All waste management activities have to fulfil two different tasks: Firstly the removal of waste from human settlements, especially in the case of pathogenic or toxic constituents, and its safe disposal and secondly the extraction of useful resources or at least energy after processing the waste. The Global Waste Management Outlook (GWMO) prioritises the safeguarding of public health and prevention or mitigation of environmental pollution. This report describes a development within the second goal that changes “the fundamental thinking away from ‘waste disposal’ to ‘waste management’ and from ‘waste’ to ‘resources’” [1
]. These goals are also at the focus of European legislation: The Waste Framework Directive (WFD) [2
] urges the Member States to align decisions made by waste owners with a hierarchy of five steps, starting with “prevention” of waste production and followed, in descending order, by “preparing for re-use”, material “recycling”, “recovery” of energy and, as the last option, “disposal” (WFD Art. 4). In the proposed amendment to this directive [3
], the European Commission aimed at the “transition to a Circular Economy with a broad set of measures to maintain the value of products, materials and resources for as long as possible, while minimising the generation of waste”. The EC focuses on resource efficiency as a new main goal along the value chain: “What was once considered as waste can become a valuable resource. To realise the potential of these so called secondary raw materials, we have to remove the existing barriers to their trade, improve the waste management practices and guarantee high quality standards” [4
]. Although the term “high quality standards” implies safe management of hazardous compounds in waste, the political discussion focuses on the “circular economy” vision, possibly losing sight of the hygienic basis of waste management.
The term “circular economy” is used widely but often understood quite differently: UNEP called for “the most efficient use and recycling of resources and environmental protection” with regard to the development of the Chinese economy and defined circular economy as a system with low consumption of energy, low emission of pollutants and high efficiency [5
]. The European Commission introduced the term in the framework of its resources strategy [6
] using “circular economy” as a synonym for “sustainable materials management” with special focus on the efficient use of minerals and metals. Ghisellini et al. [8
] and Kirchherr et al. [9
] provide an overview of definitions of the circular economy concept. According to Geissdoerfer et al. [10
], most authors writing about this concept share the idea of closed loops. Two major management consultant companies define circular economy as “an industrial system that is restorative or regenerative by intention and design” in line with the phrase “A world without waste is possible”, which was frequently used by former Commissioner Jan Potocnik, and their reports include a sort of “zero waste” goal: The consultants state that “the circular economy aims to design out waste” because “products are designed and optimised for a cycle of disassembly and re-use” and “consumables are made of biological ingredients or ‘nutrients’ that are at least non-toxic and possibly even beneficial, and can safely be returned to the biosphere” [11
]. These reports promised “a trillion-dollar opportunity (This citation follows P. Lacy, Accenture. http://www.eco-business.com/news/circular-economys-trillion-dollar-opportunity/
, accessed 15 October 2016), with huge potential for innovation, job creation and economic growth”. They considerably influenced the European discussion on the amendment of the WFD [3
] and other regulations (WEEE Directive, Packaging Directive …), as a whole known as the “waste package”. Surprisingly, the Commission omitted to define the term “circular economy” in the draft WFD.
The ongoing discussion between European Commission, European Parliament, Member States and stakeholders basically focuses on increasing binding recycling targets and tools (like extended producer responsibility), which might help to achieve greater recovery of resources from waste.
“Circular economy” implies that secondary materials obtained from recycling processes fulfil all the technical requirements necessary to substitute virgin materials. This includes a certain quality standard for secondary materials with regard to by-products and contaminants. Besides general physical and chemical restrictions to “zero waste”, which prevent the complete recycling of waste fractions [13
], recycling of certain compounds from waste fractions may lead to toxicity-related problems:
Technical requirements can vary from one application to another and this also holds true for toxicity thresholds, as has been intensively discussed for the migration of solvents from cardboard made from printed paper to food (cf. [18
] and literature cited there).
