Economic and Environmental Implications at Material End-of-Life
One of the key engineering challenges of the 21st century will be reducing the harmful effects associated with a growing population and the attendant flows of materials. The materials community is uniquely positioned to play a central role in addressing these problems by fundamentally changing the materials and processes used by society. For this to happen, materials experts must begin to consider the environmental impacts of their design choices and will require additional analytical tools to quantify those broader implications. My research work begins to address this need by examining the environmental and economic impacts of material and materials technology decisions with a focus on end-of-life (EOL). More specifically, my research focusing on increasing EOL materials recovery through the following operational, technological, policy, and manufacturing strategies:
- identifying and removing barriers and disincentives to secondary usage
- evaluating effective technologies for “upgrading” secondary materials
- designing and selecting recycling-friendly products
- creating economically efficient usage strategies
- enabling efficient collection and logistics
- identifying undervalued secondary materials
- preventing “down-cycling” through improved recycling operational practices
- informing recycling system legislation and policies
To guide technology decisions in any of these directions, it is necessary for engineers to be able to analytically evaluate their economic and environmental implications. As these implications will affect a number of stake-holders throughout the process chain, this analysis will require a systems engineering approach.
One key materials selection decision with wide economic and environmental implications is the use of recycled or secondary materials in production. The long-term sustainable usage of materials will require a robust secondary recovery industry. Secondary recovery forestalls depletion of non-renewable resources and avoids the deleterious effects of extraction and winning. For most materials, this provides strong motivation for recycling; for light metals, like aluminum, the motivation is compelling as shown in Figure 1. Despite these large energy savings, the aggregate recycling rates of most materials in the U.S. (consumption of old and new scrap/total material consumption) hover below 50% with old scrap accounting for less than half of that figure. More troubling is the general stagnancy or decrease in these figures over the last few years (Figure 2). To expand recycling, it is necessary to remove or reduce the disincentives to return, collect, and process secondary materials .
Figure 2. Aggregate recycling rates for several materials in the United States
- Which scrap streams are worth additional end-of-life processing (both economically and environmentally)?
- How does one identify efficient upgrading technologies before spending R&D dollars?
One of the primary challenges for increased secondary raw material usage is due in part to the presence of high levels of unwanted or “tramp” elements, for example iron and silicon in the case of aluminum, particularly in post-consumer scraps. A great deal of work is reported in the literature on methods to address accumulation through technological upgrading methods. Some of these methods include: dismantling of end-of-life products, spectrographic or magnetic sorting of shredded scrap, and “filtration” technologies such as fractional crystallization and vacuum distillation that remove tramp elements in the melt. Work done in my dissertation has developed a set of analytical tools, based on chance-constrained optimization, to quantify the potential environmental and economic value of several aluminum upgrading technologies. As literature cites accumulation to be a problem in a wide range of recycled material streams (Table I), this work could easily be extended to many other materials as well as new upgrading technologies, depending on current collaborators and sponsorship. Each application will yield unique strategies for mitigating accumulation issues through efficient production planning.
Material Tramp Elements Steel Ni, Cr, Sn, Cu, Zn Plastics Cd Aluminum< Mg, Ni, Zn, Pb, Cr, Fe, Cu, V, Mn, Si Brass Pb Copper Fe, Pb, Ni, Cr, Sb, Bi, Se, Te Glass Al, SiC, C, Chromite, Carborundum Cast Iron Mn, Ni, Mo, Zn, Co
Publications relating to this work: P9
Recovery of Li-ion battery materials at EOL
Environmentally Preferable End-Of-Life Management for Li-Ion Batteries
NYSERDA Project 18503 $195,320 Start date:TBD End date: TBD
This project will develop economical, environmentally preferable technologies for Li-ion battery recovery, remanufacturing, and recycling operations that simultaneously reduce the environ-mental impact of the battery life-cycle and help meet NYBEST battery manufacturing goals. A series of process modules will be developed for optimizing the remanufacturing and recycling of Li-ion batteries, components, and basic materials, including: electrolyte recovery, casing disassembly, cathode & anode separation, reconstitution of active materials, testing, and reassembly of viable battery components to match OEM specifications. Life-cycle characterization of the economic and environmental consequences of each stage will allow optimization for either cost or environmental considerations by selecting a final disposition (i.e., remanufacture, recycle, or disposal) determined by the quality and quantity of materials recovered.
