Briefing Paper:
Highest and Best Use of Recovered Materials
January 2012
Primary Author: Peter Spendelow
DRAFT
Summary
"Highest and best use" for a material is defined here as the use of that material which maximizes the
savings of energy and natural resources and minimizes environmental damage and risk to human health.
Generally, using recovered material as a feedstock in a manufacturing process, or as a source of energy,
can reduce the need for harvesting virgin materials and using fossil fuels to provide energy for
manufacturing new products. In deciding which is the highest and best use for a material, a key factor is
to consider what materials the recovered material is substituting for, and what the impacts of those
(displaced) materials are. Using a recovered material in place of a material with high energy
requirements, toxicity, and/or other impacts will have greater benefits than would be the case for using
the recovered material in place of a material with low energy requirements, toxicity, or other impacts.
Closed-loop recycling means recycling a material back into the same sort of product, while open-loop
recycling uses material to produce a different sort of product - often one that is difficult to recycle.
"Downcycling" is recycling a material into a new product of lesser value and recyclability, and is often
used synonymously with open-loop recycling.
Although recyclability is generally a good trait, there are a number of examples of non-recyclable items
that perform their function better, and with greater resource conservation, than would be true for
recyclable alternatives. Once a decision has been made to manufacture a nonrecyclable product, the use
of recycled material as feedstock to manufacture that product may save just as many, or possibly even
more, resources than would be saved by using that same recycled material to manufacture some other
(recyclable) product. In these cases, the highest and best use of a recovered material may be the product
made through open-loop recycling. The key factor again is what is avoided, in terms of harvesting of
virgin materials and use of energy, by using the recovered material to make a product.
Preserving the quality of a material through its use and recycling collection is important, because it
allow that material to be of suitable quality to be recyclable at its highest value. When it comes to using
the material though, the highest value is usually in the uses that most fully make use of the value of the
material, rather than the subsequent recyclability of the product being produced by recycling
Introduction
In this paper, "highest and best use" is defined as the manner of using materials or products at their end-oflife that results in the greatest conservation of material and energy and protection of health while minimizing
other negative environmental impacts. Usually, benefits come from displacing virgin material resources,
manufacturing products using recycled or reused materials. There are many environmental criteria by which
the use of recovered materials could be measured (see briefing paper on alternative materials impacts
criteria), and no consensus yet as to the relative importance of each, so this paper will discuss this in
conceptual form rather than provide a numerical ranking of highest and best use.
The solid waste hierarchy gives some general guidance for "highest and best use", with reuse usually
being superior to recycling, and recycling being superior to composting, energy recovery, and
landfilling. As discussed in the solid waste hierarchy background paper though, in individual cases the
order of the lower tiers of solid waste hierarchy does not necessarily reflect highest and best use for
materials. In addition though the hierarchy provides no guidance at all for different uses of a material
within a single tier, particularly in the case of recycling.
Making products typically involves a number of steps, each of which may take energy, use resources,
and create waste. The initial steps involve harvesting resources and conducting chemical and physical
processes to make materials. This is followed by processing and assembling the materials into products.
Opportunities for reuse and recycling exist at many points in the manufacturing process, but the greatest
conservation occurs when materials can be introduced back into the production process as close to the
end (production of the final product) as possible. Figure 1 demonstrates this for a refillable PET bottle.
Figure 1. Different methods of recovery result in different savings for a refillable PET bottle
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Maintaining the quality and integrity of a material through its use and collection is important if the
material is to be used for its highest and best use. In Figure 1, washing and refilling the bottle saves the
most energy and resources However, if the bottle is damaged, it will only be able to be recovered and
used through one of the lower methods. If the plastic material itself is degraded, such as if the bottle has
been subject to too much heat, then only lower methods such as hydrolysis or pyrolysis can be used.
Evaluating highest and best use.
