Very low hydrogen yields, less than 5 ml H2/gVS, were recorded
by Kobayashi et al. (2012) for the fractions ‘‘waste egg’’ and ‘‘waste
edible oil’’ in agreement with results obtained in the current study
from the fraction MFC. Similar results were also obtained by Boni
et. al. (2013) from slaughterhouse waste, by Okamoto et al.
(2000) from egg, lean meat, chicken skin and fat, and by Dong
et al. (2009) from oil, fat and lean meat, materials comparable to
the type of waste found in the MFC fraction in this study. On the
contrary, the very low hydrogen productions for MFC are not comparable
with those of the fractions ‘‘animal kitchen waste’’ (30 ml
H2/gVS) and ‘‘uneaten animal kitchen waste’’ (40 ml H2/gVS) found
by Kobayashi et al. (2012). Biological degradation of lipids and proteins
in fermentative conditions leads to very low hydrogen yields
as indicated by Okamoto et al. (2000) and Dong et al. (2009) and
confirmed by the results obtained in this study. The difference with
data obtained by Kobayashi et al. (2012) can be explained by the
presence of 6.0% and 11.4% (VS basis) of biodegradable carbohydrates
in the two fractions ‘‘animal kitchen waste’’ and ‘‘uneaten