Quantifying Life Cycle Environmental Benefits from the Reuse of

By combining these records with life cycle inventory (LCI) data, the current and potential environmental benefits of residual waste use have been asse...
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Environ. Sci. Technol. 2009, 43, 2550–2556

Quantifying Life Cycle Environmental Benefits from the Reuse of Industrial Materials in Pennsylvania M A T T H E W J . E C K E L M A N †,‡ A N D M A R I A N R . C H E R T O W * ,‡,§ Program in Environmental Engineering, Center for Industrial Ecology, and School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06520

Received August 21, 2008. Revised manuscript received January 5, 2009. Accepted January 15, 2009.

Local reuse of waste materials from industrial processes has manypotentialenvironmentalbenefits,butthesehavebeendifficult to aggregate and measure across industries on a broad geographic scale. Nonhazardous industrial waste is a high volume flow principally constituted of wastewater with some solid materials. The state of Pennsylvania produced some 20 million metric tons of these residual wastes in 2004. An innovative reporting requirement for industrial generators implemented and compiled by the Pennsylvania Department of Environmental Protection has resulted in a rich database collected since 1992 of residual waste generation, detailing the fate of more than 100 materials. By combining these records with life cycle inventory (LCI) data, the current and potential environmental benefits of residual waste use have been assessed. Results for Pennsylvania indicate a savings in 2004 of 13 PJ of primary energy, 0.9 million metric tons of CO2eq, 4300 tons of SO2eq, and 4200 tons of NOx emissions from reuse of residual wastes. While these energy savings constitute less than 1% of total industrial primary energy use in the state, it is a greater quantity of energy than that generated by the state’s renewable energy sector. The framework and constraints surroundingreuseofresidualwasteinPennsylvaniaarediscussed.

Introduction The sharing of material, energy, and water resources among proximate firms, known as industrial symbiosis, has been touted as a way to reduce the environmental impacts of industry (1, 2). Through the local reuse of secondary materials, industries can lessen demand for virgin production, save energy in manufacturing, and avoid long transport distances. In almost all cases, the processing of secondary materials requires less energy and results in less pollution than production of equivalent quantities of virgin material (3). This article examines the environmental effects of industrial byproduct reuse (including recycling) at the state level by combining life cycle inventory data with the nonhazardous industrial waste records generated by Pennsylvania’s extensive reporting requirements. Many instances of industrial symbiosis have been described in the literature (4-8). Industrial symbiosis can occur over a range of scales from adjacent firms (such as a * Corresponding author e-mail: [email protected]. † Program in Environmental Engineering. ‡ Center for Industrial Ecology. § School of Forestry and Environmental Studies. 2550

