Lost by Design

Lost by Design

Luca Ciacci *, Barbara K. Reck , N. T. Nassar , and T. E. Graedel

Center for Industrial Ecology, School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, Connecticut 06511, United States

Environ. Sci. Technol., Article ASAP

DOI: 10.1021/es505515z

Publication Date (Web): February 18, 2015

Copyright © 2015 American Chemical Society

ABSTRACT: http://pubs.acs.org/doi/abs/10.1021/es505515z

NOTE: To preserve the accuracy and precision of definitions, observations, discussions, and conclusions, many of the notes are taken verbatim from the article, identifiable by italics.

The authors define the term dissipative losses as “In the context of anthropogenic material cycles, dissipative losses are the flows of materials from the anthroposphere (i.e., human systems) to the biosphere (i.e., environment) in a manner that makes their future recovery extremely difficult, if not impossible.” Dissipative flows can be “intentional or unintentional, desirable or undesirable, and can occur during any stage of a material’s life (e.g., tailings and slag from the production stage or outputs to air, water, and soil during waste treatment) ”.

Quantifying dissipative loses and understanding their causes and the fate of metals is important because it reduces the quantity of metals available for recycling and reuse and increases dependence on primary sources.  Losses to the environment also introduce eco-toxicological risks.

In this study, the authors “investigated and categorized the main causes for dissipation of elements during use and measured the degree to which they are currently ‘lost by design’”.

MATERIALS AND METHODS

The study considered metals in all the common forms of use: pure, alloyed, and compounded.

Each metal is assigned “on a global market share basis” to one of the following material streams after it enters the use phase:

In-use dissipated stream: accounts for material flows that are not accumulated into anthropogenic stocks, and a lack of collection prevents any form of recovery at end-of-life (e.g., sacrificial anodes, fertilizers), in which scattering and dispersion into the environment is planned by design

Currently unrecyclable: accounts for material flows into use for which technological and/or economic barriers prevent elemental recycling, such as in the case of deoxidizing aluminum in steelmaking or the recovery of rare earth elements from exhausted glass polishing powders.

Potentially recyclable: those for which today’s technology is compatible with their recovery, enabling them to be functionally or nonfunctionally recycled/not recovered according to the United Nations Environment Programme definition

Unspecified: miscellaneous applications that cannot be divided among the previous material streams because of lack of data

·         Metals with a one year lifetime of use are assumed to have a material flow that results in no accumulation and exit the use after one year.

·         For metals with > one year use, material flow is calculate for its entire lifetime.

·         Most of the uncertainties are assumed to come from market shares, end-use lifetime distributions, and element release dynamic models.

·         56 metals were studied.

·         2008 was the average year of reference.

RESULTS AND DISCUSSION

METAL DISSIPATION AND RECYCLING POTENTIAL

Figure 2 shows the mass flow percentage for the 4 material streams identified above.

Elements in the same group exhibit similar uses more than elements in the same period. Some exceptions:

Many of the lanthanide and actinide metals show a different material flow distribution than the elements above their groups with most of them falling under the currently unrecyclable use.

Aluminum is an exception to a group of metals that are largely currently unrecyclable.

Scandium use primarily falls within potentially recyclable but not Y nor La below it.

In Group IV, Hf and Th have a high percentage of potential recyclability but not their co-members.

Os bucks the trend for potential recyclability in the group including iron, ruthenium, and samarium.

About a quarter of Zn, As, Se, Hg, and Bi undergo in-use dissipation.  Close to half of Tm, Yb, and Lu are categorized under in-use dissipation.  Some examples of end uses leading to in-use dissipation given in the article are:

·         medical imaging applications (mainly for thulium, ytterbium, and lutetium)

·         agriculture

·         biocide products (e.g., fungicides and pesticides)

·         pharmaceutical uses for elements such as zinc, arsenic, selenium, bismuth, and to a lesser extent, antimony and tellurium

·         sacrificial anodes or galvanic protection applications (zinc, cadmium, tin, and lead)

·         minor corrosion losses (e.g., iron and copper in architectural and building applications)

·         zinc oxide used as a vulcanizing agent and released during tire wear

·         tool abrasion (tungsten and cobalt)

·         mercury from its use in small scale artisanal gold mining (ASGM)

·         pyrotechnics to generate light, colors, and sound effects for entertainment

·         signaling (e.g., emergency)

·         military applications

More than half of the 56 metals have unrecyclable uses greater than 10%.

·         most rare earths (yttrium, lanthanum, cerium, praseodymium, neodymium, europium, gadolinium, terbium, holmium, erbium, thulium, ytterbium)

·         specialty metals (gallium, germanium, arsenic, cadmium, indium, antimony, thallium)

·         titanium, manganese, selenium, zirconium, hafnium, bismuth, thorium

Lanthanum and cerium have high dissipative losses [unrecyclable?] due to their use in applications such as glass additives and glass polishing.

