Bacterial diversity from environmental sample applied to bio-hydrogen production

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Produção biológica integrada de hidrogénio e metano a partir de resíduos da indústria do biodiesel

Dissertação de Mestrado Integrado em Engenharia da Energia e do Ambiente

Eliminação/valorização de resíduos de frutas (kiwi) por digestão anaeróbia

Este estudo tem como objetivo a valorização económica de resíduos agroindustriais, nomeadamente resíduos de kiwi, por digestão anaeróbia de forma a otimizar a produção de biogás e a sua qualidade (% CH4). Trata-se de uma pesquisa experimental que consistiu na avaliação da produção de biogás usando diferentes proporções de substrato e inóculo, quatro valores distintos para a razão C:N, inóculo de diferentes digestores e colheita do inóculo em épocas distintas do ano. Os ensaios foram desenvolvidos num reator batch em condições mesofílicas, sendo o processo acompanhado por monitorização dos parâmetros: pH, Alcalinidade, Ácidos Gordos Voláteis (AGV), Sólidos Totais (ST), Sólidos Voláteis (SV), Carência Química de Oxigénio (CQO) e Carbono. Para a totalidade dos ensaios, o valor de pH no reator praticamente não apresentou variação, mantendo-se em torno de 7,0; a alcalinidade do meio, 1500 mg CaCO3/L, revelou-se adequada uma vez que no final do processo de DA a concentração de AGV (400-600 mg/L), nunca excede os valores considerados críticos. Os resultados obtidos apresentam valores interessantes para um número considerável de ensaios. Das 10 experiências realizadas, em duas foram obtidos resultados muito significativos em relação à literatura; o ensaio com 1% de substrato (experiência 2) registou uma produção de biogás de 1628 L/kg SV com uma %CH4 de 57% e o biogás de maior qualidade, 85% de metano, foi obtido no ensaio com 5% de resíduo de kiwi (experiência 10). As experiências em que se avaliou o efeito da razão C:N foram as menos produtivas, possivelmente devido à inibição da atividade da população microbiana pelo KNO3. A qualidade do inóculo revelou-se determinante num conjunto de ensaios, nomeadamente quando a sua colheita foi realizada no inverno, com o digestor a apresentar temperaturas bastante baixas. De acordo com os valores mais favoráveis para a produção de biogás, por tonelada de resíduo de kiwi poderá ser obtido um valor monetário bruto de 102 €, resolvendo-se um problema de eliminação deste resíduo, com valorização energética simultaneamente.

Stability of endoglucanases from mesophilic fungus and thermophilic bacterium in acidified polyols

Recent developments in chemical pretreatments of lignocellulosic biomass using polyols as co-solvents (e.g., glycerol and ethylene glycol) at temperatures less than 100 °C may allow the effective use of thermostable and non-thermostable cellulases in situ during the saccharification process. The potential of biomass saccharifying enzymes, endoglucanases (EG) from a thermophilic bacterium (Thermotoga maritima) and a mesophilic fungus (Trichoderma longibrachiatum), to retain their activity in aqueous buffer, acidified glycerol, and acidified ethylene glycol used as co-solvents at pretreatment temperatures at or below 100 °C were examined. The results show that despite its origin, T. longibrachiatum EG (Tl-EG) retained 75% of its activity after exposure to 100 °C for 5 min in aqueous buffer while T. maritima EG (Tm-EG) retained only 5% activity. However, at 90 °C both enzymes retained over 87% of their activity. In acidified (0.1% (w/w) H2SO4) glycerol, Tl-EG retained similar activity (80%) to that obtained in glycerol alone, while Tm-EG retained only 35%. With acidified ethylene glycol under these conditions, both Tl-EG and Tm-EG retained 36% of their activity. The results therefore show that Tl-EG is more stable in both acidified glycerol and ethylene glycol than Tm-EG. A preliminary kinetic study showed that pure glycerol improved the thermal stability of Tl-EG but destabilized Tm-EG, relative to the buffer solution. The half-lives of both Tl-EG and Tm-EG are 4.5 min in acidified glycerol, indicating that the effectiveness of these enzymes under typical pretreatment times of greater than 15 min will be considerably diminished. Attempts have been made to explain the differences in the results obtained between the two enzymes.

A biochemical predictor of performance during mesophilic anaerobic fermentation of starch wastewater

The aim of this study was to determine the potential of biochemical parameters, such as enzyme activity and adenosine triphosphate (ATP) levels, as monitors of process performance in the Upflow Anaerobic Sludge Blanket (UASB) reactor utilizing a starch wastewater. The acid and alkaline phosphatase activity and the ATP content of the UASB sludge were measured in response to changes in flow rate and nutrient loading. Conventional parameters of process performance, such as gas production, acetic acid production, COD, phosphorus, nitrogen and suspended solids loadings and % COD removal were also monitored. The response of both biochemical and conventional parameters to changing process conditions was then compared. Alkaline phosphatase activity exhibited the highest activity over the entire study perioda A high suspended solids loading was observed to upset the system in terms of gas production, acetic acid production and % COD removala The initial rate of increase in alkaline phosphatase activity following an increase in loading was four times as great during process upset than under conditions of good performance. The change in enzyme actiVity was also more sensitive to process upset than changes in acetic acid production. The change in ATP content of the sludge with time suggested that enzyme actiVity was changing independently of the actual viable biomass present. The bacterial composition of the anaerobic sludge granules was similar to that of other sludge bed systems, at the light and scanning electron microscope level. Isolated serum bottle cultures produced several acids involved in anaerobic carbohydrate metabolism. The overall performance of the UASB system indicated that higher loadings of soluble nutrients could have been tolerated by the system.

Hydrazine-hydrate intercalated halloysite under controlled-rate thermal analysis conditions

The thermal behaviour of halloysite fully expanded with hydrazine-hydrate has been investigated in nitrogen atmosphere under dynamic heating and at a constant, pre-set decomposition rate of 0.15 mg min-1. Under controlled-rate thermal analysis (CRTA) conditions it was possible to resolve the closely overlapping decomposition stages and to distinguish between adsorbed and bonded reagent. Three types of bonded reagent could be identified. The loosely bonded reagent amounting to 0.20 mol hydrazine-hydrate per mol inner surface hydroxyl is connected to the internal and external surfaces of the expanded mineral and is present as a space filler between the sheets of the delaminated mineral. The strongly bonded (intercalated) hydrazine-hydrate is connected to the kaolinite inner surface OH groups by the formation of hydrogen bonds. Based on the thermoanalytical results two different types of bonded reagent could be distinguished in the complex. Type 1 reagent (approx. 0.06 mol hydrazine-hydrate/mol inner surface OH) is liberated between 77 and 103°C. Type 2 reagent is lost between 103 and 227°C, corresponding to a quantity of 0.36 mol hydrazine/mol inner surface OH. When heating the complex to 77°C under CRTA conditions a new reflection appears in the XRD pattern with a d-value of 9.6 Å, in addition to the 10.2 Ĺ reflection. This new reflection disappears in contact with moist air and the complex re-expands to the original d-value of 10.2 Å in a few h. The appearance of the 9.6 Å reflection is interpreted as the expansion of kaolinite with hydrazine alone, while the 10.2 Å one is due to expansion with hydrazine-hydrate. FTIR (DRIFT) spectroscopic results showed that the treated mineral after intercalation/deintercalation and heat treatment to 300°C is slightly more ordered than the original (untreated) clay.

Effect of surface conditions on flow of a micropolar fluid driven by a porous stretching sheet

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