Environmental Engineering Reference
In-Depth Information
In this perspective, one could substitute the current object-mode paradigm with
a flow-based, rheomode. In other words,
all stocks are flows.
The paper that one
writes on now is only an ephemeral stage of the energy which started in the solar
reactions, traveled to earth, was captured by a photosynthesizing organism, converted
into storage in the xylem of that organism, and harvested and transformed into the
useable product that one now holds. But that is not the end. Over time, the paper will
slowly degrade or decompose, or perhaps the energy release will be sudden through
combustion. In any case, the objects held are transitory states in a long-term dynamic
from (energy) source to (energy) sink. Changing this view would help in appreciating
better the difference between capital and income, because, for example, harvesting
natural capital stock (i.e., a forest) into a flow (deforestation) is not equivalent yet
treated as substitutable in the current accounts. The rheomode approach could help
focus clearly on the difference and thus sustainability of stocks and flows.
Concerned about sustainability over a human time horizon, one must be aware of
the constraints imposed by these sources and sinks. From the input side, clearly, it is
necessary that one does not extract resources at a rate faster than they can regener-
ate. And concerning the output, the waste emissions should not exceed to the
assimilative capacity of the local environment [
1
]. These are the most basic
constraints imposed by open-system, thermodynamics. Humans have transformed
the earth's surface to maximize the capture of photosynthetic energy - think of the
millennia over which the Chinese, Romans, Babylonians, etc., have manipulated and
manicured the landscape for agricultural production. Still, these societies rose and fell
within the solar energy domain. These societies collapsed if they overconsumed the
base resources or if they polluted their local environments [
2
]. In addition to these
persistent input-output constraints, there is a third sustainability consideration cur-
rently observed in the anthropocene, in that it is not only the input-output relations, but
also the structure which is created. Modern infrastructure demands the continual input
of high-quality (low entropy) energy of a form not naturally delivered by ecosystem
services. Furthermore, the created structure locks us into the necessity of immense
energy flows for maintenance. Perhaps an apt analogy can be offered through the
Greek myth of Erysichthon, who was King of Thessaly. He angered the gods by
cutting down a sacred tree, and as punishment was insatiably hungry. Importantly, the
more he ate, the hungrier he became. Our infrastructure, like Erysichthon, does not sit
idle but continually demands upkeep such that the more structure, the more resources
are needed to support this structure. It is not just about the present flows, but also the
life cycle debt commitment as a result of the structure. Today that energy debt is paid
almost entirely in the usage of fossil fuels - a nonrenewable resource. The scale of
human activity seen today is because the application of fossil fuels to substitute solar
fuels has released humans from one of the long-standing constraints on growth. And as
a result, humans have exploded across the landscape. This growth was easywhen there
was sufficient energy to add to the system. In fact, the first growth form is
boundary
growth
, taking energy into the system, and storing it as biomass. As long as there is
more energy available, the system growth can occur unbound. The second stage of
growth,
network and information growth
, is squeezing more utility out of the available
source by coupling processes and improving efficiencies [
3
]. This can occur in parallel
