Closing Cycles: Circular Energy, the missing link

Abstract

There are currently several approaches to evaluate environmental impact of resource and energy use all with advantages and disadvantages. However, two disadvantages are significant and require a next step in environmental impact assessment. Firstly, the impact of energy and materials combined is seldom addressed in the context energy and materials evaluations. A second issue is that regenerating resources, or counter-depletion, is still only debated in the scientific community and has not provided practical useful indicators. These become even more important with the current focus on " circular resource use ". After studying existing research into these phenomena, as in the exergy and emergy fields of research, the objective of this paper is to explore and develop a practical approach for quantifying resource impacts assuming a circular process. The methodology followed is to analyze the cycles of resources, and analyze how the exergy in such cycle can be maintained or how entropy increase can be limited as much as possible. The aim is to develop an integrated , whole system approach combining mass and energy together without weighing factors, in to a easy to use impact indicator. The result is a energy and materials combined evaluation of the full cycle, introducing Circular eergy, as the means to restore original stocks, and as such prevent depletion, or at least introduce a measure to quantify depletion. Both for biotic and abiotic resources. Circular energy can be seen as the embodied energy of restoration of stocks. A second new introduction into closed cycle evaluation is to use solar energy as the reference to make energy and materials impact comparable: either directly, via land use to regrow resources or harvest energy, of indirectly, to convert embodied energy into solar energy demand. As such it could provide a practical way to translate exergy methodology into practice, as well as being a useful indicator regarding depletion of resources (in fact dilution of resources), a factor that is so far not addressed in practice.

Full text

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
Closing Cycles: Circular Energy, the missing link
R.Rovers a, M.Ritzen b, , J.Houben b & V.Rovers c
a SBS research & consultancy
Wollenbergstraat 37,5581HH Waalre The Netherlands,
Email:r.rovers@sustainablebuilding.info
Website: www.sustainablebuilding.info
b Zuyd University UAS
Fac Built environment PO Box 550 6400AN Heerlen, The Netherlands
Email: m.ritzen@zuyd.nl , j.houben@zuyd.nl
c TNO
team Sustainability & Climate, Postbus 80015 3508 TA Utrecht, The Netherlands
Email: vera.rovers@tno.nl
Abstract
There are currently several approaches to evaluate environmental impact of resource and energy
use all with advantages and disadvantages. However, two disadvantages are significant and
require a next step in environmental impact assessment. Firstly, the impact of energy and materials
combined is seldom addressed in the context energy and materials evaluations. A second issue is
that regenerating resources, or counter-depletion, is still only debated in the scientific community
and has not provided practical useful indicators. These become even more important with the
current focus on “circular resource use” .
After studying existing research into these phenomena, as in the exergy and emergy fields of
research, the objective of this paper is to explore and develop a practical approach for quantifying
resource impacts assuming a circular process. The methodology followed is to analyze the cycles
of resources, and analyze how the exergy in such cycle can be maintained or how entropy increase
can be limited as much as possible. The aim is to develop an integrated , whole system approach
combining mass and energy together without weighing factors, in to a easy to use impact indicator.
The result is a energy and materials combined evaluation of the full cycle, introducing Circular
eergy, as the means to restore original stocks, and as such prevent depletion, or at least introduce
a measure to quantify depletion. Both for biotic and abiotic resources. Circular energy can be seen
as the embodied energy of restoration of stocks.
A second new introduction into closed cycle evaluation is to use solar energy as the reference to
make energy and materials impact comparable: either directly, via land use to regrow resources or
harvest energy, of indirectly, to convert embodied energy into solar energy demand.
As such it could provide a practical way to translate exergy methodology into practice, as well as
being a useful indicator regarding depletion of resources ( in fact dilution of resources), a factor that
is so far not addressed in practice.
Keywords: Exergy, LCA, Emergy, Circular Energy, MAXergy , resources, depletion, assessment
1. Introduction
Worldwide the use of materials is increasing, as well as the environmental impacts related
to that materials use . [SERI 2000], This process is accelerated by the desired transition to
a renewable energy based society (the Climate Agreement Paris). Since materials are

