Browsing by Author "Fragoso, Rita"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Bioconversion of Jatropha curcas seed cake to hydrogen by a strain of Enterobacter aerogenesPublication . Lopes, Sofia Lewis; Fragoso, Rita; Duarte, Elisabeth; Marques, PaulaHydrogen (H2) gas is considered the future energy carrier as a clean fuel. Biological processes to produce hydrogen are very attractive due to less energy expenditures and the possibility to use organic wastes as substrate. In this work, Jatropha curcas L. seed cake (JSC), a solid residue remaining after oil extraction from J. curcas seeds for biodiesel production, was used as substrate in a dark fermentation process by a pure strain of the bacteria Enterobacter aerogenes. Batch assays were performed using the substrate (2.5 gVolatile Solid/LFermentation Medium) submitted to thermal pretreatment in an autoclave for two different exposure times (15 and 30 min) and the results were compared with the ones obtained when the JSC was used without pretreatment. The best specific biohydrogen production (68.2 mL H2/gVSiJSC) was attained for the conditions of no substrate pretreatment, which is an advantage from the view point of energy saving. In the best conditions, the increase of the initial JSC concentration from 2.5 to 10 gVS/LFM led to the increase of the cumulative hydrogen production and to higher bioH2 production rates. However a decrease on the specific H2 production from 68.2 to 23.5 mL H2/gVSiJSC was observed.
- The Role of Mild Alkaline Pretreatment in the Biorefinery Upgrade of Spent Coffee GroundsPublication . Ribeiro, Gabriel Mota; Martins, Pedro L.; Oliveira, Ana Cristina; Carvalheiro, Florbela; Fragoso, Rita; Duarte, Luís C.ABSTRACT: This work proposes a valorization route for spent coffee grounds (SCG), a widespread lignocellulosic residue, encompassing the production of: biomethane, lignin, and oligosaccharides as value-added products obtained simultaneously during a mild alkaline (NaOH) pretreatment. The studied operational variables were the reaction time (60-240 min), temperature (25-75 degrees C), and the NaOH concentration (0-2.5 M). The severity factor suitably describes the global process kinetics, with higher severities (log Mo = 5.5) yielding high product yields, 18.02% and 13.25% (on dry SCG basis) for lignin and oligosaccharides (XGMOS), respectively. Solid yield is negatively impacted by all studied variables (at the 95% confidence level). Conversely, XGMOS yield is positively influenced both by time and catalyst concentration, whereas lignin yield is only (positively) influenced by catalyst concentration. Optimal balance between product formation and potential operational costs is putatively achieved when using 0.625 M NaOH, at 50 degrees C for 60 min. The mild alkaline pretreated biomass (MAP-SCG) was compared to untreated SCG for biomethane production by anaerobic co-digestion with pig slurry (PS), using a ratio of biomass/PS = 1/3 (volatile solids (VS) basis). The proposed valorization route enabled the sequential production of 6.25 kg lignin, 6.36 kg oligosaccharides, and 138.05 kg biomethane per 100 kg of non-extracted SCG (and 287.60 kg pig slurry), in an integrated process that is technically feasible and promotes the circular bioeconomy.