Introduction to Life-Cycle Assessment and Decision Making Applied to Forest Biomaterials 153
Consideration should also be given to the precision and accuracy of the equipment
that process direct measurement. Precision can be thought of as the ability of a mea-
surement device to measure a specified quantity, for example, mass of wood entering
a kiln, in a repeatable way. For instance, if a mass was measured five times and the
data from each measurement was 32.0 kg, the measurement device would be precise.
Measurement precisions are different than accuracy. Accuracy of a measurement device
describes the closeness of the measurement to the known value that it is measuring.
For instance, if the measurement device reported a value of 8.7 kg for a known mass of
10 kg, the scale would not be considered accurate. However, if this same device reported
8.7 kg for ten different measurements of the 10 kg mass, this would be a precise but
inaccurate measurement. Both precise and accurate measurements are important for
collecting primary LCI data. To ensure both accurate and precise data collection, it
is important to use measurement equipment with proper capabilities as well as using
equipment with recent and proper calibration.
Many different types of data can be termed “primary data” and what data are collected
depends on the product being studied. Some common primary data measurements are
listed here; however, this is only a few of the types of data that could be collected in
an LCI.
Example of data collected in an LCI:
- Raw material use
- Energy use
- Transportation distances
- Chemical use
- Waste treatment information
- Process yields
- Life times
- Water use
- Product and coproduct flows
- Other flows in or out of the system that are within the defined cutoff criteria.
Biogenic and Anthropogenic Carbon In performing LCIs for forest biomaterials and other
materials that include some form of plant materials, it is important to understand
the differences in accounting methods of carbon derived from biological resources
and petroleum resources. Carbon contained in a piece of wood is typically termed
biogenic carbon as it was taken in from the environment during tree growth through
photosynthesis. The natural uptake of carbon during tree growth and eventual decay of
wood carbon during natural decomposition in forests or in a landfill is often termed the
carbon cycle. This uptake and release of carbon within a relatively short time period,
often less than 100 years, is in contrast to anthropogenic carbon emissions that are
produced from oil and other carbon sources that have been affixed in some type of
material for thousands of years. When oil or coal is burned, additional CO 2 is released
and added to the environment, which over times increases the net concentration of
CO 2 as the coal or other source did not capture the carbon in recent time periods.
To determine the CO 2 absorbed during a biomaterials growth, the following equation
canbeused.
CO 2 uptake=Mass of Material×%CarboninMaterial×
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