Multicomponent nanoparticles as means to improve anaerobic digestion performance.

Sufficient quantity of trace metals is essential for a well performing anaerobic digestion (AD) process. Among the essential trace elements in active sites of multiple important enzymes for AD are iron and nickel ions. In the present study, iron and nickel in the form of Fe2O3 and NiO were coated on TiO2 nanoparticles to be used in batch and continuous operation mode. The effect of TiO2, Fe2O3-TiO2, and NiO-TiO2 nanoparticles on each step of AD process was assessed utilizing simple substrates (i.e. cellulose, glucose, acetic acid, and mixture of H2-CO2) as well as complex ones (i.e. municipal biopulp). The hydrolysis rate of cellulose substrate increased with higher dosages of the coated TiO2 with both metals. For instance, the hydrolysis rate was increased up to 54% at Fe2O3-TiO2 and at a concentration of 23.5 mg/L for NiO-TiO2 it was increased up to 58%, while higher dosage suppressed the hydrolytic activity. Experimental results revealed that low dosages of NiO-TiO2 increased the accumulated methane production up to 24% probably by increasing the enzymatic activity of acetoclastic methanogenesis. NiO-TiO2 showed positive effect on batch and continuous AD of biopulp and improved methane yield up to 8%.

Application of nano-structured materials in anaerobic digestion: Current status and perspectives.

Nanotechnology is gaining more attention in biotechnological applications as a research area with a huge potential. Nanoparticles (NPs) can influence the rate of anaerobic digestion (AD) as the nano-sized structures, with specific physicochemical properties, interact with substrate and microorganisms. The present work has classified the various types of additives used to improve the AD processes. Nanomaterials as new additives in AD process are classified into four categories: Zero-valent metallic NPs, Metal oxide NPs, Carbon based nanomaterials, and Multi-compound NPs. In the following, application of nanomaterials in AD process is reviewed and negative and positive effects of these materials on the AD process and subsequently biogas production rate are discussed. This study confirms that design and development of new nano-sized compounds can improve the performances of the AD processes.