"Highest and best use" can be evaluated by comparing, for an entire system, the resource and energy
conservation and relative environmental damage resulting from utilizing recovered material for different
uses. Because the amount of material recovered for potential reuse, recycling, or other purposes is
almost always substantially less than the potential demand for that material, pushing recovered material
towards one use will result in less material being available for an alternative use. So, if a material could
be recycled into either Product A or Product B, consider the case where Product A is made with the
recycled material and an equal amount of Product B is made with virgin material, and compare that with
the situation where B is made from recycled material and A is made from virgin. Whichever of these
two options results in the least use of energy and materials and the least environmental damage for the
sum of both Products A and B would be considered the higher use for that recycled material.
Defining Closed-loop recycling, Open-loop recycling, and Downcycling.
"Closed-loop recycling" can be defined as recycling material back into essentially the same sort of
product (USEPA 2010), allowing that material to potentially be used multiple times. "Open-loop
recycling" can be defined as recycling a material into a substantially different product with different
properties, often non-recyclable or with degraded recycling capabilities. It is completely "open loop"
when the new product cannot be recycled back into the old product. "Downcycling" is the recycling of a
material into something of lesser value, and is sometimes used synonymously with open-loop recycling..
"Closed loop" and "open loop" are really two ends of a continuum defined by the degree of
"downcycling" that occurs when a new product is made from recycled product. The examples below are
listed in order with the lowest degree of downcycling starting at the top.
•
Recycling glass bottles back into glass bottles. Glass retains its integrity when recycled, and
so can be recycled over and over again without being substantially degraded. Recycling glass
bottles into jars would still be considered closed loop since they have the same properties for
recycling.
•
Recycling aluminum cans back into aluminum cans. Aluminum cans lids are made from a
stiffer aluminum alloy containing more magnesium and less manganese than the body
(McDonough and Braungart 2002). Recycling cans mixes these two alloys, producing an
intermediate alloy not particularly suitable for either can bodies or lids. The recycled aluminum
must be re-alloyed with virgin or purer forms of metal to be usable again to make cans. Some
aluminum is also lost as dross in the recycling process.
•
Recycling white office paper back into office paper. The paper-making and recycling
processes causes some paper fibers to break. Thus, either virgin pulp or additional office paper
must be added to strengthen the paper and make up for the loss of fiber.
•
Recycling white office paper into white-faced corrugated boxes. Often carton manufacturers
will produce a thin white facing layer on their corrugated boxes to enhance their look and
printability. White office paper can provide that white layer with little additional bleaching, but
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the resultant box cannot easily be recycled back into office paper since it is mainly brown fiber.
It can, however, be recycled back into new corrugated boxes. Office paper can also be recycled
into corrugating medium - the wavy layer in corrugated boxes, but this does not make use of the
"bleached" property of the office paper.
•
Recycling plastic PET bottles into carpet or textiles. Polyester carpet and textiles are
theoretically recyclable, but are rarely collected and would not be practical to recycle back into
bottles.
The following examples would all be considered completely open-loop recycling, because product itself
is not considered recyclable.
•
Recycling white office paper into towel and toilet paper. Paper towel and toilet paper are
used in a manner the results in disposal, and so they are not recyclable.
•
Recycling glass into fiberglass. The fiberglass may be used for many years to insulate
buildings, but is not recyclable at the end of its life.
•
Recycling glass into aggregate. Glass is sometimes crushed and used to replace gravel in
asphalt (glassphalt), road base, utility trench bedding, or to form the drainage layer in landfills.
Glass used in this manner is not recyclable back into glass bottles.
Is closed-loop recycling a higher use than open-loop recycling?
Many policy statements rank closed-loop recycling as a higher use than open-loop recycling (City of
Austin 2008, McDonough and Braungart 2002, Plastic Pollution Coalition, Zero Waste International
Alliance 2005). Proponents argue that materials can be recycled many times over through closed loop
recycling, multiplying the environmental benefits many fold. With open-loop recycling, the material is
often no longer recyclable after open-loop recycling, limiting the environmental benefits to that single
use. However, a more careful analysis demonstrates that the situation is not so clear, and that often open
loop recycling can provide as high or even higher benefits than does closed-loop recycling.
The confusion stems from conflating the benefits of having a product being recyclable and the benefits
of having a manufacturing process use recycled feedstock to produce a new product. Using recycled
instead of virgin material to produce a product often has substantial benefits, whether or not the product
produced is itself recyclable.
