Environ. Sci. Technol. 2005, 39, 9770-9777
Parametric Analysis of Environmental Performance of Reused/Recycled Packaging C. A. TSILIYANNIS ANION Environmental Ltd., 48 Favierou Street, Athens, Greece 10438
Annual environmental performance of packaging products which are reused at least once per year is analyzed with respect to three specific criteria: (1) waste quantities, (2) virgin material demand and resource depletion, and (3) environmental impacts from manufacturing. Packaging flow performance is assessed via a combined reuse/ recycle rate index expressed solely in terms of two dimensionless parameters: the conventional recycling rate and the mean number of reuse trips. Quantitative expressions describe the effect of the following physical quantities: annual reuse frequency, lifetime, maximum number of reuse trips, amount of packaging present in the market, annual production plus net trade imports, recycle rate of consumer discard, reuse rate and consumer discard. The results may serve for packaging monitoring and assessment of alternative packaging systems and for setting more efficient environmental policy targets in terms of the reuse/recycle rate.
1. Introduction Ecological assessment of industrial products aiming at reducing environmental impacts while maintaining consumer satisfaction is gaining attention (1, 2). Manufacturing procedures are being reconsidered and process design is being revamped to incorporate best available technologies, while business decisions are shaped for environmental soundness (3). Among the prevailing considerations for achieving sustainability is the reduction of resource consumption and waste generation. Annual environmental performance is assumed to be adequately reflected by discrete data, i.e., annually reported flows: finally discarded waste (directly related to landfill airspace requirements), annual virgin raw material demand (related to virgin resource extraction and depletion) and production volumes and recycled/reprocessed quantities, which relate directly to environmental compromise from manufacturing. Products which are (a) used once or more times within the same year, i.e., the annual reuse frequency, f, is greater than or equal to one (f g 1), and (b) associated with a maximum reuse lifetime at least equal to one year (T g 1), are considered. The majority of reusable packaging falls into this category: packaging reuse (return, clean, refill) is spreading in the EU and reuse targets are set (4-5). In Finland (1997) reuse reached 87% for glass, 69% for plastic, and 86% for metals. In Germany (1997) the total number of trips * Corresponding author phone: 30-210-5205280; e-mail: anion@ otenet.gr. 9770
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(denoted by N) for plastic crates reached 37.9, for plasticdrink bottles was 25.4, for ferrous food containers/drums < 50 L reached 101.9, for pallets reached 22, and for cable holders was 14.5. Remanufacturable products which are reused less than once per year (f < 1) are not covered by the present approach. Such products include used automotive parts (6), electronic or household products, industrial equipment, single-use cameras, electronic equipment (7), and PCs, etc. Practical benefits of environmental evaluation of reusable packaging products with f g 1 and T g 1 are the following: (i) comparative assessment of alternative specific packaging forms fulfilling the same demand (e.g., containers marketing the same products), (ii) environmental monitoring and reporting, i.e., tracking of performance trend of specific packaging forms fulfilling the same demand and of the overall packaging material (e.g., glass) and of all packaging materials (glass + metals + paper + plastics + wood) over consecutive years, and (iii) implementation of ecological policy via transparent tools. Such a tool has proven to be the conventional recycling rate index r ) R/(R + W) where R and W are the annual recycle and waste flows, respectively. The recycling rate, r, is used widely as an ecological performance indicator. U.S. EPA (8) reports that the United States has reached an overall r ) 29.7% (68 million tons) recycling rate of municipal solid waste; and the European Commission Directive 94/62 imposed minimum packaging recycling rates 15% per material and minimum recovery 50% overall by 2005. Much higher targets are now required: paper and glass 60%, metals 50%, plastics 22.5%, and overall recycling between 55% and 80% (1). Assessment of environmental performance of reuse/ recycle packaging flows under constant demand can be realized via the combined reuse/recycle rate index, F ) (R + RU)/(R + RU + W), where RU is the annualy reused packaging, proposed in ref 9 as a natural extension to the recycle rate. Similarly to the recycle rate, the reuse/recycle rate does not provide a comprehensive ecological assessment of products, and does not convey a full sustainability profile. However, by using a few annual flow data, it gives the ecological performance trend in terms of three among the most important criteria: K1, limited amount of wastes finally managed (landfilled or incinerated); K2, limited virgin material extraction and depletion of natural resources; K3, limited environmental impacts from manufacturing, including water and energy demand. The key result concerning the combined reuse/recycle rate states that for packaging systems fulfilling the same overall demand, environmental performance in the criteria K1 and K2 improves if and only if the F rate increases, while improvement in K3 as well requires, in addition, that