Cork Waste Research Articles

Influence of temperature on the gasification of cork wastes

This work aimed to study the gasification of cork industry residues using a semi-batch fluidized bed reactor. The experimental tests were performed using air as oxidizing agent and sand particles as bed material. The effect of bed temperature (780 – 900 ºC) on gasification performance was evaluated. Samples of producer gas were analysed, by a gas chromatograph, allowing the quantification of CO, CO2, H2, CH4, O2 and N2. Temperature had an important role in gasification performance and all gasification parameters showed an increase with the temperature rise up to 850 ºC.

Production of added value bacterial lipids through valorisation of hydrocarbon-contaminated cork waste

This work demonstrates that cork used as oil-spill sorbents, contaminated with liquid hydrocarbons, herein demonstrated with hexadecane, can be biologically treated by Rhodococcus opacus B4 with concomitant lipids production. R. opacus B4 consumed up to 96% of hexadecane (C16) impregnated in natural and regranulated cork sorbents after 48h incubation, producing 0.59±0.06g of triacylglycerol (TAG) g−1 of C16 consumed with a TAG content of 0.60±0.06gg−1 of cellular dry weight (CDW) and 0.54±0.05g TAG g−1 of C16 consumed with a TAG content of 0.77±0.04gg−1 (CDW), respectively. TAG was mainly composed by fatty acids of 16 and 18 carbon chains demonstrating the feasibility of using it as raw material for biodiesel production. In addition, the obtained lipid-rich biomass (whole cells) can be used for biomethane production, at a yield of 0.4L CH4 g−1 (CDW).The obtained results support a novel approach for management of oil-spill contaminated cork sorbents through its valorisation by producing bacterial lipids, which can be used as feedstocks for biofuels production.

Cork Plastic Composite Optimization for 3D Printing Applications

Among natural fillers, cork has been acknowledged as a suitable alternative of other cellular materials that are widely employed in engineering applications due to their low conductivity to heat, noise and vibration, high abrasion resistance and flexibility, high compressibility ratio, among other characteristics [1]. The eco-friendly features of natural fillers based composites make them a very promising and sustainable solution to large markets mainly if additive manufacturing technologies, such as 3D printing, are used [2]. Through 3D printers, engineers, designers and architects can create design and decor products with a free complexity of geometry. In this research work, plastic matrices of HDPE – obtained from conventional suppliers – were reinforced with different ratios of cork waste and natural cork powders – obtained from cork transformation industries – to find the optimum mixture for 3D printing. The effects of cork powders content in the plastic on the morphological, physical and mechanical properties of the composites were investigated through the density, optical microscopy, wettability, thermal analysis and tensile testing. Cork-based composites were processed by an extrusion system, and the mixture of polymer, adhesive and fillers is discussed. The results show that the addition of pure cork and cork waste can be processed with polymers such as HDPE, having adequate physical and mechanical properties.

Oxidized Xanthan Gum and Chitosan as Natural Adhesives for Cork.

Natural cork stopper manufacturing produces a significant amount of cork waste, which is granulated and combined with synthetic glues for use in a wide range of applications. There is a high demand for using biosourced polymers in these composite materials. In this study, xanthan gum (XG) and chitosan (CS) were investigated as possible natural binders for cork. Xanthan gum was oxidized at two different aldehyde contents as a strategy to improve its water resistance. This modification was studied in detail by 1H and 13C nuclear magnetic resonance (NMR), and the degree of oxidation was determined by the hydroxylamine hydrochloride titration method. The performance of the adhesives was studied by tensile tests and total soluble matter (TSM) determinations. Xanthan gum showed no water resistance, contrary to oxidized xanthan gum and chitosan. It is hypothesized that the good performance of oxidized xanthan gum is due to the reaction of aldehyde groups—formed in the oxidation process—with hydroxyl groups on the cork surface during the high temperature drying. Combining oxidized xanthan gum with chitosan did not yield significant improvements.

