Abstract

Large-scale storage of sawdust. Report No. 10. The aim of this study was to evaluate the influence of storage in loose and compacted piles on the quality of the sawdust as a fuel and as raw material for pellets production. The analysed quality parameters were: moisture content (MC), heating value, contents of ash, klason lignin and extractives. Other analyses included temperature development, dry matter loss and fungal activity. The storage period was 10/5/2000 – 28/1/2001. Sawdust from soft wood species was used to build an experimental pile (42x25x8 m) with two halves containing compacted and loosely piled sawdust. In each half, two sections, marked with 5 sampling points/section, were samples after 4 and 8.5 months of storage. Ambient temperature was around 20°C at the time of sawdust piling. In the compacted part, temperature rose continuously to a maximum of 65°C after about two months of storage and remained at this level for the rest of the storage period. Similar trend was obtained in the non compacted part. The average initial MC of the material was 54% (wet basis). After 4 months of storage the MC decline marginally, due to the high temperature inside the pile and a relatively dry summer. By the end of the storage trial, an average rise in MC ( 9 %) was measured in both parts of the pile. This was probably due to the heavy rains during the autumn. Initial fungal spore counts reflected a moderate activity in the material. The total spore counts and the count of viables were declined during storage reaching a very low level by the end of the trial, especially in the compacted section. Dry matter losses were low in both sections of the pile. Most of the loss, particularly in the compacted section, was measured after four months of storage (around 1.5 % dry weight). Total dry matter loss in the non compacted sawdust was 2.3 % (dry weight). The gross calorific values of the material showed minimal changes during storage. The average value was about 20.2 MJ/kg (dry weight) in both parts of the pile. The net calorific values declined from 16 down to 14.8 MJ/kg, mainly due to the rise in MC in both parts of the pile. Changes in ash contents during storage were marginal. The concentrations of klason lignin in the material before storage was around 28-30 % (dry weight basis).The lignin content was essentially unchanged after storage in the compacted part, while it increased to an average of 31.6 % in the other part. This could be explained by the higher dry matter loss in the non compacted material. An increase in the contents of alcohol-soluble extractives was measured in the sawdust after storage, especially in samples taken from the warmest area in the pile. The content increased from 2 % (dry weight) to 6.13% and 4.24% in the compacted and the non-compacted material respectively. Changes in the extractives in the cooler parts of the pile were minimal. This may indicate that the apparent increase in the extractives was caused by the thermal degradation of otherwise insoluble compounds

Keywords

Sawdust; wood fuel; moisture content; outdoor storage; heating value

Published in

Rapport - Institutionen för bioenergi
2005, number: 11
Publisher: Inst. för bioenergi

SLU Authors

• Jirjis, Raida

  • Department of Energy and Technology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Renewable Bioenergy Research


Permanent link to this page (URI)

https://res.slu.se/id/publ/9044