Determining C/N ratios for typical organic wastes using biodegradable fractions

Belén Puyuelo, Sergio Ponsá, Teresa Gea, Antoni Sánchez

Research output: Contribution to journalArticleResearchpeer-review

87 Citations (Scopus)


It is well established that an optimal aerobic and anaerobic microbial metabolism is achieved with a C/N ratio between 20 and 30. Most studies are currently based on chemically-measured carbon and nitrogen contents. However, some organic wastes can be composed of recalcitrant carbon fractions that are not bioavailable. To know the biodegradable C/N ratio, two different methods to determine the aerobic and anaerobic biodegradable organic carbon (BOC AE and BOC AN) are proposed and used to analyze a wide variety of different organic samples. In general, raw wastes and digested products have more amount of BOC AE. On the contrast, the samples collected after an aerobic treatment have higher content of BOC AN. In any case, all the BOC fractions are lower than the total organic carbon (TOC). Therefore, the C/N ratios based on BOC are always lower than the total C/N ratio based on the TOC measure. The knowledge of the real bioavailable C/N ratio is crucial for the biological treatments of organic materials. To reduce the test time necessary for BOC determination, the values of BOC for all the samples obtained at different times were compared and correlated with the final BOC. A method that allows for the determination of BOC AE in 4d is proposed. In relation to the anaerobic assay, the biogas potential calculated after 21 and 50d was positively correlated with the final potential defined after 100d of assay. © 2011 Elsevier Ltd.
Original languageEnglish
Pages (from-to)653-659
Publication statusPublished - 1 Oct 2011


  • Bioavailability
  • Biodegradable organic carbon (BOC)
  • Biogas potential
  • C/N ratio
  • Respiration index
  • Total organic carbon (TOC)


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