2.3 Biofuels and the Environment
33
Alternatively, biofuels could help ignite a transition to more sustainable, highbiodiversity systems (IAASTD 2009; Bastos Lima 2018). For instance, biomass
and other bioeconomy markets can help increase the economic viability of agroforestry or mixed farming systems rich in biodiversity (Groom et al. 2008; Sagar
and Kartha 2007). Communities living in or near forests can diversify their activities through feedstock cultivation, obtain additional income, and be better able to
maintain their livelihoods without resorting to forest degradation (Cunha et al. 2007).
They could also produce (bio)energy locally (Kuik et al. 2011). These strategies may
help keep local communities as forest custodians, meeting both conservation and
socio-economic needs. Moreover, agroecology research has extensively shown that
high-diversity agriculture and mixed farming systems can be combined with high
yields (see Tilman et al. 2006; Altieri and Toledo 2011; Altieri et al. 2012).
Finally, although most issues seem related to how biofuels may augment or reduce
pre-existing impacts from agriculture, they can also raise new concerns about introducing exotic species. For instance, some of the most promising second-generation
feedstocks, such as switchgrass or Miscanthus spp., coincidentally have the same
typical invasive species traits. They include C4 photosynthesis, long canopy duration, no known pests or diseases, high water-use efficiency, and rapid growth in the
spring to outcompete weeds (Raghu et al. 2006). The ecological risks of introducing
such new species as feedstocks should not be underestimated. Such an invasive
potential is very well illustrated by Imperata cylindrica in Southeast Asia, a single
grass species that has dominated about 30 Mha of what used to be tropical rainforest
(Nepstad et al. 2008).
2.3.4 Water Use
Biofuel expansion requires not just more land but also more freshwater, as the latter
is at least used for feedstock processing, if not for irrigation. Water footprints vary
enormously. They depend on the crop, its yields in a specific region, as well as the
type of cultivation and processing technology used.
In general, most assessments point to large water footprints from biofuel production (De Fraiture et al. 2008; Gerbens-Leenes et al. 2009; Mulder et al. 2010). One
estimate suggests that biofuels utilize between 70 and 400 times more water than any
other primary energy source, excluding hydropower (Gerbens-Leenes et al. 2009).
Others have suggested that biofuels are 10–100 times less water-efficient than fossil
fuels (Mulder et al. 2010). Probably, the most critical question is how much biofuel
production relies on rainwater or requires additional freshwater withdrawals. For
example, De Fraiture et al. (2008) estimated that one liter of US corn-ethanol (mostly
rain-fed) uses an average of 400 L of irrigation water. In comparison, the same cornethanol in China (where irrigation is more prevalent) needs 2400 L of irrigated water
per liter of fuel. As such, biofuel production may work well in rain-fed regions, but
it is likely to aggravate present and future water scarcity in water-sensitive regions
33
Alternatively, biofuels could help ignite a transition to more sustainable, highbiodiversity systems (IAASTD 2009; Bastos Lima 2018). For instance, biomass
and other bioeconomy markets can help increase the economic viability of agroforestry or mixed farming systems rich in biodiversity (Groom et al. 2008; Sagar
and Kartha 2007). Communities living in or near forests can diversify their activities through feedstock cultivation, obtain additional income, and be better able to
maintain their livelihoods without resorting to forest degradation (Cunha et al. 2007).
They could also produce (bio)energy locally (Kuik et al. 2011). These strategies may
help keep local communities as forest custodians, meeting both conservation and
socio-economic needs. Moreover, agroecology research has extensively shown that
high-diversity agriculture and mixed farming systems can be combined with high
yields (see Tilman et al. 2006; Altieri and Toledo 2011; Altieri et al. 2012).
Finally, although most issues seem related to how biofuels may augment or reduce
pre-existing impacts from agriculture, they can also raise new concerns about introducing exotic species. For instance, some of the most promising second-generation
feedstocks, such as switchgrass or Miscanthus spp., coincidentally have the same
typical invasive species traits. They include C4 photosynthesis, long canopy duration, no known pests or diseases, high water-use efficiency, and rapid growth in the
spring to outcompete weeds (Raghu et al. 2006). The ecological risks of introducing
such new species as feedstocks should not be underestimated. Such an invasive
potential is very well illustrated by Imperata cylindrica in Southeast Asia, a single
grass species that has dominated about 30 Mha of what used to be tropical rainforest
(Nepstad et al. 2008).
2.3.4 Water Use
Biofuel expansion requires not just more land but also more freshwater, as the latter
is at least used for feedstock processing, if not for irrigation. Water footprints vary
enormously. They depend on the crop, its yields in a specific region, as well as the
type of cultivation and processing technology used.
In general, most assessments point to large water footprints from biofuel production (De Fraiture et al. 2008; Gerbens-Leenes et al. 2009; Mulder et al. 2010). One
estimate suggests that biofuels utilize between 70 and 400 times more water than any
other primary energy source, excluding hydropower (Gerbens-Leenes et al. 2009).
Others have suggested that biofuels are 10–100 times less water-efficient than fossil
fuels (Mulder et al. 2010). Probably, the most critical question is how much biofuel
production relies on rainwater or requires additional freshwater withdrawals. For
example, De Fraiture et al. (2008) estimated that one liter of US corn-ethanol (mostly
rain-fed) uses an average of 400 L of irrigation water. In comparison, the same cornethanol in China (where irrigation is more prevalent) needs 2400 L of irrigated water
per liter of fuel. As such, biofuel production may work well in rain-fed regions, but
it is likely to aggravate present and future water scarcity in water-sensitive regions