30
2 The Contested Sustainability of Biofuels …
Finally, there are major concerns about emissions from land-use change, particularly the conversion of carbon-rich areas such as tropical forests or peatlands for
agriculture. These significant upfront emissions can create a vast “carbon debt” that
biofuel utilization may take decades (or even centuries) to pay off (Searchinger
et al. 2008; Fargione et al. 2008). The most problematic cases are those of rainforest
conversion and peatland degradation. Fargione et al. (2008) calculated, for instance,
that palm-oil biodiesel produced in converted peatland rainforest areas could require
as long as 423 years before providing any net benefit in terms of emissions savings.
Accounting for indirect land-use change makes matters even more complex. For
instance, some authors have suggested that although Brazilian sugarcane is grown
far from the Amazon, it frequently displaces cattle ranching, which in turn may cause
deforestation (Nepstad et al. 2008; Sawyer 2008).
Producing an accurate overall GHG-balance estimation, therefore, is a challenging
task. Besides the above, it would also have to include the offsets provided by the coproducts of biofuel crops (Farrell et al. 2006). In the end, there is no easy answer,
and it is wise to treat conclusions with caution. What is clear is that the potential
of biofuels to reduce emissions largely depends on: (i) what land-use changes are
(directly and indirectly) caused by feedstock cultivation; (ii) how much fossil energy
input is required per bioenergy output; and (iii) the overall emission of various GHGs,
not only CO 2. Considering these three factors, it seems that Brazilian sugarcane
performs best among the dominant commercial technologies, mostly because of its
high productivity and comparatively small demand for fossil-energy inputs (Groom
et al. 2008; Goldemberg et al. 2008; Pereira et al. 2019).
Finally, one approach that has gained increased attention as part of an emerging
debate around “negative emissions” is bioenergy with carbon capture and storage
(BECCS). This process has been applied mostly to solid biomass (e.g., wood pellets).
Plant growth takes carbon from the atmosphere (as usual), but then the emissions
from its utilization as energy are captured and stored. This process could significantly
enhance the possibilities of staying within the 1.5 °C or 2 °C target (Azar et al. 2010).
However, there are pending questions regarding the viability of deploying BECCS
at scale, as well as its economic and broader environmental impacts (Muratori et al.
2016).
2.3.2 Air Pollution
Aside from its broader impacts on the climate, biofuels utilization can reduce air
pollution. At the consumption stage, different studies have shown that 10% ethanol
blends (E10) reduce carbon monoxide (CO) emissions by 25–32%, and they also
lower emissions of other pollutants such as hydrocarbons (e.g., benzene and 1,3butadiene, known carcinogens) and particulate matter (Goldemberg et al. 2008;
Coelho et al. 2006; Fulton et al. 2004). As ethanol works as an octane enhancer
for gasoline, it reduces air pollution by replacing conventional fuel additives such as
lead or MTBE, both well known for their toxicity (Fulton et al. 2004, pp. 120–121).
2 The Contested Sustainability of Biofuels …
Finally, there are major concerns about emissions from land-use change, particularly the conversion of carbon-rich areas such as tropical forests or peatlands for
agriculture. These significant upfront emissions can create a vast “carbon debt” that
biofuel utilization may take decades (or even centuries) to pay off (Searchinger
et al. 2008; Fargione et al. 2008). The most problematic cases are those of rainforest
conversion and peatland degradation. Fargione et al. (2008) calculated, for instance,
that palm-oil biodiesel produced in converted peatland rainforest areas could require
as long as 423 years before providing any net benefit in terms of emissions savings.
Accounting for indirect land-use change makes matters even more complex. For
instance, some authors have suggested that although Brazilian sugarcane is grown
far from the Amazon, it frequently displaces cattle ranching, which in turn may cause
deforestation (Nepstad et al. 2008; Sawyer 2008).
Producing an accurate overall GHG-balance estimation, therefore, is a challenging
task. Besides the above, it would also have to include the offsets provided by the coproducts of biofuel crops (Farrell et al. 2006). In the end, there is no easy answer,
and it is wise to treat conclusions with caution. What is clear is that the potential
of biofuels to reduce emissions largely depends on: (i) what land-use changes are
(directly and indirectly) caused by feedstock cultivation; (ii) how much fossil energy
input is required per bioenergy output; and (iii) the overall emission of various GHGs,
not only CO 2. Considering these three factors, it seems that Brazilian sugarcane
performs best among the dominant commercial technologies, mostly because of its
high productivity and comparatively small demand for fossil-energy inputs (Groom
et al. 2008; Goldemberg et al. 2008; Pereira et al. 2019).
Finally, one approach that has gained increased attention as part of an emerging
debate around “negative emissions” is bioenergy with carbon capture and storage
(BECCS). This process has been applied mostly to solid biomass (e.g., wood pellets).
Plant growth takes carbon from the atmosphere (as usual), but then the emissions
from its utilization as energy are captured and stored. This process could significantly
enhance the possibilities of staying within the 1.5 °C or 2 °C target (Azar et al. 2010).
However, there are pending questions regarding the viability of deploying BECCS
at scale, as well as its economic and broader environmental impacts (Muratori et al.
2016).
2.3.2 Air Pollution
Aside from its broader impacts on the climate, biofuels utilization can reduce air
pollution. At the consumption stage, different studies have shown that 10% ethanol
blends (E10) reduce carbon monoxide (CO) emissions by 25–32%, and they also
lower emissions of other pollutants such as hydrocarbons (e.g., benzene and 1,3butadiene, known carcinogens) and particulate matter (Goldemberg et al. 2008;
Coelho et al. 2006; Fulton et al. 2004). As ethanol works as an octane enhancer
for gasoline, it reduces air pollution by replacing conventional fuel additives such as
lead or MTBE, both well known for their toxicity (Fulton et al. 2004, pp. 120–121).