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steel-cement partnership at Chaparral Steel, Texas), to those in broader proximity in the same municipality (as with Kalundborg, Denmark), to regional and countrywide programs (such as the National Industrial Symbiosis Partnership in the United Kingdom). Yet, despite the promise and potential scope of industrial symbiosis, relatively few studies have quantified the environmental benefits of actual systems. Chertow and Lombardi (9) conducted an economic and environmental analysis of an industrial cluster in Guayama, Puerto Rico, including a coal-fired power plant, a wastewater treatment plant, and a petrochemical refinery. They found that resource sharing saved the system four million gallons per day of fresh water and led to significant reductions in SO2, NOx, and particulate emissions from steam production; however, emissions of carbon monoxide and dioxide were elevated compared to the base case as coal replaced oil as the source of electric power generated for the refinery. In the case of steam, only direct material inputs were considered (no upstream inputs), and no changes in environmental impacts for other industrial byproduct uses, such as coal ash used for stabilization, were considered (9). Jacobsen (10) described the economic and environmental parameters of the much-studied Kalundborg symbiosis. Again, only a few of the exchanges are assessed for their environmental implications. The sharing of steam and waste heat from the central power plant resulted in a savings of more than 7.5 PJ of heat over the period 1997-2002 and reductions of 155 000 t of CO2 and 390 t of NOx. SO2 emissions were slightly increased from the base case. Solid industrial byproducts, including flue-gas desulfurization (FGD) residue, were not considered. Interfirm waste exchanges in Kawasaki Eco-town, Japan, are on a similar scale as Kalundborg and centered around large production facilities for cement, iron, and stainless steel. Annual CO2 savings owing to virgin resource substitution with industrial byproducts there have been estimated at 600 000 t (11). On a larger scale, the National Industrial Symbiosis Programme (NISP) in the United Kingdom attempts to create a network of industries and byproduct sharing across the entire country. This project was based on several smaller local programs, including Mersey Banks, Humberside, and the West Midlands (12). NISP makes annual estimates of several environmental metrics; Laybourn and Lombardi (13) reviewed these and found a programwide savings of 2 million metric tons of CO2, 2.5 million tons of potable water, and 1.7 million tons of waste diverted from landfills between 2005 and 2007. In an older study, Porter and Roberts (14) examined the current and potential-energy savings from the recycling of select materials in the then 10-member European Community. They found that 123 PJ/year of energy savings were available with more than 90% of this being attributed to postconsumer waste and more than one-half coming from increased recycling of aluminum. There has been some effort to compile quantitative information for many different industrial symbiosis projects for comparative purposes in the industrial ecology literature (15, 16). In general, however, the lack of standard metrics and the reporting of specific materials instead of overall life cycle environmental impacts hinder comparative analysis. Another hurdle is that much of the research and data in the industrial symbiosis literature is derived from known industry clusters. As such, any discussion of environmental benefits refers to existing exchanges and usually excludes the question of how much more symbiotic potential is available and what the environmental effects could be overall. The total potential 10.1021/es802345a CCC: $40.75

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FIGURE 1. Distribution of PA’s residual waste generators of greater than 13 short tons in 2004. environmental benefits of industrial symbiosis have yet to be estimated on any large scale. While not all secondary materials are suitable for reuse, the present analysis considers both the present and potential benefits of resource sharing in Pennsylvania along more environmental parameters than have been previously evaluated. Pennsylvania is an ideal research area in which to conduct such an assessment: it is strong in diverse industries with the types of large industrial waste streams that foster industrial symbiosis kernels such as coal-fired electricity generation, metal foundries and fabricators, and food processing. Many of its largest industrial wastes are specific targets of the U.S. EPA Resource Conservation Challenge (17), including coal combustion products and foundry sands. This assessment relies on unique reporting data for nonhazardous industrial waste in Pennsylvania. In 1992, the Pennsylvania Department of Environmental Protection (PA DEP) instituted a rule based on legislation (25 Pa. Code §287, Subchapter B: Duties of Generators) requiring facilities in the state that produced more than 13 short tons of nonhazardous industrial waste to report the type, quantity, and disposal method of that waste. Reporting was required on a biennial basis including chemical analysis of the waste and plans for source reduction. The goals of the program were to help the PA DEP identify which facilities to inspect, facilitate waste sharing among Pennsylvania industries, and provide information for long-term waste management planning in the state (18). The first complete reports were filed in the early 1990s and continue through the present. While byproducts that are used beneficially are not considered to be waste under the regulation, many facilities chose to report cases where byproducts were used on site or sold to another facility. These reuse records form the core of the present analysis. While often overshadowed by municipal solid waste (MSW) in policy debates and research, nonhazardous industrial waste (or residual waste, in PA DEP parlance) is the dominant waste stream of modern societies. The United States as a whole in the late 1980s generated approximately 190 million metric tons of MSW in comparison to nearly 7250 million tons of nonhazardous industrial waste (19). At that time, most states had waste management plans concerning the disposal of nonhazardous industrial waste, but very few targeted waste minimization from generators (20, 21). Despite the overwhelming dominance of nonhazardous industrial waste in the country’s waste management system, there has been no reliable nationwide estimate of generation or disposal made in the past two decades. Pennsylvania’s reporting of residual wastes provide the most comprehensive source for data on nonhazardous industrial waste in the United States. In 2004, there were 10 825 records for residual waste generation in Pennsylvania involving some 2000 companies and over 100 possible waste