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
necessary for the generation and conversion of the renewable energy source, for instance
with PV modules, and for the reduction of energy demand, for instance by insulating
buildings (Ritzen 2016). For materials the impacts are studied in the scientific community,
but have not yet led to easy and wider application in practice .
While energy measures shift impact to materials, a combined evaluation of the two is
required. In order to have the full cycle of combined sources evaluated for practical
application, its required to find a way to translate scientific full cycle analyses into a useful
indicator for practice.
1.1 resources in global perspective.
To emphasize its importance and put the materials position in perspective becomes
apparent when the consequences of a world supplied with renewable energy is explored,
as for instance by {Kleijn 2012],. He concludes: .
The equivalent to several to hundred times (depending different materials) current annual
world production would be needed to build the required grid, wind turbines and hydrogen
pipelines For a low-carbon energy system. For certain technologies it is highly likely that
materials requirements will hinder their scale up to significant levels (hundreds of GW
worldwide) in the time frame available to address climate change (three to five decades).
Others have found similar conclusions. [ Allwood 2011] [Smil 2013],
Materials that will become a leading parameter: Its materials need to gain energy to
produce materials! [Rovers 2015]. This requires a full cycle analyses of both energy and
materials resources, not a partial analyses of a single functionality for a single source.
In order to find a useful approach for practice, it is required to know in detail the materials
resources by stock and depletion. [Valero 2010] For organic materials (biotic) the part of
cycles dealing with depletion and regeneration are quite well understood. And depletion
and re-generation are known and addressed, both in assessments (land occupation) as in
practice, with for instance the Forest stewardship council, helping securing regrowth .
For non organic (abiotic) – materials, minerals and metals, this is a more diffuse area .
Often positioned and accepted as being not-renewable. Hence the focus in daily practice
is mainly on recycling as compensation. (which anyway is not a distinctive property
between resources: all resources are recyclable). Two main questions remain: are they
depleted? And are or can they be renewed? And can we provide a indicator for that part
of the cycle?
1.2 depleting/diluting stocks
The earth as a planet consists for over 30% of iron molecules. This will not be depleted
soon. However, most of the iron is stored in the earth core, which can be regarded for the
moment as inaccessible. Therefore, the real issue is the potential mining of the part that
is accessible. Winning and mining in practice is related to finding stocks in high enough
concentrations which limit efforts for harvesting . If the concentrations decrease, it
requires ever more efforts to collect these and process into useful products. For metals
many data on stock concentrations have been published lately based on solid research
which are not optimistic: Concentrations of all metal stocks are decreasing. Copper in
most mines has gone down to 0.5%, coming from 2-4 %. In some mines in the past 20%
was even common. [Mudd 2007]. This requires increased volume of processed ores to get
the same amount of copper, causing more landscape destruction., Even more important is
the increasing input of other resources in the process, most importantly energy, which is

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
exponential growing for the same amount of copper to mine. A decrease from 1.5 % to 0.5
% copper in ores, caused a doubling in energy to invest. A further decrease to 0.25 %
would increase the energy demand by again a factor 2. [Norgate 2010] Copper will not
disappear from the world, the density it appears in, will become only that low that we
probably cannot afford the efforts anymore to mine it ready for using. The same counts for
other metals, [Mudd 2009] . Skinner and Ayres have called this the mineralogical barrier
(threshold): Below that barrier (threshold) traditional mining is unrealistic for our current
society. [Skinner 1979,1986] [Ayres 2001] Other techniques will have to be used, possibly
increasing energy input even more. This might lead to a paradigm shift in acquiring
metals, and its of increasing importance to have the use and degradation of materials
valued.
The conclusion is that original resource stocks “ deplete”. The stocks decrease in
concentrations, requiring ever more energy to collect concentrated matter. Its also clear
that evaluating materials without related energy input, creates a false evaluation. Energy
input to make resources fit for use is one part of the cycles equation, loss of
concentration, requiring ever more energy to acquire additional resources, to maintain the
same level of quality resources in society, is another part , of the fundamental cycle
approach. To answer the question, can they be renewed? requires a closer look at the
cycles directly.
2. Cycles, in the global system
To evaluate resources going through a system, the second thermodynamic law is of
importance: all matter is going from low entropy to high entropy. Sometimes defined as
chaos, but it is more secure to speak of going from organized and concentrated matter to
unstructured and diluted matter. [Carrol 2010] Materials erode and end as dust, spread
out in nature. This is an unavoidable process. For energy this is widely understood. With
every conversion step potential power is lost, (loss of exergy), ultimately (within our global
system), lost as infra-red heat of low value to space.
Materials not so much disappear from the earth, but disintegrate, as is visible in the form
of eroding mountains, from which rock dust flows via rivers through the system (or via air
and wind ends up on land somewhere).
The concentrated available resources today are the result of the natural organisational
process that has taken place in the past millions of years. The geological and biological
evolution has created that situation. In other words, it is already invested energy1 to
organise ( as in forests or some lime stone layers.) (emergy, as we will address below)
This natural organisational process for abiotic resources is still active, though on long
timescales. In general the earth is a closed system for mass resources which go round in
cycles. If we address the system boundaries as the earth surface plus or minus 10
kilometres, roughly what mankind can handle, there is still some tectonic and volcanic
activity, fuelled by the cooling down of the earth , and occasionally depositing new
1 For instance: Oil and gas are stored solar energy, and huge exergy concentrations , that can create
major changes ( in temperature for all houses , in travelling distances by all car owners) . Its the collective
power of millions of years storing of solar power in biomass , followed by a grinding , pressuring and
cooking process in the earth crust power mill to find their final form as oil and gas . The total budget in
fossil fuels is estimated by Wall as 6,6x 10*26 Joule, being the total equivalent of 120 years of all incoming
solar radiation to the earth. ) [Wall 2005]

