Recycling carbon fibre reinforced polymers for structural applications: technology review and market outlook

Both environmental and economic factors have driven the development of recycling routes for the increasing amount of carbon fibre reinforced polymer (CFRP) waste generated. This paper presents a review of the current status and outlook of CFRP recycling operations, focusing on state-of-the-art fibre reclamation and re-manufacturing processes, and on the commercialisation and potential applications of recycled products. It is shown that several recycling and re-manufacturing processes are reaching a mature stage, with implementations at commercial scales in operation, production of recycled CFRPs having competitive structural performances, and demonstrator components having been manufactured. The major challenges for the sound establishment of a CFRP recycling industry and the development of markets for the recyclates are summarised; the potential for introducing recycled CFRPs in structural components is discussed, and likely promising applications are investigated.     

Evolution of organic matter during composting of different organic wastes assessed by CPMAS 13C NMR spectroscopy

In this paper, the evolution of organic matter (OM) during composting of different mixtures of various organic wastes was assessed by means of chemical analyses and CPMAS ¹³C NMR spectroscopy measured during composting. The trends of temperatures and C/N ratios supported the correct evolution of the processes. The CPMAS ¹³C NMR spectra of all composting substrates indicated a reduction in carbohydrates and an increase in aromatic, phenolic, carboxylic and carbonylic C which suggested a preference by microorganisms for easily degradable C molecules. The presence of hardly degradable pine needles in one of the substrates accounted for the lowest increase in alkyl C and the lowest reduction in carbohydrates and carboxyl C as opposite to another substrate characterized by the presence of a highly degradable material such as spent yeast from beer production, which showed the highest increase of the alkyl C/O-alkyl C ratio. The highest increase of COOH deriving by the oxidative degradation of cellulose was shown by a substrate composed by about 50% of plant residues. The smallest increases in alkyl C/O-alkyl C ratio and in polysaccharides were associated to the degradation of proteins and lipids which are major components of sewage sludge. Results obtained were related to the different composition of fresh organic substrates and provided evidence of different OM evolution patterns as a function of the initial substrate composition.     

Optimal utilization of waste-to-energy in an LCA perspective

Energy production from two types of municipal solid waste was evaluated using life cycle assessment (LCA): (1) mixed high calorific waste suitable for production of solid recovered fuels (SRF) and (2) source separated organic waste. For SRF, co-combustion was compared with mass burn incineration. For organic waste, anaerobic digestion (AD) was compared with mass burn incineration. In the case of mass burn incineration, incineration with and without energy recovery was modelled. Biogas produced from anaerobic digestion was evaluated for use both as transportation fuel and for heat and power production. All relevant consequences for energy and resource consumptions, emissions to air, water and soil, upstream processes and downstream processes were included in the LCA. Energy substitutions were considered with respect to two different energy systems: a present-day Danish system based on fossil fuels and a potential future system based on 100% renewable energy. It was found that mass burn incineration of SRF with energy recovery provided savings in all impact categories, but co-combustion was better with respect to Global Warming (GW). If all heat from incineration could be utilized, however, the two alternatives were comparable for SRF. For organic waste, mass burn incineration with energy recovery was preferable over anaerobic digestion in most impact categories. Waste composition and flue gas cleaning at co-combustion plants were critical for the environmental performance of SRF treatment, while the impacts related to utilization of the digestate were significant for the outcome of organic waste treatment. The conclusions were robust in a present-day as well as in a future energy system. This indicated that mass burn incineration with efficient energy recovery is a very environmentally competitive solution overall.     

Printed wiring boards for mobile phones: characterization and recycling of copper

The popularization of mobile phones, combined with a technological evolution, means a large number of scrap and obsolete equipment are discarded every year, thereby causing economic losses and environmental pollution. In the present study, the printed wiring boards scrap of mobile phones were characterized in order to recycle some of the device components, using techniques of mechanical processing, hydrometallurgy and electrometallurgy. The use of the techniques of mechanical processing (milling, particle size classification, magnetic and electrostatic separation) was an efficient alternative to obtain a concentrated fraction (mainly iron in the magnetic fraction and copper in the conductive fraction) and another fraction containing polymers and ceramics. At the end of mechanical processing, a concentrated fraction of metals could be obtained with an average concentration of 60% copper. This concentrated fraction in metals was dissolved in aqua regia and sent to electrowinning to recover 92% of the dissolved copper. The obtained cathodes have a copper content above 95%, which demonstrates the technical feasibility of recovery of copper using the techniques of mechanical processing, hydrometallurgy and electrometallurgy.     