Environmental implications of the use of agglomerated cork as thermal insulation in buildings

The market for insulation material is playing a crucial role in Europe's energy transformation, due to its influence on energy consumption in buildings. The introduction of renewable materials for thermal insulation is recent, and little is known so far about its environmental implications. This study analyses the environmental performance of a cork insulation board, made of agglomerated cork from forestry cork wastes, by means of cradle-to-gate Life Cycle Assessment methodology. The results indicate that the use of natural insulation materials does not necessarily imply a reduction of environmental impacts due to manufacturing processes with a low technological development. In this case, the most influential stage is the manufacturing stage, in which the board agglomeration and the cork trituration have the highest impacts. The most influential inputs are both the transport used during the life cycle and the large quantities of electricity and diesel in the manufacturing stage. Some strategies have been identified to reduce the environmental impact, such as promote the acquisition of local raw cork to reduce transportation from the manufacturer, improve the efficiency and productivity of manufacturing processes and improve the product design to help increase its market share. Moreover, the inclusion of biogenic carbon contained in forest-based building materials affects the Global Warming Potential results considerably. However, it is very important to consider how this biogenic carbon is calculated and how the product is managed after its lifetime.

Fungal biodegradation of anthracene-polluted cork: A comparative study

ABSTRACTThe efficiency of cork waste in adsorbing aqueous polycyclic aromatic hydrocarbons (PAHs) has been previously reported. Biodegradation of contaminated cork using filamentous fungi could be a good alternative for detoxifying cork to facilitate its final processing. For this purpose, the degradation efficiency of anthracene by three ligninolytic white-rot fungi (Phanerochaete chrysosporium, Irpex lacteus and Pleurotus ostreatus) and three non-ligninolytic fungi which are found in the cork itself (Aspergillus niger, Penicillium simplicissimum and Mucor racemosus) are compared.Anthracene degradation by all fungi was examined in solid-phase cultures after 0, 16, 30 and 61 days. The degradation products of anthracene by P. simplicissimum and I. lacteus were also identified by GC-MS and a metabolic pathway was proposed for P. simplicissimum. Results show that all the fungi tested degraded anthracene. After 61 days of incubation, approximately 86%, 40%, and 38% of the initial concentration of anthracene (i.e., 100 µM) was degraded by P. simplicissimum, P. chrysosporium and I. lacteus, respectively. The rest of the fungi degraded anthracene to a lesser extent (<30%). As a final remark, the results obtained in this study indicate that P. simplicissimum, a non-ligninolytic fungi characteristic of cork itself, could be used as an efficient degrader of PAH-contaminated cork.

Cork waste in cement based materials

Abstract Cork is a natural material that has always been associated to mankind having huge potential and many uses. The cork industry worldwide consumes more than 280,000 t of cork a year. However, about 20% to 30% of the raw cork received at the processing units is rejected, mainly as cork dust. Finding useful applications for the rejected cork may have important economic and environmental implications. Trying to combine the advanced technology of self-compacting concrete and use of this waste from the cork industry, this study concerns the possibility of using cork powder as a substitute for fines in mixtures of self-compacting concrete. An experimental program was carried out to assess the behavior of this material in the mixture and define properties in terms of strength and durability of self-compacting concrete containing cork powder. It was found that it is possible to use an abundant waste material from the cork industry, cork powder, as fines in Self Compacting Concrete resulting in a good strength level (C 30/37) and suitable durability for common applications.

Cork: Sustainability and New Applications

Cork is a strategic material used in multiple applications and its use has accompanied mankind since the days of Ancient Egypt. The cork oak forests are extremely well adapted to the semi-arid regions of south- ern Europe and northern Africa (west- ern Mediterranean). These forests help to prevent the advance of desertification, improve water penetration into the soil and hydrological regulation, promote soil conservation, and being the perfect habi- tat for many animal and vegetables species. Consequently, these forests promote biodi- versity (Pereira, 2007; Gil, 2011, 2014). the extraction. During the tree lifetime in operation, an average cork oak produces about four times more cork bark than the cork tree would produce if it were not sub- ject to stripping. The sum of the various layers of cork produced and harvested is greater than the single layer of cork pro- duced if there was no extraction during the life of a tree (Gil, 1998, 2011). Related to environmental aspects of the transformation of the cork raw mater- ial, it can be mentioned the production of expanded cork agglomerate. The man- ufacture of this cork product only uses superheated steam, using generators fueled with cork waste, not introducing any other products not exclusively cork, and giving up agglomeration based on resins of the cork itself. So, this is a completely nat- ural and ecological product. In addition, in the processing of this and other cork products an important residue is produced, cork powder. This powder is commonly burned to produce steam and/or power used in the factories themselves, given the high energy content of this material. Also, all other industrial cork wastes are reused or valorized in another way (Gil, 1998). So, there is really no wasted cork.

