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).

Integrated life-cycle assessment of electricity-supply scenarios confirms global environmental benefit of low-carbon technologies

Integrated life-cycle assessment of electricity-supply scenarios confirms global environmental benefit of low-carbon technologies

Edgar G. Hertwich, Thomas Gibona, Evert A. Bouman, Anders Arvesen, Sangwon Suh, Garvin A. Heath, Joseph D. Bergesen, Andrea Ramirez, Mabel I. Vega, and Lei Shi

PNAS 2015 112: 6277-6282.

ABSTRACT AND AUTHOR AFFILIATIONS: http://www.pnas.org/content/112/20/6277.abstract

Note: Because of the technical nature of the paper, I chose to take excerpts or verbatim statements in this summary in order to preserve the precision of the content and meaning (see italicized sections).

Previous life cycle assessments of new low-carbon technologies indicate that they require more materials than fossil-fuel based energy sources on per unit power generated measure and therefore may lead to increase in other environmental impacts.  No studies, however, have answered what these environmental impacts may be, such as the impact on resource use or pollution creation.  Current energy-scenario models have not considered the manufacturing and material life cycle of energy technologies.

In the Significance section, the authors declare that this “paper presents, to our knowledge, the first life-cycle assessment of the large-scale implementation of climate-mitigation technologies, addressing the feedback of the electricity system onto itself and using scenario-consistent assumptions of technical improvements in key energy and material production technologies.”

In this paper, the authors compare different low-carbon technologies based on an analysis of their environment impacts and resource requirements under two scenarios:

1)      global deployment under the climate-change mitigation scenario of the International Energy Agency’s (IEA) BLUE-MAP program

2)      IEA’s baseline scenario

In this hybrid LCA of different low-carbon technologies, the authors consider the utilization of a mix of energy technologies and efficiencies in their analysis of the global production system.  They note that, to our knowledge, this analysis is the first to be based on a life-cycle inventory model that includes:

·         the feedback of the changing electricity mix

·         the effects of improvements in background technologies on the production of the energy technologies

The energy technologies considered are:

·         Concentrating solar power (CSP)

·         Photovoltaic power (PV)

·         Wind power

·         Hydropower

·         Gas- and coal-fired power plants with carbon dioxide capture and storage (CCS)

Two energy technologies not considered:

·         Bioenergy – would require a comprehensive assessment of the food system which is beyond the scope of the study according to the authors

·         Nuclear energy – authors were unable to reconcile conflicting results of competing assessments

Because they have to project their analysis into the future, for modeling of technologies for 2030 and 2050, they assumed improved production of aluminum, copper, nickel, iron and steel, metallurgical grade silicon, flat glass, zinc, and clinker.

Technological improvements in the electricity conversion are measured by improved:

·         Conversion efficiencies

·         load factors

·         next-generation technology adoption to achieve the technology performance of the scenarios

RESULTS

PART 1 – Comparison of low-carbon technologies with fossil fuel electricity generation without CCS

·         allows quantification of environmental cobenefits and tradeoffs for long-term investment decisions in the power sector

·         current state-of-the art technologies are used in this comparison

Impacts considered:

A.      greenhouse gas emissions (GHG)

B.      particulate-matter formation

§  From supporting information (SI): The particulate matter (PM) formation potential includes both direct emissions of fine particulates (<10 μm) and the formation of particulates from precursors such as SO2, NOx, sulfate, and ammonia. PM exposure has the highest human health impacts of any pollution type.

C.      aquatic ecotoxicity resulting from pollutants emitted in air and water throughout the life cycle of each technology

§  From SI: Freshwater ecotoxicity was chosen as an indicator to represent a wider suite of toxicity indicators (10), because it is fairly mature given the wide availability of toxicity data for aquatic species.

D.      eutrophication

§  From SI: Freshwater eutrophication addresses the addition of nutrients to freshwater bodies.

E.       life cycle use of key materials (like aluminum, iron, copper, and cement), nonrenewable energy, and land on a per unit of electricity produced

§  From SI: These materials are used for their structural and conductive properties. The production of these materials causes high environmental impacts.  Allwood et al. find that iron and steel, aluminum, and cement together cause about 50% of anthropogenic CO2 emissions from the industrial sector, although plastic (5%) and paper (4%) are also important. However, plastic and paper have much shorter average lifetimes and their use in energy technologies is not particularly high. The environmental significance of copper is related to its toxicity.

