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Bernardo, M., M. Gonçalves, N. Lapa, R. Barbosa, B. Mendes, and F. Pinto. "Characterization of chars produced in the co-pyrolysis of different wastes: decontamination study." Journal of Hazardous Materials. 207-208 (2012): 28-35. AbstractWebsite

The present work is devoted to the study of the decontamination of chars obtained in the co-pyrolysis of plastics, biomass and tyre wastes. The chars were extracted with several organic solvents of different polarities either individually or in sequence. The ability of each selected extractant to remove toxic pollutants was evaluated by comparing the extraction yields and by characterizing the crude extracts with a combination of chemical analysis and toxicity bioassays. Also, the mineral composition of the treated and non-treated chars was assessed. The results obtained in this study indicate that hexane is the more efficient extraction solvent to be used in the organic decontamination of chars obtained in the co-pyrolysis of plastics, tyres and biomass. A sequential extraction with solvents of increasing polarity can provide a better decontamination of the raw pyrolysis char than any individual extraction. The compounds removed from the char during the decontamination process are mainly aliphatic hydrocarbons and aromatic hydrocarbons, therefore a material that may be upgraded to be used as a fuel and/or as raw material for the organic chemical industry.

Teixeira, Paula, Helena Lopes, Ibrahim Gulyurtlu, Nuno Lapa, and Pedro Abelha. "Evaluation of slagging and fouling tendency during biomass co-firing with coal in a fluidized bed." Biomass & Bioenergy. 39 (2012): 192-203. AbstractWebsite

Over the last decades, several indices based on ash chemistry and ash fusibility have been used to predict the ash behaviour during coal combustion, namely, its tendency for slagging and fouling. However, due to the physical–chemical differences between coals and biomass, in this work only the applicability of an ash fusibility index (AFI) to the combustion and co-combustion of three types of biomass (straw pellets, olive cake and wood pellets) with coals was evaluated. The AFI values were compared with the behaviour of ash during combustion in a pilot fluidized bed and a close agreement was observed between them. For a better understanding of the mechanisms associated with bed ash sintering, they were evaluated by SEM/EDS and the elements present on the melted ash were identified. Evidences of different sintering mechanisms were found out for the fruit biomass and herbaceous biomass tested, depending on the relative proportions of problematic elements. The particles deposited on a fouling probe inserted in the FBC were analyzed by XRD and the differences between the compounds identified allowed concluding that the studied biomasses present different tendencies for fouling. Identification of KCl and K2SO4 in the deposits confirmed the higher tendency for fouling of fruit biomass tested rather than wood pellets.

Bernardo, M., N. Lapa, M. Gonçalves, B. Mendes, F. Pinto, I. Fonseca, and H. Lopes. "Physico-chemical properties of chars obtained in the co-pyrolysis of waste mixtures." Journal of Hazardous Materials. 219-220 (2012): 196-202. AbstractWebsite

The present work aims to perform a multistep upgrading of chars obtained in the co-pyrolysis of PE, PP and PS plastic wastes, pine biomass and used tires. The quality of the upgraded chars was evaluated by measuring some of their physico-chemical properties in order to assess their valorisation as adsorbents’ precursors. The crude chars were submitted to a sequential solvent extraction with organic solvents of increasing polarity (hexane, mixture 1:1 v/v hexane:acetone and acetone) followed by an acidic demineralization procedure with 1 M HCl solution. The results obtained showed that the upgrading treatment allow the recovery of 63–81% of the pyrolysis oils trapped in the crude chars and a reduction in the char's ash content in the range of 64–86%. The textural and adsorption properties of the upgraded chars were evaluated and the results indicate that the chars are mainly mesoporous and macroporous materials, with adsorption capacities in the range of 3.59–22.2 mg/g for the methylene blue dye. The upgrading treatment allowed to obtain carbonaceous materials with quality to be reused as adsorbents or as precursors for activated carbon.

