Osvaldo Romero

Thermo-chemical pre-treatment to solubilize and improve anaerobic biodegradability of press mud

Different pre-treatment severities by thermo-alkaline conditions (100°C, Ca(OH)2) on press mud were evaluated for different pre-treatment time and lime loading. COD solubilization and the methane yield enhancement were assessed. The biochemical methane potential was determined in batch assays under mesophilic conditions (37±1°C). The best pre-treatment resulted in a surplus of 72% of methane yield, adding 10g Ca(OH)2 100g(-1)TS(-1) for 1h. Pre-treatment also increased the COD solubilization, but the optimal severity for COD solubilization as determined by response surface methodology did not ensure the highest methane production. Inhibitory effects on anaerobic digestion were noticed when the severity was increased. These results demonstrate the relevance of thermo-alkaline pre-treatment severity in terms of both lime loading and pre-treatment time to obtain optimal anaerobic biodegradability of lignocellulosic biomass from press mud.

Anaerobic co-digestion of sugarcane press mud with vinasse on methane yield

The conversion efficiency of high solids waste digestion as sugarcane press mud (P) may be limited due to hydrolysis step. The option of co-digestion with vinasse, main liquid waste generated from ethanol production, was investigated under batch regime at mesophilic conditions (37.5±1°C) and the best mixture was evaluated under semicontinuous regime in stirred-tank reactors. The maximum values for methane yield in batch tests were for V75/P25 and V50/P50 mixtures (on basis of the chemical oxygen demand (COD) percentage added in the mixture), with an average value of 246NmL CH4g-1 CODfed, which was 13% higher than that of press mud alone. A highest methane production rate of 69.6NmL CH4g-1 CODfed-1d-1 was obtained for the mixtureV75/P25. During the experiment carried out in CSTR reactors, the organic loading rate (OLR) was increased from 0.5 up to 2.2gVSL-1d-1. Methane yields of 365L CH4 kg-1VS and biogas productivities of 1.6LL-1 were obtained in co-digestion, which was 64% higher in comparison to mono-digestion. The performance of the process in mono-digestion was less stable than in co-digestion, with a significant fall of methane yield to 1.8kgVSm-3d-1, and a partial inhibition of the methanogenic archaeas when the OLR was increased up to 2.2kgVSm-3d-1. The co-digestion of vinasse with press mud is a good option for the treatment of streams at the alcohol-sugar industry.

Energetic, environmental and economic potentialities of the anaerobic treatment of rice straw for the case of the Cuban enterprise ‘Sur del Jíbaro’

Rice harvesting and production generates a residual biomass that does not possess an environmentally sustainable disposition route; however, it could be an important carbon source for energetic processes. In this paper the energetic potential via cogeneration that can be obtained from the biogas resulting from the anaerobic treatment of the rice-harvesting wastes (rice straw), for the case of the Cuban Enterprise “Sur del Jibaro”, is estimated. Through a life cycle analysis, an assessment of the environmental profile, when using this treatment alternative, is carried out. The results prove that with the anaerobic treatment of the rice straw available, it could be profitably obtained a potential to generate 10 MW of electrical power and 15 MW of thermal power. This would also decrease the total greenhouse gas emissions in Cuba by 0.2% and the equivalent emissions of the Cuban energetic sector by 3.2%.

APROVECHAMIENTO ENERGÉTICO DE RESIDUOS ARROCEROS POR BIO-CONVERSIÓN

RESUMEN: La cosecha y produccion de arroz genera biomasa residual que actualmente no posee una ruta de disposicion ambientalmente sostenible, sin embargo podrian ser una fuente importante de carbono para procesos energeticos. En el presente trabajo se realiza una caracterizacion bioquimica de residuos arroceros: paja de arroz, cascara de arroz y residuo del proceso de secado, provenientes de la region central de Cuba con el objetivo de evaluar su potencial energetico mediante la ruta de bio-conversion a biogas. Adicionalmente se estimaron las emisiones de gases de efecto invernadero (GEI) que provoca el uso actual de estos residuos asi como el potencial de mitigacion de estas emisiones por concepto de generacion de electricidad a partir de una fuente renovable de energia. El estudio demostro que los residuos arroceros, con excepcion de la cascara de arroz que mostro muy bajo rendimiento, poseen una composicion quimica adecuada para la produccion de biogas, con limitaciones solamente en la relacion C/N. El mayor potencial de biogas de 0,52 m3kgSV-1 correspondio a la paja de arroz como mono-sustrato durante un tiempo de digestion de 36 dias, con 55% vol de metano bajo condiciones termofilicas. El analisis del uso energetico de estos residuos via biogas demostro que por este concepto se podrian generar con un indice de 0,73 MWht-1 de residuo y hasta un 1,5% del consumo de electricidad de pais, a la vez que se contribuiria a disminuir en un 0,5% las emisiones netas del pais y hasta un 7,2% las del sector energetico. Palabras clave: biogas, paja de arroz, cascara de arroz, residuo de secado, metano, emisiones de GEI