The Carbon Quandary: Essential and Detrimental - Sustainable Design: The Science of Sustainability and Green Engineering - page 283

large-scale biomass electricity-generating station. The industrial sector uses
about one-third of the primary energy in the United States. Wood as a fuel
source makes up approximately 8% of total industrial primary energy use. Most
of this is in the pulp and paper industry, where wood and its by-products are
readily available (see Fig. B7.1). It must be noted that conservation must be
factored into the life-cycle assessment for these processes. For example, we
have compared paper and pulp fuel uses; however, if society can find more
“paperless” systems, such as electronic documentation, the demand for such
wood-based products would also drop. This could be accompanied by less
tree-cutting in the first place, with the advantage of keeping the tree systems
intact and preserving the present sequestration of carbon.
Certainly, numerous industrial sectors can put the process of photosynthesis
to work to find renewable and sustainable feedstocks. Arguably, those most
heavily invested in nonrenewable resources have the most to gain by moving
to renewable resources. *
* U.S. Congress, Office of Technology Assessment, “Potential environmental impacts of bioen-
ergy crop production,” Background Paper, OTA-BP-E-118, U.S. Government Printing Office,
Washington, DC, September 1993.
The Tree
Building and landscape architecture draw increasingly on living resources as
part of good design. Thus, buildings must be incorporated within the various
scales of ecosystems. All ecosystems are comprised of a harmony of abiotic and
biotic components. The relationships of organisms to one another and to the
abiotic environment are cyclical.
Green engineering is all about applying knowledge about life cycles. A
good decision early in the life cycle makes for acceptable outcomes. A poor
decision leads to artifacts that will have to be addressed. Pollution prevention
is preferable to pollution abatement. Nature provides some excellent analogs
of how to view a life cycle. One of the best is the tree.
Sometimes, the things that we are most familiar with are the most difficult
to define. The tree is one of these. First, most of us have a working definition
of a tree. Most would agree that a tree is woody; it is a plant with persistent
woody parts that do not die back in adverse conditions. Most woody plants
are trees or shrubs. Usually, the only distinction between a tree and a shrub
is that the shrub is low-growing, usually less than 5 m tall. Usually, it also has
more stems and may have a suckering growth habit, although many trees also
have this habit (e.g., a river birch, Betula nigra , can have multiple trunks and a
suckering habit). Trees and shrubs differ from most herbs in structure.