§  From SI: Cement was quantified because its production causes substantial environmental impacts; not all limestone is calcinated and concrete may contain different amounts of cement. As a result, cement is a superior indicator for environmental impact over limestone and concrete.

§  From SI: We quantified total non-renewable primary energy as an additional resource indicator called cumulative energy demand. We calculated the indicator by multiplying the amount of fuel extracted with the higher heating value of fossil fuels and the producible heat from uranium ore using current best technology, including recycling of the plutonium.

§  From SI: We also quantified total land occupation measured in land area multiplied by the time that this land area is occupied.

§  From article: As an indicator of potential habitat change, we use the area of land occupied during the life cycle of each technology (Fig. 1E).

Technology Comparison per Unit Generation

See Figure 1.  In one set of data, the unit environmental impacts in terms of A. greenhouse gas, B. particulate matter, C. ecotoxicity, D. eutrophication, and E. land occupation.  These measurements were made for PV, concentrating solar power, hydropower, wind power, coal, and natural gas.  The impacts are further disaggregated for sub-categories of each technology.  As the authors noted at the beginning of this section, Comparative LCA indicates that renewable energy technologies have significantly lower pollution-related environmental impacts per unit of generation than state-of-the-art coal-fired power plants in all of the impact categories considered

Some noted results:

·         Natural gas combined cycle

o   produces little eutrophication

o   has a low land occupation area (see Figure 1 for units)

o   between coal and renewable technologies on ecotoxicity and greenhouse gas emissions

o   high on particulate matter emissions

·         wind

o   requires more bulk material (iron, aluminum, copper, and cement) than coal- and gas-based electricity

·         PV

o   requires more bulk material (iron, aluminum, copper, and cement) than coal- and gas-based electricity

·         For fossil fuel-based power systems, materials contribute a small fraction to total environmental impacts, corresponding to <1% of GHG emissions for systems without CCS and 2% for systems with CCS.

·         For renewables, however, materials contribute 20–50% of the total impacts, with CSP tower and offshore wind technologies showing the highest shares (SI Appendix, Fig. S1).

·         CCS reduces CO2 emissions of fossil fuel-based power plants but increases life-cycle indicators for particulate matter, ecotoxicity, and eutrophication by 5–60% (Fig. 1 B–D). Both postcombustion and precombustion CCS require roughly double the materials of a fossil plant without CCS (Fig. 1 G–J). The carbon capture process itself requires energy and therefore reduces efficiency, explaining much of the increase in air pollution and material requirements per unit of generation.

·         High land-use requirements are associated with hydropower reservoirs, coal mines, and CSP and ground-mounted PV power plants. The lowest land use requirements are for NGCC plants, wind, and roof-mounted PV. See article for definitions of land use measurement.

·         The current technologies used in the production of renewable systems consume 0.1–0.25 kWh of nonrenewable energy for each kWh of electricity produced (Fig. 1F). The situation is different for fossil fuel-based systems, for which the cumulative energy consumption reflects the efficiency of power production and the energy costs of the fuel chain and, if applicable, the CCS system.

PART 2 - we show the potential resource requirements and environmental impacts of the evaluated technologies within the BLUE Map scenario and compare these results with those of the Baseline scenario. The analysis assumes implementation and utilization of low-carbon technology prescribed by the BLUE MAP scenario:

The BLUE Map scenario posits an increase in the combined share of solar, wind, and hydropower from 16.5% of total electricity generation in 2010 to 39% in 2050.

The following are quantified and compared between the two scenarios:
requirements of bulk materials (and comparison with annual production levels of these materials)

Environmental pressures over time

Some noted results:

·         The required up-front investment in renewable generation capacity would require a combined investment of bulk materials of 1.5 Gt over the period 2010–2050, which is more than the total use of these materials in the Baseline scenario. The difference in material demand displayed in Fig. 2 G–J shows that the initial demand for iron and cement is mainly associated with wind and CSP installations whereas it is mainly PV driving additional copper demand.  The BLUE Map scenario has a lower material demand associated with conventional coal-fired power plants without CCS, which is partly offset by the material demand from coal-fired power plants with CCS. The most important contributor to the material demand from coal-fired power plants is associated with producing and transporting the ∼500 kg of coal required per MWh of electricity generated.