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
resources at the earth surface from the core of the planet. New material concentrations
can be ready for mining after new tectonic mountain push ups, (rock formation) , or a
volcanic eruption. ( the iron mining industry in Sweden is based on such volcanic
deposits). These process are on a time frame way beyond the human horizon, and
although there is still considerable geological movement providing new rock formations, its
already less as what mankind moves and depletes . [Kibert 2004]
Nevertheless, there is a geological cycle that re-concentrates matter, restores quality in
the system. Which leads to the conclusion that all resources are renewable, the difference
is in the the speed and volume, which for some resources is beyond human time horizon,
and the use is not within regeneration capacity.
Humans have for long time already understood this and learned to interfere at different
points flows of the natural cycle, even for abiotics: capturing the erosion dust from rivers
to produce functional and useful elements, like transferring this material into clay bricks.
The dust is converted from a high entropy state to a low(er) entropy brick. In some cases,
humans do not wait for rocks to become dust which passes their habitat via a river, but go
directly to cut bricks from rocks and transport them to the desired location. Many early
civilizations worked like that. Both approaches to make bricks are examples of interfering
at a different moment in a cycle flow of resources. with different combinations of mass
and energy involved Bricks as such are nothing else as rocks from re-concentrated
particles of former eroded rocks. It might seem that the entropy in the system is lowered
by fabricating bricks: Material is re-concentrated , which from a materials point of view is
correct, but only since large amounts of energy (from within the system) are invested and
downgraded, increasing entropy in that system. The energy again is not lost but the
potential to change things is (exergetic losses). The combining effect of material and
energy has at the end increased entropy in the system (by definition).
As a result, again, materials and energy cannot be evaluated separately. Except for some
basic uses, energy can only be made useful by mankind by the input of materials, and
materials only by the input of energy.
Both energy and mass from within the system, decline in quality, fast or slow. As long as
use and degeneration, stays within natural regeneration flows ( in speed and volume) this
can continue .
All resources are part of a full cycle and can or will be regenerated. The current use of
stocks is however speeding up depletion and/or dilution, way beyond natural recovery
rates. Which requires that 2
to avoid the value-free depletion of stocks , its needed to introduce a a impact measure
for depletion: for regeneration of stocks, to be able to stay within global carrying capacity,
for biotic as well as for abiotic materials . The main question therefore is : What would be
a useful and practical indicator for regeneration, or maintaining stock quality in the
system?
2 even for this resource route, mankind already depletes at rates far beyond natural restoring potentials.
Entropy increases constantly . The advantage of wood resources is that humanity can see the disappearing of forests, and
reacts by replanting. For many resources this process is out of view.
Mankind itself is nevertheless not acting different form nature: the use of resources and energy increases
entropy, only in a accelerated manner , which disrupts the natural cycles, and by depletion undermines existence of the
species itself. Its in the interest of mankind in its current form that knowledge of cycles and speeds of cycles is analyzed
and managed so that total quality remains stable for future generations .

