Will Membranes Break Barriers on Volatile Fatty Acid Recovery from Anaerobic Digestion?

Abstract

The conversion of organic waste into value-added chemicals provides a sustainable pathway toward a circular economy, but anaerobic digestion (AD) as an established technology has faced great challenges primarily due to the low value of its primary productbiogas. Recent developments on arrested methanogenesis allow the AD process to be rewired to suppress methanogenesis and promote the production of higher valued volatile fatty acids (VFAs). However, the separation and recovery of VFAs from the mixed reactor constituents (microbes, salt, and organic solids), remains a challenge. Membrane-based separation processes are showing increased promise compared to other methods, as recent studies reported high yield, high selectivity VFA recovery with low energy consumption and reactor footprint. However, competing membrane processes have not been quantitatively reviewed or compared, making it difficult to understand the current state-of-the-art. This study provided the first such analysis, comparing nanofiltration (NF), reverse osmosis (RO), pervaporation (PV), membrane contactors (MC), and membrane distillation (MD) for VFA separation and recovery. The study offers a comprehensive characterization of the different membrane’s selectivity and permeability under different conditions and compares them side-by-side using normalized measures. In addition, the energy demand and fouling potential were also analyzed. New opportunities such as mixed matrix pervaporation membrane, antifouling electroactive membrane, solar-heating membrane distillation, and integrated processes were also explored to provide insights on technology advancement and synergistic benefits.

[Retracted] Construction of the Reverse Resource Recovery System of e‐Waste Based on DLRNN

“…e study in [13] found that the first person who is different from the forward logistics network, especially the location of the recycling center, especially the distributor, needs to accept many and scattered logistics sources, and its location is characterized by "many to few" or even "many to one," and the traditional facility location model has been improved and perfected. e study in [14] summarized some basic characteristics of the reverse resource network system, including high complexity of network, complex diversity of targets, imbalance between supply and demand, and "from more to less" characteristics.…”

Enhanced volatile fatty acids accumulation in anaerobic digestion through arresting methanogenesis by using hydrogen peroxide

“…Purification and concentration of a product are critical to its value and the overall economics of the process. VFAs may be separated from a waste stream by using membrane technologies driven by either heat (e.g., membrane distillation) or electricity (e.g., electrodialysis) (Aktij et al, 2020; Zhu et al, 2020). The application of the produced VFAs that does not need separation, for example as a carbon source for biological nutrient removal, should also be explored.…”

Volatile Fatty Acid Production from Organic Waste with the Emphasis on Membrane-Based Recovery

“…The membrane contactor uses a hydrophobic porous membrane to separate the two aqueous phases on opposite sides of the membrane, avoiding mixing (Figure 2) [14,106]. The commonly used polymers in membrane contactors, selected based on their properties, such as mechanical stability, chemical resistance, and hydrophilic or hydrophobic characteristics, are polypropylene (PP), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE) [107].…”

“…The term pervaporation represents the combination of the "permeation" and "evaporation" processes [105]. Pervaporation membranes can also be broadly categorized into two groups based on the target molecule to be recovered: hydrophilic pervaporation membranes ensure rapid water transport, allowing for effective dehydration, whereas organophilic pervaporation membranes provide better transport of organic compounds, making them suitable for VFA recovery [106]. The hydrophilic membrane is made of polyvinyl alcohol (PVA) [123] and sulfonated polybenzimidazole (SPBI) [124].…”