Papermill industrial waste as a sustainable source for high efficiency absorbent production

Papermill sludge (PMS) is generated during the wastewater treatment process of paper production. Its handling and disposal techniques are of great concern for the environment. It can be landfilled as a waste, or it can be recycled and converted into useful products of high value. It has a very promising application as an absorbing agent for the cleaning of water surfaces polluted with hydrophobic substances (vegetable, synthetic and mineral oils, animal fats, fuels, organic chemicals and even coal dust). Here, we present the pretreatment procedure (hydrophobation, mechanical and thermal treatments) of PMS that produces a lightweight absorbent material (HAWSC - high efficiency absorbent for water surface cleaning), which floats on the water surface and binds hydrophobic pollutants with considerably higher efficiency than commercially available mineral and synthetic absorbents. After its application, it can be incinerated, due to its high caloric value, to produce energy. The incineration residues can then be formed into granules that can be used as an efficient absorbent for fluids spilled onto solid surfaces.     

Mass balances and life cycle inventory of home composting of organic waste

A comprehensive experimental setup with six single-family home composting units was monitored during 1 year. The composting units were fed with 2.6-3.5 kg organic household waste (OHW) per unit per week. All relevant consumptions and emissions of environmental relevance were addressed and a full life-cycle inventory (LCI) was established for the six home composting units. No water, electricity or fuel was used during composting, so the major environmental burdens were gaseous emissions to air and emissions via leachate. The loss of carbon (C) during composting was 63-77% in the six composting units. The carbon dioxide (CO(2)) and methane (CH(4)) emissions made up 51-95% and 0.3-3.9% respectively of the lost C. The total loss of nitrogen (N) during composting was 51-68% and the nitrous oxide (N(2)O) made up 2.8-6.3% of this loss. The NH(3) losses were very uncertain but small. The amount of leachate was 130 L Mg(-1) wet waste (ww) and the composition was similar to other leachate compositions from home composting (and centralised composting) reported in literature. The loss of heavy metals via leachate was negligible and the loss of C and N via leachate was very low (0.3-0.6% of the total loss of C and 1.3-3.0% of the total emitted N). Also the compost composition was within the typical ranges reported previously for home composting. The level of heavy metals in the compost produced was below all threshold values and the compost was thus suitable for use in private gardens.     

Biodegradable Water Soluble Copolymer for Antimicrobial Applications

Synthesis and characterization of novel biodegradable, water soluble and optically active DL-malic acid (DMA) and citric acid (CA) copolymers were studied for possible use as antibacterial agents. The copolymers were synthesized by direct bulk melt condensation in the absence of a catalyst above 150 °C. Characterization of obtained copolymers was carried out with the help of infrared absorption spectra, differential scanning calorimetry and thermo gravimetric analysis. The antibacterial activity of copolymers against bacteria was investigated. The results obtained shows the above copolymers possess a broad wound dressing activity against different types of bacteria and may be useful as antibacterial agents.     

Evaluation of photolysis and hydrolysis of pyraclostrobin in aqueous solutions and its degradation products in paddy water

This study evaluated the hydrolysis and photolysis kinetics of pyraclostrobin in an aqueous solution using ultra-high-performance liquid chromatography–photodiode array detection and identified the resulting metabolites of pyraclostrobin by hydrolysis and photolysis in paddy water using high-resolution mass spectrometry coupled with liquid chromatography. The effect of solution pH, metal ions and surfactants on the hydrolysis of pyraclostrobin was explored. The hydrolysis half-lives of pyraclostrobin were 23.1–115.5?days and were stable in buffer solution at pH 5.0. The degradation rate of pyraclostrobin in an aqueous solution under sunlight was slower than that under UV photolysis reaction. The half-lives of pyraclostrobin in a buffer solution at pH 5.0, 7.0, 9.0 and in paddy water were less than 12?h under the two light irradiation types. The metabolites of the two processes were identified and compared to further understand the mechanisms underlying hydrolysis and photolysis of pyraclostrobin in natural water. The extracted ions obtained from paddy water were automatically annotated by Compound Discoverer software with manual confirmation of their fragments. Two metabolites were detected and identified in the pyraclostrobin hydrolysis, whereas three metabolites were detected and identified in the photolysis in paddy water.