annual production levels do not increase below a certain level. In this work the focus is on the parametric dependence of the combined reuse/recycle rate and of environmental performance as expressed through it: how F depends on the natural parameters of the reuse/recycle system such as the lifetime, T (number of years in reuse), on the maximum number of reuse trips, N, on the annual reuse frequency, f, the conventional reuse and recycle rates, and also on consumer behavior, e.g., consumer return for reuse or on the fraction of recovered/recycled packaging after consumer discard. This may be useful for setting minimum recycling rates or possible minimum reuse rates, or for setting incentives for return, reuse, and recycle, since industrial managers or policy makers frequently relate the physical 10.1021/es050970s CCC: $30.25
2005 American Chemical Society Published on Web 11/16/2005
parameters to the ecological performance of remanufactured products. It is clear that such a quantitative analysis should be founded on a reliable dynamic and steady-state description of the annual flows of the system related to the impacts in K1-K3, as a substance flow model relating annual flows. For reusable/remanufacturable products substance flow models have been developed mainly for industrial use and operational cost optimization. A statistical methodology for the analysis of the life-cycle of reusable containers was first presented in ref 10 using a linear nth order representation of the relation between containers recovered and containers issued. In ref 11 an optimization model was proposed for planning of purchasing of returnable containers N periods ahead. In ref 12 an optimization model was given for oneweek-ahead production planning which also determines the number of returned containers and storage points. The above works did not relate substance flow models to environmental impacts, e.g., final waste and to environmental performance. A 1997-1998 survey of used automotive parts in the United States (13) revealed the huge potential for increase of reuse and recycle in this sector. Annually reported flows of recycle/ reuse products which are reused more than once per year may be simulated via the dynamic model presented in ref 14, which takes into account the dynamics of the reuse, the accumulated quantity in the market, and also the recycling of no-longer reusable items. Ecological assessment of products which are both recycled and reused may be accomplished by use of the lifecycle analysis (LCA) methodology (15). LCA gives a comprehensive ecological picture of the product; however, it requires intensive calculations while impact inventories need to be updated with the advent of technology. Significant problems also relate to data, time, expense, and expertise requirements (16). In ref 17 a hierarchical methodology (EcoSCAn) was developed which provides environmental comparison of products and is useful for screening alternative designs and revamping manufacturing and handling procedures without resorting to LCA. Fujimoto et al. (18) proposed the development of service-oriented products owned by the industry who assumes life cycle responsibility and offers services including operation support, maintenance, upgrading, and collection of disposed products and reuse, as well as recycling and reclamation of components. Design of recyclable/ reusable products for minimization of annual environmental impacts optimal number of cycles and product design parameters may be based on the stochastic method developed in ref 19 for physical or functional failures. In the present work the quantitative effect of the physical parameters on environmental performance of reusable packaging, as indicated by the combined reuse/recycle index, F, is investigated for the manufacturer-reuser-consumer (MRC) system (Figure 1), featuring annual reuse frequency, f g 1 and lifetime, T g 1 year. Substance flow modeling is provided through annual discrete-time dynamic modeling for recycle/reuse systems. Questions of interest in real cases include the following. (a) Which and how many are the key parameters affecting environmental performance in terms of K1, K2, and K3 impacts in recycle/reuse products and by how much? Intuitively, one would like to have another dimensionless parameter reflecting reuse intensity, in the same way as r reflects recycling, which, together with r, would characterize performance in K1, K2, and K3. (b) How are the physical parameters, on lifetime, on T, number of trips, N, and annual reuse frequency, f, etc., related to the key dimensionless parameters? (c) How does performance in terms of K1, K2, and K3 depend on the conventional recycling and reuse rates, and how do the latter relate to F? (d) How does an increase in the consumer discard or in the recovery
FIGURE 1. The MRC System: Manufacturer-Refiller-Consumer Packaging Flow Diagram
and recycling rate affect environmental performance in K1, K2, and K3 impacts? (e) Is it more beneficial to increase consumer return for reuse or for recycle and when? The presentation is organized as follows. Background is given, including the dynamic flow model for systems with f g 1 and T g 1, together with the definition of the rate, F. Next, expressions of F in terms of dimensionless and physical parameters are presented followed by policy mechanism and minimum reuse/recycle target applications and a case study (reusable beer bottles) from the local market. Finally, the effect of the physical parameters (N, T, etc.) on the combined reuse/recycle rate, F, is discussed.
