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All About Embodied Energy

By: Dr Gareth Evans - Updated: 24 Aug 2012 | comments*Discuss
 
Embedded Energy Embodied Lifecycle

We’re all fairly familiar with the idea of making energy comparisons, at least at the level of finding the cheapest supplier or working out if a particular source of power is greener than another one. That kind of thing works well for the sort of energy that we actually use for ourselves, but what about the energy that’s used for you, by manufacturers and service providers? Anything and everything that is made requires some sort of energy input in the process – and it doesn’t stop at that; there’s the fuel burnt during distribution, the ‘hidden’ energy packaging surrounding the product and the energy-cost of its eventual disposal to take into account too. How can you possibly begin to compare all of that?

The idea of ‘embodied energy’ can go a long way towards helping to provide the answer. It’s a simple enough concept, basically being an attempt to get a measure of the total amount of energy wrapped up in the whole manufacturing process for any given product, from start to finish.

Renewable Energy Lifecycles

One area where the idea can be particularly useful is when it comes to comparing lifecycle costs – the environmental impacts that take place over what you might call a item’s cradle-to-grave existence. This is particularly relevant for items which are primarily intended to either help replace fossil fuel usage, such as PV panels or wind turbines, or reduce energy consumption, such as high-efficiency domestic appliances.

Considering the embodied energy involved in the construction, installation and eventual decommissioning of alternative energy equipment, for instance, has begun to be used to investigate the real lifecycle costs of such devices in everyday use. Both energy saving and renewable power systems are typically judged in terms of their financial payback, but this tends to focus attention on what some people argue is the wrong issue. Looking at their embodied energy, however, allows an energy payback to be calculated – the point at which the net carbon savings of the device begins to outweigh the carbon emissions involved in its construction and commissioning. Since wind turbines and solar cells are fundamentally all about reducing carbon footprints, there is a good argument that this makes a more useful basis for assessing their worth.

Although it is still not a very easy thing for most individuals to work out for themselves, a growing number of manufacturers and industries are starting to adopt the approach. Interestingly, not all of them are in what you might normally consider to be part of the energy sector.

Construction Materials

The building industry arguably has a claim to being the birthplace of the whole idea and it is certainly one area where the concept has been widely embraced. It is, for instance, not uncommon to see articles in the construction trade magazines and journals discussing the relative merits of different materials in terms of their embodied energy, or the closely related embodied carbon, values. As the whole idea of eco-building has grown to become increasingly mainstream within the industry, novel insulating fabrics, for example, such as flax, hemp and cellulose, have gained ground on their more conventional counterparts, often on the basis of their low embedded energy.

Strictly speaking, embodied energy is an accurately calculated value of the amount of energy hidden away inside products and given in mega-joules per kilogramme (MJ/kg), though it is often used more loosely by builders themselves, without giving any hard numbers. Although this may offend the purists, in many ways it’s no bad thing, since it has led to the widespread general awareness of the idea that some types of materials, say concrete, have ‘high’ embedded energy levels, while others, such as wood have ‘low’ ones.

On the other hand, some architects have sought to extend the idea to calculate a quantifiable figure for the total embodied energy value for an entire building, or even a whole new development. It’s an intriguing idea, but it is one that is inevitably far from straightforward to work out, as there are just so many factors to take into account on that sort of scale.

A Useful Idea

From a practical point of view, for the majority of us, embodied energy is probably at its most useful when it comes to making like-for-like choices, between single types of materials, or relatively small, individual items. Using the idea to make meaningful comparisons of much larger and intrinsically more complicated things, that are composed of a whole variety of different components and materials – such as houses – is almost certainly something best left to the experts to argue over.

Even then, there’s no guarantee they’ll all agree!

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