Technical standards for materials may change during the lifetime of a product. For secondary resources originating from a recycling process only current requirements are valid. This may turn out to be a crucial problem for material recovery in cases where certain contaminants are involved: Some important chemicals previously used in products have either been restricted to certain applications (e.g., compounds containing mercury, cadmium, lead) or banned completely (e.g., asbestos, PCBs, certain brominated diphenylethers). This is partially due to international conventions (e.g., POPs are regulated by the Stockholm Convention, mercury is regulated by the Minamata Convention) or is a result of regulations at European level based on specific directives (e.g., RoHS Directive [19
]) or general chemicals regulations (e.g., restricted chemicals under the REACH regulation [20
As the use of chemicals varies from region to region, widely depending on different regulations, secondary materials including certain additives from the first use of the material in question (plastics, fibres from textiles, cardboard …) may be allowed in some countries but not everywhere. Global trade and transport of secondary materials may therefore lead to a proliferation of contaminants in parts of the world where these contaminants have already been banned [21
Materials or waste containing contaminants above permitted concentration limits may no longer be used and must either be treated in order to separate the contaminants (if possible) or disposed of completely.
2. Scope and Structure of the Study
As the recycling of products after use is also vulnerable to dangerous compounds and materials contained in these waste streams, the question arises of how hazardous chemicals or materials in the respective products influence re-use and recycling. Our study centres on two questions:
Some hazardous compounds are specifically regulated in products. To what extent separate collection and recycling and / or safe disposal of these products can be ensured?
Will those hazardous compounds already regulated today appear in waste streams other than those intended?
Therefore it is reasonable to track the fate of products containing dangerous chemicals and to evaluate past and present experiences. This paper focuses on the interface of hazardous chemicals in products and the recovery of valuable materials from used products. Cadmium (Cd) was chosen as an example because products, emissions and waste containing Cd are regulated fairly well in Europe and partially also in other areas of the world. Cd is a non-essential and toxic element for humans. Because it is similar to the essential trace element zinc, Cd can be introduced into biochemical reactions in organisms in place of Zn. The primary target of Cd is the kidney, followed by the liver. The half-life of Cd in the body (predominantly in the adrenal cortex) is 10 to 30 years. The International Agency for Research on Cancer (IARC) classifies Cd in Group 1: Carcinogenic to humans [23
]. The Regulation on classification, labelling and packaging of substances and mixtures (CLP [24
]) warns of acute toxicity (oral and inhalation), mutagenicity, carcinogenicity, reproduction toxicity and water hazard. The critical level of Cd contamination is highlighted in a report by the European Food Safety Authority [25
]: “Although adverse effects are unlikely to occur in an individual with current dietary exposure, there is a need to reduce exposure to cadmium at the population level because of the limited safety margin”.
Global Cd production increased during the 1970–2004 period from about 17,000 Mg year−1
to about 22,000 Mg year−1
. Between 1995 and 2006, global consumption remained constant at around 20,000 Mg year−1
]. According to the U.S. Geological Survey, in 2015 the world’s primary Cd production (excluding the USA) amounted to 23,200 Mg [27
]. Current data for the USA are not available; in 2010, primary Cd production ranged between 600 and 800 Mg year−1
], which is above the estimated US manufacturing demand of 500 Mg year−1
(2005) or below [30
]. According to Ellis & Mirza [31
], worldwide Cd consumption concentrates on batteries; about 80% of marketed Cd is used for NiCd batteries and accumulators. On the European market, NiCd batteries represent 89% of all Cd consumed [32
]. It is estimated that recycled Cd at the beginning of this century accounted for 3500 Mg year–1
, equating to about 18% of total global supply [26
]. According to a current source, secondary Cd production is assumed to make up approximately a quarter of all Cd metal production [33
]. The exact mass of Cd recycled on a global basis is unknown.
The major difference between overall production and the mass of secondary material used as input for production is remarkable, both in view of a more or less constant production and consumption of Cd as well as with respect to the toxicity of Cd and its compounds.
Lig and Held [34
] published a balance for Europe for 2004 that included waste streams containing Cd as only a minor component. These results showed—despite many data gaps and contradictory statistics critically commented by the authors themselves—a total production of about 6400 Mg of Cd, of which about 2200 Mg was used in products for the European market too. Data from the International Cadmium Association [35
] reveal that 9020 Mg year−1
of Cd were imported into the EU in 2007–2008 and 6900 Mg year−1
were exported from the EU. Exports were dominated by NiCd batteries (1600 Mg year−1
) and Cd oxide (5000 Mg year −1
) intended for battery production [36
]. Cd is imported to Europe as part of products (e.g., batteries …) or as unwrought metal.