Strength and Durability of Mortar Using Cork Waste Ash as Cement Replacement

Cork powder, the major waste from cork processing industries, is generated from grinding, cutting and finishing operations throughout the industrial cork process. Cork powder has been used mainly as fuel in cork industries. Cork waste ash is usually landfilled but if efficiently used in cement based construction materials it could contribute to sustainability. Strength and durability testing was undergone on mortar with 10 and 20% cement replacement with cork waste ash. Although strength is acceptable for 10% cement replacement with cork ash (5% loss at 90 days, compared to control), most durability properties (tested up to 6 months according to test type) reduced performance probably due to a broader pore structure caused by coarse particles in the ash which tested non pozzolanic. Moreover, cork waste ash does not present the necessary requirements in terms of chemical properties considering several standards. Present work has revealed that this cork waste cannot be used as a pozzolan or as a filler in cement based materials. In fact it is known that chemical composition of biomass ash is highly variable due to moisture variations, ash yield and different genetic types of inorganic matter in biomass and therefore it is important to pinpoint which types of biomass waste are adequate or not to use as cement replacement in construction.

Removal of Cr(VI) from water by cork waste

The biosorption by cork powder is considered as a promising method for heavy metal removal from industrial waste waters such as chromium tanning factories. The aim of this study is to evaluate the efficiency extent of this method using cork powder as a biosorbent for Cr(VI). The Fourier Transform Infrared spectroscopy (FTIR) analysis permits to distinguish the type of functional groups likely to participate in metal binding. A linear form of BET isotherms for all the three used temperatures (i.e., 25, 35 and 45°C) and a pseudo-second-order equation of adsorption kinetics are obtained. Other experimental results highlight the meaningful influence of parameters such as contact time, pH, concentration of Cr(VI) and the adsorbent particle size on Cr(VI) adsorption. 97% of Cr(VI) has been removed under definite conditions particularly a particle size of diameter d<0.08mm and pH of 2–3 values.

Energy recovery from cork industrial waste: Production and characterisation of cork pellets

The cork industry presents itself as one of the most entrepreneurial in the Portuguese industrial sector, contributing significantly to the increase of exports. However, it is an industry in which the use of raw materials is maximised leaving a large volume of waste. The cork industry has tried to take advantage of these residues, mainly through direct energy recovery, despite the technical and safety difficulties presented by the use of such low density material, which complicates and hinders its transportation for industrial uses outside the area in which it is produced. The densification process opens new doors for such use and also for its storage, because it produces better results when compared with other more common products, such as wood sawdust or even forest and agricultural waste. Thus, cork pellets emerge as a safer and more easily transportable alternative for energy recovery from cork dust and other granulated types of cork waste, which offer the prospects for wider use. The results demonstrate that cork pellets have higher calorific value when compared with other biomass pellets; typically, approximately 20MJ/kg with 3% volume of ashes, which is equivalent to that obtained from the combustion of pellets produced from combined forest and agricultural waste with a bulk density of 750kg/m3, which offers real advantages in terms of logistics.

Adsorption of SO2 onto waste cork powder-derived activated carbons

Three activated carbon samples have been prepared by thermal (ACchar), physical (with CO2, ACCO2) and chemical (with KOH, ACKOH) activation of waste cork powder. Cork was characterized by thermogravimetric, elemental and proximate analyses, and activated carbons were characterized by elemental and proximate analyses, adsorption–desorption of N2, acid/base and Boehm’s titration and FTIR (ATR) spectroscopy. A commercial activated carbon sample (ACcom) was subjected to the same characterization program for comparison purposes. Activation of cork conducted to an increase in BET surface area and pore volume in the sequence: ACchar<ACCO2<ACKOH, getting close to those of ACcom, and to an increase in surface acidity in the sequence: ACchar<ACCO2≈ACcom<ACKOH. The four adsorbents were tested in the adsorption of SO2, where ACKOH presented the highest adsorption capacity, while ACchar and ACCO2 presented similar behaviors, comparable to that of ACcom. Adsorption equilibrium was successfully fitted to Langmuir and Freundlich isotherms. Desorption experiments demonstrated how SO2 strong adsorption was favored when decreasing surface acidity.