Bernardo, M., N. Lapa, M. Gonçalves, B. Mendes, and F. Pinto. "Study of the organic extraction and acid leaching of chars obtained in the pyrolysis of plastics, tire rubber and forestry biomass wastes." Procedia Engineering. 42 (2012): 1909-1916. AbstractWebsite

The present work aims to perform a characterization of chars obtained in the co-pyrolysis of waste mixtures composed by plastics, tires and pine biomass, to provide knowledge about the composition, leaching behavior and risk assessment of these materials in order to define strategies for their possible valorization or safe disposal. The chars were submitted to sequential solvent extractions with organic solvents of increasing polarity that allow the recovery of significant amounts of the pyrolysis oils trapped in the crude chars improving the yield of the pyrolysis liquids. An acidic demineralization procedure was successfully applied to the chars and high efficiency removals of the majority of the heavy metals were achieved. The demineralization study also demonstrated that hazardous heavy metals such as chromium, nickel and cadmium are significantly immobilized in the char matrix, and other heavy metals of concern such as zinc and lead will not represent a leaching problem if acidic conditions were not used. The obtained chars present sufficient quality and characteristics to be used as fuel or alternatively, to be used as adsorbents or precursors of activated carbon.

Teixeira, Paula, Helena Lopes, Ibrahim Gulyurtlu, and Nuno Lapa. "Uncertainty estimation to evaluate mass balances on a combustion system." Accreditation and Quality Assurance. 17.2 (2012): 159-166. AbstractWebsite

Mass balances of ash and potassium for a fluidized bed combustor were performed incorporating measurement uncertainties. The total output mass of ash or a chemical element should be equal to the mass in the input fuel; however, this is not often achieved. A realistic estimation of recovery uncertainty can support the reliability of a mass balance. Estimation of uncertainty helps to establish a reliable evaluation of the recovery ratio of ash mass and elemental mass. This may clarify whether any apparent lack in closing the mass balance can be attributed to uncertainties. The evaluation of measurement uncertainty for different matrices, namely coal, biomass, sand and ashes from different streams was based on internal quality control data and external quality control data, namely analysis of samples from proficiency tests or use of a certified reference material. The evaluation of intermediate precision and trueness allowed the estimation of measurement uncertainty. Due to the different physic and chemical characteristics of the studied matrices, the uncertainty of precision was evaluated using R-charts of data obtained from the analysis of duplicates for the majority of samples. This allowed evaluating sample heterogeneity effects. The instrumental acceptance criterion was also considered and included in the combined uncertainty. The trueness was evaluated using data from several proficiency tests and from analysis of a certified reference material or sample spiking. Statistically significant bias was included.

Teixeira, P., H. Lopes, I. Gulyurtlu, and N. Lapa. "Use of chemical fractionation to understand partitioning of biomass ash constituents during co-firing in fluidized bed combustion." Fuel. 101 (2012): 215-227. AbstractWebsite

Three species of biomass origin (straw pellets, olive cake and wood pellets) and two coals from different countries (Coal Polish and Coal Colombian) have been studied to understand the fate of their ash forming matter during the combustion process and to investigate the influence of co-firing biomass with coal. Three different approaches to investigate the ash behaviour were employed: (1) chemical fractionation analysis to evaluate the association/reactivity of ash forming elements in the fuels as a prediction tool, (2) establishment of elements partitioning in ash streams produced in the combustion and co-combustion trials, and (3) evaluation of enrichment factors of elements in the ash streams. The chemical fractionation analysis was applied to all fuels used to evaluate how the association/reactivity of elements making up ash may influence their behaviour during combustion. Combustion tests were carried out on a pilot scale fluidized bed combustor (FBC). Four ash streams were obtained at different locations. The uncertainty of measurements was estimated allowing a critical evaluation of mass balances over the combustion system and the partitioning of elements in the ash streams. The enrichment factors of elements in the several ash streams were estimated, incorporating uncertainties associated with analytical measurements. Results obtained showed that for FBC the relation between the chemical fractionation and the experimental partitioning is strongly affected by elutriation of particles. The element enrichment factor estimated for each ash stream, using Al as a reference element, revealed better correlations with the elements reactivity obtained by chemical fractionation because it overcomes particles elutriation effects. Nevertheless, it was observed that the reactivity estimated by chemical fractionation could not be solely interpreted as tendency of the elements to volatilize on FBC system, as reaction in bed zone of boiler may also occur retaining reactive elements.

