Mott MacDonald is at the forefront of the understanding of the
impact of carbon emissions on the environment and in taking account
of the “carbon footprint” when assessing the sustainability of
proposed water and wastewater assets.
Policies introduced by the UK Government will encourage the
consideration of the total carbon emissions related to any new
facility with the ultimate aim of zero carbon development. For
carbon trading purposes, the project boundaries for assessing
carbon emissions are normally tightly drawn as, in theory,
suppliers of construction materials should have already accounted
for their own emissions in the manufacture of their products.
However, in establishing total emissions as an input to a project
appraisal, it is appropriate to consider the production of the
materials necessary for the construction of the assets
themselves.
By far the most 'expensive' of the common construction materials,
in carbon terms, are concrete and steel, with energy use being the
predominant operational carbon source. Typically, operational
emissions might be anticipated to overtake those resulting from
construction of the asset after around 10-15 years, though this
will depend on the quantum of civil works, use of alternative
materials and the sophistication of the design.
As an example for wastewater treatment facilities, conventional
wisdom suggests that conventional, large footprint design solutions
would be less energy-intensive and should be low carbon solutions.
However, this needs investigation on a case-by-case basis as the
imbedded emissions in the increased civil works usually associated
with such conventional solutions may outweigh the lower civil works
and higher energy consumption of more sophisticated, 'small
footprint' plants. With respect to sludge treatment, the argument
is heavily affected by the opportunity to generate benefit (energy)
from the sludge and therefore offset carbon used in operation. In
this instance, a higher technology solution may provide a carbon
'payback'. These issues all need assessment as part of an overall
appraisal / feasibility study.