Rare earth elements for which recycling programs exist:

·         praseodymium

·         neodymium

·         samarium

·         europium

·         terbium

·         dysprosium

Recycled from permanent magnets, phosphors (i.e., fluorescent lamps), and rechargeable batteries (e.g., NiMH)

Thulium and ytterbium in medical applications are regarded as unrecyclable when they are not inherently dissipated (i.e., when used as beta emitters in nuclear medicine).

Yttrium’s unrecyclable end-uses include phosphors, with the exception of fluorescent lamps and ceramics.

Gallium, indium, and thallium, all belonging to the same chemical group, are challenging to recycle due to their use in electronics in very low concentrations.

Titanium: Many metals are found compounded in pigments.  Titanium is a good example of a metal, while not critical, finds the largest market as titanium dioxide to provide the white pigment for paper, paint, and plastic. It is also used in glass, ceramics, and catalyst production.  Dissipation end flows for titanium occur through

·         Dispersal of cracking and flaking paint due to oxidation, physical wear, and UV degradation

·         Landfill deposits through construction and demolition waste

·         Reuse in aggregates with low-market value.

·         Minor use in toothpaste, sunscreens, and similar products (“from 2005 to 2010, nanoscale titanium dioxide used in products for personal care grew from 1 to 5 mg, raising further challenges for titanium recovery”) These end flows do not bode well for the sustainable use and sourcing of this metal.

Pigment dissipation also occurs for cadmium, selenium, and lead.

·         Selenium is also used for glass pigment processes: decolorizing green and yellow glass and coloring glasses pink for artistic purposes.

·         Cadmium sulfate is used in pigments for plastics (for instance, nylon, acrylonitrile butadiene styrene, polycarbonates, high density polyethylene, silicone resins, and other thermoplastics), glass, ceramics, and artist paints (e.g., in red and yellow colors).

·         Lead pigments have been historically used in paints for coloration and to improve drying. Although lead in paint has been restricted in many regions (e.g., United States and Europe), lead-based paints are still in use in some developing countries.

Unrecyclable use also includes chemical additives:

·         Antimony is used to prevent the release of flammable gases which comprises its largest market sector. A combination of antimony trioxide with halogens (e.g., chlorinated alkyd resin) is used as a flame-retardant in adhesives, plastics (e.g., polyvinyl chloride (PVC), polyethylene, polypropylene, and polystyrene), rubber, textiles, paper, and pigments (e.g., in chromate pigments manufacturing).

·         Tin is used as a stabilizer in PVC production

·         Arsenic is used as a wood preservative (in the form of chromated copper arsenate or CCA) (US EPA has classified CCA as a restricted use product, and CCA-containing wood is no longer being produced for residential applications).

Unrecyclability also exists for use as catalysts:

·         Antimony and germanium are used as catalysts in PET (polyethylene) production.  “The use of germanium is due to its property of avoiding undesired coloring in the final product, and germanium oxide catalysts are designed to remain in PET bottles to enhance their brightness and transparency.”

·         Iridium and ruthenium are used as catalysts for electrochemical applications

·         Tellurium is used as catalyst for the oxidation of organic compounds, hydrogenation of oils, chlorination, as a vulcanizing agent and accelerator in the processing of rubber, and as a catalyst in synthetic fibers.

·         Rhodium, palladium, and platinum are used in automobile catalytic converters.  Even these expensive metals are not immune from dissipative loses, subjected to corrosion losses due to abrasive action, vibration, improper maintenance, and poor road conditions.

REDUCING LOSS BY DESIGN. REDUCING DISSIPATIVE LOSSES BY MINIMIZING PROBLEMATIC USES

Reduction strategies are limited for:

·         For some uses such as pyrotechnics, flame retardants, and pigments where the amounts are small, reduction of use per unit product results only in “minor improvements” .

·         Reduction is not possible at all for certain uses such as pharmaceuticals because the function of the metal depends on specific concentrations to achieve the desired dose-response effect.

Reuse and recycling are sometimes not feasible and hampered by difficulty of collecting materials at the end-of-life stage.  Some of these challenges arise from a loss of quality, a lack of appropriate technology, higher energy input than for virgin materials, and lower economic incentives compared to recycling costs. Examples in this sense include elements dispersed in plastics, paints, papers, glass, and ceramics. Metals in marine pigments may end up on the ocean floor where there is no practical way to retrieve them. Depending on where the material ends up, there may, however, be potential for recovery.  For example:

·         Metals that end up within proximity of their sources provide potential for recovery.  In a recent paper, for instance, a study calculated a potential reasonable return on investment for technologies to recover metals in municipal sewage waters.  Examples of these are iron and copper compounds from buildings and other structures and zinc oxides from tire wear and copper from brake linings that end up in road dust due to abrasion/frictional dissipation.

