Browsing by Author "Silva, Carla M."
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- Assessment of the adequacy of different Mediterranean waste biomass types for fermentative hydrogen production and the particular advantage of carob (Ceratonia siliqua L.) pulpPublication . Ortigueira, Joana; Silva, Carla M.; Moura, PatríciaABSTRACT: The conversion of agro-industrial byproducts, residues and microalgae, which are representative or adapted to the Mediterranean climate, to hydrogen (H2) by C. butyricum was compared. Five biomass types were selected: brewery’s spent grain (BSG), corn cobs (CC), carob pulp (CP), Spirogyra sp. (SP) and wheat straw (WS). The biomasses were delignified and/or saccharified, except for CP which was simply submitted to aqueous extraction, to obtain fermentable solutions with 56.2e168.4 g total sugars L 1. In small-scale comparative assays, the H2 production from SP, WS, CC, BSG and CP reached 37.3, 82.6, 126.5, 175.7 and 215.8 mL (g biomass) 1, respectively. The best fermentable substrate (CP) was tested in a pH-controlled batch fermentation. The H2 production rate was 204 mL (L h) 1 and a cumulative value of 3.9 L H2 L 1 was achieved, corresponding to a H2 production yield of 70.0 mL (g biomass) 1 or 1.6 mol (mol of glucose equivalents) 1. The experimental data were used to foresight a potential energy generation of 2.4 GWh per year in Portugal, from the use of CP as substrate for H2 production.
- Biodesulphurization of fossil fuels: energy, emissions and cost analysisPublication . Alves, Luís; Paixão, Susana M.; Pacheco, R.; Ferreira, Ana F.; Silva, Carla M.In order to achieve stringent environmental and safety requirements, refineries are in search of “green” and cost-effective methods for crude oil desulphurization. Combined desulphurization technologies are being studied, including bioprocessing to upgrade fossil fuels. Using biodesulphurization (BDS), which is a biochemical process mediated by specific microorganisms, it is possible to desulphurize most of the hydrodesulphurization (HDS) recalcitrant sulphur compounds under mild operating conditions, making it a simple and eco-friendly process. In this study, two BDS process designs are compared, in terms of energy consumption, greenhouse gas emissions and operational costs by following a life cycle assessment (LCA) and life cycle cost (LCC) based methodology. The industrial HDS process is used as the reference technology for sulphur removal from fossil fuels. Different theoretical scenarios were considered and the best BDS results are scaled-up to evaluate a case study of providing ultra low sulphur diesel to an urban taxi fleet. This study exploits the potential of BDS as a cost-effective and eco-friendly alternative or complementary technology to the commonly HDS towards ultra low sulphur fuels.
- Biohydrogen production from microalgal biomass: energy requirement, CO2 emissions and scale-up scenariosPublication . Ferreira, Ana F.; Ortigueira, Joana; Alves, Luís; Gouveia, Luisa; Moura, Patrícia; Silva, Carla M.
- Biological hydrogen production by Anabaena sp. – Yield, energy and CO2 analysis including fermentative biomass recoveryPublication . Ferreira, Ana F.; Marques, Ana C.; Batista, Ana Paula; Marques, Paula; Gouveia, Luisa; Silva, Carla M.This paper presents laboratory results of biological production of hydrogen by photoautrotophic cyanobacterium Anabaena sp. Additional hydrogen production from residual Cyanobacteria fermentation was achieved by Enterobacter aerogenes bacteria. The authors evaluated the yield of H2 production, the energy consumption and CO2 emissions and the technological bottlenecks and possible improvements of the whole energy and CO2 emission chain. The authors did not attempt to extrapolate the results to an industrial scale, but to highlight the processes that need further optimization. The experiments showed that the production of hydrogen from cyanobacteria Anabaena sp. is technically viable. The hydrogen yield for this case was 0.0114 kgH2/kgbiomass which had a rough energy consumption of 1538 MJ/MJH2 and produced 114640 gCO2/MJH2. The use of phototrophic residual cyanobacteria as a substrate in a dark-fermentation process increased the hydrogen yield by 8.1% but consumed 12.0% more of energy and produced 12.1% more of CO2 showing that although the process increased the overall efficiency of hydrogen production it was not a viable energy and CO2 emission solution. To make cyanobacteria-based biofuel production energy and environmentally relevant, efforts should be made to improve the hydrogen yield to values which are more competitive with glucose yields (0.1 kgH2/kgbiomass). This could be achieved through the use of electricity with at least 80% of renewables and eliminating the unessential processes (e.g.pre-concentration centrifugation).
