153
In light of those studies with large emissions reductions, some authors suggest
biochar could potentially mitigate emissions of CO 2 , CH 4 , and N 2 O by a maximum
of 1.8 Pg CO 2 eq year
−1
(12% of current anthropogenic CO 2 eq emissions; 1 Pg = 1
Gt), and total net emissions over the course of a century by 130 Pg CO 2 eq (Das
et al. 2014). Theoretically, this makes biochar one of the top mitigation options for
rice straw management. Still, more evidence is needed on the feasibility of biochar
in CSA, especially as many studies suggest it is cost-prohibitive due to the large
volume (around 6 t ha
−1
) of biochar needed in-field to achieve mitigation.
9.4 Other Off-Field Practices and Effects on GHGEs
9.4.1 Mechanized Straw Collection
The use of combine harvesters for rice has expanded rapidly worldwide, and major
producers such as Vietnam and Cambodia almost exclusively rely on them (Gummert
et al. 2018). This has large implications for rice straw management and its associated indirect and direct effects on GHG emissions. Contrary to traditional harvesting systems that use threshers and pile straw for easy collection, combine harvesters
spread rice straw on the field. This hampers manual collection, thus promoting
straw incorporation and increased CH 4 emissions. Additionally, the added emissions from fuel consumption and machine production range around 60–165 kg CO 2
eq t
−1
of collected straw (Nguyen et al. 2016).
9.4.2 Fodder
Enteric fermentation as CH 4 from livestock is the leading source of agricultural
emissions and accounts for about 5.8% of total anthropogenic emissions (Gerber
et al. 2013). The quality of ruminant feed has a significant effect on this emission
intensity. Rice straw fodder, although used widely across Asia, is particularly inefficient as a ruminant feed. Its low digestibility equates to high yield-scaled CH 4
emissions compared to more high-quality fodder, such as cowpea straw (Hristov
et al. 2013). In fact, rice straw as fodder has been shown to increase GWP 13%
compared to straw burning (Launio et al. 2016). Because of the widespread use of
rice straw as fodder, it can be assumed that its contribution to emissions from enteric
fermentation is significant. Improving the digestibility of poor-quality fodder, such
as rice straw, may be one of the most effective emissions mitigation strategies for
9 Rice Straw Management Effects on Greenhouse Gas Emissions and Mitigation…
In light of those studies with large emissions reductions, some authors suggest
biochar could potentially mitigate emissions of CO 2 , CH 4 , and N 2 O by a maximum
of 1.8 Pg CO 2 eq year
−1
(12% of current anthropogenic CO 2 eq emissions; 1 Pg = 1
Gt), and total net emissions over the course of a century by 130 Pg CO 2 eq (Das
et al. 2014). Theoretically, this makes biochar one of the top mitigation options for
rice straw management. Still, more evidence is needed on the feasibility of biochar
in CSA, especially as many studies suggest it is cost-prohibitive due to the large
volume (around 6 t ha
−1
) of biochar needed in-field to achieve mitigation.
9.4 Other Off-Field Practices and Effects on GHGEs
9.4.1 Mechanized Straw Collection
The use of combine harvesters for rice has expanded rapidly worldwide, and major
producers such as Vietnam and Cambodia almost exclusively rely on them (Gummert
et al. 2018). This has large implications for rice straw management and its associated indirect and direct effects on GHG emissions. Contrary to traditional harvesting systems that use threshers and pile straw for easy collection, combine harvesters
spread rice straw on the field. This hampers manual collection, thus promoting
straw incorporation and increased CH 4 emissions. Additionally, the added emissions from fuel consumption and machine production range around 60–165 kg CO 2
eq t
−1
of collected straw (Nguyen et al. 2016).
9.4.2 Fodder
Enteric fermentation as CH 4 from livestock is the leading source of agricultural
emissions and accounts for about 5.8% of total anthropogenic emissions (Gerber
et al. 2013). The quality of ruminant feed has a significant effect on this emission
intensity. Rice straw fodder, although used widely across Asia, is particularly inefficient as a ruminant feed. Its low digestibility equates to high yield-scaled CH 4
emissions compared to more high-quality fodder, such as cowpea straw (Hristov
et al. 2013). In fact, rice straw as fodder has been shown to increase GWP 13%
compared to straw burning (Launio et al. 2016). Because of the widespread use of
rice straw as fodder, it can be assumed that its contribution to emissions from enteric
fermentation is significant. Improving the digestibility of poor-quality fodder, such
as rice straw, may be one of the most effective emissions mitigation strategies for
9 Rice Straw Management Effects on Greenhouse Gas Emissions and Mitigation…