Abstract
Various methods are available for the recycling and treatment of cheese whey with the objective of enhancing sustainable manufacturing. Currently, an increasing interest is on the anaerobic bioremediation of whey with the added benefit of generating electricity in microbial fuel cells (MFCs). Since microorganisms are the biocatalysts in MFCs, their initial density plays a paramount role both towards electricity generation and bioremediation. Hence, this study was aimed at evaluating the effects of anode enrichment with microorganisms on power generation. Anodes were enriched with microorganisms inherent to whey for periods of 30 and 90 days before their application in wheypowered MFCs. At the termination of reactor cycles, the one-month-old pre-incubated anodes had 0.13% coulombic efficiency (e cb ), 88.3% total chemical oxygen demand (tCOD) removal efficiency and maximum power density (P d ) was 29.1 ± 4.9 W/m 2 , whereas the three-month-old pre-incubated anode had e cb = 80.9 and 92.8%, tCOD removal and maximum P d was 1800 ± 120 W/m 2 . Two non-acclimated anodes used as control in separate setups exhibited 0.17% coulombic efficiency, 71.6% tCOD removal and maximum P d of 30.9 ± 4.2 W//m 2 . Microscopy analyses revealed different morphologies on anode surfaces depending on the length of the enrichment periods and further molecular analyses of electrode communities indicated up to 92% identity to various species from the Lactobacillus genus. This study established that, an initial acclimation step ahead of MFC setups significantly improved the performance of reactors utilising live cheese whey as fuel. Key words : Cheese whey, microbial fuel cell, enrichment, alternative energy, bioelectricity, bioremediation.
Highlights
Large volumes of cheese whey generated annually pose a serious environmental threat due to its high total chemical oxygen demand
Since microorganisms are the biocatalysts in microbial fuel cells (MFCs), their initial density plays a paramount role both towards electricity generation and bioremediation
Two non-acclimated anodes used as control in separate setups exhibited 0.17% coulombic efficiency, 71.6% total chemical oxygen demand (tCOD) removal and maximum power density (Pd) of 30.9 ± 4.2 W//m2
Summary
Large volumes of cheese whey generated annually pose a serious environmental threat due to its high total chemical oxygen demand (tCOD). 6-8 x 107 t of whey were produced on a global scale (Stevens and Verhé, 2004; Peters, 2005). The booming cheese industry has fostered research toward several practical strategies to mitigate the impact of whey discharge into the environment. The cost of recovery of whey constituents may not necessarily be economically profitable (Peters, 2005). Excessive application of whey to farm lands leads to accumulation of elements such as phosphorus and potassium that cause serious pollution both to ground and surface water. Excess minerals in the soil change the delicate salt balance for crops leading to growth abnormalities (Watson et al, 1977)
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