·         Biogeochemical cycles and undesired material releases from unintentional uses of a given element in anthropogenic cycles (e.g., outflows of lead, copper, and vanadium as trace contaminants from fossil fuel combustion and from iron and can influence the spatial and temporal magnitude of elemental accumulation in temporary and permanent deposits, and thus the amount potentially recyclable.”

How can dissipation be reduced and what actions would be most effective?

·         Bans or taxations raw materials

·         Adoption of substitutes

·         Environmental concerns based on well-established toxicity (e.g., lead in petrol and tributyl tin in antifouling marine paint)

·         Social and cultural perspectives that provide awareness of environmental improvements, cost savings, and enhanced industrial efficiencies promoted by the UN (e.g. removing mercury and achieving enhanced gold extraction efficiencies, environmental improvements, and cost savings)

·         Economic incentives for material recovery and research for substitutes for expensive metals (e.g., recovery of cobalt, tungsten, vanadium, and rhenium as catalysts)

·         Environmental challenges related to older pigments (for instance, those containing arsenic, lead, chromium, and mercury) have inspired efforts to substitute inorganic pigments that utilize lead and cadmium with organic compounds or bio-based pigments. The major barriers that limit the large scale production of these alternatives are the high cost of manufacturing, the use of fossil sources (e.g., petroleum and gas), the large quantities of solvents that are often involved in organic pigment production, and the lack of thermal stability of some bio-based pigments.

·         Adoption of substitutes are difficult for nuclear uses requiring specific radioisotopes and galvanic uses requiring specific anode and cathode materials.

Technical challenges in recovery and recycling can be mitigated by incorporating recyclability and recovery to the design and manufacture of the material: “adopting basic design for recycling and design for resource efficiency procedures in the manufacturing of new products may be among the most effective way to improve the potential recyclability of embodied elements”.

REDUCING DISSIPATIVE LOSSES BY A SYSTEMS APPROACH

Metal substitution due to economic or environmental costs may simply transfer the dissipative loss from one element to another (e.g. shift from zinc oxide to titanium oxide). 

The better approach a systems approach that focuses on solutions based on the function provided.  Examples of these include:

Substitution of nitrogen for metal powder to produce green pyrotechnics.

Substitution of talc or materials with kaolin or calcite as core material and titanium dioxide in the shell in titanium based-pigments (while retaining rheological properties)

Palladium catchment gauzes have increased the recovery of vaporized platinum from 30% to 80% and of rhodium to 50%.  These gauzes also have helped reduce the emission of nitrogen oxides by reduction to nitrogen.  This method, however, leads to 30% loss in palladium during the platinum recovery process.

REDUCING DISSIPATIVE LOSSES DURING THE DESIGN OF PRODUCTS.

The authors believe that an improved understanding of loss by design will provide guidance to industry in investigating routes for reducing material losses and supporting the development of options for increasing element recovery at EOL.

A quantitative representation of the uses and material flow some metals are provided in Figure 3 which “displays the results by use for several selected elements for in-use dissipation rate (IUDR), the current unrecyclability rate (CUR), and the current potential recyclability rate (PRR). These metrics correspond to the three material streams identified in Table 1, but have been rescaled to 100% of flow into principal uses after excluding unspecified applications. “

Figure 3 can thus be used to provide a reference as to how far off-target each current application is. A transition toward more sustainable use of a metal over time requires the shift of the spectrum of its uses toward the lower left corner of the ternary diagram, such that all principal uses are potentially recyclable (i.e., ideally to 100% PRR, 0% CUR, and 0% IUDR).

Examples of data from these charts:

·         Selenium use in electrical applications and electronics is 100% recyclable.

·         Antimony, lead, and mercury use in batteries is 100% recyclable.

·         Zinc and titanium use in metallurgy is 100% recyclable.

·         Gadolinium use in permanent magnets and antimony use in pigments and chemicals represent 0% recyclability.

·         Agricultural use of selenium represents 100% in-use dissipative loss and therefore 100% unrecyclability.  Same is true for uses of mercury not listed (“other”).

·         Intermediate values indicate potential for improvements in ”loss” by design and recyclability.

·         See authors’ detailed example for using the chart to analyze current status for selenium use and potential for recyclability and reduced loss ending with the following conclusion for this metal, “Overall, the sum of in-use dissipation and current unrecyclability for selenium reduces its potential recyclability to 30% of the element flow into use, but recycling process inefficiencies shrink that potential to 1% or less. “

In the conclusion section, the authors point to the drive to miniaturize devises using these metals and their deeper integration into other materials as further diminishing the potential for improvements on dissipative loss, recovery rates, and recyclability. Further, because dissipation loss is inherent in the design, the authors urge the following:

We thus advocate a transition from approaches that involve loss by design to those striving instead for retention by design. Such actions will likely go far in improving the long-term sustainability of the metals that are crucial to modern technology.

For more detailed information on each element addressed in this study see supporting information documents (75 pages).