Changes in Selected Organic and Inorganic Compounds in the Hydrothermal Carbonization Process Liquid While in Storage.

Although many studies have investigated the hydrothermal transformation of feedstock biomass, little is known about the stability of the compounds present in the process liquid after the carbonization process is completed. The physicochemical characteristics of hydrothermal carbonization (HTC) liquid products may change over storage time, diminishing the amount of desired products or producing unwanted contaminants. These changes may restrict the use of HTC liquid products. Here, we investigate the effect of storage temperature (20, 4, and -18 °C) and time (weeks 1-12) on structural and compositional changes of selected organic compounds and physicochemical characteristics of the process liquid from the HTC of digested cow manure. ANOVA showed that the storage time has a significant effect on the concentrations of almost all of the selected organic compounds, except acetic acid. Considerable changes in the composition of the process liquid took place at all studied temperatures, including deep freezing at -18 °C. Prominent is the polymerization of aromatic compounds with the formation of precipitates, which settle over time. This, in turn, influences the inorganic compounds present in the liquid phase by chelating or selectively adsorbing them. The implications of these results on the further processing of the process liquid for various applications are discussed.

Multi-element chemical analysis of printed circuit boards - challenges and pitfalls.

Printed circuit boards (PCB) are an essential component of electrical and electronic equipment (EEE) and account for roughly 5% of the mass of EEE. Knowledge about the chemical composition of PCB is crucial to enable an enhanced recycling, especially for elements considered critical regarding their economic importance and supply risk (e.g. precious metals or specialty metals such as tantalum, germanium, gallium). No standard reference methods exist for determining the chemical composition of PCB. Previously published element mass fractions cover a wide range and were produced with numerous methods for sample preparation, digestion, and measurement. This impedes comparability of PCB composition from different studies. To investigate sample- and element-specific effects of applied methods a PCB sample from desktop PC was analysed in two separate labs. One lab applied sample- and element-specific validated methods (aqua regia, HF, H2SO4 blend; ICP-OES, QQQ-ICP-MS), providing reference values, the other applied routine in-house methods (aqua regia; ICP-OES, ICP-MS) to assess the validity of in-house methods for chemical analysis of PCB. A t-test was used to identify elements depicting significant differences between validated and in-house methods. For base metals, in-house methods led to comparable results. For precious, specialty, and hazardous metals as well as REE investigated in this study, significant differences were detected. With respect to all results for in-house methods in this study, the combination of aqua regia and ICP-OES led to less significant differences than aqua regia and ICP-MS. The results show that sample- and element-specific quality assurance is crucial to prevent analytical bias.

Linking energy-sanitation-agriculture: Intersectional resource management in smallholder households in Tanzania.

In order to create sustainable systems for resource management, residues from cooking and ecological sanitation (EcoSan) can be employed in recycling-driven soil fertility management. However, the link between energy, sanitation, and agricultural productivity is often neglected. Hence, the potential self-sufficient nature of many smallholdings in sub-Saharan Africa is underexploited. OBJECTIVE: To compare those cooking and sanitation technologies most commonly used in north-western Tanzania with locally developed alternatives, with respect to (i) resource consumption, (ii) potential to recover resources, and (iii) environmental emissions. This study examines technologies at the household level, and was carried out using material flow analysis (MFA). The specific bioenergy technologies analysed include: three-stone fires; charcoal burners; improved cooking stoves (ICS), such as rocket and microgasifier stoves; and biogas systems. The specific sanitation alternatives studied comprise: pit latrines; two approaches to EcoSan; and septic systems. RESULTS: The use of ICS reduces total resource consumption; using charcoal or biogas does not. The residues from microgasifiers were analysed as having a substantial recovery potential for carbon (C) and phosphorus (P). The fact that input substrates for biogas digesters are post-agricultural in nature means that biogas slurry is not considered an 'untapped resource' despite its ample nutrient content. Exchanging pit latrines for water-based sanitation systems places heavy pressure on already scarce water resources for local smallholders. In contrast, the implementation of waterless EcoSan facilities significantly promotes nutrient recovery and reduces environmental emissions, particularly through greenhouse gas emission and nutrient leaching. CONCLUSIONS: Recycled outputs from the triple energy-sanitation-agriculture nexus display complementary benefits: residues from cooking can be used to restore organic matter in soils, while sanitation residues contribute to fertilisation. The combination of microgasifiers and EcoSan-facilities is the most appropriate in order to simultaneously optimise resource consumption, reduce environmental impacts, and maximise recycling-based soil management in smallholder farming systems.

Challenges for critical raw material recovery from WEEE - The case study of gallium.

