Discussion of a recent publication on Life Cycle Assessment
(LCA) of biodiesel from microalgae may be instructive (Lardon
et al., 2009). The authors state quite precisely that the potential
environmental impacts are investigated via LCA. The inventory is
compiled after defining the production system reaching from algae
culture to the use of diesel in an engine. Bench scale research and
other extrapolations are employed since industrial operation to allow
an inventory does not exist at this time. The difference of this
LCA to the mass balance approach proposed here is immediately
obvious in the production system schematic: no materials are
actually ‘‘cycled”. The schematic does not indicate quantitative or
even qualitative tracking and reconciliation of any mass flows to
allow a test for (reasonable) closure of mass balances.
After a number of assumptions and extrapolations are reasonably
made, the impact of streams to/from the production system
is quantified based on established weighing factors. Essentially,
one would assign a certain factor to, say, a kg CO2 emitted, etc. Impact
on human health, ecosystems, and resources is assigned and
then normalized so all impacts are shown on the same scale to
identify major contributions. While this may be called ‘‘LCA proper”
the authors attempt in the discussion to expand the analysis to
energy balances and this cannot succeed because a first law of
thermodynamics analysis does not suffice. This type of extension
of LCA away from the environmental impact is often attempted
and leads to wildly different results due to the absence of a proper
scientific foundation. This is perhaps demonstrated by the ongoing
debates about the net energy contributions of bio-ethanol production
from corn
Discussion of a recent publication on Life Cycle Assessment
(LCA) of biodiesel from microalgae may be instructive (Lardon
et al., 2009). The authors state quite precisely that the potential
environmental impacts are investigated via LCA. The inventory is
compiled after defining the production system reaching from algae
culture to the use of diesel in an engine. Bench scale research and
other extrapolations are employed since industrial operation to allow
an inventory does not exist at this time. The difference of this
LCA to the mass balance approach proposed here is immediately
obvious in the production system schematic: no materials are
actually ‘‘cycled”. The schematic does not indicate quantitative or
even qualitative tracking and reconciliation of any mass flows to
allow a test for (reasonable) closure of mass balances.
After a number of assumptions and extrapolations are reasonably
made, the impact of streams to/from the production system
is quantified based on established weighing factors. Essentially,
one would assign a certain factor to, say, a kg CO2 emitted, etc. Impact
on human health, ecosystems, and resources is assigned and
then normalized so all impacts are shown on the same scale to
identify major contributions. While this may be called ‘‘LCA proper”
the authors attempt in the discussion to expand the analysis to
energy balances and this cannot succeed because a first law of
thermodynamics analysis does not suffice. This type of extension
of LCA away from the environmental impact is often attempted
and leads to wildly different results due to the absence of a proper
scientific foundation. This is perhaps demonstrated by the ongoing
debates about the net energy contributions of bio-ethanol production
from corn
การแปล กรุณารอสักครู่..
