The influence of the lipid content in the mesophilic co-digestion of food waste with cow
manure was evaluated. An oily waste was used to simulate the lipid content of food
waste. Four reactors with four different concentrations of fat were run in parallel. An oily
effluent was added in pulses to simulate different fat contents. The control reactor R1
received no additional fat and R2, R3 and R4 received an increasing input of oil on days
49, 56 and 84 which corresponded to 6, 25 and 36% of Fat COD/total COD in R2, 9, 38
and 46% Fat COD/total COD in R3 and 13, 51 and 55% Fat COD/total COD in R4.
The performance was evaluated through the measurement of methane production,
effluent soluble chemical oxygen demand (COD), effluent volatile fatty acids, long chain
fatty acids (LCFA), total and volatile solids removal.
Using single factor analysis of variances (ANOVA) no statistical differences were
detected in the reactors performance, in terms of pulse response. The exception was the
LCFA adsorbed onto the solid matrix. Hence, R1 only presents palmitic acid (C16:0)
adsorbed onto the solid matrix and R2, R3 and R4 presents C16:0 along with stearic
(C18:0). The values detected of these two acids were always lower than 25 gCOD/kgTS
and no other significant differences were found between the four reactors performance.
The added fat was in this case, apparently retained in the reactor in the form of floating
yellowish aggregates. The results indicate that cow manure presents a good buffer
capacity to overcome the different lipids input of the FW.Fundação para a Ciência e Tecnologia (FCT) - SFRH/BD/18174/2004.Fundo Social Europeu (FSE