Sometimes non-recyclable products can perform a function better, with less environmental damage, than
would be the case for a recyclable product. Examples include using plastic bags for shipping goods
instead of heavier cardboard boxes (ODEQ 2004) or making a durable non-recyclable product instead of
a less-durable recyclable one. Sometime products are made to be disposed as part of their use, such as
garbage bags and toilet paper. If, based on current technology and knowledge, it makes sense to make a
non-recyclable product to serve some function, there will still be environmental benefits to using
recycled feedstock instead of virgin material to make that nonrecyclable product. The savings per pound
of recycled material used as feedstock may be just as great, or even greater, than the savings if that
feedstock were used instead to make some other recyclable product. Some possible examples follow.
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Example: Office paper recycled into paper towel (open loop) vs. new office paper (closed loop).
Consider a case where you are manufacturing both office paper and paper towels, and you have a limited
amount of recycled office paper that could be recycled and used as feedstock to make either of these two
products. You don't have enough recycled paper to make both, so you will need to use virgin wood pulp
to make up the difference. Does it make more sense to use the recycled paper to make new office paper
or to make the paper towel?
This is a realistic example, because there is a far greater need for recycled bleached fiber than there is
office paper available to fill that need, for the following reasons:
• Paper towel is generally used in a manner that precludes recycling, and may be made with wetstrength paper which also makes it difficult to recycle. Thus, this fiber is not available for
recycling after use.
• A fair amount of office paper is not recycled, and ends up in landfills, and
• Much of the recycled office paper and other bleached fiber paper gets recycled into other grades
of paper, such as newsprint or boxboard where it provides brightness and strength.
Thus, any office paper which is recycled into office paper means less recycled fiber is available for
making new paper towel. Similarly, any office paper which is recycled into paper towel means less is
available for making recycled content office paper.
DEQ has not yet seen life cycle analyses that specifically compare recycling office paper into paper
towel vs. back into office paper, and so cannot say for sure which is the higher and better use of recycled
office paper. However, the differences should be pretty small, because it takes roughly the same amount
of resources and energy to produce recycled pulp that is destined to become paper towel as it does to
produce recycled pulp that is destined to become office paper. We can even speculate that making paper
towel may be a higher and better use. Office paper has high specifications for cleanliness and
brightness. Purchasers of copier paper do not want to see little ink specks on their paper, and so the pulp
must go through intensive cleaning and bleaching processes to remove ink and other contaminants. The
extra cleaning and bleaching required to get recycled office paper up to specifications ends up using
energy and materials, and also damages the paper fibers making them weaker and causing more broken
fibers to wash out of the mix. It probably also results in some loss of paper due to failure to meet
specifications. If some grades of paper towel do not need to meet the same high specifications that
bright copier paper needs to meet, it may make more sense to use the recycled fiber to make paper towel
and use clean strong virgin wood fiber to make the office paper, instead of the other way around.
Example: Glass into glass bottles (closed loop) vs. fiberglass (open-loop)
If you are making both glass bottles and fiberglass insulation, and only have a limited amount of
recycled glass to be used as feedstock, should you use the recycled glass to make new glass bottles or to
make the fiberglass insulation?
Although fiberglass is generally considered nonrecyclable, its strong insulation properties provide huge
energy-saving properties throughout its life insulating a building. Glass bottles can be recycled either
into fiberglass (open-loop) or back into glass bottles. When glass is collected color-mixed though (as is
the case in most Oregon curbside programs), the broken glass must be passed through an optical sorter
to separate the glass back into colors if it is going to be used to make glass bottles. Small broken pieces
of glass cannot be sorted by the optical sorter, and come out as mixed fines which can only be used as
low-grade aggregate or fill material. Fiberglass manufacture does not require the glass bottles to be
color-sorted, and so there is less loss in the recycling process. In addition, a life-cycle analysis for the
City of Portland showed greater energy savings using recycled glass to manufacture fiberglass than was
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the case for recycling glass into glass bottles. This may be a case of using data from different individual
facilities that may not reflect industry-wide manufacturing practices, but still it demonstrates that
recycling glass back into bottles does not result in superior energy savings when compared to recycling
into fiberglass.