streams. Nearly 300 million metric tons of residual waste were generated; however, most of this was nonprocess wastewater. Considering only solid wastes, Pennsylvania facilities generated approximately 20 million tons in 2004, still well in excess of the state’s generation of approximately 10 million tons of MSW (excluding imports from other states) (22). Many of the largest generators of residual waste were clustered around Pittsburgh in the west of the state, along the Delaware River, and in Berks and Lancaster counties in the southeastern part of the state, as shown in Figure 1. Given the scale of residual waste generation and the significant environmental impacts of industrial activity in general, the purpose of this analysis is to use the PA DEP database to quantify the environmental effects of reusing residual wastes. This statewide assessment will cover a range of environmental impact categories and provide an estimate of the current and potential impacts of secondary material reuse on a large scale.

Methods The Pennsylvania residual waste database records both the generators of waste as well as the destination type for that waste. These 13 destination types can be divided into those related to disposal and those related to reuse of materials. The five types that relate to reuse are reuse/recycling, composting, land application, industrial kiln, and other, which mostly refer to cases of unconventional reuse. The other eight destination types are as follows: surface impoundment, incineration, landfill, on-site storage, treatment, underground injection, and on-site and off-site wastewater treatment. According to the residual waste database reporting rules facilities are not required to report many of the industrial byproducts that are sold to other companies for reuse because they are not considered to be waste under Pennsylvania statutes (25 Pa. Code §287.7). In 2004, numerous companies chose to report reuse in the residual waste database, but an unknown quantity of secondary material was reused by the industrial sector without reporting but in accordance with regulation. The results of the present analysis should therefore be seen as a lower bound estimate. The records that fall into these five reuse types were extracted and aggregated by material category, as shown in Table 1. For each material an assumption of material substitution was made (for example, bottom ash substitutes for sand fill); these were based on individual records within the residual waste database. In some cases, residual waste can be used in multiple applications, such as wood waste being used for mulch and for energy recovery. Table 1 also shows the extent to which these materials are being reused in relation to their total generation by Pennsylvania facilities, as recorded in this database with the exclusions noted previously. VOL. 43, NO. 7, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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TABLE 1. Current Substitution of Specific Secondary Nonhazardous Industrial Materials for Virgin Materials in Pennsylvania in 2004 (>1000 metric tons current reuse)a industrial byproduct

can substitute for

current use (‘000 tons)

total generation (‘000 tons)

% current reuse

coal-derived bottom ash coal-derived fly ash FGD residue other ash foundry sand slag refractory material ferrous scrap and dust nonferrous scrap and dust water/wastewater treatment sludge food waste and sludge oil/oily sludge generic sludge lime-stabilized spent pickle liquor machine coolants wood wastes paper products textile waste glass cullet plastic waste asphalt ceramic waste containers baghouse dust used drywall spent catalysts debris and sediment nonhazardous batteries

sand lime gypsum sand sand cement refractory material virgin steel virgin nonferrous compost animal feed fuel/ engine oil sand hydrochloric acid ethylene glycol coal/ mulch mixed paper textiles glass mixed plastic asphalt sand steel drums sand drywall metal catalysts sand lead

1116 1732 1435 265 70 362 7 49 6 286 256 62 61 38 4 71 152 2 6 13 18 3 3 166 1 3 18 3

1499 3621 3242 279 153 1074 45 117 20 3787 340 380 305 63 4 101 202 18 17 50 30 8 7 180 8 6 85 3

74% 48% 44% 95% 45% 34% 16% 42% 31% 8% 75% 16% 20% 60% 89% 71% 75% 10% 38% 24% 61% 39% 39% 92% 17% 45% 21% 98%

a Note: Categories for which the substituted material was not known were excluded, including wiring/electrical conduit waste, electronic waste, and plant trash. Source (22).