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
3. Methods: whole system approaches
Lowe investigated four different approaches, aimed at managing resources for the built
environment and concluded that these were to complicated , and a fifth approach should
be developed based on global carrying capacity. [Lowe 2006]. Conclusion: It only works
with a total system view , not by evaluating a partial system.
Another route of exploration, as the name suggests , is Life Cycle analyses. This is
currently a leading approach in environmental science. the debate about introducing
depletion into the evaluation has gained much attention lately, but for the moment lacks
consensus (Klingmair 2014 ] It includes the consequences of processing energy and
materials, but as Amini concludes, the depletion of stocks is not well assessed by lca, as
well as the losses by recycling. [Amini 2007] The subjective weighting between
categories is a problem as well [deWulf 2008] . Another issue might be that LCA is used to
evaluate and compare several functionalities/services in society, but not the resource
flows itself.
Most approaches to value depletion use a mix of secondary systems in their evaluations,
like depletion rated versus societal value, versus products stocked in society, or refer to
cost decrease and increase in society, due to scarcity or mining. [Constanza 1997, Steen
2006, Klingmair. 2014] Which are in fact subsets of the physical state, and mix pure
physical evaluation with subjective and variable reference frameworks. One of the more
interesting concepts is The Surplus energy approach [Goedkoop 2000] It refers to
degrading ore ratios and the increased energy input for mining successive amounts of
resources. The approach combines mass and energy in one kind of evaluation .
Interesting, except that it measures depletion in terms of increased exergy spending to
continue the flow, but not the restoration of original quality.
The Recipe approach [Owsianiak 2015] used this as a basis, but has related this again to
economic values as a measuring unit. Which makes it difficult to use as a physical
parameter in a closed cycle approach . As a side effect some major disadvantages could
turn up: its creates a gliding scale: the values changes by time, which could have its own
effects in society, regardless quality of resources.
Most of these approaches are also not related to carrying capacity of the whole system(to
the total of stocks-maintaining total global quality) , as well as focus at the impacts of a
given activity or product in a subsystem, not to a resource potential. . To evaluate the
cycle of resources is a different evaluation, from a functional unit for mankind.
3.1 Exergy
There is however a approach that does so, focusing at entropy growth in the system by
means of measuring Exergy. And exergy is what has value for humans [Finnveden 1997]
: “ a measure of usefulness is exergy” . Ayres has studied exergy intensively and
proposes that exergy ( services) should be regarded as and additional factor of
production, besides labor and capital. [Ayres 2009]

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
Essentially this should lead to a practical way to evaluate resources , where the focus is
not on production, nor consumption, but on quality(loss) of resources within the boundary
of the whole system . Exergy seems indeed the most promising approach for this.
Exergy analyses, gains increasing interest and has seen many studies lately. [Amini
[2007] introduces new ideas to determine depletion, based on the decline of concentration
of Ores, evaluated via exergy analyses . Following the second law of thermodynamics
changes in the environment create losses of potential since entropy is generated. The
potential to change things is defined as exergy: the part of energy and mass that creates
change and gets lost in the process.
Entropy growth and exergy loss are the natural flow of resources, and accelerated when
humans interfere, and as such a good measure for humans influence on the decrease of
quality ( potential) in the system.
Valero has quantified this exergy loss globally, and states the irreversible exergy
destruction of all analysed commodities is at least 51 Gtoe. [Valero 2010b] Which would
require with current technology a minimum of a third of all current fuel oil reserves on
earth for the replacement of all depleted non fuel mineral commodities. This hints already
in the direction of not addressing exergy loss , but to regeneration as a useful indicator, as
we will address below.
Stewart and Weidema (Stewart 2005) pose that exergy and entropy are very abstract
indicators,. Which of course is at the same time their strength. . Another point they make
is that the reference environment used in exergy evaluations is debatable. But in exergy
there is general consensus that dilution in oceans , air and soil are the reference
environments, within the earth system boundaries. Its resources that have reached
average global concentrations in air ocean or soil which act as the highest entropy
environment within the global system.
3.2 emergy
The emergy approach , introduced by Odum end of last century, takes exergy one step
further: it introduces solar energy as the driver of all systems on earth, and the only net
contributor to the potential within the earth system. [Odum 1996] The emergy approach
calculates how much solar energy has already been stored in the available resource
stocks within the earth system, Where exergy calculations show how much organized
matter/exergy is lost after using it, emergy quantifies how much was already stored (
exergy gained) , by solar driven concentrations. (Solar energy joules, SeJ) The model
documents the budget in solar energy encapsulated in current resource stocks, as well as
the budget available for transformations to natural and human required functionalities.
(“transformity factor”) . Emergy, specifically Solar Emergy, is the available solar energy
used up to directly and indirectly to make a service or product.[Odum 1996] Or as another
scolar described: emergy can be seen as “memorized energy” [Scienceman 2013]
Emergy can be seen as the most complete methodology to attempt to value resource
cycles in the earth system, however on the other hand is seen as “sheer impossible “to
calculate how much energy is involved in transforming the earth [Ayres 2001]
But its obvious that the ultimate process is one of solar energy upgrading resources to
more useful forms. And if resources are dispersed, more has to be invested. Either by
“nature”or by man to speed up processes.

