EFFECT OF CoCl2, NiCl2 AND FeCl3 ADDITIVES ON BIOGAS AND METHANE PRODUCTION

Anaerobic digestion is a biological process used to convert organic wastes into biogas and a stable biofertilizer for agricultural applications as environmentally friendly products. The produced biogas is used as an alternative renewable energy source. The objective of this study was to investigate the effect of the additives CoCl2, NiCl2 and FeCl3 on biogas and methane yield from fresh raw manure. A series of laboratory experiments using 2 L biodigesters were carried out in batch anaerobic mode. Each biodigester was fed with 1600 ml of slurry with individual addition of 1 mgL-1 CoCl2, 1 mgL-1 NiCl2 and 10 mgL-1 FeCl3. All of the treatments were carried out by triplication for the statistical analysis purposes, and analyzed using MStat-C software v.2.1. The results showed that the highest biogas and methane production (p<0.05) were achieved with the addition of 1 mgL-1 NiCl2 to the slurry, which were 507.9 and 279.3 ml g-1 VS, respectively; after 50 days of hydraulic retention time (HRT) compared with other additives. Furthermore, the biogas and methane production were in the order of NiCl2>CoCl2>FeCl3 in comparison with the control. These results indicated that, the addition of aforementioned salts increased biogas yield by 1.44, 1.33 and 1.17 times the biogas yielded with the control, respectively. Moreover, the methane yield was increased by 1.55, 1.43 and 1.21 times the methane yielded with the control, respectively.