Morais, J., R. Barbosa, N. Lapa, B. Mendes, and I. Gulyurtlu. "Environmental and socio-economic assessment of co-combustion of coal, biomass and non-hazardous wastes in a power plant." Resources, Conservation & Recycling. 55 (2011): 1109-1118. AbstractWebsite

Under the framework of the European project named COPOWER, the possibility to partially substitute coal used in a 243 MWth Power Plant by biomass and non-hazardous wastes for the production of electricity and steam was assessed. Three combustion scenarios were studied, based on the combustion tests performed in a Power Plant located in Duisburg (Germany): Scenario 0 (Sc0) – combustion of coal; Scenario 1 (Sc1) – combustion of coal + sewage sludge (SS) + meat and bone meal (MBM); Scenario 2 (Sc2) – coal + SS + wood pellets (WP). An environmental and socio-economic assessment of these three scenarios was performed. In the environmental point of view, Sc0 was the worst scenario, mainly due to the emission of greenhouse gases (GHG). Sc1 was the best scenario, mainly due to the reduction of GHG emission, eutrophication chemical species and ozone depletion gases. In the socio-economic point of view, Sc0 was the worst scenario, mainly due to the absence of GHG abatement, and Sc1 was the best scenario due to the best cost of electricity production and negative cost of avoided emissions.

Barbosa, R., N. Lapa, H. Lopes, I. Gulyurtlu, and B. Mendes. "Stabilization/solidification of fly ashes and concrete production from bottom and circulating ashes produced in a power plant working under mono and co-combustion conditions." Waste Management. 31.9-10 (2011): 2009-2019. AbstractWebsite

Two combustion tests were performed in a fluidized bed combustor of a thermo-electric power plant: (1) combustion of coal; (2) co-combustion of coal (68.7% w/w), sewage sludge (9.2% w/w) and meat and bone meal (MBM) (22.1% w/w).

Three samples of ashes (bottom, circulating and fly ashes) were collected in each combustion test. The ashes were submitted to the following assays: (a) evaluation of the leaching behaviour; (b) stabilization/solidification of fly ashes and evaluation of the leaching behaviour of the stabilized/solidified (s/s) materials; (c) production of concrete from bottom and circulating ashes. The eluates of all materials were submitted to chemical and ecotoxicological characterizations. The crude ashes have shown similar chemical and ecotoxicological properties. The s/s materials have presented compressive strengths between 25 and 40 MPa, low emission levels of metals through leaching and were classified as non-hazardous materials. The formulations of concrete have presented compressive strengths between 12 and 24 MPa. According to the Dutch Building Materials Decree, some concrete formulations can be used in both scenarios of limited moistening and without insulation, and with permanent moistening and with insulation.

Bernardo, M., M. Gonçalves, N. Lapa, and B. Mendes. "Determination of alkylphenols in eluates from pyrolysis solid residues using dispersive liquid-liquid microextraction." Chemosphere. 79.11 (2010): 1026-1032. AbstractWebsite

Dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–mass spectrometry (GC–MS) was applied for the determination of 11 alkylphenols in eluates of chars produced in the co-pyrolysis of different wastes.

The optimized DLLME procedure, 4 mL of sample solution, 15 μL of trichloroethylene as extraction solvent, 1 mL of acetone as dispersion solvent and addition of 15% (w/v) of NaCl, was validated. Under the optimum conditions, the enrichment factors were in the range of 82–180. Calibration curves were constructed for each analyte in pure water in the concentration range of 0.5–8 μg/L with correlation coefficients higher than 0.999. The limits of detection were between 0.07 and 0.17 μg/L. The repeatability of the method was evaluated using water samples fortified with the analyte mixture at two concentration levels: the relative standard deviation (RSD) values were between 3.7% and 8.0% for a concentration of 0.5 μg/L, and between 4.2% and 6.4% for a concentration of 3 μg/L. The recoveries of the analytes evaluated by fortification of real eluate samples were in the range of 67.9–97.9% for eluate 1 (obtained from a decontaminated char) and in the range of 61.9–101.4% for eluate 2 (obtained from the untreated char). o-Methylphenol presented low recoveries for both eluates showing a possible matrix effect. The results obtained show that this method is adequate for the determination of alkylphenols in environmental aqueous samples and presents itself as a fast and inexpensive technique, using minor amounts of organic solvents.

