Energetic valorization of algal biomass in a hybrid anaerobic reactor

ABSTRACT: This study evaluated the operation of a hybrid anaerobic reactor fed with algal biomass cultivated in effluent from the brewery industry. Three stages of operation were distinguished during the 72 days of semi-continuous functioning of the reactor: Stage 1 (S1), in which algal biomass was used as substrate; Stage 2 (S2), in which 10% (v/v) of the algal biomass was substituted by olive mill wastewater (OMW); and Stage 3 (S3), in which algal biomass was heat pre-treated. During Sl, a loss of solids was observed, with an increment of organic matter in the outlet. The substitution of 10% of the volume of algal biomass by OMW tripled the methane productivity obtained in the previous stage by digestion of pure algal biomass. Heat pre-treatment was not efficient in rupturing the cell wall, and consequently did not have any effect on the increase in biogas production. The complementarity of substrates in the assessed conditions led to better results than the pre-treatment of the algal biomass.info:eu-repo/semantics/publishedVersio

Biodiesel from wastewater: lipid production in high rate algal pond receiving disinfected effluent

The production of different species of microalgae in consortium with other micro-organisms from wastewaters may represent an alternative process, to reduce the costs, for obtaining biofuels. The aim of this study was to evaluate the influence of pre-ultraviolet disinfection (UV) in the production of lipids from biomass produced in high rate ponds. Two high rate algal ponds were evaluated: a pond that received domestic sewage without disinfection and the other receiving domestic sewage previously disinfected by UV radiation (uvHRAP). The UV disinfection did not lead to significant differences in fatty acid profile and total lipid productivities, although it increased algal biomass concentration and productivity as well as lipid content. Moreover, the overall biomass concentrations and productivities decreased with the UV disinfection, mostly as a consequence of a loss in bacterial load. We thus conclude that uvHRAP disinfection may represent a potential strategy to promote the cleaner and safer growth of algal biomass when cultivated in consortium with other microorganisms. Mainly regarding the use of wastewater as culture medium, together with a cheaper production of lipids for biodiesel, pre-disinfection may represent an advance since extraction costs could be significantly trimmed due to the increase in lipid content

Combining biotechnology with circular bioeconomy: from poultry, swine, cattle, brewery, dairy and urban wastewaters to biohydrogen

ABSTRACT: The ability of microalgae to grow in nutrient-rich environments and to accumulate nutrients from wastewaters (WW) makes them attractive for the sustainable and low-cost treatment of WW. The valuable biomass produced can be further used for the generation of bioenergy, animal feed, fertilizers, and biopolymers, among others. In this study, Scenedesmus obliquus was able to remove nutrients from different wastewaters (poultry, swine and cattle breeding, brewery and dairy industries, and urban) with removal ranges of 95-100% for nitrogen, 63-99% for phosphorus and 48-70% for chemical oxygen demand. The biomass productivity using wastewaters was higher (except for poultry) than in synthetic medium (Bristol), the highest value being obtained in brewery wastewater (1025 mg/(L.day) of freeze-dried biomass). The produced biomass contained 31-53% of proteins, 12-36% of sugars and 8-23% of lipids, regardless of the type of wastewater. The potential of the produced Scenedesmus obliquus biomass for the generation of BioH(2) through batch dark fermentation processes with Enterobacter aerogenes was evaluated. The obtained yields ranged, in mL H-2/g Volatile Solids (VS), from 50.1 for biomass from anaerobically digested cattle WW to 390 for swine WW, whereas the yield with biomass cultivated in Bristol medium was 57.6 mL H-2/gvs.info:eu-repo/semantics/publishedVersio

Energetic valorization by anaerobic digestion of algal biomass cultivated in wastewater

