الفهرس 
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Abstract
Depletion of conventional energy sources requires exploring new sources of energy, one of the most attractive and important source of energy is the biogas. Biogas is considered as a clean and renewable source of energy. Many different ways had been used to enhance the biogas production via numerous biological additives (crops residues, microbial culture, etc) and chemical additives (inorganic additives, etc) under different operating conditions. In our work we concern in enhancement of biogas production chemically using different nanoparticles as a catalyst to stimulate the microbial activity of the methanogenesis bacteria. Two different ways had been performed to prepare the nanoparticles; co-precipitation method used to prepare the ferrites (Fe3O4, CoFe2O4, NiFe2O4) nanoparticles, and liquid laser ablation in water used to prepare a nanoalloy of ablated stainless steel at different laser energies. The effect of addition 100 ppm of different nanoparticles to the biogas digester of working volume 800 ml, pH adapted at 7 and the digester temperature was adjusted to 37◦C had been investigated. As well as, a comparison between the biogas production from a substrate treated with chemically prepared nanoparticles and a substrate treated with the nanoalloy synthesized by ablation of stainless steel was discussed. We noticed that, Fe3O4, CoFe2O4, NiFe2O4 nanoparticles increase the biogas production comparing the control. Whereas, the lag phase of the bacterial growth and activity was shorten, and the cumulative gas volume at the incubation period increased to 221٪, 172٪ and 211٪ for CoFe2O4, NiFe2O4, and Fe3O4 respectively. Also it was noticed that the digester treated with nanoalloy synthesized by stainless steel ablated by laser at (26 mJ/pulse) produced more biogas than that treated with NiFe2O4 nanoparticles which may be attributed to several parameters including the different shape of the nanoalloy synthesized at (26 mJ/pulse). Additionally, the ablation mechanism of laser ablation of stainless steel in water at different laser energies was studied in terms of surface temperature and crater’s volume. We noticed that, the crater’s diameter, depth, and the temperature at the surface increase by increasing the laser energy. However, the melting time of stainless steel decrease by increasing the laser energy.