152 Introduction to Renewable Biomaterials
Inputs Outputs
Technosphere
flow
Technosphere
flow
Products
Unit process/
Product system
*The functional flow of the process
Products*
Waste* (for treatment) Waste (for treatment)
Goods
Services
Materials
Energy
Goods
Services
Materials
Energy
Chemicals to the air
Chemicals to water
Chemicals to the soil
Radionuclides
Sound
Waste heat
Causalities
Etc.
Elementary
flow Elementaryflow
Abiotic resources
Biotic resources
Land transformation
Land occupation
Figure 5.4Life-cycle inventory data from product systems.
life-cycle stage. Identifying the material flows into and out of the defined system is the
first step of an LCI performed by the LCA practitioner.
Elementary flows originate in the environment and are mined or retrieved to be used
in a process or flows that are released from processes that are released to the environ-
ment and are not used by other processes. One can think of these elementary flows as the
actual material used and materials released to the environment as a result of the studied
product system. In Figure 5.4, the two types of LCI data can be seen. On the top half of
thefigure,technosphereflowssuchasproducts,services,andothergoodsarelisted.The
lower half of figure lists the elementary flows such as chemicals released to soil or air.
After the materials flows have been determined through interviews, literature
searches, and measurement, LCA software can be used to track the material process
flows back elementary flows to and from the environment.
5.3.2.2 Data Collection
Primary Data When collecting data needed to perform an LCA, there are multiple types
of data that are collected in different ways. Primary data and secondary data describe
the two data types that are collected. Primary data are data specific to the studied
product or service that are collected by the practitioner or someone working with the
practitioner. For instance, if an LCA of plywood was being conducted, the material
weights of wood, glue, and other materials would be measured as well as the energy
required in the kiln. Primary data could be collected from natural gas flow meters from
the kiln furnace, which would be classified as primary data. Primary data are unique
to the process under study, which often results in more accurate data describing the
system under study. Often there is generic data in literature describing the studies
system; however, primary data should be used when it is available, specifically when
the measurements are describing the major components of the studies system.
When collecting data from flow or electricity meters, it is important to collect data
with statistical descriptors to ensure data that represents the processes. This can
be achieved by collecting data from multiple pieces of similar equipment and from
different times in different production runs to achieve multiple measures describing
the processes. The median, mean, and standard deviation of the measured primary
data should be reported as part of the primary data collection.