Várias abordagens têm sido feitas de forma a confirmar o potencial atrativo das microalgas como matéria prima para a produção de biogás. No entanto, limitações advindas do substrato biomassa algal são ainda na atualidade descritas. As maiores complexidades da digestão anaeróbia da biomassa algal são reportadas como sendo a baixa digestibilidade da parede celular das algas e a inibição do processo pela presença de amônia. De forma a propor estratégias de superação dessas limitações, esse estudo teve como objetivo avaliar o potencial energético de biomassa algal cultivada em efluentes a partir da digestão anaeróbia. Estratégias de pré-tratamentos (térmico e prévia extração lipídica) e complementariedade de substratos foram aplicadas. A extração lipídica aumentou o rendimento da produção de biogás em até 10 vezes, tornando mais disponível o conteúdo intracelular. No entanto, após análise energética, concluiu-se pelo pouco ganho energético acumulado da etapa de extração lipídica, devido principalmente ao baixo acúmulo lipídico da biomassa produzida em efluentes. O aproveitamento lipídico da biomassa se mostrou inviável energeticamente e a geração de biogás da biomassa bruta foi a rota energética mais favorável, tanto para biomassa produzida em lagoas de alta taxa com esgoto doméstico, como para biomassa cultivada em fotobiorreator coluna de bolhas com efluentes da indústria de processamento de carnes. A complementariedade de substratos foi avaliada utilizando-se efluente da indústria de extração de azeite (água ruça) na digestão anaeróbia de biomassa algal produzida em lagoa de alta taxa (LAT) utilizando efluente da indústria cervejeira e esgoto doméstico como meios de cultivo. Adicionalmente, a geração de biogás e a eficiência de degradação da matéria orgânica foram monitoradas ao longo de três fases (72 dias) de operação de um reator híbrido anaeróbio, caracterizadas pelo também uso da água ruça como um substrato complementar à biomassa algal e à aplicação de um pré-tratamento térmico para ruptura da parede celular da biomassa algal. Análises de citometria de fluxo foram realizadas para estimar a integridade da membrana e viabilidade metabólica das células algais de forma a mensurar a eficiência do pré-tratamento aplicado. A água ruça se mostrou um substrato complementar eficiente para digestão anaeróbia da biomassa algal, permitindo melhorar rendimento do processo, além de economia de recursos, facilidade operacional e aproveitamento energético de mais de um resíduo. Para os testes em batelada, o rendimento da digestão foi 36% maior para os testes com 10% de água ruça adicionada à biomassa algal cultivada em esgoto doméstico. Para biomassa cultivada em efluente da indústria cervejeira, valores de até 20% de água ruça puderam ser adicionados à biomassa algal, no entanto, teste utilizando somente a biomassa algal como substrato apresentou os melhores resultados de produção de biogás. Mesmo com a aplicação de pré-tratamento térmico, o melhor rendimento do reator híbrido foi obtido quando operado com 10% de água ruça, cerca de 3 vezes superior ao rendimento obtido somente com biomassa algal. Acredita-se que através do presente estudo foi possível avaliar uma rota promissora de produção de biocombustíveis a partir do tratamento de efluentes, elucidando limitações importantes para a aplicação e ampliação do processo. Temas emergentes e de grande importância no contexto mundial e principalmente nacional foram abordados, nomeadamente o aproveitamento de resíduos e a questão energética, tornando o saneamento ambiental mais atrativo dos pontos de vista econômico e de sustentabilidade, e propondo alternativas de diversificação da matriz energética com o uso de biocombustíveis oriundos de biomassa algal.Several approaches to confirm the attractive potential of microalgae as a feedstock for biogas production have been undertaken. However, limitations arising from the algal biomass substrate are still described today. The main complicators of anaerobic digestion of algal biomass are reported to be the low digestibility of the algal cell wall and the inhibition of the process by ammonia. In order to propose strategies to overcome these limitations, this study aimed to evaluate the energy potential of anaerobic digestion of algal biomass grown in wastewaters. Thermal and lipid extraction pre-treatments and complementarity of substrates were evaluated. Lipid extraction increased biogas yield ten-fold, by making intracellular content more available. However, an energy analysis showed the lipid extraction stage produced only a small accumulated energy gain, mainly due to the low lipid accumulation in the biomass produced in wastewaters. Utilization of biomass lipid was shown to be energy-infeasible and biogas generation from the crude biomass was the most favorable energy route, both for biomass produced in high rate ponds with domestic sewage and for biomass cultured in a bubble column photobioreactor with effluents from the meat processing industry. The complementarity of substrates was evaluated using olive mill wastewater in the anaerobic digestion of algae biomass produced in a high rate algal pond using effluents from the brewery industry and domestic sewage as culture media. In addition, biogas production and organic matter degradation efficiency were monitored during three phases (72 days) of an anaerobic hybrid reactor, characterized by the use of the olive mill wastewater as a complementary substrate to the algal biomass and the application of a thermal pretreatment for algal biomass cell wall rupture. Algal cell membrane integrity and metabolic viability were analyzed through flow cytometry in order to measure pretreatment efficiency. Olive mill wastewater proved to be an efficient complementary substrate for anaerobic digestion of the algal biomass, allowing better process efficiency, both in batch and semi-continuous feeding modes of the hybrid reactor, as well as resource savings, operational ease and energy utilization of more than one waste. For batchs tests, digestion yield was 36% greater when using 10% of olive mill wastewater together with algal biomass grown in domestic sewage. Values of up to 20% of olive mill wastewater could be added to algal biomass grown in brewery wastewater, however, tests using only algal biomass as the substrate showed the best biogas production results. Even with the application of thermal pretreatment, the best performance of the hybrid reactor was obtained when operated with 10% olive mill wastewater, resulting in about 3 fold higher yield than obtained with algal biomass alone. Through the present study, it was possible to evaluate a promising route for biofuels production through wastewater treatment and identify important limitations to the application and expansion of the process. Emerging issues of great importance worldwide and especially at the national level were addressed, namely waste reuse and renewable energy, making environmental sanitation more attractive from both the economic and sustainability points of view, and alternatives for diversifying the energy matrix with the use of biofuels from algal biomass were proposed.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

