Comparison of Free Air Space Test Methods |
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| Authors: | Danlin Su Daryl McCartney Qunfeng Wang |
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| Institution: | 1. Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Alberta, Canada;2. University of Manitoba, Winnipeg, Manitoba, Canada |
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| Abstract: | Air space within a compost material can be measured using several methods. This project, focusing on bulking materials, compared five air space (AS) test methods: particle density (PD) method, modified PD (MPD) method, air pycnometer (AP) method, modified air pycnometer (MAP), and a quick method. There were significant differences between results obtained using the different tests. PD and MAP methods yielded results representing total air space (TAS), while the AP and MPD methods yielded values which were thought to represent free air space (FAS). The Quick method resulted in AS values dramatically different from the other methods, and further development and validation of the method was recommended. The MPD was found to be unsuitable for samples containing fine material, such as biosolids. Both the PD and the MAP tests were precise; however, results were biased to TAS values. This was illustrated through the similarity between AS values measured by the two tests and the predicted TAS. The MAP was the simplest method and was recommended for use with compost samples. Strong linear correlations were observed between TAS and bulk density (BD; kg m?3: TAS = 100 – 0.096*BD (R2=0.98) for PD and 100 – 0.090*BD (R2=0.90) for MAP. The effect of storage time on FAS, TAS, and moisture content was examined in this study. Straw samples were stored for a month and showed no change in the physical properties. Woodchip samples were stored for over 5 months. A slight change in both FAS and TAS was observed, but the differences were minor compared to variations induced by different particle sizes and moisture levels. |
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