A comprehensive model of anaerobic bioconversion of complex substrates to biogas

TLDR

The authors developed a dynamic model of anaerobic degradation and codigestion of diverse waste streams, building on the Angelidaki et al. 1993 framework. The model represents substrates by their carbohydrate, lipid, and protein fractions, tracks intermediates such as VFAs and LCFAs, and incorporates 2 enzymatic hydrolytic steps, 8 bacterial steps, 19 chemical compounds, and detailed pH and temperature dynamics, with free ammonia, acetate, VFA, and LCFA as key modulators. The model successfully simulated dynamic shifts in substrate composition, was validated in lab‑scale reactors with manure plus glycerol trioleate or gelatin, and confirmed in a full‑scale plant codigesting manure with proteinous wastewater and bentonite‑bound oil.

Abstract

A dynamic model describing the anaerobic degradation of complex material, and codigestion of different types of wastes, was developed based on a model previously described (Angelidaki et al., 1993). In the model, the substrate is described by its composition of basic organic components, i.e., carbohydrates, lipids, and proteins, the concentration of intermediates such as volatile fatty acids and long-chain fatty acids, and important inorganic components, i.e., ammonia, phosphate, cations, and anions. This allows dynamic changes of the process during a shift of substrate composition to be simulated by changing the input substrate data. The model includes 2 enzymatic hydrolytic steps, 8 bacterial steps and involves 19 chemical compounds. The model also includes a detailed description of pH and temperature characteristics. Free ammonia, acetate, volatile fatty acids, (VFA) and long-chain fatty acids (LCFA) constitute the primary modulating factors in the model. The model was tested with success in lab-scale reactors codigesting manure with glycerol trioleate or manure with gelatin. Finally, the model was validated using results from a full-scale biogas plant codigesting manure together with a proteinous wastewater and with bentonite-bound oil, which is a waste with high content of lipids. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 363–372, 1999.