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
The emergy approach could be very valuable to analyse the whole integrated historical
earth forming process. However, a more practical approach is to accept the current
conditions evolution has created, and start from that point . The Exergy approach, as
described before, does just that: it starts from the available exergy, the potential to do
work, as has been created by the historical forming process, and determines how much of
that potential is lost by that activity. Exergy refers tot a reference environment , which is
more or less the highest entropy environment within the addressed system, the end
station of dilution . For metals the ions dissolved in oceans is regarded as a working
reference environment.[Valero 2010, Amini 2007] As such its a reference measure for
depletion of our resources.
3.3 Findings from part 3
A considerable amount of research and knowledge is available on how to bring a full
(resource) cycle analyses to the table. On the other hand, calculations are complex, in
many approaches they are connected to secondary evaluation frameworks, and do not
provide a direct useful approach for practical applications. While exergy seems the best
candidate to have a value free evaluation of the potential of resources , and the loss of
that, as part of a a full cycle evaluation. It also seems a good measure for the 'usefulness
for the human kind'. Emergy is the ultimate attempt to grasp everything physically, but far
too complicated for daily practice.
Valero provides detailed calculations in exergy regarding the state of resources.
Concluding that a drastic limitation is required in extraction of resources. But also
mentioned that this approach should be connected to the world of practice , and avoid the
risk of remaining in only dialectic speeches. It should be brought from conventional
accounting of resources to physical accounting of systems.
Its obvious that it is of utmost urgency that we incorporate a measure for depletion or
value of flows in whole system cycles , into our evaluations. Closing cycles or circular
approaches as are required to sustain our existence on earth, require to address the full
loop of resources ( 'of a resource') , and this includes depletion , and the more :
regeneration.
Amini already speaks as of the earth of being in a state of “ Exergy countdown” , toward
complete equilibrium. [Amini 2007]
The question can be posed, , if calculation of (exergy) losses will be the right measure,
especially for the world of practice. As Valero before already showed its also possible to
calculate the energy it takes to restore qualities in the mineral stock . [Valero 2010]
Calculating what is needed to compensate loss, or in other words, to bring back the
resources concentration to its original state could make it possible to relate the exergy
loss value to a practical value in terms of required energy investment . Also Lindeijer
already hit the clue when writing: the amount of energy necessary to bring the resource
back into the state before extraction can be described as exergy loss (Lindeijer 2002).
This is what this paper proposes, a measure to restore qualities. Based on following
findings:
1 all cycles are naturally closed cycles, that naturally regenerate. Though with different
time scales and volumes, but can be closed again , when overexploited.
2 regeneration of quality in stocks is what has to valuated , to come to a circular approach
in our earth system, and to maintain lowest entropy as possible

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
3 Solar energy is the only contribution to earth system that adds quality/exergy, and its
use does not increase entropy.
4. Circular Energy
For a complete cycle evaluation the following starting points are relevant: Material stocks
decline fast, and beyond carrying capacity of the earth; biotic materials have a known
method to include regeneration of stocks into the evaluation, abiotic materials being part
of a cycle as well, should have regeneration be taken into account just as for biotic
resources; the evaluation is energy related mass evaluation since its energy that is the
driver of cycles ie flows. And important, solar radiation should be introduced as the
reference, the only source entering our global system not depleting any resources. (as a
source, making the source useful requires in many cases in-system resources : land or
materials , see below).)
Based on the previous evaluation , this paper proposes to combine elements from
emergy and exergy advantages in a condensed form: However not starting from the point
of decline of resources, but to calculate , similar to the approach for biotics, what is
needed to maintain or to reinstate the original situation: what is needed to compensate
the human caused wrinkles created in the natural cycles of all resources. This is the step
to regain /restore the original stocks, to compensate loss of entropy. To remain a
balance requires to recover diluted materials up to the level of the former quality , being
the step that actually leads to closing of cycles, to counter entropy.
Where Embodied energy is a measure for the investments to provide a function or service
in society, there is a additional measure to counter entropy growth, to close the resource
cycle ( complementary to “exergy countdown”) caused by providing that function (-al unit).
To restore original concentration: to be introduced as 'Circular Energy'.
Circular Energy is then the counterpart of Embodied energy: the latter is the directly
invested energy to make a raw mined resource fit for products and use , and Circular
Energy compensates for
the loss of stock in the
system, and compensates
for the speeding up for
degradation of quality in
the system, beyond natural
regeneration.
EE and CE are both parts
that make the cycle going
continuously. This way
energy and materials are
evaluated together, in
their process through the
global cycles, and in a
practical way as we will
analyse below.
Fig.1 : global system depicting entropy growth and the energy flows as
defined in paper.

