Abstract:
One of the emergent challenges in meat processing industries is producing biogas with animal
waste associated with high-fat content. This research attempts to find out the effect of animal fat (poultry)
on anaerobic co-digestion and process optimization by means of food waste as the co-substrate and cow dung
(CD) as the inoculum by considering the trend in biomethane production at different quantities of animal
fat. A series of batch fermentations were carried out in a lab-scale batch reactor (>500mL) based on the
VDI 4630 protocol. One control batch experiment was conducted with inoculum alone and five other dif
ferent co-digestion experiments were implemented in triplicates with the proportions of rendered chicken fat
emulsion:food waste at 0:100, 25:75, 50:50, 75:25, and 100:0 (w/w) in the presence of inoculum. The propor
tion of substrates to inoculum was 100:300 (w/w) in all the co-digestion experiments. Each experiment was
implemented for four (4) days continuously under mesophilic (35°C) conditions and at 200rpm mixing speed
by ensuring continuous mixing. Experimental data proved that the highest total biogas potential is achiev
able with co-digestion experiments incorporated with high quantities of food waste (0:100, 25:75), though a
sudden process failure of acidification occurred eventually, along with minimal organic material conversion
rate (mL/gCODremoval). Experiments utilizing relatively high quantities of fat emulsion showed relatively
low total biogas production without any sudden process failure and with a high organic material conver
sion rate. The highest pH reduction with high COD and volatile solid removal efficiencies were represented
by high-quantity food waste incorporated batch experiments. The most viable co-digestion proportion was
50:50 (w/w) among the batch experiments incorporated by food waste with regard to the limited pH drop of
the feedstock mixture. Another satisfactory fermentation was the co-digestion of animal fat associated with
inoculum (cow dung) without using food waste (100:0), which produced continuous biomethane production
with a high rate of organic material conversion. Continuous mixing and stable temperature at 35°C may
optimize gas production efficiency, and pH adjustment will be a further optimization technique for achieving
the highest possible biomethane production.
