268
K. Asai et al.
19.2.2 Multitiered Circulation
Problems of management in circular manufacturing are that circulation is not a
single-loop circulation, but a multi-loop one. Circulation flow management for
multi-loop needs to overcome very complex systems (Fig. 19.1c). There are many
life cycle options, such as maintenance, closed-loop reuse/recycling, and cascade
reuse/recycling; thus, we must consider all their characteristics and design to combine
the life cycle options appropriately.
Furthermore, to manage various life cycle options properly, we must consider the
right timing of transferring the items from the inner loop to the outer loop. Generally,
items are circulated in the same loop unless an item can’t realize a function that is
demanded by the user. However, some items are better to be transferred from the inner
loop to the outer loop because supplying a reasonable number of items to the outer
loop based on users’ requirements may provide more overall values to users than
oversupplying items to the inner loop. Therefore, controlling the timing of transfer
is important. It is necessary to overcome these problems in multitiered circulation
along with that mentioned in Sect. 2.1. Thus, it is inevitable to build a mechanism
for properly evaluating the life cycle scenario and overcoming these problems.
19.3 Evaluation of Circular Manufacturing
19.3.1 LCS
In management of circular manufacturing, the evaluation of life cycle scenario is
necessary. There are some methods to evaluate product life cycles. Life cycle assessment (LCA) is one of the most prominent methods. LCA evaluates an entire or a
specific range in the life cycle of products quantitatively and yields their environmental load in a static manner. A conventional type of LCA can estimate the differences in response to possible decisions in scenarios (Ekvall and Weidema 2004).
LCA can evaluate environmental impacts of a single life cycle of products; however,
it cannot estimate the effectiveness of material circulations dynamically, which is
an inevitable feature for evaluating circular manufacturing system. If behavior of
material circulations cannot be perceived, then conducting proper management of
circular manufacturing and realization of scenarios related to circular manufacturing
is impossible.
To calculate material circulations and evaluate their economic and environmental
impacts of products’ life cycle, LCS (Umeda et al. 2000) has been developed. LCS
is a method that simulates material circulation flow based on a discrete event simulation method. From late 1990s the concept of LCS was developed in the academic
field (Kimura 1999; Umeda et al. 2000; Takata and Kimura 2003) and various LCS
systems have been developed thus far (Kawakami et al. 2017; Nassehi and Colledani
2018; Komoto et al. 2005; Ekvall and Weidema 2004; Takata et al. 2019). Murata
K. Asai et al.
19.2.2 Multitiered Circulation
Problems of management in circular manufacturing are that circulation is not a
single-loop circulation, but a multi-loop one. Circulation flow management for
multi-loop needs to overcome very complex systems (Fig. 19.1c). There are many
life cycle options, such as maintenance, closed-loop reuse/recycling, and cascade
reuse/recycling; thus, we must consider all their characteristics and design to combine
the life cycle options appropriately.
Furthermore, to manage various life cycle options properly, we must consider the
right timing of transferring the items from the inner loop to the outer loop. Generally,
items are circulated in the same loop unless an item can’t realize a function that is
demanded by the user. However, some items are better to be transferred from the inner
loop to the outer loop because supplying a reasonable number of items to the outer
loop based on users’ requirements may provide more overall values to users than
oversupplying items to the inner loop. Therefore, controlling the timing of transfer
is important. It is necessary to overcome these problems in multitiered circulation
along with that mentioned in Sect. 2.1. Thus, it is inevitable to build a mechanism
for properly evaluating the life cycle scenario and overcoming these problems.
19.3 Evaluation of Circular Manufacturing
19.3.1 LCS
In management of circular manufacturing, the evaluation of life cycle scenario is
necessary. There are some methods to evaluate product life cycles. Life cycle assessment (LCA) is one of the most prominent methods. LCA evaluates an entire or a
specific range in the life cycle of products quantitatively and yields their environmental load in a static manner. A conventional type of LCA can estimate the differences in response to possible decisions in scenarios (Ekvall and Weidema 2004).
LCA can evaluate environmental impacts of a single life cycle of products; however,
it cannot estimate the effectiveness of material circulations dynamically, which is
an inevitable feature for evaluating circular manufacturing system. If behavior of
material circulations cannot be perceived, then conducting proper management of
circular manufacturing and realization of scenarios related to circular manufacturing
is impossible.
To calculate material circulations and evaluate their economic and environmental
impacts of products’ life cycle, LCS (Umeda et al. 2000) has been developed. LCS
is a method that simulates material circulation flow based on a discrete event simulation method. From late 1990s the concept of LCS was developed in the academic
field (Kimura 1999; Umeda et al. 2000; Takata and Kimura 2003) and various LCS
systems have been developed thus far (Kawakami et al. 2017; Nassehi and Colledani
2018; Komoto et al. 2005; Ekvall and Weidema 2004; Takata et al. 2019). Murata