(94f) A Systematic Study of Co-Digestion of Fishery Sludge and Food Waste for Biogas Production

The global population is projected to reach 8.5 billion by 2030 and 9.7 billion by 2050 (UN DESA, 2022). This growth will be accompanied by a projected 40–75% increase in total protein demand. Compared to other animal production systems, aquaculture has the greatest overall efficiency (D’Abramo, 2021). As a result, intensification has emerged as a promising pathway for increasing aquaculture production. However, aquaculture intensification leads to increased demand for feed and increased waste production. In terms of waste, only about 30% of the nutrients supplied to the farmed aquaculture animals are converted to product, while the rest is excreted as soluble nutrients or settleable solids (e.g., ammonia and feces, respectively) (Chiquito-Contreras et al., 2022). The waste produced by aquaculture farms is often discharged into the environment to maintain water quality in the aquaculture systems. Such waste disposal practice can cause eutrophication of the surrounding areas of fish farms and threaten the sustainability of local ecosystems (Bannister et al., 2016; Pędziwiatr, 2017). Therefore, sustained intensification of aquaculture production must be coupled with a sufficient supply of sustainable nutrients (feed) and efficient waste management. If feed can be produced from waste, it solves two problems with a single solution.

Previously, we have proposed to convert aquaculture waste into single cell protein (SCP) as aquafeed supplements via a two-step process: 1) utilizing commercially proven anaerobic digestion (AD) to produce biogas from fishery sludge (FS); 2) cultivating microbial biomass as feedstock for SCP production. In this work, we systematically study co-digestion of fishery sludge (FS) and food waste (FW) for optimizing biogas production. Previous studies have found that carbon/nitrogen ratio (C/N ratio) and percentage solid content (PSC) of the feed are two of the most important factors that affect AD operation and performance. The optimal C/N ratio for biogas production is about 15 - 25, while the optimal PSC is 8% - 12% (Linville et al., 2015). FS usually has a low C/N ratio (~4-12) and low PSC (~0.5-5%), while FW in general has a high C/N ratio (~18 - 30) and high PSC (~ 15-25%)(Shi et al., 2018). It has been reported that co-digesting low C/N waste with high C/N waste often produces significantly improved biogas yield and productivity (Angelidaki and Ellegaard, 2003; Mshandete et al., 2004; El-Mashad and Zhang, 2010). Therefore, in this work, we perform a comprehensive experimental study to determine the optimal FS/FW feed ratio and PSC to optimize AD performance. The AD performance of different combinations of FS/FW ratios and PSC values were assessed through multiple metrics, including biogas yield, biogas productivity, BOD reduction rate, COD reduction rate, etc. A response surface model was constructed to capture the impacts of operation conditions on biogas production performance, which serves as the model to guide the biogas production step in the overall waste-to-feed (W2F) application.

References:

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Bannister, R. J., Johnsen, I. A., Hansen, P. K., Kutti, T., and Asplin, L. (2016). Near-and far-field dispersal modelling of organic waste from Atlantic salmon aquaculture in fjord systems. ICES Journal of marine Science 73, 2408–2419.

Chiquito-Contreras, R. G., Hernandez-Adame, L., Alvarado-Castillo, G., Martínez-Hernández, M. de J., Sánchez-Viveros, G., Chiquito-Contreras, C. J., et al. (2022). Aquaculture—Production System and Waste Management for Agriculture Fertilization—A Review. Sustainability 14, 7257.

D’Abramo, L. R. (2021). Sustainable aquafeed and aquaculture production systems as impacted by challenges of global food security and climate change. J World Aquac Soc 52, 1162–1167.

El-Mashad, H. M., and Zhang, R. (2010). Biogas production from co-digestion of dairy manure and food waste. Bioresour Technol 101, 4021–4028. Available at: http://www.sciencedirect.com/science/article/pii/S0960852410000842.

Linville, J. L., Shen, Y., Wu, M. M., and Urgun-Demirtas, M. (2015). Current state of anaerobic digestion of organic wastes in North America. Current Sustainable/Renewable Energy Reports 2, 136–144.

Mshandete, A., Kivaisi, A., Rubindamayugi, M., and Mattiasson, B. (2004). Anaerobic batch co-digestion of sisal pulp and fish wastes. Bioresour Technol 95, 19–24.

Pędziwiatr, P. (2017). Aquaculture waste management. Acta Innovations, 20–29.

Shi, S., Li, J., Guan, W., and Blersch, D. (2018). Nutrient value of fish manure waste on lactic acid fermentation by Lactobacillus pentosus. RSC Adv 8, 31267–31274.

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