The mechanical, transport and thermal properties of mortar and concrete containing waste cork

Abstract This study examines the impact of cork used as sand replacement or stone replacement on the plastic, mechanical, transport, microstructural and thermal properties of mortar and concrete. Mix design variables include the percentage of cork, cork size, and the cork blend. Key findings from this study revealed that: (i) The greatest early age (days 3 and 7) cube strengths were achieved by 24 h moisture saturation of the cork followed by draining it prior to use in concrete. Heat exposure of 50 °C or 100 °C resulted in detrimental effects on cube strength gain. (ii) Finer cork sizes were most beneficial to achieve optimum mechanical, and transport properties however high permeability values indicate that concrete-cork composites considered in this study may be vulnerable to poor durability performance. (iii) Greater percentages of cork as sand or stone replacement had the greatest impact on thermal resistance. (iv) Blending multiple cork sizes to achieve a greater size distribution of cork granules used as sand or stone replacement did not yield notable beneficial results.

Use of Cork Waste as Biosorbent for Hexavalent Chromium

The biosorption by cork powder is considered as a new method for heavy metal removal from industrial waste waters such as chromium tanning factories. The aim of this study is to evaluate the efficiency extent of this method using a cork powder as biosorbent for hexavalent chromium Cr(VI). The Fourier Transform Infrared spectroscopy (FTIR) analysis permits to distinguish the type of functional groups likely to participate in metal binding. A linear form of BET isotherms for all the three used temperatures (25, 35 and 45°C) and a pseudo-second-order Lagergren equation of adsorption kinetics are obtained. Other experimental results highlight the meaningful influence of parameters such as contact time, pH and concentrations of the solution, on chromium adsorption rate that reach a 97% value under definite conditions particularly a pH of 2-3 values.

Cork-based activated carbons as supported adsorbent materials for trace level analysis of ibuprofen and clofibric acid in environmental and biological matrices

In this contribution, powdered activated carbons (ACs) from cork waste were supported for bar adsorptive micro-extraction (BAμE), as novel adsorbent phases for the analysis of polar compounds. By combining this approach with liquid desorption followed by high performance liquid chromatography with diode array detection (BAμE(AC)-LD/HPLC-DAD), good analytical performance was achieved using clofibric acid (CLOF) and ibuprofen (IBU) model compounds in environmental and biological matrices. Assays performed on 30 mL water samples spiked at the 25.0 μg L −1 level yielded recoveries around 80% for CLOF and 95% for IBU, under optimized experimental conditions. The ACs textural and surface chemistry properties were correlated with the results obtained. The analytical performance showed good precision (<15%), suitable detection limits (0.24 and 0.78 μg L −1 for CLOF and IBU, respectively) and good linear dynamic ranges ( r 2 > 0.9922) from 1.0 to 600.0 μg L −1. By using the standard addition methodology, the application of the present approach to environmental water and urine matrices allowed remarkable performance at the trace level. The proposed methodology proved to be a viable alternative for acidic pharmaceuticals analysis, showing to be easy to implement, reliable, sensitive and requiring low sample volume to monitor these priority compounds in environmental and biological matrices.

The use of cork waste as a biosorbent for persistent organic pollutants–Study of adsorption/desorption of polycyclic aromatic hydrocarbons

The aim of this study is to determine the sorption-desorption behavior of a mixture of thirteen aqueous PAHs on cork waste at a particle of size 0.25–0.42 mm obtained from the remains of cork strips. The final purpose is to use this natural adsorbent as an alternative to activated carbon in an innovative approach for the removal of this class of toxic compounds, and significantly reduce the regeneration costs of the process. The chemical composition of the selected cork revealed that suberin (38.5 %) and lignin (31.6 %) were the main structural components of the cell wall. The high efficiency of cork as a biosorbent of PAHs is shown by the fact that just over 80 % of adsorption occurred during the first two minutes of contact time. Both Freundlich's and Langmuir's isotherms gave good fits to the sorption process. The highest adsorption affinities were exhibited for pyrene, anthracene, and phenanthrene. Desorption studies indicate a high degree of irreversibility for all PAHs, and especially so in the case of high molecular PAHs. The correlation with KF and low molecular weight PAHs was the most significant. The quantity of cork required to reduce water pollution was estimated to be between 3 and 15 times less than the quantities required in the case of other materials (i.e. aspen wood and leonardite). This study demonstrates for the first time that cork is a potential biosorbent for PAHs and may have relevance in the future treatment of PAH-contaminated waters.