- A biorefinery from Nannochloropsis sp. microalga – Energy and CO2 emission and economic analysesPublication . Ferreira, Ana F.; Ribeiro, Lauro A.; Batista, Ana Paula; Marques, Paula; Nobre, B. P.; Palavra, António F.; Silva, Patricia P. da; Gouveia, Luisa; Silva, Carla M.Are microalgae a potential energy source for biofuel production? This paper presents the laboratory results from a Nannochloropsis sp. microalga biorefinery for the production of oil, high-value pigments, and biohydrogen (bioH2). The energy consumption and CO2 emissions involved in the whole process (microalgae cultivation, harvest, dewater, mill, extraction and leftover biomass fermentation) were evaluated. An economic evaluation was also performed. Oil was obtained by soxhlet (SE) and supercritical fluid extraction (SFE). The bioH2 was produced by fermentation of the leftover biomass. The oil production pathway by SE shows the lowest value of energy consumption, 177-245 MJ/MJprod, and CO2 emissions, 13–15 kgCO2/MJprod. Despite consuming and emitting c.a. 20% more than the SE pathway, the oil obtained by SFE, proved to be more economically viable, with a cost of 365€/kgoil produced and simultaneously extracting high-value pigments. The bioH2 as co-product may be advantageous in terms of product yield or profit.
- Dark fermentative hydrogen production: from concepts to a sustainable productionPublication . Moura, Patrícia; Ortigueira, Joana; Valdez-Vazquez, Idania; Saratale, Ganesh D.; Saratale, Rijuta G.; Silva, Carla M.ABSTRACT: The use of renewable sources and environmentally friendly processes is considered a priority for the construction of a sustainable energy future. The harmful impact of fossil fuels and the fact that we are reaching a disrupting point regarding environmental damage require the rapid implementation of new energy systems and a substantial increase in the use of alternative, unconventional energy sources. Hydrogen (H2) is considered one of the most promising sources as a clean energy vector, because of its high energy density (120 MJ/kg) and carbon-free combustion (Argun and Kargi, 2011). Hydrogen is the simplest and most abundant element on earth; however, it barely exists in nature in its molecular state. Instead, it is almost always found as part of other compounds from which it should be separated, either by thermochemical processes or through biological conversion.
- Energetic and environmental evaluation of microalgae biomass fermentation for biohydrogen productionPublication . Ferreira, Ana F.; Ortigueira, Joana; Alves, Luís; Gouveia, Luisa; Moura, Patrícia; Silva, Carla M.This paper presents an energetic and environmental evaluation of the fermentative hydrogen production from the sugars of Scenedesmus obliquus biomass hydrolysate by Clostridium butyricum. The main purpose of this work was to evaluate the potential of H2 production and respective energy consumptions and CO2 emissions in the global fermentation process: hydrolysis of S. obliquus biomass, preparation of the fermentation medium, degasification and incubation. The scale-up to industrial production was not envisaged. Energy consumption and CO2 emissions estimations were based on SimaPro 7.1 software for the preparation of the fermentation medium and the use of degasification gas, nitrogen. The functional unit of energy consumption and CO2 emissions was defined as MJ and grams per 1 MJ of H2 produced, respectively. The electricity consumed in all hydrogen processes was assumed to be generated from the Portuguese electricity production mix. The hydrogen yield obtained in this work was 2.9 ± 0.3 mol H2/mol sugars in S. obliquus hydrolysate. Results show that this process of biological production of hydrogen consumed 281-405 MJ/MJH2 of energy and emitted 24-29 kgCO2/ MJH2. The fermentation stages with the highest values of energy consumption and CO2 emissions were identified for future energetic and environmental process optimisation.
