Energy Assessment: Anyone up for an emergy discussion?

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- CommentAuthorsunshine
- CommentTimeJan 24th 2009
Anyone in the UK either heard of or applied emergy synthesis for environmental sustainability assessments? If so, I'd be interested in hearing about your experiences and thoughts.

Thanks
- CommentAuthormark_s
- CommentTimeJan 24th 2009
Go on then....

eMergy?
- CommentAuthorbiffvernon
- CommentTimeJan 25th 2009
Embodied energy.
- CommentAuthorsunshine
- CommentTimeJan 25th 2009
OK - just as a starter for ten: emergy (not energy misspelled) concerns energy memory (rather than just pure embodied energy) - the amount of (solar) energy that it takes to produce a given product or service. An emergy synthesis would examine the amount of transformations solar energy has had to undergo to result in that service or product of interest. The classic example given by H.T. Odum (the originator of the concept) is that 1 joule of solar energy has a lower capacity to do work (i.e.power) than 1 joule of anthracite, but that it has taken (for example) 3 x 10^7 J of sunlight to make the anthracite. In such a way, an energy hierarchy can be mapped out, because different types of energy are not all capable of doing the same amount of work. The greater the concentration of solar energy, the higher the number of transformations solar energy has undergone, and hence the greater the emergy of a product/ service the higher up the energy hierarchy that good/ service is. This also includes information, wood, animals, water, coal, stones, construction materials, etc.

One of the key benefits of using an emergy synthesis is that it is the only environmental assessment method that evaluates environmental and human services on the same basis of value (solar emjoules or sej). Consequently, it is a powerful tool that by-passes all of the hassles and short-comings associated with LCA and is scientifically robust as a methodology.

So, the above threadbare description notwithstanding, I was wondering if anyone had actually ever heard of emergy and - even better - has had the opportunity to have used it?
- CommentAuthorjon
- CommentTimeJan 25th 2009
It doesn't sound like a powerful tool Sunshine. It sounds like a useful descriptor for cataloguing very long term environmental changes so has some relationship with LCA descriptors. 'Emergy' could be incorporated into an LCA substituting 'emergy' for the relevant material descriptor (of which embodied and/or financial value of components are two descriptors)

But this isn't a substitute for LCA. When used for Carbon, it is a substitute of material 'emergy' factors (descriptors) for the factory to gate (or whatever similar material values have been chosen for the LCA).

I doubt it has practical use in the short term because we are not yet at a stage where embodied LCA calculation (for CO2) is accepted as necessary and with an agreed implementation strategy. If it (LCA) were accepted as necessary, the cradle or gate values for carbon (say using Bath ICE) only show that it's not really that important. Using 'Emergy' as a substitute for gate or cradle carbon would change this perspective and rule out certain processes and materials: For instance, all concrete and all quarried natural stone (unless you fudged the 'emergy' calculation so that the energy required to make and bring these materials to the surface in a sustainable cycle did not count)
- CommentAuthorsunshine
- CommentTimeJan 25th 2009
Sorry Jon, but you've lost me with your comment. Why are you reducing it to LCA? They are clearly different approaches and while LCA examines embodied energy, emergy would be more of a study of exergy - available energy used up in the production of something from cradle through to grave (and beyond, if recycled). Emergy is also unlikely to be incorporated into LCA and I'm not sure how you would get there by "substituting 'emergy' for the relevant material descriptor". That makes no sense to me. Perhaps you could explain how you have equated the two.

I also beg to differ: I think that using emergy is a very powerful tool for undertaking sustainability and impact assessments for, unlike LCA, biological processes can be evaluated, just as well as material processes, manufacturing, economic feedbacks, and environmental services. This becomes especially relevant when sustainability is not regarded statically as a steady state, but rather seen as a series of oscillations. An assessment tool for dynamic sustainability must be able to cope with oscillations. As far as I now, LCA is unable to do that. LCA also uses mixed units which get in the way of conducting detailed analyses between competing services/ processes.

I described emergy synthesis as a tool, by which I mean that it demonstrates utility for making informed policy decisions on the basis of the information generated, of which 3 indices are readily calculated - Environmental Yield Ratio (EYR), Environmental Load Ratio (ELR) and Environmental Sustainability Index (ESI). These have been used in a multitude of studies for diverse processes, including the environmental costs of recycling systems, agricultural endeavours, sustainability at a state and national levels, impact assessments of building materials, etc.

Concerning the use of concrete and quarried stone, as I understand it (rightly or wrongly) an emergy evaluation may argue that under one set of conditions (local, geological, economic, etc.) using concrete may be more sustainable than quarried stone, or vice versa given alternate circumstances. Anyway, this was the point of me posting originally - to see what the general take was on it. So thanks for the replies so far.
- CommentAuthorjon
- CommentTimeJan 25th 2009
I understand what you're saying but I don't understand what purpose you would be using 'emergy' for if not for some social purpose. I equated it to LCA input factors because that is the only potential social purpose I can see for this type of evaluation. (LCA for instance has a social purpose of the evaluation of Carbon Emissions and/or the impact of Peak Oil on future generations). However, I would argue that 'emergy', which seems to be a play on entropy, could easily be misused if it were used as a substitute for ordinary LCA inputs.