ADSORPTION, KINETICS, AND EQUILIBRIUM STUDIES ON REMOVAL OF 4,4-DDT FROM AQUEOUS SOLUTIONS USING LOW-COST ADSORBENTS

The removal of a chlorinated pesticide (4,4-DDT) from aqueous solutions by a batch adsorption technique using different low-cost adsorbents was investigated. Two adsorbents, wood sawdust (A) and cork wastes (B), were used to determine adsorption efficiency. The influence of the adsorbent particle size and the organic matter of water (humic acids) on the removal process was studied. The obtained results were compared to those obtained with a commercial powdered activated carbon (PAC, F400, Chemviron) (C). Kinetic studies were performed to understand the mechanistic steps of the adsorption process. The rate of the adsorption kinetics of 4,4-DDT on the low-cost adsorbents was found best fitted with a pseudo-second-order kinetic model. This is in contrast to the rate of the adsorption kinetics of the PAC F400, which was best fitted with the Lagergren model. The application of the Morris-Weber equation showed that the adsorption process of 4,4-DDT on these adsorbents was complex. Both the adsorption on the surface and the intraparticle diffusion were the rate-controlling mechanisms. Langmuir and Freundlich adsorption isotherms were applicable to the adsorption process and their constants were evaluated. The adsorption capacity (qm) calculated from the Langmuir isotherm (69.44 mg·g−1, 19.08 mg·g−1, and 163.90 mg·g−1, respectively, for A, B, and C) showed that the process is highly particle size dependent, that the organic matter influenced the adsorption process negatively, and that wood sawdust is the most effective adsorbent for the removal of 4,4-DDT from aqueous solutions. The adsorbents studied exhibited a possible application in water decontamination, as well as in treatment of industrial and agricultural waste waters.

Activated carbons for the adsorption of ibuprofen

Powdered activated carbons prepared from cork waste were studied for the ibuprofen removal from liquid phase. Two carbons were used: CAC obtained by chemical activation with K 2CO 3, and CPAC prepared by a two-step method, chemical activation with K 2CO 3 followed by steam activation. The ash content analysis showed that, for this raw material, the previous acid treatment can be omitted. The textural properties of the samples, evaluated by low temperature N 2 adsorption, show that the main difference is related with the volume of the larger micropores (supermicropores), which is more developed for CPAC. The surface chemistry characterization, made by the determination of the point of zero charge (PZC) and Boehm’s titration, show that the second activation step led to an activated carbon with less acidic groups, associated with the absence of the strongest acidic groups. Kinetic and equilibrium adsorption data show that the process obeys to the pseudo-second order kinetic equation and Langmuir adsorption model. Between 25 and 40 °C no significant influence of the temperature on ibuprofen adsorption was observed. Results indicate that the removal efficiency is higher than 90% between pH 2 and 4 and decreases as pH values increase to a value of 11. The results show that both samples are suitable for ibuprofen removal, although CPAC has advantages, namely, high initial adsorption rate, high adsorption capacity and high removal efficiency, in some cases 100%, for a large range of pH.

Cortiça: uma nova perspectiva

With this work we aim to increase the range of applications for cork wastes, presenting a new perspective on their use, namely in the preparation of porous carbon materials. These materials were prepared by physical activation and chemical activation with different chemical agents (carbon dioxide, water vapour, sodium hydroxide, potassium hydroxide and phosphoric acid). The results obtained by a representative group of samples, show the potential use of some of these new materials in the field of gas and liquid phase adsorption applications. This contribution complements many others, such as the application of cork in agglomerates, coatings and isolations, in an attempt to valorise the exploration of a tree, the cork-oak, which is fundamental for Portuguese agriculture. The waste materials involved can result from activities both upstream and downstream, involving not only forestry production, but also industrial treatment and transformation, as well as derived products of the cork, amongst others.

Fine particle capture in biomass boilers with recirculating gas cyclones: Theory and practice

This paper addresses the theoretical development and experimental validation of optimized recirculating reverse-flow gas cyclones. The simulation of these systems is based on the predictive properties of a finite diffusivity model, modified to include partial recirculation of the cyclones' emissions. Experimental validation was obtained at laboratory and pilot scales at low temperatures (up to 350 K) and for cork waste biomass boilers at higher temperatures (up to 600 K). Under certain circumstances, with recirculation, the proposed system showed a better performance than an online pulse jet bag filter, and substantially better than with multicyclone systems. The generally observed unexpected high collection of submicron particles, which occurs with inlet concentrations as low as 100 μg/m 3, is attributed to turbulent dispersion, either by promoting fine particle capture by larger ones, much like what occurs in recirculating fluidized beds, or by bringing fine particles near the cyclone wall. The extremely fine particle size distributions exiting from the recirculation system, as measured off-line at laboratory, pilot and industrial scales, were confirmed at pilot scale using online measurements through a laser monitor.