- Energy requirement and CO2 emissions of bioH2 production from microalgal biomassPublication . Ferreira, Ana F.; Ortigueira, Joana; Alves, Luís; Gouveia, Luisa; Moura, Patrícia; Silva, Carla M.This paper presents the life cycle inventory (LCI) of hydrogen production by Clostridium butyricum fermentation of Scenedesmus obliquus hydrolysate. The main purpose of this work was to evaluate the potential of H2 production from microalgal biomass and the respective energy consumption and CO2 emissions in the bioconversion process considering the microalga production, acid hydrolysis of S. obliquus biomass, preparation of the inoculum and culture media, and fermentation. The scale-up to industrial production was not envisaged. The hydrogen yield obtained in this work was 2.9 ± 0.3 mol H2/mol sugars in S. obliquus hydrolysate. Results show that this process of biological production of hydrogen can achieve 7270 MJ/MJH2 of energy consumption and 670Kg CO2/MJH2. The microalgal culture is the stage responsible for 98% of these total final values due to the use of artificial lighting. All stages and processes with the highest values of energy consumption and CO2 emissions were identified for future energetic and environmental optimisation.
- Energy requirements for the continuous biohydrogen production from Spirogyra biomass in a sequential batch reactorPublication . Ortigueira, Joana; Ferreira, Ana F.; Silva, Carla M.; Gouveia, Luisa; Moura, PatríciaThe current energy market requires urgent revision for the introduction of renewable, less-polluting and inexpensive energy sources. Biohydrogen (bioH2) is considered to be one of the most appropriate options for this model shift, being easily produced through the anaerobic fermentation of carbohydrate-containing biomass. Ideally, the feedstock should be low-cost, widely available and convertible into a product of interest. Microalgae are considered to possess the referred properties, being also highly valued for their capability to assimilate CO2 [1]. The microalga Spirogyra sp. is able to accumulate high concentrations of intracellular starch, a preferential carbon source for some bioH2 producing bacteria such as Clostridium butyricum [2]. In the present work, Spirogyra biomass was submitted to acid hydrolysis to degrade polymeric components and increase the biomass fermentability. Initial tests of bioH2 production in 120 mL reactors with C. butyricum yielded a maximum volumetric productivity of 141 mL H2/L.h and a H2 production yield of 3.78 mol H2/mol consumed sugars. Subsequently, a sequential batch reactor (SBR) was used for the continuous H2 production from Spirogyra hydrolysate. After 3 consecutive batches, the fermentation achieved a maximum volumetric productivity of 324 mL H2/L.h, higher than most results obtained in similar production systems [3] and a potential H2 production yield of 10.4 L H2/L hydrolysate per day. The H2 yield achieved in the SBR was 2.59 mol H2/mol, a value that is comparable to those attained with several thermophilic microorganisms [3], [4]. In the present work, a detailed energy consumption of the microalgae value-chain is presented and compared with previous results from the literature. The specific energy requirements were determined and the functional unit considered was gH2 and MJH2. It was possible to identify the process stages responsible for the highest energy consumption during bioH2 production from Spirogyra biomass for further optimisation.
- Evaluation of energy consumption and CO2 emissions in the production of biohydrogen from sugar rich feedstockPublication . Ferreira, Ana F.; Moura, Patrícia; Silva, Carla M.The use of alternative fuels is increasing in order to reduce the energy consumption and emissions. The 2003/30/EC European Directive aims to promote the use of biofuels and other renewable fuels instead of oil derivatives for transport purposes. In long term this is expected to contribute to the fulfillment of European climate change agreements. Therefore, hydrogen appears as a promising alternative fuel and “energy carrier”. Hydrogen can be produced from renewable sources, namely biomass [1], and more particularly by the photobiological method and dark fermentation process [2], being designated as “biohydrogen” (bioH2) [3]. This study regards to life cycle analysis considering energy, emissions and costs of bioH2 production from microalgae, sugarcane (SC) and potato peels (PP).