greenhouse gases, water, and land associated with the system. In short, this stage of
the process is the input to characterize the life cycle assessment (ISO 14040 2006).
In addition, as data are collected and more thoroughness is assigned to the
system, new requirements or data limitations may be identified that require a change
in the collection procedures so that the study objectives are still met (ISO 14041
1998). Problems that require revisions to the purpose or scope of the study can
sometimes be identified.
2.3 Life Cycle Impact Assessment
The life cycle impact assessment (LCIA) aims to assess the magnitude and
importance of the potential environmental impacts of a product/service (ISO 14042
2000). Therefore, as factors such as choice, modeling, and evaluation of impact
categories can add subjectivity to the study, transparency in this stage of the LCA
becomes extremely relevant, ensuring that the facilities are clearly described (Jolliet
et al. 2003).
Due to this, flows are associated with the possible categories of environmental
impact. The choice of an impact category is based on characterization methods
according to the objectives and scope of the study. Each flow can contribute to
various categories of environmental impact, as categories associated with human
toxicity, acidification, and ecotoxicity (Carneiro et al. 2017).
In this sense, in order to compile and quantify the effects caused by the systemic
process of producing microalgae biofuels, the quantification steps are subdivided
into three categories: energy balance, water footprint, and greenhouse gas
emissions.
2.3.1 Balance Energy
The concerns about energy balances are related to both the life cycle energy efficiency of biofuels and the saving of nonrenewable energy between biofuels and
fossil fuels (Soccol et al. 2011).
The LCA literature defined, according to Eq. (1), the net energy ratio (NER) as
the ratio of the total energy produced (energy potential of the oil or feedstock) to the
energy content of the construction and materials, in addition to the energy required
for all plants (Jorquera et al. 2010).
NER ¼
P
energy produced
P
energy requirements
ð1Þ
Through this equation, it is possible to estimate the fossil energy needed to feed
the process. The functional units used are megajoules (MJ).
144
M. C. Deprá et al.
the process is the input to characterize the life cycle assessment (ISO 14040 2006).
In addition, as data are collected and more thoroughness is assigned to the
system, new requirements or data limitations may be identified that require a change
in the collection procedures so that the study objectives are still met (ISO 14041
1998). Problems that require revisions to the purpose or scope of the study can
sometimes be identified.
2.3 Life Cycle Impact Assessment
The life cycle impact assessment (LCIA) aims to assess the magnitude and
importance of the potential environmental impacts of a product/service (ISO 14042
2000). Therefore, as factors such as choice, modeling, and evaluation of impact
categories can add subjectivity to the study, transparency in this stage of the LCA
becomes extremely relevant, ensuring that the facilities are clearly described (Jolliet
et al. 2003).
Due to this, flows are associated with the possible categories of environmental
impact. The choice of an impact category is based on characterization methods
according to the objectives and scope of the study. Each flow can contribute to
various categories of environmental impact, as categories associated with human
toxicity, acidification, and ecotoxicity (Carneiro et al. 2017).
In this sense, in order to compile and quantify the effects caused by the systemic
process of producing microalgae biofuels, the quantification steps are subdivided
into three categories: energy balance, water footprint, and greenhouse gas
emissions.
2.3.1 Balance Energy
The concerns about energy balances are related to both the life cycle energy efficiency of biofuels and the saving of nonrenewable energy between biofuels and
fossil fuels (Soccol et al. 2011).
The LCA literature defined, according to Eq. (1), the net energy ratio (NER) as
the ratio of the total energy produced (energy potential of the oil or feedstock) to the
energy content of the construction and materials, in addition to the energy required
for all plants (Jorquera et al. 2010).
NER ¼
P
energy produced
P
energy requirements
ð1Þ
Through this equation, it is possible to estimate the fossil energy needed to feed
the process. The functional units used are megajoules (MJ).
144
M. C. Deprá et al.