Example: PET plastic into PET bottles (closed loop) vs. textiles and carpet (open loop).
PET is a polyester that has many uses. Most people are familiar with PET drink bottles, and that is the
source of almost all of the PET recycled in Oregon, but PET can also be used to make t-shirts and other
clothing, carpet, strapping, and even the fuzz on tennis balls. Although PET can be recycled back into
drink bottles, doing so is difficult because the recycled plastic must be thoroughly cleaned in order to
meet FDA requirements for sanitary food packaging. Procedures that satisfy FDA requirements include
intensive cleaning systems and/or making multi-layered bottles where the recycled PET is sandwiched
between virgin PET layers. These steps add to the cost and the energy used in the recycling and bottle
manufacturing process. PET can also be extruded into polyester fiber, and that is the use where most
recycled PET ends up being used. Generally these recycled fibers cannot be recycled, because they are
difficult for the public to identify and they get mixed up with other fibers or used in composite products
that contain glue or other plastic resins. However, every ton of PET recycled into fiber means one less
ton of PET that has to be manufacture from virgin feedstocks, resulting in roughly the same
environmental savings as would come from recycling the PET into bottles.
If closed loop recycles the same material many times, doesn't that multiply the benefits?
The argument that "recycling the same fiber many times over multiplies the benefit" is also a confused
argument that does not stand up to analysis. It is true that the more you can collect for recycling, and the
more you can use that recycled material as feedstock in manufacturing new material, the greater the
benefits. However, there is no benefit to preferentially recycling only the previously-recycled products
if it means that the products made from virgin materials are correspondingly less recyclable.
Considering again the office paper/paper towel example. In every cycle, the same amount of virgin fiber
will be needed to make office paper and paper towel in total, regardless of whether the recycled content
is used to make paper towel or to make office paper. It can even be argued that using the weaker
recycled paper fiber to make paper towel instead of office paper gives superior recycling results, because
in each cycle the recycled fiber will be derived more from strong virgin wood fiber instead of from
recycled paper fiber. Using recycled wastes to product new products conserves resources regardless of
whether the resulting products can be subsequently recycled or not. Put differently, the presence or
absence of recycled content in a product has little to no bearing on whether or not the product will be
again recycled at end of life. Further, as discussed above, as long as non-recyclable products are being
made and demand for feedstock by product manufacturers exceeds the supply of recycled wastes that
might satisfy that feedstock, directing recycled wastes to one use means that less feedstock is available
for other uses.
Examples where downcycling and open loop are a lower use.
As discussed above, "downcycling" in the "open-loop" sense is often a misnomer in that it implies lower
use, when in fact the environmental benefits of open-loop recycling can equal or even exceed the
benefits of closed-loop recycling. However, there are many cases where materials are "downcycled" in a
different sense - in that the utilization does not fully make use of the material's properties, and other
lower impact alternatives would be better. Three examples are discussed below.
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Office paper into corrugating medium.
Since the amount of white office paper available for recycling is limited, using office paper as
corrugating medium means that less will be available to make office paper, so more virgin wood pulp
will be needed to make new office paper. The kraft paper-making process is used to make both
corrugating medium and office paper, but office paper further requires strong bleaching steps to turn that
pulp white. Those bleaching steps take significant materials and energy and can produce toxic byproducts, depending on the bleaching technology used. If instead virgin pulp were used to make
corrugating medium, the office paper could be recycled into new office paper, reducing the requirement
for strong bleaching.
Glass into aggregate.
Transportation costs and poor collection and sorting practices can make it difficult to get some glass
back to a glass manufacturing plant where it can be made into new products. This is particularly true for
rural areas. In these cases, the glass is often used as aggregate, replacing crushed rock for applications
such as road beds (under the asphalt), "glassphalt"(in the asphalt itself), utility trench bedding,
temporary road base in landfills, or in the drainage layer of new landfill cells. It takes very little energy
though to crush rock into aggregate, so using glass in this manner saves little energy, and may even
require more energy if the glass has to be transported any significant distance. In contrast, recycling
glass into new glass products saves considerable energy, since recycled glass melts at a lower
temperature than does sand and the other virgin raw materials used to make glass.
