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Indicators for sustainability assessment 83

the characteristics of the biofuels produced by each selected route. Therefore
fuels that are produced from biomass have different properties and charac-
teristics, depending on the type of biomass employed.
According to Jong and Jungmeier (2015), biorefineries could be classified
in accordance with the selected route:
• Biorefineries that utilize oleaginous crops for the production of biodiesel,
glycerin, and food.
• Biorefineries that utilize C6 sugars and amylaceous crops for the produc-
tion of bioethanol and livestock food.
• Biorefineries of synthesis gas for the production of diesel, gasoline,
naphtha, methanol, and other FT fuels.
• Lignin biorefineries that use wood and C5 and C6 sugars for the produc-
tion of ethanol, electricity, heat, and phenols.

6 Sustainability in biorefineries
It is necessary to establish the sustainability degree of a biorefinery, in relation
to conventional production techniques, and then compare the sustainability
of different biorefineries as well as the environmental impacts generated by
biomass conversion.
However, sustainability is a complex aspect to analyze, as the concept
encompasses environmental, economic, and social variables. Currently,
quantitative assessment of sustainability comprehends the calculation of
economic, social, and environmental indicators, separately. The most com-
monly employed indicators are as follows:
• Economic indicators (production costs).
• Energy and exergy efficiencies.
• Net energy ratio—NER, relationship between the net input and output of
energy.
• Fossil fuel substituted per hectare.
• Carbon emissions: avoided GHG emissions (reduction in the CO 2 -
equivalent emissions).
• Environmental impacts (different impact categories).
• Carbon emissions due to land use.
• Renewability indicators (exergy).
• Social indicators.
With these indicators, it is possible to compare different production
schemes, providing decision tools for the implementation of a project.