G.3 Life Cycle Assessment
311
G.3.3 Phase 3: Impact Assessment
Table G.5 shows the calculated impacts for each of the three indicators across
all of the material and energy flows identified in the LCI. Remember that the
characterization factors assumed to represent some of the material and energy flows
may not accurately reflect reality, and this will be considered further in the final
phase of interpreting the results.
G.3.4 Phase 4: Interpretation
(a) Table G.5 shows the total midpoint impacts for climate change, CED, ecotoxicity, and human toxicity for this process step assuming the waste solvents
are incinerated. The production of 3-chloro-2-isopropylthio aniline and 3methylpyridine have the highest greenhouse gas emissions and cumulative
energy demand, whereas production of copper(I) cyanide is overwhelmingly
responsible for the human toxicity and ecotoxicity.
(b) According to the treatment processes applied that incinerate the waste solvents,
a negative impact occurs. This is due to the energy produced by the incineration
offsetting the need for production of energy from other fuels. Considering the
significant impacts generated from virgin production of the solvents, it is almost
certainly worthwhile to more closely consider recycling the solvents rather than
using them just once and then incinerating them. The credits received from
incineration do not nearly offset the impacts from virgin production of these
solvents.
(c) This LCA could be seen as a first, rough calculation to identify hotspots within
this process step. Some of the limitations and uncertainties include:
• Due to data limitations, the characterization factors applied are not completely representative of the material flows being assessed. More specific data
able to describe the specific reactants and solvents used in this case study are
needed.
• More data are needed to describe the efficiency of recycling systems that
could be applied for solvent reuse. Characterization factors would then be
needed to model these impacts and assess options.
• Energy use for other equipment involved in the process has not been
considered. Other energy sources could also be considered for heating the
reactor. For example, waste solvents could potentially be incinerated on-site
to support steam generation, or use of renewable energy sources could be
implemented.
• The quality of the available LCI data could also be checked to ensure
accuracy and completeness before making any investment decisions.
• The other waste streams produced in this process step (e.g., Cu 2 S, NaCl,
HCN) should also be considered in the LCA.
311
G.3.3 Phase 3: Impact Assessment
Table G.5 shows the calculated impacts for each of the three indicators across
all of the material and energy flows identified in the LCI. Remember that the
characterization factors assumed to represent some of the material and energy flows
may not accurately reflect reality, and this will be considered further in the final
phase of interpreting the results.
G.3.4 Phase 4: Interpretation
(a) Table G.5 shows the total midpoint impacts for climate change, CED, ecotoxicity, and human toxicity for this process step assuming the waste solvents
are incinerated. The production of 3-chloro-2-isopropylthio aniline and 3methylpyridine have the highest greenhouse gas emissions and cumulative
energy demand, whereas production of copper(I) cyanide is overwhelmingly
responsible for the human toxicity and ecotoxicity.
(b) According to the treatment processes applied that incinerate the waste solvents,
a negative impact occurs. This is due to the energy produced by the incineration
offsetting the need for production of energy from other fuels. Considering the
significant impacts generated from virgin production of the solvents, it is almost
certainly worthwhile to more closely consider recycling the solvents rather than
using them just once and then incinerating them. The credits received from
incineration do not nearly offset the impacts from virgin production of these
solvents.
(c) This LCA could be seen as a first, rough calculation to identify hotspots within
this process step. Some of the limitations and uncertainties include:
• Due to data limitations, the characterization factors applied are not completely representative of the material flows being assessed. More specific data
able to describe the specific reactants and solvents used in this case study are
needed.
• More data are needed to describe the efficiency of recycling systems that
could be applied for solvent reuse. Characterization factors would then be
needed to model these impacts and assess options.
• Energy use for other equipment involved in the process has not been
considered. Other energy sources could also be considered for heating the
reactor. For example, waste solvents could potentially be incinerated on-site
to support steam generation, or use of renewable energy sources could be
implemented.
• The quality of the available LCI data could also be checked to ensure
accuracy and completeness before making any investment decisions.
• The other waste streams produced in this process step (e.g., Cu 2 S, NaCl,
HCN) should also be considered in the LCA.