Effect of solar radiation and pre-disinfection in lipid characterization of high rate pond biomass grown in domestic sewage

Microalgas são, atualmente, consideradas como uma das mais promissoras fontes alternativas para a produção de biodiesel. Variações nas condições de cultivo, aliadas ao cultivo em águas residuárias, são usualmente empregadas, visando maximizar o acúmulo de lipídeos a um custo relativamente baixo. Esse estudo objetivou investigar a influência de diferentes intensidades luminosas e da prédesinfecção por radiação ultravioleta na caracterização lipídica de microalgas cultivadas em lagoas de alta taxa, utilizando esgoto doméstico como meio de cultivo. Foram operadas em paralelo doze lagoas de alta taxa. Uma linha era composta de seis lagoas que receberam efluentes domésticos diretamente do reator UASB, e a outra linha de seis lagoas que tiveram como meio de cultivo efluente doméstico do UASB que passou por processo prévio de desinfecção ultravioleta. As unidades foram ainda cobertas com telas de sombreamento para o bloqueio de 9, 18, 30, 60 e 80% da radiação solar. Os resultados mostraram que os gêneros Chlorella e Desmodesmus foram os dominantes em todas as unidades. O teor de lipídeos totais não variou significativamente entre as unidades, ficando em torno de 9,5%. As unidades com maior bloqueio da radiação solar foram as que menos acumularam lipídeos. Além da radiação solar fotossinteticamente ativa medida no ar (PAR), as variáveis PAR subaquática, concentração de SSV e de clorofila a explicaram o acúmulo de lipídeos. Em termos de produtividade lipídica, a unidade com maior sombreamento e sem a pré-desinfecção UV foi a mais produtiva, com valor médio de 1,21 g. m-2.d-1. O perfil lipídico teve maior predominância dos ácidos graxos C16, C18:1 e C18:3. De forma geral, a condição com 60% de sombra e sem a pré-desinfecção UV, foi a que aliou as melhores características, em termos de quantidade e qualidade, dos lipídeos acumulados para produção de biodiesel.Microalgae are currently considered to be one of the most promising alternative sources for biodiesel production. Variations in growing conditions, combined with the cultivation in wastewater are usually employed in order to maximize lipids accumulation at a relatively low cost. The aim of this study was to investigate the influence of different light intensities and ultraviolet predisinfection system in the lipid characterization of microalgae cultivated in high rate ponds, using wastewater as growing medium. Twelve high rate algal ponds were operated in parallel. Six of them received UASB effluent, and the others six had as growth medium UASB effluent that had previously passed through an ultraviolet pre-disinfection system. The units were also covered with shade screens for blocking 9, 18, 30 and 60% of solar radiation. The results showed that Chlorella and Desmodesmus were the dominant genera in all units. The total lipid content did not vary significantly among the units; the medium value was 9.5%. Units with higher solar radiation blocking were the ones that least accumulated lipids. Besides photosynthetically active radiation measured in the air (PAR), the variables subaquatic PAR, VSS concentration and chlorophyll-a concentration were the ones that best explained lipid accumulation. In terms of lipid productivity, the unit with more shadow and without the pre-disinfection system was the most productive, with mean value of 1.21 g. m-2.d-1. The lipid profile had a predominance of C16, C18:1 e C18:3 acids. The condition with 60% shade and without the pre-disinfection system was the one that combined the best lipids characteristics, qualitative and quantitative, for biodiesel production.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Biofuel from wastewater-grown microalgae: A biorefinery approach using hydrothermal liquefaction and catalyst upgrading