On this basis, I see the logic of the argument as an interesting esoteric idea. However, I can't see why it would allow politicians to make informed judgements.

If there is a social purpose, what is the purpose? Perhaps I have misunderstood what the evaluation is for. Do you use it?
- CommentAuthorTuna
- CommentTimeJan 25th 2009
There are lot of things I don't understand here...

Looking at the energy capacity of anthracite, doesn't that work out as being the equivalent to amount of carbon being burnt? Then, looking at the 'cost' (emergy - terrible term?!) of that carbon, how does it differ from the cost of the equivalent amount of carbon being bound up by a present day tree? Isn't the only difference the density of the different materials, which is a product of geological processes that have no intrinsic solar cost?

How then does the calculation allow for which emergy costs are essentially renewable, other than heavily penalising fossil fuels? That same calculation must favour nuclear as the embodied energy of nuclear material is not derived from solar input? Unless there is some arbitrary weighting?

Having calculated the cost of something (product, service, whatever), how do you calculate the benefit it derives? Information may have a cost, but if I told everyone on this board how to save half of their fuel bills each year with some simple process then that information has a huge benefit. More so than if I just told you all what I had for tea. Similarly, you cold imagine a natural form of insulation that performs less well than an artificial insulation with higher emergy cost - but if the natural form has a shorter lifespan, and the artificial one can be kept in place for a century saving fuel costs, then which is the better?

I'm nervous of any process that attempts to boil environmental concerns to a single number. Just as the focus on u-values of glazing has diverted some attention from increasingly poor g-values, any method that boils the world down to a single number is pretty much by definition weighting the various factors (and even ignoring some) in a way that suits the designer of the methodology.
- CommentAuthorsunshine
- CommentTimeApr 14th 2009
Hi Tuna (& others)

Sorry about the delay in responding to your comments.

I'm not sure if I am using words that have the shared meaning I am assuming them to have, so I will back up a little and start again. I suppose that I should also qualify my statements by noting that I am a student trying to get my own head around the concepts which are actually proving to be quite subtle the more I (think I) understand them. Anyway ...

As I am understanding it, the bottom line with emergy is that it is similar to calculating the replacement value of something. If an item gets broken or stolen in one's home, the replacement value is calculated as the amount of money it will take to replace (or repair, if appropriate). However, how does this work in natural systems? One cannot throw money at pollution in the hope that it will go away (although, of course, investment in cleansing will help), but the effected system will never again be in a pristine pre-pollution condition, the birds that died as a result of the pollution cannot be recreated (although, with time, new generations will take their place, one assumes). Emergy calculates or measures the amount of work that has gone into the generation of a product or service, such as an ecosystem, or the production of anthracite, or a rock, or the ecological services of wind and water which dilute and disperse emissions, etc.

The work that generates something is the expenditure of exergy - available (or potential) energy - that is used up in the processes of production. Emergy measures the sum total of that used up exergy, over time, used directly or indirectly.

With this in mind, I'm not sure that your questions still apply Tuna; or, if they do, they probably would need phrasing differently perhaps. It is not so much reducing whole systems to one index, but rather it concerns the degree of relative fit between an item and the environment in which it operates or was produced. Bearing in mind that sustainability is not a static steady-state condition, but rather a series of stages in a pulsed context, what is appropriate for one stage of a pulsation may not be relevant for another. For instance, given where we are now, the continued use of fossil fuels is not an appropriate endeavour due to both emissions as well as depletion of reserves. Emergy, in this instance, would calculate what it would take for the fossil fuel reserves to be replenished, and - on the basis of these calculations - would probably suggest that a non-fossil fuel-based economy that is "powering down" is the more context-appropriate way forward.

Anyway, I have to go again, but am happy to keep discussing these ideas if others are similarly interested. If nothing else, it does help me clarify things in my own head ... so thank you very much, if only for that.

Best wishes all
- CommentAuthorDaveOxford
- CommentTimeApr 30th 2009
Hi Sunshine,

I've not read any of the work of the author you quote, and I, too, am struggling to understand how this index or metric, or whatever you would call it, could be helpful.

I would appreciate a worked example, even if you have to make up the emergy values. One thing that has interested me for some time is the trade-off between embodied energy/carbon and the longevity of buildings. For example, a yurt has little embodied energy, but a short(ish) lifespan, and a massive concrete building has huge embodied energy, but a very long lifespan. Would you be able to apply emergy analysis to this trade-off?

In my experience, the most difficult (and arbitrary) bit of LCA lies in defining the system boundaries. That's bad enough, but seems unsurmountable if you are using the notion of emergy. For example, where are the system boundaries when you think of a block of granite? The energy involved in forming such a rock was not derived from the sun, so do we try to track everything back to the big bang? Sorry if that sounds facetious. It's not meant to be. I just don't understand where the system boundary lies.

Dave
- CommentAuthorjon
- CommentTimeApr 30th 2009
Have you read the Green Building Bible section on embodied/longevity Dave?
(Shameless self promotion )

I too struggle with this idea for the same reasons (though phrased differently)
- CommentAuthorDaveOxford
- CommentTimeApr 30th 2009
Jon,

Not yet - a gap in my education, but I intend to. I seem to have fallen for the gushing endorsements scattered about this site

Dave

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