Some materials are near full utilization, while several materials are experiencing a discard rate (without reuse) of 80-90%, as shown in Table 1. The wide range of utilization efficiencies is due to the underlying value of the industrial byproduct and regulatory ease with which it can be reused. Ferrous scrap is obviously of high value, and use of FGD residue as a substitute for gypsum is widely practiced (and expected to increase greatly as more coal plants add these types of air pollution control systems). In contrast, air emission control sludge, a complicated mixture that can include potentially toxic metals and organic pollutants, has a limited range of reuse options. For potentially dangerous industrial byproduct materials reuse can be partially restricted or prohibited outright by regulation. For example, land application of water and wastewater treatment sludge (or biosolids) is highly regulated in Pennsylvania (25 Pa. Code §271 and 275, as amended), even while it represents an enormous mass of potentially beneficial material in the state. Biosolids applied to agricultural lands can confer many of the benefits of synthetic fertilizers, for which they can theoretically substitute, although environmental parameters must be carefully monitored to ensure that cropland receives appropriate nutrient mixes and is free of pathogens. In order to characterize and quantify the effects of residual waste reuse in Pennsylvania, each substitution listed in Table 1 was evaluated for the difference in environmental impacts between reuse and production of the substituted (virgin) material using the life cycle inventory (LCI) databases of GREET (23) and Ecoinvent (24). Table 2 shows unit impact factors for each virgin material that is being substituted for as well as each industrial byproduct that requires treatment before reuse. In keeping with previous research (9) the environmental impact categories considered were primary energy, greenhouse gas emissions, SO2, and NOx emissions. Net unit energy and emissions values for each substitution 2552

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(Table 2) were multiplied by the total mass of beneficial use (Table 1) to calculate aggregate statewide environmental benefits. In cases such as fly ash, where substitution for lime can be made without the need for significant treatment of the industrial byproduct, the environmental benefits were taken to be the avoided impacts of virgin production. For other residual wastes such as nonferrous scrap or spent catalysts the quality of the byproduct and the displaced material differ, so that the functional unit of analysis is not consistent. Reprocessing or treatment is necessary to transform the byproducts into usable materials with the same properties as virgin materials. In these cases, the environmental impacts of reprocessing or treatment are subtracted from the avoided impacts of virgin production, thus ensuring a common functional unit for each substitution. In the two cases of residual waste being used for energy recovery (waste oil and wood waste) the ratio of the heat contents of virgin and waste material was used to scale the environmental benefits of each substitution (25, 26). It was assumed that 85% of waste oil is burned for energy recovery, while 15% is rerefined (3, 27), and that 82% of wood waste is burned, while 18% of wood is shredded for use as mulch (22). Heterogeneous residual waste must be considered carefully. For nonferrous scrap and dust, which is made up primarily of aluminum, copper, lead, and zinc, beneficial use must be allocated among these four metals. An allocation of 85% Al, 8% Cu, 2% Pb, and 5% Zn was assumed for industrial waste in Pennsylvania based on a comparative survey of the relative amounts of new scrap (not internal) generated by fabrication and manufacturing facilities globally for each metal (28-31). While the sources and reuse sites are known for Pennsylvania’s residual waste, it is difficult to determine statewide average transport distances for virgin materials from their production origin to their points of use in Pennsylvania. A

TABLE 2. Unit Environmental Impacts of Virgin Material Production and Industrial Byproduct Treatmenta emissions virgin material/industrial byproduct

primary energy, GJ/ton

GHG, kg CO2eq/ton

SO2, kg/ton

NOx, kg/ton

sand lime gypsum cement slag cement refractory material steel ferrous dust/scrap nonferrous metals nonferrous dust/scrap compost land application of sludge animal feed land application of sludge fuel oil (including combustion) waste oil (including combustion) engine oil (excluding combustion) rerefined engine oil hydrochloric acid ethylene glycol coal wood waste virgin wood chips mixed paper recycled paper textiles rag collection and processing glass glass cullet processing lixed LDPE recycled LDPE asphalt/bitumen asphalt reprocessing metal containers vinyl recycled vinyl drywall drywall recycling metal catalysts spent catalyst reprocessing lead for batteries lead waste reprocessing

