The processing of food waste along with animal manure through anaerobic digestion (AD) is a popular waste management strategy. However, there is the concern that with the proliferation of AD the management of its nutrient-rich effluent, known as digestate, becomes a challenge. Current digestate management practices not only present environmental risks, but also issues related to the seasonality of field spreading and the storage and transportation of large volumes of material. The integration of the AD process with thermochemical conversion (TC) could help reduce some of these issues. The production of biochar from materials already available in the digester setting, such as the solid fractions of digestate and dairy manure, could be used to recover the phosphorus present in the liquid fraction of the effluent. The resulting phosphate enriched biochar will finally be applied as an alternative fertilizer. Both solid digestate and solid manure biochar were produced through pyrolysis at three different temperatures (500, 800, and 1000˚C). To assess the suitability of biochar as a soil amendment, we performed a complete characterization of the material based on the standard proposed by the International Biochar Initiative (IBI). For evaluating biochar as an adsorption medium, phosphate adsorption was tested using a synthetic solution and the effluent from the actual anaerobic co-digestion process. The environmental benefits and drawbacks of combining these two technologies were evaluated using life cycle assessment (LCA) methodology. Results showed that the amount of solid digestate biochar produced is sufficient to adsorb approximately 20% of the total phosphate present in the liquid fraction of the digestate. While, solid manure biochar has the potential to fulfill the site requirements to adsorb most of the phosphate in a synthetic solution but not actual digestate. The LCA results show that the combination of technologies could reduce the impacts to freshwater, only if most of the phosphate present its recovered into the biochar.
Library of Congress Subject Headings
Sewage--Purification--Anaerobic treatment; Biochar--Environmental aspects; Sewage--Purification--Phosphate removal
Department, Program, or Center
Rodriguez Alberto, Diana Carolina, "Sustainable food waste management through the integration of anaerobic digestion and thermochemical processes" (2022). Thesis. Rochester Institute of Technology. Accessed from
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