Low grade plastic into various products.
Most plastic items that we use are potentially recyclable, but there are many reasons that make it
difficult to recycle some types of plastics:
•
•
•
•
•
Difficulty in identification. Many types of plastic look similar and show similar properties, but
may be incompatible with each other for recycling. Examples include PVC and PET, where just
one PVC bottle can ruin a whole batch of PET for recycling. PLA also looks very much like
PET, but will cause difficulty for PET recycling if present in too high of a concentration.
Different melting points within resins. The same resin may come in different forms, such as
polymer chain lengths or different chain lengths which can greatly affect the melting point of the
plastic or it viscosity when melted. Plastic that is suitable for injection molding would be too
runny to be used effectively in blow-molding.
Different additives, co-polymers, and fillers. Many plastic bottles have thin layers of other
plastics included in the bottle, for purposes such as providing an oxygen barrier to prevent
oxidation of the product in the bottle. Plastic items will also have plasticizers, colors, and fillers
to modify their properties, improve performance, and/or lessen the cost.
Contamination. Often the way plastics are used result in contaminants being present, such as
food residue or oils and dirt that are difficult to separate. The amount of contamination might be
significant relative to the amount of plastic present, particularly for film plastic due to its
thinness and light weight.
Expansion. Foamed polystyrene and polyethylene are very light weight, so a large volume is
needed just to supply a small amount of plastic resin by weight. This can make transportation
and processing expensive relative to the value of the plastic.
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Because of the difficulty in separating and cleaning all the many different formulations of plastic resins,
people have identified certain types of products that can tolerate some mixture of the different resins and
some level of contamination. Examples include:
•
Recycling polyethylenes and polypropylene into plastic lumber, to be used for park benches,
decking, and similar uses. Frequently the plastic is combined with wood fiber or other fillers to
provide better rigidity and reduce the amount of plastic needed. This "plastic lumber" does not
have the strength and rigidity of alternative materials such as pressure-treated wood. Unlike
many plastic items that can serve functions with relatively little material, it takes a lot of plastic,
with a lot of embodied energy, to make a single decking board of plastic lumber. Far more
energy is needed to make recycled plastic lumber than is needed to make the equivalent amount
of pressure-treated lumber, if the energy embodied in the plastic is taken into account. However,
the plastic lumber has one big environmental advantage - avoiding the need for the toxic
chemicals used to preserve the wood. Energy and toxicity are two very different measures, and
there is no standard way to balance the benefits of energy vs. toxicity. Makers of plastic
composite lumber usually use only low-grade or contaminated plastics to make their product due
to price reasons, as using pure plastic would make the plastic lumber prohibitively expensive.
•
Plastic pyrolysis can be used to convert plastics back into the equivalent of crude oil. The plastic
is heated to very high temperatures in the absence of oxygen, causing the molecules to break and
reform into various products. Pyrolysis of certain types of plastic (PS, HDPE, LDPE, PP)
produce high yields of oil that can be refined into fuel. Polyesters and chlorinated plastics have
relatively low yields or create other problems. Pyrolysis does recover much of the energy value
embodied in the "high yield" plastic, but recycling plastic additionally saves much of the energy
used in manufacturing the plastic resin in addition to maintaining the plastic's embodied energy.
Thus from an energy standpoint, pyrolysis is better than landfilling but not as good as recycling.
From a greenhouse gas standpoint though, for pyrolysis, the burning the resultant fuel results in
about the same amount of greenhouse gases as would be true for burning other petroleum-based
fuel, and both release all their carbon into the atmosphere. From this greenhouse gas standpoint,
pyrolysis is no better than landfilling.
Maintaining material for highest and best use.
Although it sometimes makes sense to downcycle materials into non-recyclable products, degrading
material prior to its final use almost always lowers the environmental savings from using a material.
Activities that can degrade the value of recyclable material include:
•
•
•
mixing different types of recyclable material together in ways that make it difficult to later
separate them
contaminating material with dirt or other incompatible materials
allowing material to degrade through exposure to sunlight, moisture, or high temperatures
For example, plastic that has been degraded through exposure to sunlight or heat may not be recyclable,
and may only be able to be used for pyrolysis or as a direct fuel source.
