Environmental Engineering Reference
In-Depth Information
and others could be irregular and unexpected (capital maintenance). Bene
t flows
take place in future years. In order to make project appraisals comparable between
products or services all these costs and bene
ts need to be assessed at the current
year. In cases where LCCA is taken up at a later stage of the project, historical costs
and bene
ts are used where costs and bene
ts would accrue in the past as well as in
the future. These costs and bene
ts are inflated to the current year level. Various
deflators (future bene
ts) are being
suggested in the literature (Barringer and Weber 1996 ). These range from the
National GDP inflator/deflator (inflation based) to
ts) or inflators (past investments and bene
fixed consumption (depreciation)
and accelerated depreciation or appreciation. In the case of environmental bene
lower discount rates are often proposed.
Different systems have different lifespans, including technical, economic and
useful. In order to make the projects comparable the lifespans need to be stan-
dardized by annualizing the costs. In order to arrive at the unit costs per year, all the
capital costs (CapExHrd) are annualized using the normative lifespans of the sys-
tems (i.e., the technical lifespan). Arriving at the lifespan of a system becomes
complicated where different components of the system have different lifespans.
Using component wise lifespans for hardware such as boreholes, pumps, pump
houses, overhead reservoirs, hand pumps, etc., is more realistic. While normative
lifespan is determined technically, it may not hold well in reality. Systems may last
longer or shorter than their normative life due to various factors such as poor
maintenance, natural factors like hydrogeology; precipitation, temperature, humid-
ity, etc., natural disasters like floods, droughts, etc. The actual lifespan is the actual
number of years the component lasts. By comparing these two, one can assess
whether the actual cost of provision is more or less than the estimated costs. Besides,
actual lifespan takes into account the risk and uncertainty associated with the system.
Standardization is also necessary for comparing the environmental bene
ts or
ed for each assessment and they should be
comparable across the products or services. For instance, emissions per unit (kg) of
produce or wastewater generated per unit of water in
ts. Functional units are speci
filtering (litres).
3.3 Components of Life Cycle Cost Model
The basic LCCA functional form should include the components as indicated in
Eq. 1 .
f X
t¼1 ð CapExhw xt ; CapExsw xt ; CapManEx xt ; CoCap xt ;
LCC xt ¼
ð 1 Þ
DsCost xt ; IDsCost xt ; OpEx xt Þþ CoEExt xt g
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