2. Background: Reuse/Recycle System Modeling and Combined Rate Index Combined reuse and recycle packaging, for which flow data are annually reported, may be represented by the MRC system of Figure 1. Annual empty packaging production is denoted by Pe. Net trade balance in the material is denoted by Inet,t : at any year t (denoted by subscript t) Inet is defined as Inet ) def(Ie,t - Ee,t + If,t - Ef,t) where Ef ) annual export of filled packaging (t/year), Ee ) annual export of empty packaging (t/year), If ) annual import of filled packaging (t/year), and Ie ) annual import of empty packaging (t/year). Recycle flows are denoted by R (t/year), and reused packaging flow is denoted by RU (t/year). Cf,t is the consumption flow (t/year) of filled packaging, i.e., the total annual amount of packaging reaching the consumer in year t, virgin materials and finally discarded waste are denoted by M (t/year) and W (t/year), respectively, recycled material emanating from other forms of the material fed to packaging manufacturing is denoted by OM (t/year), exported recycled scrap is denoted by Re (t/year), and recycled packaging material fed to the manufacturing of other-than-packaging products is denoted by OP (t/year). The system takes into account the amount of reusable product which is replaced by the refiller (e.g., worn beer bottles sent for recycling) after completing its lifetime. Reusable packaging exits the market by the following routes: (i) discarded by the consumer as recyclable material or as waste, or (ii) sent for material recycling by the industrial reuser at the end of its (finite) lifetime (T years). Let Rc denote the recycle flow (t/year) from recovered consumer discard, Rr the recycle of no-longer marketable reusable product by the refiller (industrial reuser) (t/year), and let Ω denote the total consumer discard (t/year). Result 1. An annual discrete time dynamic model of the MRC system (Figure 1) with annual reuse frequency f g 1 and lifetime T g 1 years is as follows (14): VOL. 39, NO. 24, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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Input to reuse loop ) at ) Pe,t + Ie,t - Ee,t + If,t - Ef,t ) Pe,t + Inet,t (1) Output from the reuse loop ) bt ) Rt + Wt
(2a)
bt ) Ωt, for 0 < t e T, and bt ) Ωt + (T year old packaging) for t > T (2b) Recycle loop feedback: Rpt ) Rt - OPt - Ret
(3)
Recycle loop feed: OMt + Mt ) Pe,t - Rpt-1
(4)
Accumulation: Ut+1 ) Ut + at+1 bt+1, all t, U0 is known (5) Overall consumption: Cf,t ) ftUt-1+ 1/2 (ft + 1)at 1/2 (ft - 1)bt (6) Reuse: RUt ) ftUt-1 + 1/2 (ft + 1)(at - bt) ) Cf,t - bt (7) Total recycle: Rt ) Rc,t + Rr,t ) Ret + Rpt + OPt (8) Consumer discard: Ωt ) Rc,t + Wt
(9)
materials, F may not compare packaging products of different materials with respect to K3 impacts.
3. Environmental Performance of Combined Reuse/ Recycle Packaging Flows Recycled and reused products with T g 1, f g 1 are characterized by a finite market lifetime: if they are not discarded by the consumer (in which case they become waste or they are recycled through the manufacturer to new forms), their features gradually degrade (e.g., worn beer bottles) and at some point (end of their lifetime, say after T years), being no longer suitable for the market, they are sent to the manufacturer for material recycling. It is clear that if the consumer discard is zero, then every tonne of the product stays in the market for exactly T years. With consumer discard > 0, as in practice, some product stays in the market for one year, some for two years, and finally, some for T years, the latter constitutes the only part which achieves the maximum number of trips, say, N. Thus, a mean residence time, τ years, τ e Τ, and a mean number of trips, n ) N × τ/T become meaningful. 3.1. The environmental performance index, F, defined in eq 11 is related to the conventional recycling rate, r (r ) R/(R + W)) and reuse rate, ru (ru ) RU/Cf), for any year, t, as follows:
F ) r + ru - (ru × r)
Following a step change in the input the steady-state flows are
U ) Ta - B
(10a)
RU ) fU
(10b)
Cf ) fU + a
(10c)
where B is the total losses of the reuse loop in the transient period, i.e., B ) b1 + b2 +... + bT-1 + bT. Result 2. (9): Environmental performance of packaging flows in the citeria K1, K2, and K3 is assessed via the single rate index, defined in ref 9 as follows:
Ft )
RUt + Rt RUt + Rt Wt ) )1Cf,t RUt + Rt + Wt Cf,t
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0 e r e F e r + ru
(12b)
ru ) (F - r)/(1 - r)
(12c)
r ) (F - ru)/(1 - ru)
(12d)
3.2. Main Result. Let n be the dimensionless parameter n ) fU/a ) Nτ/Τ. From eq 10a since in the nontrivial case B g 0, U/a e T or τ e T, it follows that
τ ) U/a ) T - B/a, 0 e τ e Τ n ) fU/a ) Nτ/Τ ) N(1 - B/aT),
0 e n e N (13)
and
(11)
