Civil Engineering Reference
In-Depth Information
In the first place, it is the environment that provides the land on which buildings and
infrastructure are located. Second, it is the environment that provides many of the
resources that are used to make building material products. As acknowledged in the
State of the World Report
, the construction industry consumes more than one third
of global resources, over 10 per cent of all fresh water, and is responsible for 30 to
40 per cent of solid waste. Buildings also account for 25 to 40 per cent of the total
energy used and approximately 30 to 40 per cent of global carbon dioxide emissions
(Taipale 2012). Finally, but by no means least important, it is also the environment
that is ultimately responsible for assimilating and processing the waste that arises
from the various phases of construction, from building through to demolition. In
other words, without the environment there would be no resources for construction
and no way of managing some of the waste and outputs arising from the processes
involved in maintaining the building stock and associated infrastructure.
In this chapter, we concentrate specifically on the ways in which the
environment and economy interact and explore three important conceptual areas
that characterise environmental economics. These are the mass balance model,
private costs versus social costs, and environmental valuation.
THE MASS BALANCE MODEL
The mass balance model has become a standard introductory reference for students
new to environmental economics. It focuses on the energy used and wasted by
economic activity. The first law of thermodynamics provides the starting point. This
law explains the 'physics' of economic activity, since it states that we cannot destroy
matter, we can only change it. Any resource that is extracted from the environment
must be returned to it in some form or other - what goes in must come out.
The model conveys the process of production as the transformation of a certain
number of inputs into certain a number of outputs. Some of the outputs may be
positively valued, but other outputs will be undesired and of negative value. In other
words, all economic activity produces a desired output (the conventional good or
service) plus undesired output (such as pollution). For example, when clay and sand
are combined and heated at high temperatures for several days there are several
outputs: the conventional or desired output of bricks, and the undesired output
of carbon particles and sulphur dioxide. In short, we have introduced two related
notions: the principle of
joint production
that highlights how any economic activity
inevitably produces several types of output; and the
mass balance model
that
works from the premise that matter cannot be created or destroyed. The concept
of joint production is derived from classical economics and the mass balance model
from physical science. Their general significance to environmental economists is to
emphasise that everything is connected to everything else.
Figure 11.2
presents the basic idea behind the mass balance model, that the mass
of material inputs into an economy is balanced by the mass of products and waste
outputs leaving the system. In other words, there is equivalence between the mass
of resource inputs (raw materials) flowing into a system and the mass of outputs
(product and waste) flowing out of it - hence the term mass balance.