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
Its important to notice that this approach does not start from providing a function or
service for human use, but evaluates the impact involved in matter going through cycles.
As soon as resources are harvested, mined or else, the entropy process starts. Iron may
seem to be upgraded by producing millions of nails for example, in fact via energy
invested, and dilution of iron as nails over thousands of projects/customers, the iron is
spread and entropy is growing constantly, until lost and dissolved in the background.
(fig.1)
EE+CE are the mass related energy components that deal with the human interrupted
part of the natural cycle. Important is to define which real world options are available to
restore qualities ie concentrations. For organic matter like wood the situation is obvious
and is practised: Most of the work input, to concentrate molecules in a high quality form
('exergy'), has been automatically incorporated in a m2 of soil (the 'conversion device')
receiving solar radiation . The cycle time is within the horizon of mankind, in say 40-50
years a forest has reorganised and grown a new layer of wood-stock, after clear-cut.
Expressed as land use in many assessments. This process of restoring the wood cycle is
well known , within human time horizon and as such addressed in many assessment tools
( as embodied energy and “land occupation”) [Koellner 2013]
For abiotics the situation is less obvious Nonetheless, abiotics are in principle also a part
of a cycle, as argued 3. The moment metals ions are dissolved in the ocean they reached
the states of highest entropy -within the system earth- and act as the reference
environment for exergy calculations. Comparable with diluted nutrients in the organic
cycle . From the ocean starts the natural or human induced restoration of quality.
5. Fist experiences quantifying CE
To illustrate the methodology, a exploring calculation has been made for biotics using the
ocean water reference to restore iron concentrations , by means of filtering dispersed
metal ions from oceanwater,
[Swochau1984] and later [Bardi2010] have explored this in detail. Bardi writes: “The
oceans contain immense amounts of dissolved ions which, in principle, could be
extracted without the complex and energy intensive processes of extraction and
beneficiation which are typical of land mining. In addition, an important fraction of the
minerals which are lost as waste at the end of the economic process end up in the sea as
dissolved ions”. In this sense, “the oceans could be considered an infinite repository of
3 For example iron , though maybe not in a continuous process, has been concentrated from time to time in
geological history, in rock formations and in higher concentrations in so called banded iron formations, BIF [BIF 2016] (
the ones most used for iron mining ) From mountain deposits or rock formations , eroding over time and form which
iron particles pass through nature, mainly carried by water flows. The main part flows with rivers to end in oceans. The
ocean is regarded as the highest entropy environment in exergy analyses, and used as “reference environment” . In the
oceans the cycle re-starts, for instance via metal ions that get clustered and concentrated again via bacteria in so called
manganese nodules. Exploration to harvest these from the ocean crust are ongoing. From ocean bed subduction , parts
are fed back in the earth core system, to become available again in new deposits via tectonic movements and volcanic
eruptions . ( the iron mining in Sweden) . In fact on a geological scale iron , or metals in general, are part of a cycle
system .

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
materials that could be used for closing the industrial cycle and attain long term
sustainability.4 “
Bardi calculated how much
ocean water needs to flow
through the filters , to
compensate the total mining
capacity on land. He has based
his case on data from
desalination installations, which
require around 2,5 kWh per ton
of sea water. Further
calculations are made assuming
a 100% efficient process , and
supposing membranes can
filter out just one element.
The figures by Bardi are
recalculated for obtaining 1 kg
of iron related to the amount of
ocean water and the energy for
the processing. The table
shows these recalculated data
and for iron it will require 2,5
million MJ for 1 kg of concentrated iron. (this does not include investments in installations,
and transport for instance.) [table1 provides data for more metals]
It shows its possible to have a relative easy and practical reference for obtaining iron via
the ocean water route, or in other words, to compensate the loss of quality of our iron use
at the 'end' of the cycle in seawater, and to add a energy reference to it. This acts as the
energy reference for the recollection of metals in concentrated form , and can act as a
measure for circular energy in the metals cycle. ( which is also a measure for exergy of
concentrated molecules, since referred to by a reference environment.). It could also be
seen as a compensation measure for depletion .
A basic way to illustrate the approach is to calculate and compare the use of a wooden
beam versus a steel beam to support a similar functional unit, a building floor section .
Here we have to introduce a second step in close cycles calculation, the reference to
Solar energy, as the only source not increasing entropy directly in system earth. Solar
energy comes in a flux per m2, so we can introduce a indicator called “Embodied Land”
(EL), the amount of land over time required to capture and convert solar energy for use in
our system: expressed in m2-year .
Beams with similar strength (-service) require slightly different mass , which is the basis
for the caculation: The embodied energy differs by around a factor 4 , 100 for wood and
450 for steel, using a generic database [Hammond 2011].
4 A rough estimate of the amount of copper cycled by the continental biomass is of the order of 1 × 10*4 tons
per year . It is a very small amount compared to the human copper production (ca. 1 × 10*7 tons per year), showing the
difference in speed of natural cycles, versus the throughput of human use . . (Bardi 2010)
table 1: energy inputs for extraction of re-concentrating metal
ions from ocean water reference environment. V.Rovers,
recalculated from Bardi, 2010.