·         The BLUE Map scenario would be able to keep the emissions of particulate matter and ecotoxicity stable despite the doubling of annual electricity generation from 18 petawatt hours per annum (PWh/a) to 36 PWh/a for the technologies investigated.

·         Compared with the situation in 2010, a substantial reduction in GHG emissions (from 9.4 Gt CO2 eq. to 3.4 Gt CO2 eq.) and eutrophication would be achieved (SI Appendix, Fig. S4) in the BLUE MAP scenario.

·         The difference in pollution between the BLUE Map and Baseline scenarios would grow dramatically over time (Fig. 2) whereas the additional required material investment would rise only moderately.

·         For the BLUE Map scenario, the higher material requirement per unit of renewable electricity and a projected increase in energy demands cause a substantial increase in material use (SI Appendix, Fig. S4). The overall material requirement per unit of electricity produced would be 2.3 kg/MWh compared with 1.2 kg/MWh for the Baseline scenario.

·         The authors add, “That increase appears manageable in the context of current production volumes, the long lifetime of the equipment, and the ability to recycle the metals.”

·         Compared with material production levels in 2011, the construction and operation of the 2050 electricity system envisioned in the BLUE Map scenario would require less than 20% of the cement, 90% of the iron, 150% of the aluminum, and 200% of the copper, all relative to their respective 2011 production quantities (Table 1). Meeting copper demand could be problematic due to declining ore grades, and it would result in potential increases in the environmental costs of copper production.

·         Displacing fossil fuels through the widespread deployment of solar and wind energy could limit air and water pollution (Fig. 2).

·         Over the study period (2010–2050), emissions of GHG connected to the power plants investigated are 62% lower in BLUE Map than they are in the Baseline Scenario whereas the particulate matter is 40% lower, freshwater ecotoxicity is almost 50% lower, and eutrophication is 55% lower.  Furthermore, both cumulative energy consumption and land use are reduced.

DISCUSSION

In this section, the authors give a broad summary of their goal for this study and what they have achieved, reiterating the novelty of this hybrid LCA that allows incorporation of how increasing use of renewable energy sources may impact and, in some cases, mitigate the potential environmental impacts of the manufacture and material use of new renewable energy technologies.  They also note that their analysis leads to further questions and, in the discussion section, they offered some brief responses for thought (see article).

CONCLUSIONS

·         Our analysis indicates that the large-scale implementation of wind, PV, and CSP has the potential to reduce pollution-related environmental impacts of electricity production, such as GHG emissions, freshwater ecotoxicity, eutrophication, and particulate-matter exposure.

·         The pollution caused by higher material requirements of these technologies is small compared with the direct emissions of fossil fuel-fired power plants.

·         Bulk material requirements appear manageable but not negligible compared with the current production rates for these materials. Copper is the only material covered in our analysis for which supply may be a concern.

MATERIALS AND METHODS

Methods for calculations, modeling software, assumptions, information use, and information sources are summarized.  For detailed descriptions and definitions, see supporting information documents.  Spreadsheets use for calculations and tabulation of information are given in the PNAS website.

Forensic Chemistry: The Revelation of Latent Fingerprints

Forensic Chemistry: The Revelation of Latent Fingerprints

J. Brent Friesen *

Physical Sciences Department, Rosary College of Arts and Sciences, Dominican University, River Forest, Illinois 60305, United States

J. Chem. Educ., 2015, 92 (3), pp 497–504

DOI: 10.1021/ed400597u

Publication Date (Web): October 8, 2014

Copyright © 2014 The American Chemical Society and Division of Chemical Education, Inc.

ABSTRACT: http://pubs.acs.org/doi/abs/10.1021/ed400597u

This article seeks to fill in some gaps on information regarding chemical reactions and interactions taking place in the visualization techniques used to reveal fingerprints.

HISTORICAL

·         At the end of each finger is the volar pad consisting of skin ridges designed for gripping.  These skin ridges create a unique pattern for each person that allows matching the fingerprint with its origin.

·         Latent fingerprints are formed when the volar pad touches a surface and leaves a transparent thin layer of chemical residue on it in the distinct patter of the skin ridges.

·         Fingerprint analysis has been used in crime investigations for over 100 years.