Bernardo, M., N. Lapa, M. Gonçalves, R. Barbosa, B. Mendes, F. Pinto, and I. Gulyurtlu. "Toxicity of char residues produced in the co-pyrolysis of different wastes." Waste Management. 30.4 (2010): 628-635. AbstractWebsite

Char residues produced in the co-pyrolysis of different wastes (plastics, pine biomass and used tyres) were characterized using chemical and toxicity assays. One part of the solid chars was submitted to extraction with dichloromethane (DCM) in order to reduce the toxicity of the char residues by removing organic contaminants. The different volatility fractions present in the extracted char (Char A) and in the raw char (Char B) were determined by progressive weight loss combustion. A selected group of heavy metals (Cd, Pb, Zn, Cu, Hg and As) was determined in both chars.

The chars were subjected to the leaching test ISO/TS 21268 – 2, 2007 and the resulting eluates were further characterized by determining a group of inorganic parameters (pH, conductivity, Cd, Pb, Zn, Cu, Hg and As contents) and the concentrations of several organic contaminants (volatile aromatic hydrocarbons and alkyl phenols). An ecotoxicological characterization was also performed by using the bio-indicator Vibrio fischeri.

The chemical and ecotoxicological results were analyzed according to the Council Decision 2003/33/CE and the criteria on the evaluation methods of waste ecotoxicity (CEMWE).

The results obtained in this work indicated that the extraction with DCM is an effective method for the removal of organic contaminants of high to medium volatility from pyrolysis solid residues, thus decreasing their toxicity potential. Zn can be leached from the chars even after the DCM extraction treatment and can contribute to the ecotoxicity of the eluates obtained from chars.

Both chars (treated and non treated with DCM) were classified as hazardous and ecotoxic wastes.

Bernardo, M., N. Lapa, R. Barbosa, M. Gonçalves, B. Mendes, F. Pinto, and I. Gulyurtlu. "Chemical and ecotoxicological characterization of solid residues produced during the co-pyrolysis of plastics and pine biomass." Journal of Hazardous Materials. 166.1 (2009): 309-317. AbstractWebsite

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 °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 (EC50 (30 min) ≥10%), but it was considered to be ecotoxic by the chemical criterion (Ni ≥ 0.5 mg/L). Residue B was considered to be ecotoxic by the ecotoxicological criterion: EC50 (30 min) ≤ 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.

Barbosa, R., N. Lapa, D. Boavida, H. Lopes, I. Gulyurtlu, and B. Mendes. "Co-combustion of coal and sewage sludge: chemical and ecotoxicological properties of ashes." Journal of Hazardous Materials. 170.2-3 (2009): 902-909. AbstractWebsite

The co-combustion of sewage sludge (SS) and coal is widely used for the treatment and thermal valorization of SS produced in wastewater treatment plants. The chemical and ecotoxicological properties of the ashes produced in this thermal treatment have not been fully studied. Two combustion tests were performed in a fluidized bed combustor. Colombian coal was used as fuel in test A. A blend (1 + 1) of this coal and a stabilized SS (Biogran®) was used in a second test B. Samples of the bottom and fly ashes trapped in two sequential cyclones were collected. The characterization of the ashes was focused on two main aspects: (1) the bulk content of a set of metals and (2) the characterization of eluates produced according to the European Standard leaching test EN 12457-2. The eluates were submitted to an ecotoxicological characterization for two bio-indicators. In what concerns the bulk content of ashes, both combustion tests have produced ashes with different compositions. The ashes formed during the co-combustion test have shown higher concentrations of metals, namely Cr, Cu, Ni, Pb, Zn and Fe for all ashes. The leaching test has shown low mobility of these elements from the by-products produced during the combustion and co-combustion tests. Cr and Cr(VI) were mainly detected in the eluates of the 1st cyclone ashes produced in both combustion tests and in the 2nd cyclone ashes produced in the co-combustion test.

Considering the ecotoxicity assays, the eluates of bottom and fly ashes for both combustion and co-combustion tests have shown low ecotoxic levels. The micro-crustacean Daphnia magna was generally more sensitive than the bacterium Vibrio fischeri. CEMWE criterion has allowed to classify the bottom ashes for both combustion and co-combustion tests as non-toxic residues and the fly ashes collected in both cyclones as toxic.