- How much should municipalities charge/pay for disposal of certain scraps?
- What are reasonable targets for recycling mandates created by legislators?
- Can one estimate recycling limits for products and/or materials systems in the U.S. and globally?
Firms and legislators are often tasked with creating recycling targets. For example, Alcoa had a recent press release outlining goals of 25% recycled content in their fabricated product by 2010 and 50% by 2020. In 2000, the European Union set out legislation to require 95% of end-of-life vehicles be recycled by 2015. However, legislators in particular are often not equipped with the data and analytical tools necessary to make sure these targets are physical and economically possible. In fact, work done by Reuter, van Schaik, and others[14-16] has utilized dynamic modeling and extensive product data to examine optimal end-of-life vehicle recycling rates in the EU and concluded the 2015 directive an impossibility. This work demonstrates that detailed characterization of recycling systems is required to inform policy-makers in government and firms alike. One of the complexities in predicting recycling rates for recycling systems is the ever-changing nature of supply and demand. In light of the global trends, arguments could be made that nearly all materials are transitioning to exponential growth patterns and that sinks for recycled materials may be disappearing. To determine the gross limits on recycling rates, it will be necessary to forecast this demand growth, evaluate scrap recovery rates, and determine product lifetimes and compositional deterioration.
Publications relating to this work: P11, P12
Currently funded research:
Economic and Environmental Trade-offs at EOL for Printer Cartridges
Research underway focuses on exploring the environmental impacts for each EOL decision available to a consumer for empty print (inkjet and toner) cartridges. Consumers can reuse (e.g., refill inkjet cartridges), throw out, donate, drop-off at a retailer or ship the empty cartridge to the manufacturer or third party at no cost to the consumer. Interestingly, the consumer disposal option results in the printer firm earning the most profit since the firm (1) does not incur a cost for each disposal, (2) avoids the cost of voluntary recycling, and (3) ensures the disposed cartridge will not re-enter the market as a refilled or remanufactured product which would displace profits earned from the sale of a new cartridge. First steps are to identify the environmental impacts of each EOL route by conducting a Life Cycle Assessment (LCA). The LCA results can be used to inform consumers of the environmental impacts of their EOL decision options, given assumptions in the model based on existing market conditions. Sensitivity analysis on the LCA results will be performed to show “what if” results based on different market dynamics (e.g., consolidation in the cartridge remanufacturing industry), or the introduction of regulations (e.g., ban on exporting empty cartridges from the U.S.).
In addition to environmental impact analysis, economic modeling is underway to identity the economic welfare of the current variable proportion product tying business model employed by printer firms. Under product tying, the tying product (printer) is sold at a lower price and the tied product (cartridge) is sold at a higher price than if both products were sold in competitive markets.
Under this business model and current regulations, the printer manufacturing firm choosing not to remanufacture their own cartridges is better off producing a cartridge that is disposable, since the firm is not responsible for disposal costs related to empty cartridges. Hence the printer firm may use intellectual property rights and other product attributes (e.g., non-replaceable fasteners) in the cartridge design in order to strengthen the tie and reduce the reusability (recyclability) of the cartridge. Economic welfare analysis will be used to show the welfare effects related to the printer firm’s selection for the level of intellectual property and product attributes, and vice versa. The economic model will be used to evaluate the welfare effects of potential regulations or policies aimed at reducing the level of cartridge disposal. The environmental impact analysis from the LCA, combined with the economic analysis, will provide a comprehensive method to inform consumers, businesses, and policy makers.
- How does the level of variance in scrap stream composition effect production costs?
- Can compositions of scrap streams be characterized more effectively?
- Does demand side uncertainty (which and how much product to manufacture) or supply side uncertainty (composition, availability and price of materials) have a larger adverse effect?
A significant set of economic disincentives emerge due to the various types of operational uncertainty that confront secondary processors [5, 6]. In particular, depending on where one is in the production chain, business-critical sources of uncertainty include capricious demand, unstable availability of raw materials (particularly scrap materials), the precise composition of those raw materials, and the cost of factor inputs. These uncertainties have the largest adverse effect on those furthest from the customer, e.g., materials producers, due to the feedback mechanisms inherent to typical market-based supply-chains . Managing these uncertainties will require improved characterization of scrap composition and variance; this can be accomplished through statistical analysis and probabilistic modeling. Fluctuations can then be tested with this model to evaluate the resulting effects on production cost and scrap utilization. This work can be extended to other sources of uncertainty by creating models that make use of forecasting techniques for customer demand and scrap supply.
