Now a days, different nanoparticles are used to enhance biogas production from anaerobic digestion of different wastes. i.e, Nickle, magnetite, maghemite, cobalt etc. If we talk about magnetite nanoparticles, the main purpose of adding magnetite nanoparticles is to provide Fe+2 and Fe+3 ions to microbes as a nutrient to increase their capacity to degrade the substrate and in turn enhance biogas production. If the purpose is to provide Fe+2 and Fe+3 ions to microbes, then why iron salts like FeCl3, FeCl2 or FeSO4 are not used instead of nanoparticles which are much cheaper than nanoparticles??
Hello Junaid Khalid,
I've been working on the same topic and during the course of my study, have studied many papers related to the enhancement of biogas using NPs. I have been lucky in finding some related studies in which FeCl3, NiCl2 and CoCl2 salts have been used for AD of cattle dung slurry. The salt and Fe NPs both improve the startup of anaerobic digestion however 10 mg/L FeCl3 produced 421 ml/g VS biogas whereas 20 mg/L Fe NPs produced 512 ml/g VS biogas. It means NPs are surely more beneficial than their salts and are worth every penny even if they are expensive. Now what actually is happening is unclear up till now. May be some shifts in microorganism community studies may help.
Regards Asad A. Zaidi
Agreed. But the question is why nanoparticles are preferred over their salts? We have seen that some commercial scale biogas plants in European countries specially in Germany, they are using magnetite nanoparticles instead of its respective salts for enhancing biogas production.
The insoluble metal oxides you mention have been implicated in direct interspecies electron transfer (DIET). Targeting syntrophy in this manner is a fairly recent AD optimisation strategy and appears valid from an engineeeing sense (as you yourself have pointed out) and has a convincing theoretical basis.
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