Air permeability of compost as related to bulk density and volumetric air content

Tjalfe G. Poulsen*, Per Moldrup

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Compost air permeability controls air flow through compost during composting or when using compost as biofilter material. Air permeability is therefore an important characteristic of compost. The relationships between air permeability (ka) in compost and compost dry bulk density (ρb), gravimetric water content (ω), and volumetric air content (ε) was investigated for two types of composts. The composts used were produced from a digested sewage sludge-straw mixture and from garden waste and measurements were conducted on sieved and repacked 100 cm3 compost samples. Results showed a linear relation between log(ka) and ρb at constant values of ω for both composts, indicating an exponential relationship between ka and ρb. The slopes of these relationships generally became more negative with increasing ρb. The results further showed a linear relationship between log(ka) and log(ε) for both composts as also often observed for soils. It was observed that the log(ka) and log(ε) relationships for the garden waste compost all intercepted at the same location despite having very different slopes. This means that it is possible to predict the entire ka -ε relationship using only one measurement of corresponding (ka, ε) for garden waste. It was not possible to determine whether this was also the case for the sewage sludge compost due to difficulties in sample preparation at low and high water content.

Original languageEnglish
Pages (from-to)343-351
Number of pages9
JournalWaste Management and Research
Issue number4
StatePublished - Aug 2007
Externally publishedYes


  • Air permeability
  • Air-filled porosity
  • Compost
  • Dry bulk density
  • Garden waste
  • Sewage sludge
  • Wmr 1101-6


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