Page 76 - Materials Chemistry, Second Edition

58 LIFE CYCLE ASSESSMENT HANDBOOK

3.4.3 Postconsumer Recycling
There are a number of approaches that can be used for modeling the impacts of
postconsumer recycling. Commonly used approaches include system expan-
sion, boundaries drawn between successive useful lives of the material, and
allocated approaches.
System Expansion. This approach avoids the need for allocation. For mate-
rial that is recycled at end of life, the system that produced the material is
assigned the burdens for collection of the postconsumer material and repro-
cessing the recovered material into a form that is ready for its next use. Credit
is then given for avoided production of the material that is displaced by the
recycled material. The credit is given to the system producing the recycled
material. The rationale is that because the first system is supplying material as a
feedstock for future systems, less virgin material must be produced.
Cut-Off Method. This approach also avoids the need for allocation. Distinct
boundaries are drawn between systems producing and using recycled mate-
rial. The initial system is assigned all virgin production burdens for the mate-
rial, and material going to recycling leaves the first system's boundaries at end
of life. The user system (second system) burdens begin with collection and
reprocessing of postconsumer material. 2
Since collection and reprocessing burdens are generally much lower than
virgin production burdens, this approach tends to favor the system using recy-
cled material. The rationale can be expressed as follows: Because the second
system is using recycled material, demand for virgin material is reduced and
less virgin material must be produced.
Allocated Burdens. The rationale for the allocated approach is that all prod-
uct systems using a given quantity of material should share equally in recy-
cling burdens and benefits. This includes the system first using the material in
virgin form as well as all subsequent systems using the material after recovery
and reprocessing.
The following equation can be used to illustrate the general concept of the
allocated approach:

(
V/n + F + U + n-l)/n x R + D/n

where V = virgin production, F = fabrication, U = use, R = recycling, D = dis-
posal, and n = the total number of useful lives of the material (including virgin
use and all subsequent uses until the material is disposed). The recycling
allocation factor (n-1) is one less than the total number of uses since there is no
recycling preceding the initial use.
In reality, with each recycling cycle there will be collection and reprocessing
losses, and subsequent uses of the recycled material are likely to be in products
with a mix of virgin and recycled content. To illustrate the general concept,

2 This method is outlined in EPA/600/R-92/245 Life-Cycle Assessment: Inventory Guidelines
and Principles, where it is identified as recycling allocation method 2.