RESUMO
A significant part of whey generated in Brazil is from small and mid-size dairy companies. Cheese whey has great potential for methane production through anaerobic biological processes but presents instabilities due to its high biodegradability. To study an alternative for the destination of this residue, the aim of this work was to investigate methane from the co-digestion of whey with glycerin and its environmental compliance at 55 °C in an anaerobic sequencing batch biofilm reactor. The best performance indicators were obtained with an influent composed of 88% cheese whey and 12% glycerin (by volume), fed-batch mode and organic loading rate of 19.3 kgCOD m-3 day-1 at 55 °C. This operational condition allowed us to achieve a methane productivity of 203 molCH4 m-3 day-1, a methane yield close to theoretical value, and to remove 68% of all organic matter in the influent. A kinetic metabolic model was fitted to the experimental data, which indicated methanogenesis with preference for the acetoclastic route. Finally, the energy production (approximately 197 MWh month-1) from an industrial scale reactor and its volume (three reactors of 152 m3) were assessed for a mid-size dairy industry, which could save up to US$ 22,000.00 per month in oil demand.
Assuntos
Técnicas de Cultura Celular por Lotes/métodos , Indústria de Laticínios , Glicerol/metabolismo , Indústrias , Metano/biossíntese , Análise de Sequência , Soro do Leite/metabolismo , Anaerobiose , Meio Ambiente , Cinética , Modelos BiológicosRESUMO
This study investigated methane production in an anaerobic sequencing batch biofilm reactor (AnSBBR) by co-digesting sugarcane vinasse and cheese whey. The assessment was based on the influence of feed strategy, interaction between cycle time and influent concentration, applied volumetric organic load (OLRA), and temperature over system stability and performance. The system showed flexibility with regard to the feed strategy, but the reduction of cycle time and influent concentration, at the same OLRA, resulted in lower methane productivity. Increasing organic load, up to the value of 15.27 gCOD L-1 day-1, favored the process, increasing methane yield and productivity. Temperature reduction from 30 to 25 °C resulted in worse performance, although increasing it to 35 °C provided similar results to 30 °C. The best results were achieved at an OLRA of 15.27 gCOD L-1 day-1, cycle time of 8 h, fed-batch operation, and temperature of 30 °C. The system achieved soluble COD removal efficiency of 89%, methane productivity of 208.5 molCH4 m-3 day-1 and yield of 15.76 mmolCH4 gCOD-1. The kinetic model fit indicated methanogenesis preference for the hydrogenotrophic route. At the industrial scale estimative, considering a scenario with a sugarcane ethanol plant with ethanol production of 150,896 m3 year-1, it was estimated energy production of 25,544 MWh month-1.
Assuntos
Biotecnologia/métodos , Queijo , Metano/biossíntese , Saccharum/metabolismo , Soro do Leite/metabolismo , Anaerobiose , Reatores Biológicos/microbiologia , Cinética , Temperatura , Águas Residuárias/químicaRESUMO
Vinasse, from sugar and ethanol production, stands out as one of the most problematic agroindustry wastes due to its high chemical oxygen demand, large production volume, and recalcitrant compounds. Therefore, the viability of using glycerin as a co-substrate in vinasse anaerobic digestion was tested, to increase process efficiency and biogas productivity. The effect of feeding strategy, influent concentration, cycle length, and temperature were assessed to optimize methane production. Glycerin (1.53% v/v) proved to be a good co-substrate since it increased the overall methane production in co-digestion assays. CH4 productivity enhanced exponentially as influent concentration increased, but when temperature was increased to 35 °C, biogas production was impaired. The highest methane productivity and yield were achieved using fed-batch mode, at 30 °C and at an organic loading rate of 10.1 kg COD m-3 day-1: 139.32 mol CH4 m-3 day-1, 13.86 mol CH4 kg CODapplied, and 15.30 mol CH4 kg CODremoved. Methane was predominantly produced through the hydrogenotrophic route. In order to treat all the vinasse produced by a mid-size sugar and ethanol plant, nine reactors with 7263.4 m3 each would be needed. The energy generated by burning the biogas in boilers would reach approximately 92,000 MW h per season and could save up to US$ 240,000.00 per month in diesel oil demand.
Assuntos
Glicerol/metabolismo , Resíduos Industriais , Saccharum/metabolismo , Anaerobiose , Biofilmes , Análise da Demanda Biológica de Oxigênio , Temperatura Alta , Cinética , Metano/biossínteseRESUMO
The most common approach to deal with vinasse (sugarcane stillage) is fertigation, but this technique compromises soil structure and surrounding water bodies. A possible solution is to transport vinasse to local cheese whey producers and perform the co-digestion of these wastewaters together, reducing their organic load and generating bioenergy. Therefore, this study investigated the application of an AnSBBR (anaerobic sequencing batch biofilm reactor) operated in batch and fed-batch mode, co-digesting vinasse and whey at 30 °C. The effect of influent composition and feeding strategy was assessed. In all conditions, the system achieved high organic matter removal (approximately 83%). Increasing the percentage of vinasse from 0 to 100% in the influent resulted in a decrease in methane productivity (76.3 to 51.1 molCH4 m-3 day-1) and yield (12.7 to 9.1 molCH4 kgCOD-1), but fed-batch mode operation improved reactor performance (73.0 molCH4 m-3 day-1 and 11.5 molCH4 kgCOD-1). From the kinetic metabolic model, it was possible to infer that, at the best condition, methane is produced in a similar way from the acetoclastic and hydrogenotrophic routes. A scheme of four parallel reactors with a volume of 16,950 m3 each was proposed in the scale-up estimation, with an energy recovery estimated in 28,745 MWh per month.