ABSTRACT: Third-generation biofuels from microalgae are becoming necessary for sustainable energy. In this context, this study explores the hydrothermal liquefaction (HTL) of microalgae biomass grown in wastewater, consisting of 30% Chlorella vulgaris, 69% Tetradesmus obliquus, and 1% cyanobacteria Limnothrix planctonica, and the subsequent upgrading of the produced bio-oil. The novelty of the work lies in integrating microalgae cultivation in wastewater with HTL in a biorefinery approach, enhanced using a catalyst to upgrade the bio-oil. Different temperatures (300, 325, and 350 degrees C) and reaction times (15, 30, and 45 min) were tested. The bio-oil upgrading occurred with a Cobalt-Molybdenum (CoMo) catalyst for 1 h at 375 degrees C. Post-HTL, although the hydrogen-to-carbon (H/C) ratio decreased from 1.70 to 1.38-1.60, the oxygen-to-carbon (O/C) ratio also decreased from 0.39 to 0.079-0.104, and the higher heating value increased from 20.6 to 36.4-38.3 MJ kg(-1). Palmitic acid was the main component in all bio-oil samples. The highest bio-oil yield was at 300 degrees C for 30 min (23.4%). Upgrading increased long-chain hydrocarbons like heptadecane (5%), indicating biofuel potential, though nitrogenous compounds such as hexadecanenitrile suggest a need for further hydrodenitrogenation. Aqueous phase, solid residues, and gas from HTL can be used for applications such as biomass cultivation, bio-hydrogen, valuable chemicals, and materials like carbon composites and cement additives, promoting a circular economy. The study underscores the potential of microalgae-derived bio-oil as sustainable biofuel, although further refinement is needed to meet current fuel standards.info:eu-repo/semantics/publishedVersio

Algal biomass production and wastewater treatment in high rate algal ponds receiving disinfected effluent

Algal biomass production associated with wastewater is usually carried out in high rate algal ponds (HRAPs), which are concomitantly used in the treatment of such effluent. However, most types of wastewater have high levels of bacteria that can inhibit the growth of algal biomass by competing for space and nutrients. The objective of this study was to assess the influence of ultraviolet (UV) pre-disinfection on the performance of HRAPs used for wastewater treatment and algal biomass production. Two HRAPs were tested: one received effluent from an upflow anaerobic sludge blanket (UASB) reactor – HRAP – and the second received UASB effluent pre-disinfected by UV radiation – UVHRAP. Physical, chemical and microbiological parameters were monitored, as well as algal biomass productivity and daily pH and dissolved oxygen (DO) variation. The UVHRAP presented highest DO and pH values, as well as greater percentage of chlorophyll a in the biomass, which indicates greater algal biomass productivity. The average percentages of chlorophyll a found in the biomass obtained from the HRAP and the UVHRAP were 0.95±0.65% and 1.58±0.65%, respectively. However, total biomass productivity was greater in the HRAP (11.4 gVSS m-2 day-1) compared with the UVHRAP (9.3 gVSS m-2 day-1). Mean pH values were 7.7±0.7 in the HRAP and 8.1±1.0 in the UVHRAP, and mean values of DO percent saturation were 87±26% and 112±31% for the HRAP and the UVHRAP, respectively. Despite these differences, removal efficiencies of organic carbon, chemical oxygen demand, ammoniacal nitrogen and soluble phosphorus were statistically equal at the 5% significance level