Margarida Gonçalves

Ecological risk assessment of sediment management areas : application to Sado Estuary, Portugal

The purpose of this work was to integrate different methodologies to assess the potential ecological risk of estuarine sedimentary management areas, using the Sado Estuary in Portugal as case study. To evaluate the environmental risk of sediment contamination, an integrative and innovative approach was used involving assessment of sediment chemistry, sediment toxicity, benthic community structure, human driving forces and pressures and management areas organic load levels. The basis for decision-making for overall assessment was a statistical multivariate analysis appended into a score matrix tables, using a best expert judgment. The integrated approach allowed to identify from the 19 management areas analyzed, three with no risk but other three with high risk to cause adverse effects in the biota, related with the contaminants analyzed. The methodologies used showed to be effective as a support for decision making leading to future estuarine management recommendations.

Chemical and ecotoxicological characterization of solid residues produced during the co-pyrolysis of plastics and pine biomass

A mixture of 70% (w/w) pine biomass and 30% (w/w) plastics (mixture of polypropylene, polyethylene, and polystyrene) was subjected to pyrolysis at 400 degrees C, for 15 min, with an initial pressure of 40 MPa. Part of the solid residue produced was subjected to extraction with dichloromethane (DCM). The extracted residue (residue A) and raw residue (residue B) were analyzed by weight loss combustion and submitted to the leaching test ISO/TS 21268-2 using two different leachants: DCM (0.2%, v/v) and calcium chloride (0.001 mol/L). The concentrations of the heavy metals Cd, Cr, Ni, Zn, Pb and Cu were determined in the eluates and in the two residues. The eluates were further characterized by determining their pH and the concentrations of benzene, toluene, ethylbenzene and xylenes (BTEX). The presence of other organic contaminants in the eluates was qualitatively evaluated by gas chromatography, coupled with mass spectrometry. An ecotoxicological characterization was also performed by using the bio-indicator Vibrio fischeri. The chemical and ecotoxicological results were analyzed according to the French proposal of Criteria on the Evaluation Methods of Waste Ecotoxicity (CEMWE). Residue A was not considered to be ecotoxic by the ecotoxicological criterion (EC(50) (30 min) >or=10%), but it was considered to be ecotoxic by the chemical criterion (Ni>or=0.5mg/L). Residue B was considered to be ecotoxic by the ecotoxicological criterion: EC(50) (30 min)<or=10%. Besides that, residue B was considered to be hazardous according the European legislation (BTEX concentrations higher than 100 ppb). The results indicate that volatile organic contaminants can be present in sufficient amounts in these residues and their eluates to induce ecotoxicity levels. The extraction of the pyrolysis residue with DCM was an efficient method for removing lighter organic contaminants.

Life cycle assessment of advanced bioethanol production from pulp and paper sludge

This work evaluates the environmental performance of using pulp and paper sludge as feedstock for the production of second generation ethanol. An ethanol plant for converting 5400 tons of dry sludge/year was modelled and evaluated using a cradle-to-gate life cycle assessment approach. The sludge is a burden for pulp and paper mills that is mainly disposed in landfilling. The studied system allows for the valorisation of the waste, which due to its high polysaccharide content is a valuable feedstock for bioethanol production. Eleven impact categories were analysed and the results showed that enzymatic hydrolysis and neutralisation of the CaCO3 are the environmental hotspots of the system contributing up to 85% to the overall impacts. Two optimisation scenarios were evaluated: (1) using a reduced HCl amount in the neutralisation stage and (2) co-fermentation of xylose and glucose, for maximal ethanol yield. Both scenarios displayed significant environmental impact improvements.

Impact of torrefaction and low-temperature carbonization on the properties of biomass wastes from Arundo donax L. and Phoenix canariensis

The impact of torrefaction and low-temperature carbonization on the properties of biomass wastes from Arundo donax L. and Phoenix canariensis was studied. Thermal treatments were performed at temperatures from 200°C to 350°C during 15 to 90min and temperature was the parameter that more influenced mass and energy yields as well as biochar composition. Torrefaction reduced moisture, volatile matter, O/C and H/C ratios of the biomass, while increasing heating value, ash content and fixed carbon. For torrefaction at 250°C or higher temperatures grindability of the biochars was significantly improved. The low volatile matter contents and high ash contents of these biochars restricts their use as solid fuels but they can be valorized otherwise. Raw biomasses and the biochars torrefied at 200°C could remove methylene blue from an aqueous solution, in fast adsorption test with a contact time of only 3s, with efficiencies higher than 50%.

Hydrothermal Torrefaction of Mixtures of Biomass and Hydrocarbon-Rich Sludge in the Presence of Fossil Fuels

A new process for the torrefaction of mixtures of biomass and oily sludges is proposed. A fossil fuel (gasoline or diesel) was added to mixtures of biomass and hydrocarbon-rich sludge (10:1), and this mixture was subject to distillation until all liquids are recovered. The fossil fuel partially dissolved the sludge components and promoted their evenly distribution over the biomass particles. During distillation, the fossil fuel and all the distillable components present in the biomass and sludge were collected and the mixture was subject to temperatures at which a considerable transformation of the non-distillable fraction occurred. The biomass lost water and suffered partial decomposition and rearrangement to yield biochars with HHV of 23.6 and 33.2 MJ/kg. The original biomass had a HHV of 17.9 MJ/kg, but the hydrothermal torrefaction process as well as the fortification with heavy hydrocarbons from the oily sludge significantly increased its calorific value. The distillable liquids were recovered in the form of two immiscible liquid phases: (a) an organic phase mainly composed by the added fossil fuel but also containing the nonpolar volatile components present in the sludge and the biomass, and (b) an aqueous phase that contained the free and emulsified water present in the biomass and in the sludge, but also the water and polar organic components released from the mixture during this thermal treatment. This process takes place at atmospheric pressure and temperatures lower than 300 °C and can be applied to different sludges with high carbon content to promote their energetic valorization.

Bioremediation of Agro-industrial Effluents Using Chlorella Microalgae

Two microalgae species (Chlorella vulgaris and Chlorella protothecoides) were tested at lab scale in order to select the optimal conditions for biomass production and the efficient remediation of effluents from poultry and pig industries. Both microalgae showed biomass productivities in the agro-industrial effluents that were comparable to the Chlorella synthetic medium used as control. C. protothecoides presented the higher productivities both for poultry effluents (46.13 and 41.75 mg.L−1.day−1 for raw and flocculated effluents) and for pig manure (95.86 mg.L−1.day−1). The supplementation of pig effluents with biomass ash increased by 50 % the microalgae productivity with the highest results obtained for C. protothecoides and C. vulgaris at ash concentrations of 1.5 g/L and 3.0 g/L, respectively. The optical density of both effluents was efficiently reduced by both microalgae but particularly by C. protothecoides and in the presence of added ash, indicating that significant reductions of suspended solids and organic matter occurred. The results showed that poultry and pig effluents may be efficiently remediated with microalgae and the fortification with biomass ash benefits the process.