·         Fingerprint analysis continues to be an important process despite the development of DNA analysis.  Fingerprints can distinguish between two people who have identical DNA.

·         The chemical methods used to visualize fingerprints fall into two categories:

o   Those that involve chemical reactions

o   Those which are based on intermolecular forces to create adhesion

·         Difficulties arise from

o   The quality of the surface

o   The quantity of the fingerprint residue

CHEMICAL COMPOSITION OF FINGERPRINT RESIDUE

·         Chemicals left behind as fingerprint residue can originate from exogenous and endogenous sources.

·         Exogenous sources:

·         Chemicals from anything handled by the fingers

·         Personal hygiene chemicals (commonly found in latent fingerprints)

·         Endogenous sources:

·         Sweat and/or body oil from eccrine, apocrine, apoeccrine, and sebaceous glands.  Each of these glands may have slightly different chemical compositions.

·         Eccrine glands general secrete “classic sweat, an aqueous solution of electrolytes and hydrophilic compounds such as urea”.

·         Other three glands general secrete “lipophilic fatty and waxy substances such as squalene and cholesterol”.

·         Almost all families of organic functional groups have been detected in fingerprints and/or sweat: alcohols, phenols, aldehydes, ketones, esters, carboxylic acids, amines, amides, and amino acids

·         Common endogenous components of fingerprints can be detected by GC-MS (e.g. squalene, cholesterol, and fatty acids) except for a few like inorganic and organometallic salts.  Amino acids are easily detected with ninhydrin but not GC-MS without prior derivatization.

·         The specific chemical composition of fingerprints may be a unique characteristic for each person as well.

·         Fingerprints likely change as a person ages.

CHEMICAL REACTIONS IN THE REVELATION OF LATENT FINGERPRINTS

REACTIONS OF FREE AMINO ACIDS: NINHYDRIN AND ITS MIMICS

·         Figure 1 shows a possible 4-step mechanism for the reaction of ninhydrin with amino acids to produce a visible product. The final product is the chromophore diketohydrindylidenediketohydrindamine or “Ruhemann’s purple (see Figure 1 for structure).

·         Chemical revelation of choice when trying to visualize prints on paper.

·         Dansyl chloride and Lawsone are two other reagents that have been developed to react with amino acids to produce a colored and/or fluorescent compound.  The highly fluorescent adducts can be more easily contrasted from the background than ninhydrin-treated fingerprints.  See Figure 2 for structures of these 2 and other ninhydrin-related compounds.

SILVER NITRATE

·         Has been used in law enforcement since the 1930’s.

·         In this method, an aqueous solution of silver nitrate is sprayed on the surface, left to dry, and then exposed to sun or UV light until dark ridges appear.

·         The series of reactions involves precipitation of silver chloride when the silver reacts with chloride ions in the fingerprint.  A disproportionation reaction in which both silver and chlorine are converted to their elemental forms occurs under UV light.

·         See paper for reaction equations.

PHYSICAL DEVELOPER

·         The solution contains, Ag+, Fe2+, and Fe3+ ions and citrate.

·         In one reaction, Ag+ + Fe2+ à Ag(s) + Fe3+. The Fe3+ and citrate stabilize the solution by suppressing the spontaneous redox reaction above.

·         In an alternate reaction, silver nanoparticles attached to an organic anion are formed.  These negatively charged silver nanoparticles are attracted to the positive charge of the latent fingerprint residue.  N-dodecylamine acetate is a cationic surfactant that prevents the attachment of the silver nanoparticles to the fingerprint surface thus allowing the nanoparticles to selectively attach only to the fingerprint residue. The presence of hypochlorite ion in bleach creates a darker print from the formation of silver oxide through the following reaction: OCl- + 2 Ag(s) àAg2O + Cl-.

GUN BLUE

·         This method was developed in 1995 to reveal fingerprints on brass shell casings.

·         Brass is an alloy of copper and zinc.  Gun blue is a solution of copper (II) sulfate and selenous acid.  The brass shell casing is immersed in this solution.

·         In the presence of these chemicals, both Cu and Se are produced by the following redox reactions:

·        

·         The metallic copper and selenium form on shell casing except on surfaces that have fatty fingerprint residues.

CHEMICAL REACTION AND PHYSICAL ADHERENCE: CYANOACRYLATE ESTERS

·         This method was discovered by a law enforcement agency in Japan. 