Between two alternative reuse/recycle products satisfying the same overall consumption, system 2 is superior to system 1 with respect to criterion K1, both during dynamic and steady state conditions, if and only if F2 > F1. If the net flows of Re, OP, Inet, and OM are equal for two systems (i.e., if Fnet1 ) Fnet2 or, with ∆ denoting difference, if ∆Fnet ) 0, where Fnet ) Inet + OM - Re - OP, as well) then system 2 is superior to system 1 with respect to criterion K2 at steady state, if and only if F2 > F1. If the systems have the same net imports, that is, if Inet1 ) Inet2, or ∆Inet ) 0, the system with higher F is associated with lower environmental impacts from production (K3) at steady state, if and only if its production level, Pe2, remains below a critical level given by Pe2 < Pe2max ) Pe1 + Cf(q/p - 1) ∆F, or, equivalently, if and only if its recycle flow remains below a critical value, R2 < Rmax ) R1 + Cfq/p ∆F, where p ) ∂I/∂R, q ) ∂I/∂M are the marginal environmental impacts from production via recycled material and virgin resources, respectively (values for p and q, related to various impacts, for glass, aluminum, ferrous, and various plastic packaging materials are given in ref 15). For packaging products made from different materials (e.g., glass versus paper) the rate F still provides K1 and K2 impact information (annual waste and virgin material quantities). Since the manufacturing and reprocessing impacts and the associated factors p and q differ for different 9772
0 e ru e F e r + ru
(12a)
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 39, NO. 24, 2005
F)
n+r n+1
(14)
Equation 14 gives the main result: performance of packaging flows as measured by the single rate, F, is a function of only two dimensionless parameters, n, related to the physical process of reuse, and r, related to recycling/remanufacturing. Environmental performance in terms of K1, K2, and K3 impacts is an increasing function of both n and r under constant demand: it increases hyperbolically with respect to n and linearly, with slope 1/(n + 1), with respect to r. 3.3. Dependence of the Combined Reuse/Recycle Rate on Physical Parameters. The following is valid:
F)
N(τ/T) + rr + rc N(τ/T) + 1
) ru +
rr + rc N(τ/T) + 1
)
n+r ) n+1 w 1(15) n+1
where r is the conventional recycling rate, r ) rc + rr, w ) the final waste rate (w ) 1 - r), ru is the conventional reuse rate (ru ) n/(n + 1) e N/(N + 1)), rr is the recycle rate achieved by the refiller, and rc is the recycling rate achieved by the post-consumer recovery and recycling system. Equation 15 quantifies the dependence of F on the physical paremeters. In light of Section 3.2, annual environmental flow performance in the criteria K1 and K2 is a nonlinearly
TABLE 1. Parameter and Flow Values for Application 3 packaging
N
T
a ) Pe
U
Cf
r
τ ) U/a
n
G
W
M
1 2
28 6.36
2 2
1 2
0.50 1.89
8.0 8.0
0.15 0.43
0.50 0.94
7 3
0.894 0.857
0.85 1.14
0.85 1.14
increasing function of τ, Ν, rr, and rc, and a nonlinearly decreasing function of T. The same holds true for criterion K3, if the total annual production or annual recycle flow remain below the critical value. It also follows that total impact over a full lifetime is not directly proportional to T. Impact of Consumer Discard on the Combined Reuse/ Recycle Rate. If consumer discard is a constant fraction, ω, of phenomenological consumption, C ) U + a, or overall consumption, Cf, that is, if Ω ) ω (U + a) or if Ω ) ω′Cf then at steady state
ω ) (1 - rr)/(1 + τ)
(16)
ω′ ) (1 - rr)(1 - ru) ) (1 - rr)/(n + 1)
(17)
The dependence of F on the consumer discard parameters ω, ω′ is as follows:
rc + 1 τ+1 F ) ru - ω + ) N(τ/T) + 1 N(τ/T) + 1 n - ω(τ + 1) + (rc + 1) rc - ω(τ + 1) )1+ (18) n+1 n+1 F ) ru - ω′ +
rc + 1 N(τ/T) + 1
)
n + rc + 1 - ω′ ) 1 - ω′ + n+1 rc (19) n+1
Equations 18 and 19 express the combined reuse/recycle rate in terms of the two dimensionless parameters, n and r, together with consumer discard fraction, ω (or ω′), which is a dependent parameter (determined exactly from rr, via eqs 16 and 17). In both cases performance deteriorates with increasing consumer discard (in eq 18 (τ + 1)/(Nτ/T + 1) e 1 since N/T ) f g 1). 3.4. Link to Environmental Policy. Equation 14 is useful to the policy maker, industrial manufacturer of intermediate materials (e.g., aluminum), industrial container manufacturer, material recycler (paper, plastic, ferrous, aluminum, glass cullet), industrial packager/refiller, and the consumer. The policy target should be to increase both n (n ranges from 0 to N) and the recycling rate, r (r ranges from 0 to 1), and the consumer may choose to buy a product with higher n and higher r or simply with higher F, for K1, K2, and K3 impact reduction. EC 2004/12 Directive (1) requires minimum recycling rate per packaging material and minimum overall packaging recovery rates. If expressed via the rate F ) (n + r)/(n + 1) then, since n is nonnegative, F g r and for n ) 0 (recyclable but not reusable packaging) the usual recycling rate, r, is obtained. Thus new objectives may be proposed: Fmaterial g 60% for paper, glass and Fmaterial g 50% for metals, etc., and also for overall packaging, 80% g Fpackaging g 55%. The extended definitions of Fmaterial and Fpackaging are given in ref 9. For instance, for glass packaging the overall combined reuse/recycle rate in the local market achieved 70% (1998) while the overall glass recycling rate was at 21%, with the latter figure not reflecting important benefits of reuse, e.g., overall fulfilled demand being almost 1 order of magnitude larger than what it would be without reuse. If the rate rr is known from refiller monitoring data, it can be substituted in eq 16 or 17 to find ω or ω′. If, on the other
