Table 4.

Different nano-particles pretreatment applied to the biogas production and yield

S/N	Biomass	Pretreatment	Size	Concentration	Anaerobic digestion condition	Effect	Refs
1	Fresh raw manure	Fe3O4	7 nm	20 mg/L	37 °C for 40 Days	73% and 115.66% increase in biogas and methane yield, respectively	[204]
2	Sludge from UASB reactor	CeO2	192 nm	10 mg/L	30 °C for 40 Days	11% Increase in biogas production	[203]
3	Fresh raw manure	Co	28 nm	1 mg/L	37 °C for 40 Days	71% and 45.92% improvement in biogas and methane released, respectively	[204]
4	WAS	ZnO	140 nm	10 mg/g-TSS	35 °C for 40 Days	No effect	[202]
5	WAS	Fe2O3	< 30 nm	100 mg/g-TSS	37 °C for 40 Days	117% increase in methane production	[201]
6	AGS	CuO	37 nm	1.4 mg/L	30 °C for 83 Days	15% Decrease in methane production	[205]
7	Waste sludge	Ag	40 nm	184, 77 and 6.3 mg/kg	36 °C for 38 Days	No effect	[200]
8	WAS	TiO2	185 nm	150 mg/g-TSS	35 °C for 105 Days	No effect	[199]
9	Sludge from UASB	ZnO	850 nm	10 mg/l	30 °C for 40 Days	8% Decrease in biogas production	[203]
10	Sludge from UASB	ZnO	850 nm	1000 mg/l	30 °C for 40 Days	65% Decrease in biogas production	[203]