Page 37 - ICJ Jan 2026

TECHNICAL PAPER

[63]
leaves an ecological footprint (EFP) . Sustainability is linked to yield variation with respect to world average yield for a given
ratio of EFP to BC. type of land use. It may vary from year to year, and this temporal
variation is taken care of through a factor called intertemporal
The UN appointed Brundtland Commission in 1987 defined yield factor. The product of actual area, yield factor and
sustainable development as: “Development that meets the intertemporal yield factor is then multiplied by equivalence
needs of the present without compromising the ability of future factor to obtain BC or EFP. The equivalence factor (EQF) takes
generations to meet their own needs”. Sustainability is currently care of difference among productivity of different land use class
understood as ability to exist constantly. Total matter in the on a global basis. The EFP is calculated as the area required for
earth’s eco-system is constant according to Law of conservation product consumed considering national yield for the given year
of mass postulated by Lavoisier in 1789. “Nothing is created nor and equivalence factor [63,93,94] . However, carbon land required
destroyed only transformed”. The energy received by the earth for CO 2 does not appear in BC. Crop land and built-up areas
from the sole source, that is the sun, in a year is also transmitted are assumed to have highest productivity and are awarded
back to cosmos and hence, internal energy of the earth is also maximum equivalence factor. Carbon land and forest land have
conserved. Materials are transformed from one state to another same equivalence factor.
by expense of energy and thereby energy remains stored
in the material. Such energy e.g., chemical energy stored in Area occupied by structure contributes to BC and EFP of
fossil fuel is harvested by human beings and consumed. The structure, like that of crop land, corresponding to the same
transformation of materials e.g., CO 2 to biomass materializes area. Contribution to EFP additionally, includes carbon land it
through carbon cycle. The natural process of photosynthesis requires for CO 2 waste generated in addition to area occupied
by plant enables capture of solar energy for conversion of CO 2 as mentioned above. The CO 2 generated comprises of CO 2
to biomass. The CO 2 is produced by living beings through contribution from fossil fuel accounted in the embodied
respiration and by other anthropogenic activity such as use of energy and direct CO 2 gas emission from calcination of lime,
fossil fuel for energy and calcination of limestone for cement magnesia etc. Thus, EFP of structure is greater than BC, unless
etc. Thus, extra CO 2 is produced by human beings by virtue of net carbon dioxide emission from the structure is zero during
consumption of fossil fuel and cement production [63,93] . its intended design life, or if specific forest land is earmarked in
the planned green area to counter the life cycle CO 2 emission
The annual consumption by humanity is accounted in term of from structure. The life cycle CO 2 emission would comprise of
ecological footprint (EFP). This consumption includes food, initial CO 2 emission up to construction and inception plus the
livestock product, space used for built environment, space CO 2 emission during repair and rehabilitation that might be
required for disposal of waste etc. The land mass needed to undertaken on several occasions during the period culminating
produce these items of human consumption and forest land at the end of intended design life. Thus, contribution of
required to absorb CO 2 generated accounts for EFP. The unit structure to equivalent number of earths is always likely to be
for this is global hectare (GHa) [93,94] . Similarly, bio capacity (BC) more than unity. Aiming at sustainability, this value of ratio of
of the available space i.e., land, water etc., to generate the EFP to BC shall be maintained as close as possible, to unity by
consumables is also accounted in GHa. The ratio of ecological minimizing the net CO 2 emission during the intended design
footprint to bio capacity is the number of earths required to life of the structure. The gross CO 2 emission, less the possible
sustain the current population with its present-day consumption sequestration and recycling after demolition would account for
pattern. Number of earths required for average consumption the net emission. Equivalent number of earth contribution of the
and living pattern of every country as well as for the entire concrete in structure N es , can be written as,
humanity is calculated on annual basis using the above-
mentioned accounting system. More than unity value of number (59)
of earths is unsustainable. The CO 2 generation is the major issue
as sequestration requires forest land. Land and water surfaces Thus, N es is a measure of sustainability of structure. EFP
are classified into different classes according to their productive (structurecarbon) is the net CO 2 emission during the intended
capacity. For example, productive capacity of agricultural land design life of the structure.
is different than that of grazing land. Weightage factors are The EFP of structure in terms of forest land required to absorb
introduced to convert physical values of different classes of areas the carbon emission, comprises of the forest land requirements
available, to uniform normalized scale. Since productivity of land during initial construction phase and that during service phase,
can vary from time to time hence, EFP and BC are calculated spanning up to the end of intended design life. Carbon emission
on annual basis for a country or the world as a whole. The land is contributed by the fossil fuel component of embodied
classes are crop land, grazing land, forest land, built-up area, energy of the structure and direct carbon emission through
inland water area, marine area, carbon land. The actual area is calcination of lime etc., used in construction material . The
[95]
multiplied by yield factor for a nation to account for national embodied energy of a structure can be estimated from the

42 THE INDIAN CONCRETE JOURNAL | JANUARY 2026