side, any of the consumer behavior related parameters, ω or ω′ are known together with τ and n, then rr may be found from eqs 16 and 17. In reality, knowledge of ω or ω′ is rare and unreliable since consumer discard is rarely a constant fraction of overall or phenomenological consumption, and also it requires analysis of consumer discard data (urban solid waste analysis), while rr may be monitored easily by the refiller. Thus, monitoring rr is an essential part of any policy and relates directly to consumer behavior at steady state. Incentives for Reuse or Recycling. It is evident from eqs 15-19 that incentives must depend on the parameter values, i.e., they must be system or packaging specific: for a system with N ) 8, n/N ) 0.5 (the losses due to consumer no-return amount to half the annual production plus net imports) a 10% rise in ru results in an increase of F by >10%, and from eq 11 wastes are reduced by >10%. An increase by 10% in rc results in an increase in F (and decrease of waste volumes produced) by only 2%. Thus, any incentives may be at least five times () n + 1) higher for reuse than for recycling independently of the relative values of p and q. Recycling Targets by EC94/62 and EC2004/12. If a minimum recycling target is set for a certain material, i.e., r min ) 15%, (EC94/62 rate per packaging material by year 2005) then, for large relative values of n (e.g., n > 0.4 N) this target is met and actually already exceeded by the industrial refiller recycling. Thus, consumer discard recovery schemes (collection, transportation, material recovery facilities, etc.) for which the citizen pays considerably, may not be necessary. If an overall new minimum rate standard is to be decided it should be greater than rr. By setting much higher limits for r by year 2008, e.g., for glass r min ) 60%, ref 1 may incorporate the refiller’s contribution for large n. 3.5. Applications. 1. Packaging Which is Only Recycled (not Reused). Recycled as materials after their first use, e.g. 0.75-L wine bottles to glass cullet. Then
n ) 0, and F ) r ) rc
(20)
and increasing the recycle rate guarantees environmental enhancement in all criteria K1, K2, and K3 (for K3 provided that p < q). The following are also true: U ) 0, τ ) 0, rr ) 0, ω ) ω′ ) 1, ru ) 0. 2. Only Reused Packaging (not Recycled). The industrial refiller does not send no-longer marketable packaging for recycling but discards all of it as final waste. In addition no post consumer recovery exists. Thus Rr ) Rc ) R) 0, Ω ) b ) W. Evidently
r ) 0 and F ) ru ) n/(n + 1)
(21)
Any minimum rate policy is then expressed in terms of ru. For instance, if for a certain material the EC94/62 limit was to be followed this would mean that ru g 15% or from eq 14 that at steady-state n g 3/17 or from eq 10c, a/Cf e 0.85 or a e 0.85 Cf. With regard to the new EC 12/04 stricter requirements this would mean that ru g 60% or n g 3/2 or a e 0.40 Cf. 3. Compare two reuse/recycle packaging forms of the same material fulfilling the same annual market demand () 8 kt/ year) with the parameters as in columns 1-5 of Table 1. First it is seen that the recycling rate alone indicates (erroneously) that packaging 2 outperforms packaging 1. Using eqs 13 and 14 we find n and F (Table 1) and hence from VOL. 39, NO. 24, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 2. Parameter and Flow Values for Application 4 packaging
N
T
a ) Pe
U
Cf
R
r
τ
n
G
W
M
1 2
10 14
1 2
2.00 1.78
0.44 0.66
6.4 6.4
1.20 0.80
0.60 0.45
0.22 0.37
2.20 2.59
0.88 0.85
0.80 0.98
0.80 0.98
the result 3.2 packaging 1 is the better one ecologically: it results in less annual wastes and virgin material demand. Indeed simulation via model eqs 1-10 gives at steady state the flows of W and M. From Result (3.2) it also follows that packaging 1 is superior with respect to annual impacts from manufacturing, since Pe and F move in opposite directions ∆Pe × ∆F < 0. This assessment was made possible without resorting to LCA or to the marginal impact factors p and q. 4. Compare two reuse/recycle packaging forms fulfilling the same annual market demand () 6.4 kt/year) and made of different materials, with respect to criteria K1 and K2 with the parameters as shown in Table 2 columns 1-5. First, it is seen that the parameters N and T, as well as the reuse rate ru, indicate (wrongly) that packaging 2 outperforms packaging 1. Using eqs 13 and 14 we find n and F and from result 3.2 packaging 1 is the better one ecologically in K1 and K2 (less annual wastes and virgin material demand). Indeed, simulation via model eqs 1-10 gives at steady state the values of W and M. 5. Consider a packaging system, which evolves through successive steady states, i to ii, due to unpredictable and unknown (as is always in reality) consumer discard disturbances. Determine the characteristics of a policy mechanism which guarantees no degradation in environmental performance in terms of the criteria K1, K2, and K3, while fulfilling the same demand (constant Cf) at the new steady state. Both steady states should correspond to the same value of F: Fi ) Fii or, using eq 14, (ni + 1)/(1 - ri) ) (nii + 1)/ (1 - rii), giving
nii ) -1 + (ni + 1) (1 - rii)/(1 - ri)
(22)