0.03 0.3 0.03 2.7 1.9 22.8 23.9 13.1 171 43.8 0.4 0.1 4.3 0.1 62.2 0.4 53.3 37.3 10.4 45.5 30.0 0.5 0.1 22.1 14.6 9.7 0.9 13.5 0.7 72.2 10.2 51.2 0.3 26.4 48.4 10.2 5.1 0.1 119 59 12.5 1.6

2.4 19 2.1 762 446 2307 3934 822 11 380 3004 368 1.2 289 1.2 4253 3580 825 577 788.7 1449 3935 48.7 5.90 1483 1400 847 152 881 51.6 2101 748 426 114.3 1595 2174 748 364 3.3 10 720 5360 1530 211

0.02 0.11 0.04 1.22 0.80 6.23 0.73 1.60 50.9 7.17 3.25 0.01 3.48 0.01 28.5 31.4 0.97 0.68 4.24 8.57 28.1 1.28 0.05 8.30 2.59 4.87 2.11 7.65 0.29 15.1 3.65 4.95 0.15 7.29 16.9 3.65 1.25 0.03 1445 723 47.8 0.81

0.02 0.13 0.08 1.43 0.90 5.63 2.38 0.81 14.2 3.71 4.87 0.01 2.85 0.01 8.14 2.47 1.93 1.35 2.04 5.96 11.3 2.02 0.06 6.12 3.14 4.55 3.46 4.39 0.38 11.5 1.98 1.88 0.13 5.19 12.3 1.98 1.23 0.05 112 56 22.9 1.06

a Notes: Where treatment of industrial byproduct is not required, only LCI data for the substituted materials are listed; where treatment is required, differences between primary material and byproduct values were used for the overall calculation; please see the Electronic Supplement for inventory details. Sources (23-26).

regional input-output LCA (REIO-LCA) tool has been developed for Pennsylvania (32), which could in theory be used to estimate transportation energy costs for virgin materials produced in the state; however, this would require specific information on the economic output of the various facilities in the database that is not readily available. Therefore, the environmental impacts associated with the delivery of virgin materials are not considered here, though the upstream transportation (that used for production) is generally included in LCI data themselves. The environmental impacts of waste management are likewise not considered as the disposal methods are assumed to be independent of whether the product is made from primary materials or reused residual waste.

Results and Discussion In general, using secondary materials for production has fewer life cycle environmental impacts than using primary (or virgin) materials because the former are already partially refined and so have embedded much of the needed material and energy. The net environmental benefits (above zero) or costs (below zero) of residual waste reuse are shown in Figure 2 for each of the four impact categories. Each substitution category has the form ‘industrial byproduct/substituted material’.

