The calculation of the anaerobic biodegradability requires the knowledge of the COD of the organic waste considered. Unfortunately, standard COD measurements are not available for solid wastes. In addition, sample processing generally requires a drying step (for TS and VS assessment for instance). What is shown here is that important amounts of COD might be lost upon drying (around 30% in the case of spent apples). We propose an alternate method based on the separation of the waste in two fractions: water soluble (WS) and non water soluble (NWS, particulate). The two fractions have been characterized individually and both the COD and the biodegradability could be assessed with a greater accuracy. For spent apples, the biodegradability of the NWS fraction is much lower than that of the WS fraction (36.6% vs. 95.2%), and can be well predicted from a previously established model based on the measurement of the cellulose and lignin fractions.

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