and SOL fraction balancing their decrease by mineralisation and
explaining the observed relative stability of the fractions after
13 days of composting (Sánchez-Monedero et al., 1999; Said-Pullicino
et al., 2007; Francou et al., 2008).
The organic matter evolution during composting was thus consistent
with previous observations in larger reactors and even in
full-scale composting plants. However in industrial plants, compost
screening at the end of the thermophilic phase separates the
most stabilised organic matter from the coarsest non degraded
fractions mainly composed of CEL and LIC fractions (Doublet
et al., 2011) and accentuates the decrease of these two fractions
in the final screened compost. In our case, no screening was realized
because of the initial rather small size of the organic mixture
and the low amounts of organic matter in the small-scale reactors.
It could thus be a limitation to the simulation of the industrial
composting process at small-scale, but it was difficult to evaluate
because the screening effect has been rarely studied in the literature.
Another possible limitation of the composting simulation in
laboratory devices is the lack of colonization by macrofauna observed
on full-scale composting plants although the influence of
macrofauna on organic matter evolution during maturation remained
poorly documented.
4. Conclusions