Publication
Impact of metallic nanoparticles on anaerobic digestion: A systematic review.
Zhu Xiaowen, Blanco Edgar, Bhatti Manni, Borrion Aiduan
This systematic review examines how metallic nanoparticles affect anaerobic digestion (AD), a major waste treatment technology for biodegradable materials. The authors synthesized findings from 2010–2019 literature on the impacts of metallic nanoparticles on both hydrogen and methane production during AD processes.
The review found that trace-element-based nanoparticles (iron, cobalt, nickel) generally enhance both hydrogen and methane production by improving gas yields, effluent quality, and process efficiency. These nanoparticles function as nutrient sources and co-factor providers that stimulate anaerobic microorganism activity and enzyme synthesis. Non-trace-element nanoparticles promoted AD performance through different mechanisms—providing active sites for microorganisms and absorbing inhibitory compounds. A key finding was that the methane-production phase showed greater sensitivity to nanoparticle additions than the hydrogen-production phase.
The review addresses how the increasing industrial use of metallic nanoparticles introduces them into waste streams, where they may significantly impact AD efficiency. Understanding these effects is relevant for optimizing AD systems in waste management and biofuel production applications.
Abstract
Anaerobic digestion (AD) is one of the most energy-efficient waste treatment technologies for biodegradable wastes. Owing to the increasing trend of metallic nanoparticle applications in industry, they are ubiquitous to the waste streams, which may lead to remarkable impacts on the performance of the AD process. This review addresses the knowledge gaps and summarises the findings from the academic articles published from 2010 to 2019 focusing on the influences on both AD processes of biochemical hydrogen-generation and methane-production from selected metallic nano-materials. Both qualitative and quantitative analyses were conducted with selected indicators to evaluate the metallic nanoparticles' influences on the AD process. The selected metallic nanoparticles were grouped in the view of their chemical formulations aiming to point out the possible mechanisms behind their effects on AD processes. In summary, most metallic nanoparticles with trace-element-base (e.g. iron, cobalt, nickel) have positive effects on both AD hydrogen-generation and methane-production processes in terms of gas production, effluent quality, as well as process optimisation. Within an optimum concentration, they serve as key nutrients providers, aid key enzymes and co-enzymes synthesis, and thus stimulate anaerobic microorganism activities. As for the nano-additives without trace-element base, their positive influences are relied on providing active sites for the microorganism, as well as absorbing inhibitory factors. Moreover, comparisons of these nano-additives' impacts on the two gas-production phases were conducted, while methane-production phases are found to be more sensitive to additions of these nanoparticles then hydrogen-production phase. Research perspectives and research gaps in this area are discussed.