According to the Pollution Release and Transfer Register (PRTR), which publishes data on emissions from European point sources, 9.33 Mg of Cd were released to air and 12.8 Mg of Cd to water in 2015 [37
]. These mass flows are very low compared to former emissions in Europe and present emissions in China with its rapidly growing non-ferrous metal industry. According to different sources, China’s total Cd emissions are estimated at about 744 Mg for 2009, of which industrial processes and combustion sources contributed approximately 56.6% and 43.4% respectively. Non-ferrous metal smelters, including copper, lead and zinc, ranked as the main source, accounting for about 40.6% of the total [38
]. Shao et al. [39
] calculated atmospheric Cd emissions in China of 2186 Mg in 2010. A comparison between developments in Europe and China shows
the successful implementation and enforcement of regulations for the reduction of emissions from point sources in Europe
the increasing relevance of diffuse sources in Europe in parallel to the restriction of emissions from point sources
the growing importance of the waste sector, that means opportunities for recycling Cd, but
risks from new diffuse sources due to cross-contamination from recycling operations or leaching from landfills
The following Cd compounds are investigated in this study:
EC regulations have been in place for many years for Cd applications. In the case of NiCd batteries and accumulators, the use of Cd is still allowed but strictly limited, depending on different international (EU) regulations. The use of Cd compounds in window frames and other construction products is banned in the EU (for details see Section 3.1
Obviously, these two product groups represent only some of the opportunities and risks for the recycling of used products or materials from separated waste streams. Others, such as persistent organic molecules (volatile or non-volatile) or dangerous fibres, should be investigated, too.
This study relies on experience gathered in Europe (EU) and especially Germany. German, Swedish, Danish, Dutch and some other European governments have often acted as forerunners, together with countries outside Europe (e.g., Japan, amongst others), with respect to environmental legislation. In these countries, control and enforcement strategies for waste management as well as for hazardous chemicals have been gradually introduced since the 1970s, which allows a review of processes already regulated over a long period. It can be assumed that Europe is a model example for action taken against contamination by the compounds mentioned above in contrast to many other regions, where no specific regulations exist, implementation is delayed and enforcement is lacking.
Examples from other countries are taken into consideration if interesting legislative approaches exist there that differ considerably from the European approach. If detailed European figures were not available, facts and figures from Germany or other Member States, which are representative for advanced implementation and enforcement of environmental standards, were used instead. German legislation for the products in question is in line with the corresponding European directives. There are some German standards and recommendations in cases where European standards are lacking.
This study is based on intensive desktop research, discussions with experts from collection systems, recycling companies, associations in the battery and PVC industries, and environmental agencies as well as own experience in the waste management of fractions containing cadmium.
Despite the enormous data gaps detected during our work and reported in the previous chapter, the magnitude of unsolved problems for the two evaluated waste streams is clear: Even if the collection rate stated in the Batteries Directive were met (this is not the case), a loss of about 50% of portable NiCd batteries that are not collected separately has to be taken into account. A rough estimate arrives at about 1000 Mg Cd year−1, which are disposed of from this source. No data are available on Cd salts in PVC outside Europe; a very rough calculation results in about 100 Mg year−1 of Cd to be disposed of or recycled with PVC frames and other PVC products within Europe.
Apart from the products/waste investigated here, there are many material streams that contain Cd as a minor component, e.g., zinc ores, wrought metal, various scraps and products. In these cases, a small Cd concentration means that a considerable freight is entering the technosphere due to the enormous mass flow of iron, steel, zinc and some alloys sold as scrap. The authors of two Cd balances for Europe for 2004 [34
] and Austria for 2005 [99
] deplore a “high level of uncertainty of how heavy metals in waste streams are related to heavy metals in the original products”. The specific figures for batteries are more reliable due to reporting obligations [49
], but even in this case there are important gaps:
The unknown number of portable batteries used or stored in households impedes a reliable calculation of the amount stored in the technosphere.
