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.
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?
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:
In ISO 14040 the term "product" is replaced by "economic good", which can be either a product or a service.
CED = CEDM + CEDU + CEDD
where M = manufacture, U = use, D = disposal. The transport, as well as "half-finished, auxiliary and operating materials", should be included. Use includes maintenance.
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 ).
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