Commingled recycling collection often significantly increases the amount of recyclables collected and
used when compared to other recycling methods, but one trade-off is the degrading of the material
collected. For example, the paper collected from residences includes newspaper, cardboard, magazines,
office-type paper, and junk mail. A mixture like this can only be sold to make relatively low-grade
products such as boxboard or corrugating medium, where the "bleached" value of office paper is
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completely useless. On the other hand, sorting can be used to separate out the cardboard, boxboard, and
other "unbleachables" from the mix, and then the paper could be used into newsprint or other papers
where the "bleached" characteristic of the office paper does add value. However, sorting is never
perfect, and a fair amount of cardboard and unbleachable paper remains in the mix. This incompatible
paper ends up either being screened out in the pulping process, or worse, it does not get screened out but
instead gets pulped with the other fibers, degrading the quality of the final product.
Product design and consumption choices are also of key importance in maintaining material for highest
and best use. Often small changes, such as avoiding sticky labels or choosing water-soluble glues, using
common plastic resins instead of rarer, more difficult to recycle resins, making sure caps, closures and
labels are compatible for recycling with the body of containers, and avoiding bright, non-bleachable
paper for brochures, can result in materials being recyclable at a higher use than if recyclability was not
considered in the design of products or the decision to purchase different products.
Conclusion
The use of recovered material as a feedstock in manufacturing or as a fuel can reduce the need for
energy and for the harvesting virgin materials and using them to manufacture new products. This can
result in significant energy and material savings, and reduce the environmental damage cause by the
harvesting of materials and the manufacturing processes. The highest and best use of a material is that
use which maximizes the savings of energy and natural resources and minimizes environmental damage
by replacing the most resource-intensive and polluting virgin resources and processes.
Closed-loop recycling means recycling a material back into the same sort of product, while open-loop
recycling uses material to produce a different sort of product - often one that is difficult to recycle.
Although recyclability is generally a good trait, currently there are a number of examples of nonrecyclable items that perform their function better, and with greater resource conservation, than would
be true for recyclable alternatives. In these cases, the highest and best use of a material at end-of-life
may be to recycle it into a different product via open-loop recycling. The key for determining highest
and best use is evaluating the resources conserved and processes avoided (and their associated impacts)
by using the material to produce a product, not the recyclability of that product itself. Still though,
making changes to increase the recyclability of products, if done without compromising the function of
the item or without increase other environmental costs, will almost always be beneficial in increasing the
amount of material that can be used, at end of life, to displace the harvesting of virgin resources.
References:
City of Austin (2008) Zero Waste Strategic Plan. Page 40 Figure 6: Highest and Best Use Hierarchy
Formerly located on the web at www.cityofaustin.org/sws/downloads/arr_masterplan_10262011.pdf
McDonough, W and Braungart, M (2002). North Point Press. ed. Cradle to Cradle: Remaking the Way We Make
Things. North Point Pr.. ISBN 9780865475878. References to downcycling on pp 4 and 56-59. Reference to
aluminum on pp 56-57
ODEQ (2004) Life Cycle Inventory of Packaging Options for Shipment of Retail Mail-order Soft
Goods. Available on the Oregon Department of Environmental Quality website at
http://www.deq.state.or.us/lq/pubs/docs/sw/packaging/LifeCycleInventory.pdf
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Plastics Pollution Coalition. Common Misconceptions: The Recycling Myth. Downloaded from
http://plasticpollutioncoalition.org/learn/common-misconceptions/ on January 5, 2012.
USEPA (2010) Documentation for Greenhouse Gas Emission and Energy Factors Used in the Waste
Reduction Model (WARM): Chapter on Recycling: page 1.. Downloaded from
http://epa.gov/climatechange/wycd/waste/downloads/recycling-chapter10-28-10.pdf on December 22,
2011.
Zero Waste International Alliance (2005) Zero Waste Business Principal #7. Downloaded from
http://zwia.org/joomla/index.php?option=com_content&view=article&id=8&Itemid=7 on Jan. 5, 2012
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