Gallium and gallium compounds are more frequently used in future oriented technologies such as photovoltaics, light diodes and semiconductor technology. In the long term the supply risk is estimated to be critical. Germany is one of the major primary gallium producer, recycler of gallium from new scrap and GaAs wafer producer. Therefore, new concepts for a resource saving handling of gallium and appropriate recycling strategies have to be designed. This study focus on options for a possible recycling of gallium from waste electric and electronic equipment. To identify first starting points, a substance flow analysis was carried out for gallium applied in integrated circuits applied on printed circuit boards and for LEDs used for background lighting in Germany in 2012. Moreover, integrated circuits (radio amplifier chips) were investigated in detail to deduce first approaches for a recycling of such components. An analysis of recycling barriers was carried out in order to investigate general opportunities and risks for the recycling of gallium from chips and LEDs. Results show, that significant gallium losses arose in primary production and in waste management. 93±11%, equivalent to 43,000±4700kg of the total gallium potential was lost over the whole primary production process until applied in electronic goods. The largest share of 14,000±2300kggallium was lost in the production process of primary raw materials. The subsequent refining process was related to additional 6900±3700kg and the chip and wafer production to 21,700±3200kg lost gallium. Results for the waste management revealed only low collection rates for related end-of-life devices. Not collected devices held 300 ± 200 kg gallium. Due to the fact, that current waste management processes do not recover gallium, further 80 ± 10 kg gallium were lost. A thermal pre-treatment of the chips, followed by a manual separation allowed an isolation of gallium rich fractions, with gallium mass fractions up to 35%. Here, gallium loads per chip were between 0.9 and 1.3mg. Copper, gold and arsenic were determined as well. Further treatment options for this gallium rich fraction were assessed. The conventional pyrometallurgical copper route might be feasible. A recovery of gold and gallium in combination with copper is possible due to a compatibility with this base-metal. But, a selective separation prior to this process is necessary. Diluted with other materials, the gallium content would be too low. The recycling of gallium from chips applied on printed circuit boards and LEDs used for background lighting is technically complex. Recycling barriers exist over the whole recycling chain. A forthcoming commercial implementation is not expected in nearer future. This applies in particular for chips carrying gallium.

Data availability and the need for research to localize, quantify and recycle critical metals in information technology, telecommunication and consumer equipment.

The supply of critical metals like gallium, germanium, indium and rare earths elements (REE) is of technological, economic and strategic relevance in the manufacturing of electrical and electronic equipment (EEE). Recycling is one of the key strategies to secure the long-term supply of these metals. The dissipation of the metals related to the low concentrations in the products and to the configuration of the life cycle (short use time, insufficient collection, treatment focusing on the recovery of other materials) creates challenges to achieve efficient recycling. This article assesses the available data and sets priorities for further research aimed at developing solutions to improve the recycling of seven critical metals or metal families (antimony, cobalt, gallium, germanium, indium, REE and tantalum). Twenty-six metal applications were identified for those six metals and the REE family. The criteria used for the assessment are (i) the metal criticality related to strategic and economic issues; (ii) the share of the worldwide mine or refinery production going to EEE manufacturing; (iii) rough estimates of the concentration and the content of the metals in the products; (iv) the accuracy of the data already available; and (v) the occurrence of the application in specific WEEE groups. Eight applications were classified as relevant for further research, including the use of antimony as a flame retardant, gallium and germanium in integrated circuits, rare earths in phosphors and permanent magnets, cobalt in batteries, tantalum capacitors and indium as an indium-tin-oxide transparent conductive layer in flat displays.

Environmental evaluation of waste treatment scenarios for the towns Khanty-Mansiysk and Surgut, Russia.

Khanty-Mansiysk Autonomous Okrug - Ugra in Siberia has recently started to play a major role in the Russian economy because key oil and gas extraction sites are located in this region. As a result, the extensions of infrastructure and higher incomes have been leading to an accelerated population growth and consequent increase in the generation of solid household waste. The current methods of waste disposal have now reached their limits, especially in the towns Khanty-Mansiysk and Surgut. The key objectives of this study were to identify the influence of waste composition and transport routes on the life cycle assessment (LCA) results and to assess the current waste treatment option for solid household waste and to compare it with proposed scenarios. Furthermore, recommendations for an optimal use of LCA within a decision-making process for a waste management plan are presented. LCA methodology was used to evaluate different waste management scenarios such as landfilling and incineration. One result was that the options 'incineration with recycling' and 'anaerobic mechanical-biological treatment with recycling' demonstrated lower environmental impact in both Khanty-Mansiysk and Surgut. Another finding was that there were hardly any differences in the ranking of the scenarios for Surgut and Khanty-Mansiysk. However, the special socio-cultural circumstances and location of each town have to be considered seriously in the development of a sustainable waste management plan.

Practicalities of individual producer responsibility under the WEEE directive: experiences in Germany.

In theory, individual producer responsibility (IPR) creates incentives for 'design-for-recycling'. Yet in practice, implementing IPR is challenging, particularly if applied to waste electric and electronic equipment. This article discusses different options for implementing IPR schemes under German WEEE legislation. In addition, practical aspects of a German 'return share' brand sampling scheme are examined. Concerning 'new' WEEE put on the market after 13 August 2006, producers in Germany can choose between two different methods of calculating take-back obligations. These can be determined on the basis of 'return shares' or 'market shares'. While market shares are regularly monitored by a national clearing house, the 'return share' option requires sampling and sorting of WEEE. Herein it is shown that the specifics of the German WEEE take-back scheme require high sample sizes and multi-step test procedures to ensure a statistically sound sampling approach. Since the market share allocation continues to apply for historic waste, producers lack incentives for choosing the costly brand sampling option. However, even return share allocation might not imply a decisive step towards IPR, as it merely represents an alternative calculation of market shares. Yet the fundamental characteristics of the German take-back system remain unchanged: the same anonymous mix of WEEE goes to the same treatment operations.