Several waste categories are worth noting. The reuse of waste oil for energy recovery had the largest primary energy savings due to the fact that the substituted material (fuel oil) is an energy carrier and has a high energy content relative to the energy required to treat the waste oil before combustion (as seen in Table 2). Substitution of virgin paper by recycled mixed paper also has large environmental benefits overall-, with 152 000 tons of industrial material being recovered for reuse. While this volume is much less than the millions of tons of coal combustion byproducts that were reused, there are relatively large differences in the unit environmental costs of producing virgin and recycled paper; virgin paper requires roughly 8 GJ/ton more primary energy than recycled paper and produces approximately three times as much SO2eq and twice as much NOx (24). Metal catalysts are another lowvolume, high-impact waste category. The absolute differences in environmental impacts of producing these catalysts (assumed here to be nickel) from primary and secondary sources are higher than for any other substitution. With only 3000 tons of metal reprocessed, the total energy savings is more than 100 TJ. In contrast, bottom ash and FGD residues are very large in terms of overall quantity of reuse, but the low unit environmental impacts of virgin sand and gypsum VOL. 43, NO. 7, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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FIGURE 2. Life cycle environmental benefits for each major material substitution (>10 000 GJ primary energy savings) in Pennsylvania in 2004. production result in relatively low total environmental benefits for those substitutions. Nearly all material substitutions considered here have positive environmental effects. One exception is the substitution of heavy fuel oil by waste oil, which leads to higher SO2 emissions than just burning virgin fossil fuel. The other is the substitution of virgin steel by scrap steel. Both are assumed to be melted in an electric arc furnace, but the virgin ore must first undergo reduction, which is assumed here to occur in a blast furnace. GREET shows an SO2 credit rather than emission at this stage due to coproduction of steam and electricity from the blast furnace (23). This credit is large enough to make the total SO2 emissions from producing virgin steel lower than those from producing steel from scrap. In total, the net environmental benefits of residual waste reuse amounted to 13 PJ (1015 J) of fossil-derived primary energy, 0.9 million metric tons of CO2eq, and 4300 and 4200 t of SO2eq and NOx, respectively. For comparison, the entire industrial sector in the state uses 1369 PJ of primary energy 2554

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(including nonfossil sources), so the energy savings from beneficial use constitute 0.9% of the total (26). These energy savings are greater than the output of Pennsylvania’s renewable energy sector (8.2 PJ), which includes solar, wind, wood and wood waste, landfill gas, and other biomass such as sludge waste (26). Because some unknown amount of reuse of secondary materials takes place that is not reported to the residual waste database, these results actually underestimate the total environmental savings currently enjoyed by the state. Savings based on residual waste reuse can be viewed as a systemwide increase in primary energy efficiency for industry that was previously hidden because the energy is embodied in materials that are not energy carriers (except for wood scrap and waste oil). Demonstrating the energy and environmental benefits of materials management is a major focus of industrial ecology research. Considering emissions, Pennsylvania industry produced 156 million metric tons of CO2eq (26). For CO2, reuse of residual waste represents a savings of 0.6% of the total industrial burden of this pollutant in the state. If Pennsylvania

industries were able to claim credit for these carbon reductions under an emissions trading scheme, reasonable carbon prices of $10-20 per ton CO2eq would result in $9-18 million in additional revenues. The higher savings of primary energy relative to CO2 emissions is due to the fact that the use of waste oil and wood for energy recovery requires much less energy than is required for virgin oil and coal production but still emits comparable levels of air pollutants. While these results reflect the beneficial use that is currently occurring, there is still a large surplus of many residual wastes that are now being landfilled or surface impounded. Using a similar analysis but considering instead the total generation of all usable residual waste, the statewide potential environmental benefits are roughly four times as large as those currently enjoyed, amounting to 47.2 PJ primary energy, 3.6 million metric tons of CO2eq, 19 600 t of SO2eq, and 29 100 t of NOx (assuming the unlikely scenario that all residual waste is suitable for reuse). It must be noted that Pennsylvania industry imports some of its feedstock material from other states and countries, and so replacing this material with in-state industrial byproducts results in environmental benefits that occur outside the state borders but that are still attributable to the state itself. This analysis also excludes environmental costs and benefits that occur as a result of residual waste reuse that is not related to material substitution such as land use impacts. For example, some fly ash is mixed with lime (increasing its alkalinity) and backfilled into old mines in order to alleviate acid mine drainage. One caution is that even though there is potential for expanded beneficial use of residual wastes, such a scenario might not actually be possible. In some cases, the amount of a waste may far exceed the capacity to reuse it. There are only so many landfills to be capped, road beds to be laid, or structural fill that is needed in construction. In other cases, residual wastes are too contaminated to be reused, such as foundry sands from the inner layer of a mold. For these, landfilling is the only reasonable disposal option under current technology. There are also unavoidable losses during recovery and reprocessing of materials that should be taken into account. Porter and Roberts (14) incorporated some of these factors in their study of energy savings potential in Europe. Such information was readily available as their analysis was limited to a small number of conventional materials but was not possible to gather for the present study given the diverse residual wastes considered. Thus, while the analysis in the previous paragraph assumes complete reuse, this reflects the best-case scenario. While the potential to reuse resources to close material and energy loops is very promising, it cannot be done at the expense of a clean environment. This is a sensitive issue in Pennsylvania given the legacy of environmental damage from coal mining and other industrial activity prior to current regulatory regimes. Some residual wastes, such as contaminated soil or oily sludge, clearly have decreased potential for beneficial use. Thus, these wastes cannot be considered simply as opportunities for material substitution; instead, environmental efforts should focus on green engineering and pollution prevention in order to decrease their potency and overall generation. One of the legal philosophies that governed the shaping of the residual waste management chapter of the Pennsylvania code (25 Pa. Code §287) was to set limits as clearly as possible on what was included and excluded in the law as a means of providing incentives for reuse as well as for avoiding constant litigation over definitions (18). As a result, there are multiple tiers governing resource recovery. Some materials are excluded altogether from residual waste reporting, such as coal ash, then there are excluded materials based upon designation as “co-products” rather than wastes, while additional materials are eligible to be regulated under