Publications relating to this work: J3, P6, P8
- What compositional components are the most limiting in terms of increased usage?
- Can we develop simple metrics to characterize efficient resource use?
- How does the volatility of scrap markets effect operational planning in secondary production?
My dissertation work has shown it is possible to increase the use of recycled material without compromising the likelihood of compositional or performance errors, when using more advanced analytical mixing strategies compared to current practice. This improvement is especially beneficial as computational modifications require little to no capital investment in equipment and space. The strength in computationally modeled usage strategies for secondary materials is time and money saved. For example, sensitivity analysis of linear batch mixing optimization programs can be utilized to predict which recycled components are the most limiting (economically and environmentally), thus preventing the need for time-consuming and expensive physical testing (such as x-ray diffraction or spectroscopy).
Publications relating to this work: P5, P4
- What collection, market, and manufacturing changes would need to occur to shift currently non-profitable recycled streams (e-waste, metallic dross, CRT glass) to a net positive?
- What drives secondary material availability and price?
Many material streams are currently being recycled due to regulations; unfortunately not because a commercially viable business market exists. This is often due to decreased performance with introduction of recycled material. One example includes electronic waste whose disposal is regulated due to the toxic heavy metals they contain. Another prime example is lead whose recycling rate is much higher than most materials (cf. Figure 2) despite a lack of manufacturing sinks for recycled lead. Making these environmentally beneficial recyclers more economically viable would decrease the financial burden placed on other firms and tax-payers. Pinpointing the changes necessary for profitability to occur would be the first step in this direction.
Publications relating to this work: J2, J1
- Are current operational strategies such as dilution and down-cycling economically and environmentally efficient?
- What untapped markets or higher value sinks exist for currently down-cycled secondary materials?
As discussed above, many recycled materials often include high levels of unwanted, or “tramp” elements that prevent their increased utilization. While upgrading strategies are one way to mitigate this, current practice relies heavily on dilution and down-cycling. Dilution is when secondary materials must be mixed with primary material in order to ensure the finished products meet compositional and performance specifications. While dilution is common; it has a negative impact on recycling as the required dilution results in a compositionally determined cap to recycling rates. “Down-cycling”, where materials are recycled into lower value products, is another common method of dealing with highly contaminated secondary materials; this enables higher usage but negatively effects recycling economics. A specific example of down-cycling for the case of aluminum is when wrought scrap is used in cast products due to their ability to accommodate higher silicon contamination. To date, secondary aluminum production has focused on satisfying demand for compositionally forgiving cast alloys and the carefully designed alloy systems used for can stock. If secondary production is to sustain its current growth trend (which is far outpacing the growth in primary production), the sinks for secondary material will also need to expand.
Publications relating to this work: P2, P1
- Which products provide issues and/or opportunities in regards to increased scrap consumption potential?
- How will the incorporation of recycled materials affect the performance of finished products?
The primary challenge in evaluating a product’s recycling-friendliness is that it is a context dependent property; how much scrap a product can accommodate will be based on not only the compositional characteristics of the product itself, but also the types of scraps available to producers, the compositional characteristics of those scraps, and their yields. As a result, a method to evaluate recyclability must be able to account for the confluence of these detailed effects. Work done in my dissertation utilizes a chance-constrained based optimization method to explore the effects of strategic alloy choice in aluminum production on the ability to utilize secondary materials in the alloy’s raw material portfolio. Two cases were examined to demonstrate the model’s ability to both directly evaluate the recyclability of specific alloy formulations and proactively identify the most effective alloy modification strategies that can drive increased recycling. Industry experts and literature have provided a variety of other suggestions to increase a product’s ability to accommodate secondary materials including higher maximum compositional specifications for certain elements that will not adversely affect product properties, wider specification targets (i.e. higher maximums and lower minimums), or translating compositional constraints to specifications based on performance. Other suggestions involve modifying forming and joining, for example, replacing conventional welding with mechanical joining, laser welding, or friction stir welding. Some even propose legislation or regulations to limit the number of alloys that can be used in certain products such as cars or aircraft. The model previously developed can be extended to provide a quantitative assessment of the efficacy of these suggestions on the ability of a recycler or recycling system to use more secondary raw materials as well as to which products they should be applied.
Publications relating to this work: J1, J4, P7
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