Eq 22 states explicitly what reuse characteristics (nii) should be attained in the new steady state (i.e., how much reuse should be intensified: increase τ (e.g., by decreasing return losses, B/a, in the reuse cycle) or increase f (with the consequent decrease in T, since N () fT), is analogous to the product durability which has not changed), to have no environmental performance degradation in K1, despite a potential decrease in the recycling rate. Table 3 in the Supporting Information presents several cases of interest for the values of n, r, and F, (e.g., if r ) 1 then W ) 0 and from eq 11, F ) 1), as well as for waste, virgin material and manufacturing flows in terms of the overall fulfilled demand at steady state. Flow values at steady state are determined using eqs 10a and c. The main result guarantees that under ∆Fnet ) 0, performance in K2 will follow K1 and not deteriorate (∆M ) 0). For criterion K3 since ∆M ) 0 it follows that the difference in annual environmental impacts from manufacturing is due solely to remanufacturing and is equal to p∆R. But at steady state, a ) R + W, or since ∆W ) 0, ∆a ) ∆R or the difference in annual environmental impacts is equal to p∆a and since p > 0, it follows, in this specific case, that K3 performance will not deteriorate only if the reuse loop feed, a, does not grow, i.e., if annual production level does not grow, under constant net trade balance. In this case, from the equality W ) (1 - ri) ai ) (1 - rii)aii, this is equivalent to no drop in recycling percentage. (This condition is not needed for no deterioration in K1 and K2 - it is an additional requirement only for no deterioration in criterion K3). In brief, if eq 22 is satisfied annual waste and virgin material quantities remain the same, while environmental impacts from manufacturing 9774
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are reduced if, in addition, production level of empty packaging at the new steady state does not increase. The above quantitative results relating directly to policy mechanisms were obtained without resorting to LCA or qualitative hierarchical attribute categorization for ecological assessment of remanufacturable products.
4. Case Study: Analysis of the 0.5-L Beer Bottle Packaging in Greece The case study is given in the Supporting Information.
5. Discussion: Environmental Policy and Performance 5.1. Performance Limits. In Table 3 (Supporting Information) various cases of interest were presented. The following relations have been used. From eq 11: W ) Cf(1 - F), from eq 10c the input, a, at steady state following a step change in a, from level 0 to level a, t/year, is related to the overall consumption (demand) by the relation Cf ) a(n + 1). Hence for a given demand level, the required input, a, tends to its minimal value when n v N, i.e., when ru tends to its maximal value, ru v N/(N + 1), ru max ) N/(N + 1), that is if there are no losses in the reuse loop during the transition period, B ) 0. In this case, Ω ) 0, i.e., all reusable packaging is taken out of the market by the refiller, that is, r ) rr v 1, w V 0, and F v rumax + r/(N + 1) ) N/(N + 1) + 1/(N + 1) ) 1. This corresponds to the minimal possible environmental impacts in all criteria K1, K2, and K3. It may be assumed that the losses at the refiller site, are negligible, i.e., the refiller collects and sends all no-longer marketable products (e.g., worn bottles) to the reprocessor (glass industry) for manufacturing of new products (recycling). From eq 12 it also follows that if limits are placed on F then the recycling and reuse rate cannot be both arbitrarily set by the regulator, e.g. for F g 0.6 it follows from eq 12a that if the regulator decides to place limits on reuse, these limits should satisfy ru g (0.6 - r)/(1 - r) for any recycling rate, r, and vice versa r g (0.6 - ru)/(1 - ru) for any possible ru. It is also clear that if the refiller achieves a recycling level rr then the consumer recovery system cannot aim higher than rc max ) 1 - rr. This implies that at high levels of reuse post consumer recovery and recycling investments may not be necessary, which is in the same linespotentially a predecessor in practicesof the proposed new state of service-oriented products in ref 18. 5.2. Parametric Dependence. Figures 2-6 present the parametric effect on the combined reuse/recycle rate. The recycle of consumer discard was assumed at 20% (rc ) 0.2). For any other level of post consumer discard recycling the results are similar, since the contribution of consumer return for recycling, rc, on F, by eq 15, is equal to rc/(n + 1). Recall that 0 e n e N and 0 e r e 1. Impact of Mean Trippage (n) and Lifetime (T) on the Reuse/Recycle Rate, F. Figure 2 gives the impact of n and of T as a parameter on the environmental performance rate, F for N ) 6: F is a hyperbolically increasing function of n tending to one and starting at F ) 0.2 (for n ) 0). Being a hyperbola this suggests faster enhancement of performance at lower values of n. Also for higher T, the F curve lies lower. The inferior environmental performance of the longer lived product is more pronounced in the medium range values of n (recall that 0 e n e N). Figure 2 suggests that increasing
FIGURE 2. Impact of lifetime, T, and of the dimensionless parameter, n, on the combined reuse/recycle rate.
FIGURE 4. Impact of reuse rate, ru, on the combined reuse/recycle rate, G.
FIGURE 3. Impact of trippage (N) and of the normalized dimensionless parameter, n, on the combined reuse/recycle rate, G. FIGURE 5. Impact of consumer discard fraction, ω, on the reuse/ recycle rate, G.