The number of batteries integrated in electric appliances, which are not separated from WEEE, is unknown.
There is no information concerning the number of industrial batteries imported into the EU and their recycling in Europe or elsewhere.
The assessment above shows that Cd freight in product and waste streams by far exceeds the emission freights from point sources into air and water. On the basis of this fact, the question arises of how to optimise the collection of used products containing Cd or its compounds from waste, with the aim of interrupting further contamination of the environment (especially emissions from landfills) and recycled products. The opportunities, problems and risks associated with the recovery of materials from waste streams can be assessed by means of a simple scheme that was developed empirically from studies on the life cycle of hazardous compounds and complex waste streams [100
]. The scheme covers seven “obstacles” that have to be considered with regard to intended collection, recycling and recovery operations. Some of these obstacles can help to answer the question of how to optimise the collection of used products containing Cd or its compounds.
4.1. Economic Perspective
The market prices for cadmium, nickel, copper and zinc have been subject to considerable fluctuations in the last ten years (cf. Table 4
): Prices have fallen since 2011, except the price for Zn which remained at a constant level. Although Cd is a relatively scarce metal from a geological perspective, the price is as low as that of Zn and often lower.
It should be noted that average costs for recycling of NiCd batteries and accumulators range from €1600 to 2000 Mg−1
]; revenues from scrap (mostly NiFe) are in the range of €700 Mg−1
. Clearly the market does not provide an economic incentive for recycling. This is true for PVC, too (economic figures for PVC recycling including used profiles from windows are not available). The price of granulated rigid PVC on the European market is about €500 Mg−1
]. The efforts undertaken by PVC manufacturers and recyclers to establish a threshold limit for Cd in recovered PVC waste mixtures and items tenfold higher compared to other plastics indicate that lower (more ambitious) limit values cannot be reached at economically viable costs.
4.2. Entropy Perspective
According to statistical thermodynamics, entropy can be used as a yardstick for the disorder of a closed system (see, for example, [106
]). It is very difficult to recover valuable materials encased in products and energy is needed for their separation. According to a model based on information theory [107
], the profitability of a recycling operation can be derived from just a few economic figures and physical data, including the absolute measure of material mixture within a used product. The entropy dilemma is critical for Cd in PVC profiles because Cd concentration is low and no recycling techniques are available for Cd. Present efforts at PVC recycling lead to an even greater entropy dilemma due to the “dilution” of recovered PVC powder in new profiles. As far as NiCd batteries are concerned, their high Cd content makes separation easier, but also demands high energy input.
4.3. Application and Consumption
Consumption of goods means a dissipative dispersion of products. Waste management companies collect dissipated goods after use. The higher the dissipation rate, the less devices can be collected separately in relation to the number of devices sold (see, for example, [108
]). Portable batteries are globally dissipated since they are found in almost every household. A high rate of separately collected items requires:
identification of the type of battery, also in the case of accumulators integrated in electrical appliances
take-back stations that are easily accessible for citizens
public awareness and incentives for the return of batteries
Even in Europe, these requirements are only partially met. Large accumulators for industrial use are only used in a comparatively small number of facilities. The potential for high return rates is therefore better, as can be seen in European statistics ([70
], see chapter 3). Because of their use in mobile equipment (e.g., locomotives), a second dimension to dissipation emerges when second-hand vehicles etc. are exported. The level of dissipation of PVC profiles is also very high and it is not clear yet how many new frames containing secondary PVC are on the market, related to the mass of waste PVC. It is important to note that window frames can be re-used in other countries where Cd stearate has not been banned for use in the construction industry.
4.4. Time Perspective
Time is a crucial challenge for waste management. Firstly, chemicals banned for use in new products are still present in products in use and in different waste streams, and thus disrupt recycling processes. Secondly, consumption habits change with time and thus lead to unforeseen changes in the volume/mass and/or the composition of waste. A further problem arises through different legislative restrictions for Cd compounds in other regions. It is not clear when and to what extent legislators abroad (especially in China, the USA) will copy European regulations, particularly because this issue is often an integral part of overall trade policy.