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of bio-fuels is free of any environmental impacts. Some biomass-derived products may
in certain concentrations exhibit toxic effects to the environment – ethanol, butanol or
FTS liquids. Others like biohydrogen or biogas pose risk of explosions or contain potent
greenhouse gasses (methane) that need to be controlled. Various liquid bio-fuels differ in
both environmental impacts and hazards. Bio-ethanol although easily biodegradable is
toxic at high concentrations and miscible with water in any concentrations. Bio-butanol
is more difficult to degrade by microorganisms than ethanol is [46]. Both of these
bio-fuels have cleaner combustion profiles with respect to PM (particulate matter), CO
and NOxthan gasoline; however, their emission profiles of carbonyl species are worse
[47]. Biodiesel as a fuel has numerous advantages from the environmental point of view.
It is renewable, non-toxic, biodegradable and has better handling properties than diesel
fuel [48]. Combustion of biodiesel results in lower PM, hydrocarbons (HC) and CO
emissions and about 10% higher NOxemissions than those of conventional diesel fuel.
3.5.4 Sustainability Metrics in Biomass and Bioenergy Policies
In recent years, the application of metrics of environmental impact and sustainability
resulted in significant shifts in bioenergy support policies worldwide. The debate about
the impact of bio-fuels made from edible feedstocks can be traced back to 2008 and a
surge of food prices [49]. It became apparent that bio-fuel and biomaterial production is
the area where interconnected aspects of energy, security, environment, economy and
social impacts need to be considered simultaneously [50]. There exist several schemes to
assist the estimates of environmental impacts of processes: carbon footprint (CF) [51],
ecological footprint (EF) [51, 52], environmentally extended input–output analysis [53]
and many others. Early policies that were used to promote bio-fuel production were
focused on volumetric mandates and subsidies for producers. Type and the origin of
feedstocks for bio-fuel was not considered [54]. This resulted in the rapid conversion
of land for the production of bio-fuels worldwide, very often in developing countries.
These activities were profit driven and did not take into consideration any environmen-
tal impact of changing land use and greenhouse gas emissions required to transport
these bio-fuels to the final users. These raised concerns about both economic efficiency
and sustainability of early bio-fuel support policies especially in the EU and later the
United States. These concerns resulted in introducing LCA-based sustainability criteria
to bio-fuel policies in the EU and higher greenhouse gas emission reduction targets in
the United States [54]. Although currently there is no obligation to include direct and
indirect land-use change as one of the criteria for bio-fuel sustainability assessment,
such modifications to policies are envisaged [54], and very strict sustainability criteria
have been already implemented in biomass sector in the UK. In order to ensure that the
transition from fossil carbon economy to renewable carbon economy in performed in a
sustainable way without replacing one environmentally damaging practice with another,
further advancement in creating appropriate policies are required. Utilisation of taxa-
tion of non-renewable carbon should become an important factor in the development
of more sustainable fuels and materials.
3.5.5 Renewable and Non-Renewable Carbon – Taxation and Subsidies
Decision support tools such as EROI, LCA and estimations of environmental footprints
should have a major impact on selection of policies to support the development of