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
The circular energy for the wood beam is the solar energy required to grow over time the
amount of wood mass5, expressed in land 'embodied' for growth: 26 m2-year ( supposing
5ton/year yield per hectare from forestry excl. some losses ) . For the steel beam the
figures from Bardi are taken, and 2,5 million MJ/kilo gives 45 million MJ for the beam.
Using again the solar energy route requires for instance PV solar panels to generate the
energy , producing 432 MJ/m2-year , requiring (EL) 104.166 m2-year, the Circular energy
expressed m2 solar land required, comparable with the land occupation from wood,
Similarly the Embodied Energy can be transferred to Solar occupied land via PV.
The Embodied Land from Embodied Energy is four times larger for steel as for the wood
beam (very similar to embodied energy in MJ) . The Circular energy difference is much
larger: a significant area for wood: and a huge area for the steel CE. In the total the EE is
hardly significant anymore. 6 The same approach can be applied for other abiotic
resources 7.
A detailed calculation is more complex, since there are for instance second order effects
to be dealt with ( like the EL from solar panels used). Its not further detailed here, since
the main purpose of this paper is to introduce Circular Energy as a main component to
treat closing cycles evaluations. See also [Houben 2016} and 'discussion”.
6. Discussion and observations
Every flow or cycle is characterized by type of resources, volume, speed (time) and
energy input . With Circular Energy, expressed in Embodied land, EL, the time-component
( speed), volume and energy of cycle parts have been brought together in one unweighed
approach. The combination of Embodied energy and Circular energy is however only a
first step in a mature assessment to characterize the closing of a resource cycle. Though
its useful to relate resource use to loss of quality in the system as well as to relate it to
carrying capacity of the earth system, there are other issues still to solve: most important
is the second and third level effects of evaluating: to produce the energy for both EE and
5 This process of restoring the wood cycle is well known , within human time horizon and as such addressed in
many assessment tools ( as embodied energy and “land occupation”) [Koellner 2013]
6 A more elaborate comparison of beams from different materials has been carried out in the Research project
IMDEP, at Zuyd university, by Jos Houben, [Houben 2016. Its available in the download section of www.MAXergy.org
7 The same approach can be used for other resources, not being known as directly “ renewable” . as an example
for minerals: : Gypsum is found in concentrated layers formed by natural processes, , but a high entropy reference level
is, similar to iron, the gypsum dissolved in ocean water: The return route could be obtaining gypsum from ocean water
evaporation farms: Driven by direct solar energy. (which shows that also for the driving energy source different routes
can be defined, here direct solar radiation induced heat)[Gypsum 2016]
Gypsum harvest from salt pans give following results: : A m3 ocean water contains 1,26-1,66 kg gypsum
[Michgan Tech 2016, Al-Shammiri 2002] . With an evaporation of 4-5 mm per day, solar driven, [Abdelrady 2013,
Akridge 2008] and a harvest period from 75 days, [Akridge 2008 ] , the harvest can be 2 kg/m2-year (20 tonnes/ha-year)
. Which is the Circular energy for Gypsum regeneration. ( expressed in m2 solar radiation receiving surface) 0,5 m2-
year/kg

