Emergy

Emergy is a type of energy (exergy) that is consumed in direct and in indirect transformations needed to make a product or service. Emergy is a measure of quality differences between different forms of energy. Emergy is an expression of all the energy used in the work processes that generate a product or service in units of one type of energy. Emergy is measured in units of emjoules, a unit referring to the available energy consumed in transformations. Emergy accounts for different forms of energy and resources (e.g. sunlight, water, fossil fuels, minerals, etc.) Each form is generated by transformation processes in nature and each has a different ability to support work in natural and in human systems. The recognition of these quality differences is a key concept.

History

The theoretical and conceptual basis for the emergy methodology is grounded in thermodynamics, general system theory and systems ecology. Evolution of the theory by Howard T. Odum over the first thirty years is reviewed in Environmental Accounting and in the volume edited by C.A.S. Hall titled Maximum Power.

Embodied energy

Embodied energy is the sum of all the energy required to produce any goods or services, considered as if that energy was incorporated or 'embodied' in the product itself. The concept can be useful in determining the effectiveness of energy-producing or energy-saving devices, or the "real" replacement cost of a building, and, because energy-inputs usually entail greenhouse gas emissions, in deciding whether a product contributes to or mitigates global warming. One fundamental purpose for measuring this quantity is to compare the amount of energy produced or saved by the product in question to the amount of energy consumed in producing it.

Embodied energy is an accounting method which aims to find the sum total of the energy necessary for an entire product life-cycle. Determining what constitutes this life-cycle includes assessing the relevance and extent of energy into raw material extraction, transport, manufacture, assembly, installation, disassembly, deconstruction and/or decomposition as well as human and secondary resources. Different methodologies produce different understandings of the scale and scope of application and the type of energy embodied.