Coffee pulp represents 40 % of the total weight of the berry. Pressing this
by-product for further utilization yields a sugar-rich effluentjuice which
has been considered as raw material for the production of biogas.
Experiments with one- and two-phase anaerobic systems wereperformed.
Loading ratesfor the one-phase methanogenic reactor rangedfrom 0,5 to
3 g Volatile Solids liter-l day-l, with hydraulic retention times of 10
days. When separated acidogenic and methanogenic digesters were used,
thefirst phase was operated at 0.5 days HRT and a load of 56 g Volatile
Solids liter-l day-l, while the retention times for the second phase
rangedfrom 10 to 5 days, with loads of 0,6 to 2.4 g Volatile Solids liter-l
day-l.
It was concluded,from the results of the experiments, that a two-phase
anaerobic digestion system is better for treating coffee pulp juice than a
one-phase unit. Hydraulic retention times of 0.5 daysfor the acidogenic
phase and 8 daysfor the methanogenic seem to produce stable conditions,
when daily Volatile Solids loads are of the order of 55 g liter-l and
J'8 g liter-l, respectively.