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
CE requires conversion technologies, that involve materials and energy to produce as
well. The 2nd and 3rd level effects will have to be documented [Rovers 2013 ].
The EE /CE approach make clear that its not needed to calculate the historical
embodied (memorised) energy in resources . Calculating the circular/restoring energy, via
a practical state of technology route, can be a more easy way to introduce a 'depletion'
value and balance the cycles, and even relate to the input of Solar energy , as was also
the intention of Odum in his work. Even more of an eye-opener is that obtaining iron
from concentrated ores on land is in fact more destructive as mining from seawater: to
start with concentrated ores requires embodied energy plus circular energy, to maintain
entropy levels. Directly starting from the lowest entropy level, requires only investing the
circular energy.
The Circular energy approach moves away from more traditional LCA approaches, and
from approaches related to social needs or monetary concerns. In order to maintain
quality potential in the earth system this is an unavoidable route: Nature makes no
difference , values is what human give to something, while nature has no values, it just is.
Which is not an issue in itself, but requires us first to have the physics right, before the use
adds non-natural ie subjective values to it. The illustration brings the different approaches
together.(fig.2)
Recycling: so far this has not been addressed, but in general the arguing is that
physically, recycling is just prolonged use of the resource in the chain, delaying entropy
growth. (of mass, under input of energy for processing probably) , and can be dealt with
in the EE part of the approach8 .
The current preference for mining ores from land concentrations, has many reasons, one
is the fact that materials in society are still hardly seen as problematic, and therefore not
addressed. There is no country in the world which has a legal ambition set for materials
use9, like most have for (renewable) energy targets. While the approaches discussed,
8 See http://www.ronaldrovers.com/?p=34
9 As of january 2018 The Netherlands will have a materials performance standard, with a legally set
performance level, though not so ambitious to start with.
Fig 2: Characterisation of different
approaches
Emergy starts from historical invested
Solar energy in stocks and flows.
Exergy starts from stocks as a given
fact, and the Exergy lost or entropy
growth by loss of stocks/converting
Ecological Footprint refers to CO2:
either direct, in landuse to (re-
)produce, or indirect land to
compensate for mineral and metal CO2
LCI/A starts from function, and related
flows, indicating all (side) effects from
applying
MAXergy Starts from Stocks and flows,
and (solar)Exergy to invest to restore
entropy/quality.

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
either exergy, emergy or circular energy, show that system destruction is huge, and has to
be addressed.
Another observation is that the Circular Energy actually has to be invested , either for
biotics(organics) like wood or abiotics (non organics) like metals, 10, to avoid entropy or
degradation of the system . Its not about the baseline value (stored exergy) but about
the restoration ie recovery value , (exergy to be invested) And when regeneration is
applied for biotics ie organic resources (via solar powered land occupation for instance) ,
it should also be applied for abiotics - non organics. Physically there is no difference. If
humans do the job, that’s somehow 'nature' as well.11
The reference for energy to be invested is chosen as solar energy. Still, which routes from
solar radiation to useful converted energy carriers are the most optimal is still to explore ,
taking into account the circular energy involved in producing the devices for solar
harvesting, either direct ( radiation) or indirect ( like wind etc)
7. Conclusions
The paper aimed to explore the role of resources within the earth system, and the
interaction between energy and materials in maintaining a certain level of exergy /or low
entropy balance, the consequences of depleting or diluting matter in the system , and the
role of energy to restore original levels of quality in the system. It was concluded that
given that materials (and energy) will ultimately lead to increased entropy, that it requires
additional energy to maintain potential in the system, ie exergy levels. If mankind speeds
up the use and degradation of energy and materials resources, beyond the natural
regeneration levels , either biotic or abiotic, it requires not only to measure impact in terms
of embodied energy for the direct process, but also to invest energy to restore previous
levels of (low) entropy, or organised matter. Here introduced as Circular Energy.
Circular energy provides a useful and practical indicator for the restoration of the cycle,
and provides an easier approach as compared to other methods . It could be used as an
easy indicator for practice indicating entropy growth, or more popular introducing : a value
as “compensation for depletion” . in addition to embodied energy for the processing of
materials.
It has become apparent that thermodynamically organic and inorganic matter are in fact
similar cycles: both are part of a cyclic process within the earth system. Difference only
exist in time and volume ( speed of flows through the system). Organics can reorganise
via natural processes within a time frame of human generations. Inorganic matter may
take up to millions of years to reorganize, or require the interference by man to shorten
that time. However, If organic matter is brought to high entropy, it requires equally direct
interference by man to restore original entropy levels. The speed of depletion of stocks is
such that currently both organic and inorganic matter requires the hand of man to restore
qualities, : large forestry programs are in place to fight forest loss. It could be that large
ocean filtering programs are actually required in future , needed to fight other stock
losses.
10 Hau /Bakshi in emergy referred to this as “replacement time energy” , but it was not detailed further
.[Hau 2004]
11 If not equally treated its a kind of 'Resource racism': resources not equally treated: either treat both
with regeneration or both without.

5th International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS5)
09 -11 July, 2017, NISYROS - GREECE
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