The dry matter losses and reduction offuel quality can have economical effects. The aim of this thesis project is to developguidelines on how to store large amount of biomass at Vattenfalls heat and powerplants in an optimal way. Storage trials at Idbäckens CHP were done in order to studythe effect of storage on fuel quality, dry matter losses and temperature development.Two storage trials were performed over six weeks with waste wood chips and stemwood chips stored in about 4.5 m high outdoor piles. A trial over four days in whichwaste wood chips was placed on a heated surface was evaluated. A study to test thepossibility of using waste heat to dry waste wood chips was performed.Small but not negligible dry matter losses were observed in both of the piles of storedmaterial. The largest weekly losses were found during the first week of storage and adeclining behavior could thereafter be seen. The accumulated losses during six weeksof storage were 2.0 % and 1.7 % respectively, for waste wood and stem wood. Storageduring six weeks of waste wood and newly chipped stem wood did not cause anymajor deterioration of the fuel quality as such, beside the substance losses.No drying effect could be seen in the heated surface trial. The surface became warm,about 50°C, but it was not sufficient to dry the chips. The conclusion is that it is notpossible to dry large amount of chips on a heated surface with the design used hereand during four days.The overall conclusion is that in order to minimize the dry matter losses the materialshould be handled according to the LIFO (last in first out) principle. Wheneverpossible, try to purchase fuel that has been stored for a while since the more easilydegraded compounds has already been degraded through microbial activity. There is apossibility that the largest losses has already occurred. Furthermore, try also tocomminute the material (reduce the particle size) at the plant and as close in time tocombustion as possible.