New techniques for the characterization of refuse-derived fuels and solid recovered fuels.

Solid recovered fuel (SRF) today refers to a waste-derived fuel meeting defined quality specifications, in terms of both origin (produced from non-hazardous waste) and levels of certain fuel properties. Refuse-derived fuel (RDF) nowadays is more used for unspecified waste after a basic processing to increase the calorific value and therefore this term usually refers to the segregated, high calorific fraction of municipal solid waste (MSW), commercial or industrial wastes. In comparison with conventional fuels, both types of secondary fuel show waste of inherently varying quality and an increased level of waste-specific contaminants.The transition from RDF to SRF in the emerging national and European market requires a quality assurance system with defined quality parameters and analytical methods to ensure reliable fuel characterization. However, due to the quality requirements for RDF and SRF, the current standardized analysis methods often do not meet these practical demands. Fast test methods, which minimize personnel, financial and time efforts and which are applicable for producers as well as users can be an important supporting tool for RDF- and SRF-characterization. Currently, a fast test system based on incineration and correlation analyses which enable the determination of relevant fuel parameters is under development. Fast test methods are not aimed at replacing current standardized test methods, but have to be considered as practical supporting tools for the characterization of RDF and SRF.

Status of pre-processing of waste electrical and electronic equipment in Germany and its influence on the recovery of gold.

Waste electrical and electronic equipment (WEEE) contains gold in low but from an environmental and economic point of view relevant concentration. After collection, WEEE is pre-processed in order to generate appropriate material fractions that are sent to the subsequent end-processing stages (recovery, reuse or disposal). The goal of this research is to quantify the overall recovery rates of pre-processing technologies used in Germany for the reference year 2007. To achieve this goal, facilities operating in Germany were listed and classified according to the technology they apply. Information on their processing capacity was gathered by evaluating statistical databases. Based on a literature review of experimental results for gold recovery rates of different pre-processing technologies, the German overall recovery rate of gold at the pre-processing level was quantified depending on the characteristics of the treated WEEE. The results reveal that - depending on the equipment groups - pre-processing recovery rates of gold of 29 to 61% are achieved in Germany. Some practical recommendations to reduce the losses during pre-processing could be formulated. Defining mass-based recovery targets in the legislation does not set incentives to recover trace elements. Instead, the priorities for recycling could be defined based on other parameters like the environmental impacts of the materials. The implementation of measures to reduce the gold losses would also improve the recovery of several other non-ferrous metals like tin, nickel, and palladium.

Chlorine characterization and thermal behavior in MSW and RDF.

Chlorine, as a key element causing high temperature corrosion and low efficiency in waste-to-energy plants, and its thermal behavior has widely drawn attention. In this study, the chlorine content in eight fractions of municipal solid waste (MSW) was quantified and characterized using five analytical methods. The influence of the operating temperature, and fuel additives like sulfur and silica on the volatilization of chlorine in combustion process was also investigated. The results showed: these fractions cover a wide range of chlorine content from 0.1 wt.% in wood to >6 wt.% in non-packaging plastics (dry basis). Polyvinylchloride (PVC) from packaging, electrical wire insulation etc. in plastics and chloride salts (mainly NaCl) in kitchen waste are the main sources of organic and inorganic chlorine. The increase of the operating temperature from 700 degrees C to 1000 degrees C has more influence on the HCl formation for kitchen waste than that for PVC. Sulfur addition leads to 20-40% higher HCl formation rate in most fractions. Silica supports the chlorine release at relatively low temperatures between 700 degrees C and 850 degrees C. These findings enhance to understand the thermal behavior of chlorine in MSW and RDF (refuse derived fuel) in waste-to-energy plants and lead to the suggestions for a fuel management for waste derived fuels in order to avoid chlorine induced corrosion.

Material flow analysis of RDF-production processes.

The authors evaluate the possibilities of modifying the chemical characteristics of refuse-derived fuels (RDF) that are processed from residual household waste by mechanical operations to achieve and assure quality targets for relevant chemical concentrations, especially for heavy metals and chlorine. Quality assurance in the production of RDF demands that, together with an enrichment of the calorific value, highly toxic waste components are selectively separated and concentrated in a small stream to produce high yields of a relatively low polluted fuel. Based on the method of material flow analysis, a process evaluation is developed that considers the aspect of minimizing hazardous chemicals along with classical process data such as yield and product quality. Data on specific concentration of hazardous chemicals in waste components and their distribution in residual household waste as well as the results from large-scale test runs using different separation techniques demonstrate that mechanical operations alone are insufficient for separating hazardous chemicals. In the test runs, chemical compounds such as chlorine, cadmium and lead were often concentrated in the product. Even using optimized techniques, the ability to reduce hazards in the product is limited due to the distribution of the element concentration in the various components of the waste stream.