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Cumulative Energy Demand

Are Life Cycle Inventories fair in their calculation and weighting of energy balances?

In preparing an EA, as part of an LCA, an inventory of impacts and materials is prepared. There are many energy mix systems and databases available to choose from. Some are based on resources and their depletion. Some concentrate on the effects of the choices of energy types.

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Along with the Ecological Footprint (EF), and CEENE, the cumulative exergy extraction in the natural environment, there is the CED, the Cumulative Energy Demand. How is CED calculated?

Cumulative Energy Demand (CED)

The calculation of the Cumulated Energy Demand is useful when making comparative studies of primary energy consumption of technical processes and product cycles.

VDI Guideline 4600:

Cumulative Energy Demand (CED) provides the total primary energy cost associated with the manufacture, use and disposal of an economic good (product or service), or indirectly result from this good. The sum of the cumulated energy costs for the manufacture, use and disposal of an economic good, as well as the product of service phase sub-totals must be provided.

In ISO 14040 the term "product" is replaced by "economic good", which can be either a product or a service.

CED = CEDM + CEDU + CEDD

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where M = manufacture, U = use, D = disposal. The transport, as well as "half-finished, auxiliary and operating materials", should be included. Use includes maintenance.

Sub-Divisions

CED = CPE + CNE

where CPE = cumulated process energy cost

CNE = cumulated non-energy cost

VDI Guideline 4600 defines CNE as:

CNE = NEU + CBE

where NEU = non-energy use (of energy resources)

CBE = compound-bonded energy content (of materials)

Comments: primary energy assessments for both groups, with distinction made between energy resources and combustable materials. CNE calculates the two sub-divisions together. The weighting factors are derived from the effective use (e.g. if 80% of the primary energy is lost as heat during a process, then gt = 0.2 ).

Article by Andrew Bone, December 31, 2015

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