Resumen:
In this study, a systematic comparison between methanogenic and acidogenic potential tests of five waste streams from urban and agro-industrial origin was investigated. Methanogenic potential tests were performed under neutral pH (7.0) and thermophilic temperature (55 degrees C). Additionally, acidogenic potential tests consisted of mono-fermentation tests at acidic pH (5.5) and co-fermentation tests performed at alkaline pH (9.0), under thermophilic temperature (55 degrees C). The methanogenic yield increased up to 0.54 gCH(4) g(-1) CODfed while the acidogenic yield ranged within 0.04-0.24 g VFA g(-1) CODfed. The VFA (volatile fatty acids) yield was boosted when adding co-substrates that complemented the optimal C/N balance, i.e. 0.27-0.36 gVFA g(-1) CODfed. Herein, highest total volatile fatty acid (tVFA) concentration was attained by microalgae biomass (MB), with 8769 mg COD L-1. During mono-fermentation tests under acid pH, butyric acid was promoted as main fermentation product, which varied between 1526 and 6114 mg COD L (-1), whereas shifting to alkaline pH in co-fermentation tests promoted acetic production, from 3387 to 5415 mg COD L-1. The results of the current research revealed a significant potential of organic waste to enrich the carboxylic platform (e.g. acetic and butyric acids), which have higher industrial applicability and economic potential than methane. [GRAPHICS] .
