Take the diptych of renewable energy and renewable raw materials as an example, the former label being older and more consensually defined than the latter.
Renewable energy
Renewable energy (1) is energy which is derived from an infinite resource (2), as opposed to resources that may run out in a finite future (3). Thus renewable energy is related to the issue of scarcity of resources, to the finitude of nature and, eventually, to time and also the dynamics of the economy. As an example, solar energy is deemed to be available for ever, even if the sun will eventually die out, but in so distant a future (billions of years) that it is indeed infinite for all practical purposes. On the other hand, fossil energy resources are finite and thus may die out eventually - or not, depending on whether the speaker belongs to the neo-malthusian school of thought or not, thus opening up the connection to economic thinking.
More difficult: are biomass and biofuel renewable sources of energy?
Almost everyone takes for granted that the answer is yes.
This way of thinking, however, is a kind of metonymy, not an "obvious" conclusion. Biomass and biofuel are indeed derived to a large part from solar energy, but only in part. Thus deciding whether biomass is renewable or not is a complex matter: the only obvious statement is that biomass, to some partial extent, is renewable. The metrics to access the size of "this partial extend" could be LCA, or the subset of an LCA which deals with energy accounting, and it would add up all energy resources needed to make one unit of biofuel, for example: the almost infinite - and thus renewable? - amount of literature written about the LCA of biofuels and the incoherency of the conclusions show that the matter is not settled. It actually, depends on a very large number of issues, like whether the biomass originates from a "renewable" forest, or plantation or agriculture, whether it is a steady-state process or to what extend the land use change that took place initially should be taken on board, how large was the accumulation of carbon, nutrients, oligo-elements in the soil, how much water is used beyond the rain input, etc.
The issue is usually solved by someone taking a decision and classifying something as renewable. The definition of wikipedia (1) proceeds in this way by listing what resources are renewable. This is akin to a legal way of thinking, where concepts are defined by lists, finite lists in this case. Whoever takes the decision has been vested the authority to do so by a higher level authority. Again a complex matter and a Pandora box that one should not open here!
Renewable raw material
Incidentally, how do we proceed from the concept of renewable energy to that of renewable raw materials or materials or something else, like logistics? Biomass is considered rather commonly as a renewable raw material, thus it seems similar to renewable energy, mutatis mutandis. Renewable raw materials would thus be a raw material resource that is either infinite or is replenishing itself regularly. Thus wood is renewable, with the caveat that wood collected from the Amazon forest has a footprint which is very negative, thus probably not leading to this particular type of wood as being actually labeled as renewable. Anyway, once tress from the Amazon forest have felled, they are gone and more wood will not be forthcoming: thus not really renewable!
In a closed-loop economy, partial or complete, recycled materials are constantly replenishing a secondary raw materials resource. Thus recycled paper, or aluminum, or steel are renewable materials, alongside wood. Claims to that extent have been made15 years ago. The statement, for example, that steel is a renewable material is thus not a marketing slogan but reflects reality.
Recycling is often analyzed as resource savings, as compared to the use of primary raw materials. Recycled materials are thus referred to rather often as secondary raw materials. One may also speak of a nega-resource, in analogy to the concept of negawatts (see further).
Negawatts, nega-energy, nega-resources
Energy savings have been advocated as a negative recourse to natural resources, thus they have been called negawatts (Amory Lovins of the Rocky Mountain Institute). This expression was forged in analogy to the habit of the electricity sector of speaking of the power of its facility rather than of the energy spent or produced. Nega-energy would probably be a more appropriate expression in the context of the present analysis.
Nega-energy avoids any kind of "positive" energy use, even of renewable energy. It does not deplete fossil resources and avoids investing in primary energy production; of course, it will incur investment of its own and one of the brakes to its development is the low return on investment of most of its embodiments. It is similar to secondary raw materials, mutatis mutandis, and thus it could also be called secondary energy resource.
As nega-energy is similar to renewable energy, in as far as it is constantly replenished, not out of some natrual phenomenon, but out of the way society and the economy function, it would make a lot of sense to consider it on the same footing as renewable energy. This would actually be acknowledging that the biosphere and the anthroposphere are deeply connected and operate in profoundly similar manners.
Take-away messages
Energy savings, or nega-energy, are similar to renewable energy and thus could be considered in a similar way, they could actually also be considered as renewable energy. This means some lobbying in the scientific community, especially in the LCA community, which is fond of the concept of renewable energy, which is one of the common mid point indicators hat it calculates. At a more political lobbying level, this means that nega-energy should be encourage through subsidies or special feed-in tariffs (4).
Recycling material, such as scrap but also blast furnace slag, etc., has also the status of a a renewable material.
The key to understanding and accepting this is the industrial ecology concept of the anthroposhere and of industrial/urban metabolism, which analyze what is fluxes and stocks of energy and raw materials similarly, irrespective of whether they stem from nature of from the economy/society.
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(1) Renewable energy is energy that comes from natural resources such as sunlight, wind, rain, tides, waves and geothermal heat, which are renewable because they are naturally replenished at a constant rate. Wikipedia in English.
(2) the wikipedia definition of renewable energy, and probably the one that stems from the use of the word renewable, stresses the flux of energy rather than the stock. The connection is that the flux is generated by a stock. Breaking things down further ends up with the concept of nuclear fuel present in the sun, which is first converted into radiation and then ends up on the ground of the earth. Considering the rather quick way of accepting the concept and using it in the political economy circles, flux and stocks are equivalent at the relevant level of analysis. In other words, infinite is the same as regularly replensihed, the difference is only a difference in analyzing the same thing.
(3) finitude is related to earth and solar energy comes from outside the earth. Obvious as it seems, it makes all of the difference between what is commonly considered as non-renewable or as renewable. The former category originates from the finite planet and the latter from the universe, also deemed infinite although it is not either... If one would allow importing resources from space, in some undefined way, then fossil fuel might become renewable, or iron ore, etc.
(4) renewable energy has become a production sector, which competes with combustion-based electricity utilities to provide electricity to he grid. Nega-energy has remained at the level of a concept, a balance in energy budget calculations, and probably ought to become more organized in a similar direction to reach the critical level were is lobbying voice would be heard. Off-gas rich in latent heat, for example, belongs to this category of nega-energy objects.
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