Linear and Circular Economies

Table of Contents:

The economic model prevailing since the industrial revolution has been one that is described as a linear model, based on “extract-make-consume-discard.” The alternative circular model aims to decouple economic growth from the use of natural resources and ecosystems by using them more efficiently.


Sustainable development is defined (by the United Nations initially and now adopted by most nations) as “development which meets the needs of current generations, without compromising the ability of future generations to meet their own needs.” It is linked with renewability which is defined later.


Renewability is defined as “any material or energy that can be replenished in full without loss or degradation in quality.” Biological as opposed to mineral and fossil raw material sources are preferred in the circular model, as they are seen as renewable

Table 1 The main levels of recycling that are generally recognized

ASTM D7209-06

Equivalent ISO 15270

Other terms

Primary recycling

Mechanical recycling

Closed loop recycling

Secondary recycling

Mechanical recycling

Downgrading, open loop recycling

Tertiary recycling

Chemical recycling

Feedstock recycling

Quaternary recycling

Energy recovery


and thus not finite. This simple definition is, however, coming under criticism. Plant sources are themselves finite and have many alternative uses, particularly for food production. Even where they do not directly compete, plants used for materials production occupy land which could often have been used for food crops. Finally there is a loss of biodiversity and habitat when land is cleared for their growth.

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