Bernardo, M., M. Gonçalves, N. Lapa, R. Barbosa, B. Mendes, F. Pinto, and I. Gulyurtlu. "Determination of aromatic compunds in leachates from pyrolysis solid residues using HS-GC-MS and DLLME-GC-MS." Talanta. 80.1 (2009): 104-108. AbstractWebsite

A method for the determination of 15 aromatic hydrocarbons in eluates from solid residues produced during the co-pyrolysis of plastics and pine biomass was developed. In a first step, several sampling techniques (headspace solid phase microextraction (HS-SPME), static headspace sampling (HS), and dispersive liquid–liquid microextraction (DLLME) were compared in order to evaluate their sensitivity towards these analytes. HS-SPME and HS sampling had the better performance, but DLLME was itself as a technique able to extract volatiles with a significant enrichment factor.

HS sampling coupled with GC–MS was chosen for method validation for the analytes tested. Calibration curves were constructed for each analyte with correlation coefficients higher than 0.999. The limits of detection were in the range of 0.66–37.85 ng/L. The precision of the HS method was evaluated and good repeatability was achieved with relative standard deviations of 4.8–13.2%. The recoveries of the analytes were evaluated by analysing fortified real eluate samples and were in the range of 60.6–113.9%.

The validated method was applied in real eluate samples. Benzene, toluene, ethylbenzene and xylenes (BTEX) were the compounds in higher concentrations.

The DLLME technique coupled with GC–MS was used to investigate the presence of less volatile contaminants in eluate samples. This analysis revealed the presence of significant amounts of alkyl phenols and other aromatic compounds with appreciable water solubility.

Paradela, F., F. Pinto, I. Gulyurtlu, I. Cabrita, and N. Lapa. "Study of the co-pyrolysis of biomass and plastic wastes." Clean Technologies and Environmental Policy. 11.1 (2009): 115-122. AbstractWebsite

This work aimed to study the recovery of two types of waste by the process of pyrolysis. The obtained results show that the adding of a plastic mix improves the overall efficiency of the slow pyrolysis of pine. Therefore, it was possible to achieve higher liquid yields and less solid product than in the classic slow pyrolysis carbonization of biomass. The obtained liquids showed heating values similar to that of heating fuel oil. The gas products had energetic contents superior to that of producer gas, and the obtained solid fractions showed heating values higher than some coals. There were also identified some typical products of fast biomass pyrolysis used as raw material in several industries. The effects of experimental conditions in product yield and composition were also studied. The parameters that showed higher influence were (with its increase): reaction time on gas product composition (increase of the alkane content) and on liquid composition (increase in aromatics content); reaction temperature on product yield (decrease of liquid yield with increase of solids and gases) and on gas product composition (increase in alkane content); initial pressure on liquid composition (increase in the aromatics content) and mainly the pine content of the initial mixture on products yield (increase of gas and solid yield with a decrease in liquids) and on the gas product composition (favouring CO and CO2 formation).

Lapa, N., J. Morais, C. Borges, B. Mendes, and J. F. Santos Oliveira. "An integrated approach to assess the biodegradability of a wastewater containing chromium by using chemical and biological methods." Global Symposium on Recycling, Waste Treatment and Clean Technology, REWAS’2004. Eds. I. Gaballah, B. Mishra, R. Solozabal, and M. Tanaka. San Sebastián: TMS/INASMET, 2004. 1351-1362. Abstractrewas04_lapa_et_al.pdf