TABLE 3. Impact of Doubling n under Constant N () 6) and Constant Overall Demand, Cf steady state
n
G
a
W
M
τ
f
T
1 2 3
0.5 1 2
0.40 0.70 0.85
Cf/1,5 Cf/2 Cf/3
0.60 Cf 0.30 Cf 0.15 Cf
0.60 Cf 0.30 Cf 0.15 Cf
1/3 1/3 1/3
1.5 3 6
4 2 1
n to levels above N/2 (e.g., by increasing reuse frequency, f, or reducing return losses, B) secures most of the benefits of reuse and higher performance, despite the decrease in lifetime T. Parametric Dependence at Constant Demand Level. Consider doubling of n, n1 ) 0.5, n2 ) 1, n3 ) 2, due to doubling of f under constant trippage, (N ) 6) (and hence halving of T), Table 3: wastes are reduced from 60% Cf to 30% Cf to 15% Cf, while production levels fall from Cf/1.5 to Cf/2 to Cf/3. Impact of Trippage (N) on Reuse/Recycle Rate, F. Figure 3 gives F versus the normalized index, n/N (since 0 e n e N) parametrized by N for T ) 2: larger N corresponds to higher values of F. Also, the superior environmental performance of the more durable product is more pronounced in the medium range values of n/N. Figure 3 suggests that any increase in N, e.g., substitution of a container by a new more durable container should be implemented under equal increase in n (increase in f or U) to ensure no performance loss.
Impact of Reuse Rate. Figure 4 presents the effect of reuse rate, ru, on F: performance increases with ru, (faster at high values of ru). This effect is less pronounced for larger T or N: For N ) 26.25, F follows approximately a straight line (0, 0.2) to (26.25/27.25, 1). Therefore for the same reuse rate, the system featuring larger T shows inferior performance. Larger environmental gains are realized by increasing the reuse rate in a shorter lived or less durable reusable product. Also as T increases the marginal effect of N on F diminishes: essentially for long-lived products the F curves differ only for large values of ru, (> ru ) 0.6) where F increases faster for smaller N. Thus it is more beneficial to intensify reuse for products with low lifetimes. Effect of Consumer Discard on Environmental Performance. Figures 5 and 6 show the detrimental effect of increasing consumer discard, ω or ω′, on environmental performance (eqs 18 and 19). In practice the effect of ω′ is independent of the parameters N and T. In contrast, the effect of ω is less pernicious for more durable systems (higher N) and for systems with lower maximum lifetime, T (higher F). On the basis of the above, the questions raised are answered in brief as follows: (a) and (b) Performance in K1, K2, and K3 under constant demand is assessed via the combined reuse/recycle rate F, which is expressed in terms of two dimensionless parameters (n and r) or in terms of the physical parameters (N, T, τ, rc, rr, ω, ω′) via eqs 13 and 14, 16-19. (c) The rate F and performance in K1, K2, K3 depend VOL. 39, NO. 24, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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OP
flow of secondary products produced from recycled feedstock different from the original form (t year-1)
Pe
production flow or empty packaging (t year-1)
p
marginal environmental impacts from production through recovered product
q
marginal environmental impacts from production through virgin material
R
total recycling flow ) Rc + Rr ) Re + Rp + OP (t year-1)
Rc
recycle from recovered consumer waste (t year-1)
Re
exported recycled scrap (t year-1)
Rp
recycled flow to produce the same form of product or packaging form (t year-1)
FIGURE 6. Impact of consumer discard fraction, ω′, on the reuse/ recycle rate, G.
Rr
recycle of no-longer marketable reused product by the refiller (t year-1)
on the conventional reuse and recycling rates as given by eq 12 and the physical parameters N, T, τ, relate to n, r, F, via eq 15. (d) Any change in the consumer discard or recovery and recycling rate affects environmental performance in K1, K2, K3 via eqs 18 and 19sthe impact depends on lifetime and number of trips (Figures 5 and 6). (e) From eq 14 and Figures 2 and 3 it is more beneficial to increase consumer return for reuse than consumer drop for recycle, especially for low values of N and T.
RUt
reused product flow (t year-1)
r
recycling rate ) R/(R + W) ) rr + rc
rc
consumer recycling rate Rc/(R + W)
rr
industrial reuser recycling rate Rr/(R + W). Rr is the annual amount of reusable product which the refiller sends for recycling at the end of its lifetime as non-longer marketable product
ru
reuse rate ) RU/Cf
Supporting Information Available The case study with associated Figures 2 and 3 and Tables 4 and 5, Appendix, and Table 3. This material is available free of charge via the Internet at http://pubs.acs.org.
