Occurrence, Fate, and Implications of Heavy Metals during Anaerobic Digestion: A Review

Abstract

Over the years, anaerobic digestion (AD) has evolved as a competent technology to retrieve energy potential from various organic substrates, including wastewater. However, the energy metabolisms of anaerobic microorganisms, biochemical reactions, and biogas production are affected by various parameters, including heavy metals. It is important to understand the interaction of heavy metals with anaerobes and their potential influence on the process to enhance energy potential. This review methodically outlines the occurrence and role of heavy metals in the AD process. Additionally, the repercussions of the most common heavy metals (i.e., Cu, Zn, Cd, Fe, and Ni) on each stage of AD (i.e., hydrolysis, acidogenesis, and methanogenesis) have been discussed. We found that traces of heavy metals can endorse anaerobic digestion, but inhibition increases with increasing concentration. Methanogenic archaea are more susceptible to heavy metal inhibition than hydrolytic and acidogenic archaea. An improved understanding and relevant intuition will help to promote biogas production along with heavy metal management.

A Review on the Anaerobic Co-Digestion of Livestock Manures in the Context of Sustainable Waste Management

“…Nevertheless, the composting of livestock manures comes with certain drawbacks that might impede the industrialization of composting technology. These drawbacks encompass the loss of N during the composting process, the heightened bio-availability of heavy metals, the diminished humus content of organic matter, the residue of antibiotics, and GHG emissions [42]. During composting, the transformation of substrates is influenced by the degradability of organic matter, a factor affecting the decomposition rate, gas emissions, process duration, and oxygen requirements.…”

Anaerobic co-digestion of sewage sludge with other organic wastes: A comprehensive review focusing on selection criteria, operational conditions, and microbiology

“…Therefore, the protein-rich wastes, such as pig and chicken manure and SHW, may lead to digester instability and failure [30,31]. In addition, the presence of heavy metals and some other toxic substances, which may present in industrial and agricultural wastes, can make the process instable [32,33]. Accordingly, in choosing a co-substrate for the AD process, care must be taken to ensure it does not contain toxic and inhibitory substances, helps to adjust the C/N ratio, and dilutes the inappropriate substances that may be present in the SS composition.…”

Revealing the Adverse Impact of Additive Carbon Material on Microorganisms and Its Implications for Biogas Yields: A Critical Review

“…Biochar could also present a harmful influence on microorganisms by releasing toxic elements directly into an anaerobic digestion solution; for example, biochar modified by KH 2 PO 4 could increase arsenic mobility in swine manure used as a biogas substrate [52]. This property of biochar, despite the quite good stabilization of heavy metals, such as Cr, Cu, Pb, and Zn, should be taken into account when trying to use waste containing high concentrations of heavy metals for energy purposes [199]. Further, it is worth paying attention to the feedstock used for the production of biochar, because if we want to use waste material by turning it into biochar directly created for carbon material additives, there may be a risk of releasing heavy metals from the biochar into the methane fermentation solution.…”