beneficial use permits with specific conditions. Because these materials do not have to be reported on the residual waste database, they are likely under-reported. Coal ash is the largest and most important of these permit-exclusion materials. It is used as structural fill in construction projects, as a soil substitute or additive, as backfill in coal mining operations, in abandoned mines, and for several other beneficial uses (25 Pa. Code §287.661-665). Other material categories unlikely to be fully reported based on the regulatory regime described above include: nonhazardous agricultural waste from normal farming operations, food processing waste and sludge from normal farming operations, soil, rock, stone, gravel, concrete and used asphalt, and scrap metal. The Pennsylvania law also includes a number of protections concerning reuse of residual wastes such as the following: • Meeting or exceeding specified material characteristics where residual waste substitutes for a commercial product; • Demonstrating that residual waste used as industrial inputs confers significant properties to the end product; • Securing approval from the Department of Transportation Product Evaluation Board for the use of a certain residual waste for highway construction; • Demonstrating that residual wastes used as soil or otherwise land applied have benign effects on public and ecosystem health and meets minimum standards required for disposal in Class III residual waste landfills; • In the case of mixed residual wastes all constituents must confer significant properties on the mixture. Although one of the policy intents that justified the collection of such extensive residual waste data was for planning purposes, current DEP management considers this an underutilized opportunity and would like to make the data more available and informative. One obvious use in an era of fluctuating raw material prices is the identification of potential residual streams that could find value in commerce. FGD sludge is abundant in PA and will become more so in the coming years as many plants plan to install desulfurization equipment. Given the strength of the higher education infrastructure in the state this could provide an excellent opportunity for technological innovation involving material substitution of FGD sludge for other primary materials (33). Policy uses include geocoding the data so that researchers and entrepreneurs can easily learn how much of which residual streams are available in different parts of the state. Further research is needed to complete the estimate of nonhazardous industrial waste from all excluded or uncounted areas so a total picture of the environmental costs and benefits of one state’s reuse of secondary materials can be more fully understood and the appropriate environmental and energy impact noted. Other states may want to examine Pennsylvania’s model to learn what secondary materials are available locally as part of their own economic development programs promoting green jobs, new technology ventures, and the underlying research and development needed to capitalize on available opportunities.

Acknowledgments We thank Carlos Camara Ortiz and Tara Parthasarathy for their compilation and geocoding of the Pennsylvania residual waste database and Daniel Lang and the anonymous reviewers for helpful comments and suggestions.

Supporting Information Available Details regarding the life cycle inventory records and allocations used in the analysis. This material is available free of charge via the Internet at http://pubs.acs.org. VOL. 43, NO. 7, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY

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