·         The fingerprint is revealed in this method by exposing the surface to cyanoacrylate ester fumes for a period of time until hardened, tan-colored fingerprint images form.  Methyl, ethyl, and n-butyl cyanoacrylate esters are the most commonly used.

·         Superglue is a cyanoacrylate ester discovered by Harry Coover in 1942.

·         Figure 3 in the article shows the reaction mechanism for the polymerization chain growth of cyanoacrylate ester using lactate anion for initiation.  Higher pH increases the amount of accumulated superglue polymer.

·         In an alternate mechanism scenario, a competing theory is that clumps of superglue form during the fuming process which then sticks to the oily fingerprint residue.

PHYSICAL ADHERENCE: INORGANICS

Iodine fuming:

·         Oldest form of fingerprint revelation best used for paper or cardboard surface.  The fingerprint residue is exposed to iodine fumes in a sealed chamber. A yellow-brown color forms which fades quickly once the print is removed from the fumes.  Spraying with starch enhances the color and preserves it with a blue-black color.  (Rigorous studies indicate that the formation of the I5- trapped in the amylose helix structure gives rise to this blue-black color.)

Ruthenium tetroxide (RuO4 or RTX)

·         A dark-colored ruthenium dioxide is formed when fingerprints are exposed to RuO4 fumes.  The mechanism is unknown.  See article for a description of the synthesis of water-insoluble RuO4.

Dyes:

·         Sudan black is a lysochrome azo dye especially useful for revealing fingerprints on wetted surfaces and waxy paper.  The object is immersed in a methanol solution of Sudan black that washes off the non-fingerprinted surface leaving the fingerprint image behind. a lysochrome is a dye used for staining lipids.  See Figure 4 for the structure of Sudan black.

·         Oil red O is a lipophilic dye already used for biological staining.  It works well on wet porous surfaces of paper or cardboard.  The dye is dissolved in methanol made basic with sodium hydroxide.  After the stain has developed, it is made neutral using a buffer solution.

·         Fluorescent dyes like Rhodamine adhere to the lipophilic surface of a fingerprint.  This adherence method requires a special light source for excitation of the fluorophores and/or photographing the fluorescent emission light.  An advantage is the ability to selectively enhance ridge details.  See paper and Figure 5 for other examples and structures of fluorescent dyes used for fingerprint revelation.

·         Gentian violet (crystal violet) is useful for revealing fingerprints on the stick side of adhesive tape.  Crystal violet is also used to fix and stain certain bacterial cells.

Powders:

·         Commercial powders are available but commonplace talcum powder and charcoal dust powder can be used to reveal fingerprints.  The powder must stick only to the fingerprint residue and not the surface around it.  These powders are categorized according to their appearance as metallic, photoluminescent, and regular:

o   Regular – finely divided polymeric resin with a colorant

o   Metal – metallic oxides

o   Photoluminescent – fluorescent or phosphorescent organic dyes or ground up fish scales

·         Sticky-side wet powders (dry powders suspended in an aqueous solution containing an anionic surfactant) are useful for revealing prints on the sticky side of adhesive tape, bonding through noncovalent interactions. These sticky side powders are commonly titanium oxide based with traces of aluminum and silicon; the role of the anionic surfactant is not clear (could be for better wetting ability or to facilitate powder bonding).  Figure 6 gives the structures of examples of surfactants.

Small particle reagent:

·         This method is useful for wet surfaces.  The small particle reagent is a suspension of molybdenum disulfide in a surfactant solution.  The powder adheres to the fatty fingerprint residue insoluble in the wet aqueous environment.  Other powders used are titanium dioxide, zinc oxide, magnetite (Fe3O4), graphite, or zinc carbonate.

Vacuum metal deposition

·         In this rather expensive but popular technique, evaporated gold is deposited on the fingerprint. Ridges and troughs are resolved by different gold nanoparticle formation. The image is enhanced by exposure to evaporated zinc resulting in a negative print that stands out better upon photography.  This method works well on hard-to-print surfaces and has potential for smooth surfaces like polyethylene.

ANTIGEN – ANTIBODY INTERACTIONS: IMMUNOASSAY BASED TECHNIQUES

In this newly developed method, certain substances left on the fingerprint (drugs, etc) are targeted for detection by antibodies attached to gold nanoparticles.