Bränslekvalitet och arbetsmiljö vid lagring och hantering av grotstockar
Jirjis, Raida; Nordén, Berndt
Most of wood fuel supply systems involve procurement, storage, chipping and transport. What happens during this chain of handling affects both fuel quality and the price of the fuel. An optimal supply system has to meet the demands of end user, fulfil quality criteria and, moreover, maintain an acceptable working environment. Densifying logging residues into bundles (or composite residue logs, CRL) can be an alternative method to improve wood fuel transport and handling properties. This work reports on storage effect on CRLs weighing around 400-600kg, made of green and summer-dried residues using two prototypes bundling machines Fiberpac and Wood Pac. The former presses residues into a continuous long bundle, 75cm in diameter, and cut it at a length of 3m. Wood Pac rotates and presses logging residues into a log like unit with the same dimension as Fiberpac-CRLs. Working environment related to microbial presence in the surrounding air during chipping was assessed. Average moisture content was lower in all the CRLs by the end of the storage (February-August) in covered stacks. Higher dry matter losses were measured in CRLs made from green residues compared to the summer-dried ones. The average loss was around 1% per month in all treatments. Microbial activity was generally higher in CRLs made from green residues irrespective of the machine used. Changes in heating values and ash content were marginal in all the treatments. Ash contents were higher in the CRLs made from green residues than the summer-dried material. Loss of needles during the summer is the main reason since needles normally have high contents of minerals. The concentrations of air-borne fungal and bacterial particles in air samples taken during the chipping and handling of the CRLs were at levels that does not constitute a health risk for the workers.
Rapport / Institutionen för bioenergi, SLU
Publisher: Institutionen för bioenergi, Sveriges lantbruksuniversitet
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