T
lifetime, years
Ut
net accumulation in the market at the end of year t (t)
W
final waste flow (waste to landfills or incinerated, etc) (t year-1)
w
final waste rate ) 1 - r
Nomenclature reuse loop input flow (feed) for year t (t year-1)
at
year-1)
a
steady-state value of at (t
bt
reuse loop output flow, b ) steady-state level (t year-1)
B
b1 + b2 + ...bT total market output during the transition period 0 < t e T. Constant for t >T (steady state) (t)
Ct
phenomenological consumption, used product flow ) Ut + bt ) Ut-1 + at (t year-1)
Cf,t
overall consumption (t) ) annual packaging amount reaching the consumer
Fnet
net input of external flows apart from waste and virgin materials between two systems. Fnet) OM + Inet - Re - OP (t year-1). If ∆Fnet ) 0, then ∆W ) ∆M.
f
number of reuse cycles per year
Inet
flow of net imported material (empty and filled) (t year-1)
If net
net imported filled and Ie net ) net imported empty, Inet ) If net + Ie net
M
virgin or raw material flow (t year-1)
N
N ) f × T total number of reuse trips in lifetime
n
n ) f × τ mean number of reuse trips
OM
flow of other forms of the same material entering production feed (t year-1)
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Greek ∆
difference, e.g., ∆r ) change in r, ∆W ) difference in finally discarded wastes, W
τ
mean residence time (years) ) U/a, τ/T ) U/(Ta) dimensionless ) n/N
F
) combined reuse/recycle rate ) 1 - W/Cf
Ω
total consumer discard ) Rc+ W (t year-1)
ω, ω′
consumer discard fraction with respect to phenomenological or overall consumption
Literature Cited (1) European Commission. Directive 2004/12 modifying EC 94/62 on Packaging and Packaging Wastes; European Commission, 2004. (2) Wenzel, H.; Hauschild, M.; Alting, I. Environmental Assessment of Products; , Chapman & Hall: London, 1997; Vol. 1. (3) Lamming, R. C.; Faruk, A. C.; Cousins, P. D. Environmental Soundness: A pragmatic alternative to expectations of sustainable development in business strategy. Business Strategy Environ. 1999, 8 (3) 177-188. (4) Environment & Pira International. Evaluation of Costs and Benefits for the Achievement of Reuse and Recycling Targets for Different Packaging Materials in the Frame of the Packaging and Packaging Waste Directive 94/62 EC Proposed Draft Final Report RDC, www.epinet.org, Washington, DC; 2001. (5) Pricewaterhouse-Coopers. Review of 1997 Data on Packaging and Packaging Waste Recycling and Recovery; PricewaterhouseCoopers: Utrecht, The Netherlands, 1999. www.pwcglobal.com.
(6) Hammond, R.; Amezquita, T.; Brass, B. Issues in the automotive parts remanufacturing industry: a discussion of results from surveys performed among remanufacturers. Int. J. Eng. Des. Automation - Special Issue on Environmentally Conscious Design, 1998. (7) U.S. Environmental Protection Agency. Remanufactured Products: As Good As New; WasteWise Update; EPA530-N-97-002 USEPA: Washington, DC, 1997. (8) U.S. Environmental Protection Agency. Municipal Solid Wastes in the United States: 2001 Facts and Figures; USEPA: Washington, DC, 2001. (9) Tsiliyannis, C. A New Rate Index for Environmental Monitoring of Combined Reuse/Recycle Systems. Waste Manage. Res. 2005, 23 (4), 304-313. (10) Goh, T. N.; Varaprasad, N. A statistical methodology for the analysis of the life-cycle of reusable containers. IIE Trans. 1986, 18 (1), 42-47. (11) Kelle, P.; Silver, E. A. Purchasing policy of new containers considering the random returns of previously issued containers. IIE Trans. 1989, 21, 349-354. (12) del Castillo, E.; Cochran, J. Optimal Short Horizon Distribution Operations in Reusable Container Systems. J. Oper. Res. 1996, 47, 48-60. (13) Duranceau, C.; Lindell, T. Automotive Recycling as Reuse: Investigation to Establish the Contribution of Reuse on Recyclability; SAE 1999-01-0987; Society of Automotive Engineers: Warrendale, PA, 1999.
(14) Tsiliyannis, C. Dynamic Modeling of Packaging Material Flow Systems. Waste Manage. Res. 2005, 23 (2), 155-166. (15) White, P. R.; Franke, M.; Hindle, P. Integrated Solid Waste Management: A Lifetime Inventory; Blackie: Glaskow, 1995. (16) Owens, J. W. Life-cycle impact assessment: Constraints on moving from inventory to impact assessment. J. Ind. Ecol. 1997, 1 (1), 37-49. (17) Faruk, A. C.; Lamming, R. C.; Cousins P. D.; Bowen F. E. Analyzing, mapping, and managing environmental impacts along supply chains. J. Ind. Ecol. 2002, 5 (2), 13-36. (18) Fujimoto, J.; Umeda, Y.; Tamura, T.; Tomiyama, T.; Kimura, F. Development of Service Oriented products Based on the Inverse Manufacturing Concept. Environ. Sci. Technol. 2003, 37, 53985406. (19) Okumura, S.; Morikuni, T.; Okino, N. Environmental effects of physical life span of a reusable unit following functional and physical failures in a remanufacturing system. Int. J. Product. Res. 2003, 41 (16), 3667-3688. (20) YPEHODE. Packaging Materials in Greece; Survey commissioned by the Ministry of Environment, Planning and Public Works (YPEHODE), Athens, Greece, Final Report, December 2001. http://www.minenv.gr.
Received for review May 23, 2005. Revised manuscript received September 20, 2005. Accepted October 5, 2005. ES050970S
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