The Water Company of the North Alentejo (Águas do Norte Alentejano) (Portugal) has decided to implement a treatment plant to treat an urban wastewater with a significant influence of tannery effluents. The design of the wastewater treatment plant was attributed to a consortium coordinated by Sisaqua Company. Since the levels of the biodegradability and toxicity of the wastewater to be treated were unknown, Sisaqua Company asked the New University of Lisboa to develop and execute a monitoring plan to define the chemical composition and the levels of the biodegradability and toxicity of the wastewater.
A composite sampling procedure of the wastewater was performed during a daily working cycle of the tanneries. The composite sample was characterized for 19 chemical parameters. Five of these parameters were total Cr, Cr (VI), Zn, Cu and Al, which were determined in the dissolved and suspended fractions. The composite sample was also submitted to a biological test to assess its biodegradability degree. This assay was performed according to the methodology indicated in the test 301E of OECD [1], taking into account the amendment of 1992. A respirometric assay was carried out, to assess the toxic effect of the composite sample on the biological populations involved in the biological stabilization of organic compounds. This assay followed the “Sapromat” methodology developed by Brabander and Vandeputte [2]. Finally, the composite sample was submitted to a coagulation-flocculation process according to the methodologies proposed by Eckenfelder [3, 4] and Pereira [5]. The supernatants were characterized for the same chemical and biological parameters as it was described for the composite sample.
It was possible to conclude that the high levels of Cr present in the composite wastewater were mainly in the trivalent oxidation state. Since this oxidation state is less toxic for biological populations than the Cr (VI) and this metal was mainly in the suspended fraction, it was possible to obtain a biodegradability of the organic compounds quite similar to those observed for domestic wastewaters. The toxicity determined by the “Sapromat” method was slightly higher than those determined for domestic wastewaters. Nevertheless, this toxicity did not affect significantly the wastewater biodegradability. The Cr (III) was easily removed by a chemical coagulation-flocculation process.

Lopes, M. H., P. Abelha, N. Lapa, J. S. Oliveira, I. Cabrita, and I. Gulyurtlu. "The behaviour of ashes and heavy metals during the co-combustion of sewage sludges in a fluidised bed." Waste Management. 23.9 (2003): 859-870. AbstractWebsite

Co-combustion tests of dry sewage sludges with coal were performed in a pilot bubbling FBC aiming at the characterization of ashes and determining the behaviour of heavy metals in the process. The tests showed compliance with the regulatory levels as far as heavy metal emissions were concerned. The bottom ashes, which accounted for about 70% of the total ash production, were obtained in a granular form, with diameters ranging from 0.5 to 4 mm. The heavy metals were distributed in ashes obtained from different locations of the installation and their concentrations were found to vary depending on the location of capture. The increase in heavy metals content in bottom ashes was not found to lead to higher leachability and ecotoxicity compared to sewage sludges, suggesting that there could be opportunities for their further use. Mercury suffered vaporisation inside the reactor, thus leaving bottom ashes free of contamination by it. However, there was observed a strong retention of mercury in cyclone ashes due to the presence of unburned carbon which probably acted as an adsorbent. The effluent mercury was also found to be mostly associated with the particulate fraction, being less than 20% emitted in gaseous forms. The results suggested that the combustion of the sewage sludge could successfully be carried out and the amount of unburned carbon leaving the combustor but captured in cyclone was large enough to ensure substantial retention of mercury at low temperatures, hence could contribute to an improvement of the mercury release which still remains an issue of great concern to resolve during combustion of waste materials.

Guerrero, C., J. Carrasco de Brito, N. Lapa, and J. F. Santos Oliveira. "Re-use of industrial orange wastes as organic fertilizers." Bioresource Technology. 53.1 (1995): 43-51. AbstractWebsite

The aim of this study was to evaluate the possibility of the re-use of industrial orange wastes as organic soil fertilizer. The assay was performed with a lettuce variety widely produced and consumed in Portugal and, consequently, with great commercial interest. Lactuca sativa L. (osteolata variety) was cultivated in Mitcherlich pots containing samples of a poor soil of the Algarve region. This soil was prepared with different amounts of either pulp or peel orange-wastes from an orange-juice industry. The wastes were applied according to an increasing amount of nitrogen. The results obtained were submitted to statistical tests, in order to find the relations between the production of fresh and dry matter, and the percentages of nutrients (nitrogen, phosphorous, potassium, calcium, magnesium and iron) that were obtained in the dry matter, with the types and amounts of wastes applied. An increase in the average production of both fresh- and dry-matter with increasing amounts of either pulp or peel wastes applied, and high positive correlation coefficients between the average percentages of nitrogen, phosphorus and potassium obtained in the dry matter with the average production of both fresh- and dry-matter were found. No phytotoxicity was observed.