2.3.2 Water Footprint
Water footprint (WF) is used to assess water use along the supply chains, sustainability of water uses within river basins, water use efficiency, water allocation
equitability, and dependence of water on the supply chain. This is characterized by
quantifying the freshwater consumption of a process or product per functional unit
(Hoekstra 2016).
The concept of water footprint comprises three components: green WF, blue
WF, and gray WF, according to Eq. (2). Green WF is defined as rainwater that is
evaporated during the growing period of the culture. The blue water footprint is the
volume of surface and groundwater consumed during the production of a particular
product or service. Consumption includes the volume of freshwater evaporated or
incorporated into a product or service. However, WF gray refers to the amount of
water that cannot be reused, that is, the volume that needs treatment or that has been
contaminated (Farooq et al. 2015).
WF ¼
X
WFgreen þ WFblue þ WFgray
ð2Þ
Processes for microalgae biofuels, the direct withdrawal of water footprint
represents the water that is consumed by each step in the process, including, for
example, water for microalgae cultivation, water required to compensate evaporation of the bioreactor, water loss of the process during filtration, and the water
reached during the conversion of the fuel (Mekonnen and Hoekstra 2010; Garcia
and You 2015). These footprints are estimated by units of volume (m
3 ) per kilogram of biofuel (kg) or megajoules of biofuel (MJ) (Guieysse et al. 2013).
2.3.3 Greenhouse Gas Emissions
Absorption capacity, concentration, and residence time of the gases are used to
evaluate the so-called global warming potential (GWP). In turn, the GWP is
characterized as a simplified index in the Intergovernmental Panel on Climate
Change (IPCC), along with the land use change coverage (LUCC) that quantifies
the environmental impact generated by greenhouse gases as well as the potential of
acidification, eutrophication, and depletion of the ozone layer (Forster et al. 2007).
In 2002, the United Nations Environment Program (UNEP) joined the Society of
Environmental Toxicology and Chemistry (SETAC) to initiate the life cycle initiative which is an international partnership aimed at putting the cycle into practice
and improving the tools of support through better data and indicators (Klöpffer
2006).
Usually, it can be quantified according to Eq. (3), sum the masses of substances
that contribute to the impact (Mi), whether masses of gases (CO 2 , CH 4 , NO x )
contribute to these same substances impact that are published annually in reports
6 Life Cycle Assessment of Biofuels from Microalgae
145
Water footprint (WF) is used to assess water use along the supply chains, sustainability of water uses within river basins, water use efficiency, water allocation
equitability, and dependence of water on the supply chain. This is characterized by
quantifying the freshwater consumption of a process or product per functional unit
(Hoekstra 2016).
The concept of water footprint comprises three components: green WF, blue
WF, and gray WF, according to Eq. (2). Green WF is defined as rainwater that is
evaporated during the growing period of the culture. The blue water footprint is the
volume of surface and groundwater consumed during the production of a particular
product or service. Consumption includes the volume of freshwater evaporated or
incorporated into a product or service. However, WF gray refers to the amount of
water that cannot be reused, that is, the volume that needs treatment or that has been
contaminated (Farooq et al. 2015).
WF ¼
X
WFgreen þ WFblue þ WFgray
ð2Þ
Processes for microalgae biofuels, the direct withdrawal of water footprint
represents the water that is consumed by each step in the process, including, for
example, water for microalgae cultivation, water required to compensate evaporation of the bioreactor, water loss of the process during filtration, and the water
reached during the conversion of the fuel (Mekonnen and Hoekstra 2010; Garcia
and You 2015). These footprints are estimated by units of volume (m
3 ) per kilogram of biofuel (kg) or megajoules of biofuel (MJ) (Guieysse et al. 2013).
2.3.3 Greenhouse Gas Emissions
Absorption capacity, concentration, and residence time of the gases are used to
evaluate the so-called global warming potential (GWP). In turn, the GWP is
characterized as a simplified index in the Intergovernmental Panel on Climate
Change (IPCC), along with the land use change coverage (LUCC) that quantifies
the environmental impact generated by greenhouse gases as well as the potential of
acidification, eutrophication, and depletion of the ozone layer (Forster et al. 2007).
In 2002, the United Nations Environment Program (UNEP) joined the Society of
Environmental Toxicology and Chemistry (SETAC) to initiate the life cycle initiative which is an international partnership aimed at putting the cycle into practice
and improving the tools of support through better data and indicators (Klöpffer
2006).
Usually, it can be quantified according to Eq. (3), sum the masses of substances
that contribute to the impact (Mi), whether masses of gases (CO 2 , CH 4 , NO x )
contribute to these same substances impact that are published annually in reports
6 Life Cycle Assessment of Biofuels from Microalgae
145