Introducing a new tool for greenhouse gas calculation tailored for cropland: rationale, operational framework and potential application

Figures & data

Table 1. Overview of specific Tier 2 requirements for GHG calculations in cropland within mitigation projects and approach in SECTOR.

Specific requirement		Approach implemented in SECTOR
Emission factors (EFs)	Free choice of EFs from IPCC and other sources	Emission library that can easily be expanded by location-specific EFs
Activity data	Rapid transfer of activity data from statistics or survey data for large number of patches	Entry format allows ‘copy-paste’ of area, yield and fertilizer data for up to 100 patches
	Entry of activity data with frequencies (percentages) of water management practices	See new procedure described in “New procedure for entering frequencies of different BAU water management practices”
Aggregation	Aggregation for multiple seasons and scenarios	Aggregation framework with triangulation of GHG data (patch/season/scenario)
Scenario setting	Accounting for efficiencies in adoption of mitigation options	New coefficients for fertilizer-use efficiency as well as biophysical and economic barriers to adopting mitigation options

Figure 1. (a) Schematic overview of spatial aggregation from patches to domain; (b) possible patch-domain pairs at different scales.

Figure 2. (a) Schematic overview of patches, seasons and scenarios; (b) triangulation of GHG data points.

Table 2. Example for frequency (percentage) survey data for different SF_w values and frequency-weighted SF_w value for entire GHG data point (patch/season/scenario).

Water management	IPCC value	Frequency in survey	øSFw
Continuous flooding	1	0.2	0.64 (= 1* 0.2 + 0.6* 0.3 + 0.52 * 0.5)
Single aeration	0.6	0.3
Multiple aeration	0.52	0.5

Figure 3. Flowchart of operations in SECTOR.

Figure 4. Operations in the ‘Data Points’ worksheet for an example with two seasons and two scenarios: (a) scenario-wide and data-specific entries (over-writing); and (b) setting and cancelling of scenarios.

Table 3. Activity data and emission factors in spring (Spr) and summer (Sum) rice seasons in Thai Binh province; emission factors for CH₄ (EF_CH₄) and N₂O (EF_N₂O) comprise IPCC default values for continuous flooding (CF) and empirical data (shaded in gray) for the Red River Delta from Tariq et al. [24] for CF, single aeration (1xAe) and double aeration (2xAe).

	Cumulative CH4 emissions (kg/ha)	EF_CH4 (kg/ha/d)	Cumulative N2O emissions (kg/ha)	EF_N2O (%)
Spring season* (total area: 78,590 ha; avg. season length: 100 d; avg. N fert.: 106.7 kg/ha)
Spr_IPCC		1.3		0.3
Spr_CF	129.6	1.296	129.6	1.296
Spr_1xAe	92.1	0.921	92.1	0.921
Spr_2xAe	36.1	0.361	36.1	0.361
Summer season* (total area: 79,500 ha; avg. season length: 85 d; avg. N fert.: 104.6 kg/ha)
Sum_IPCC		1.3		0.3
Sum_CF	698.5	8.218	0.3	0.22
Sum_1xAe	485.5	5.712	0.1	0.07
Sum_2xAe	222.6	2.619	0.7	0.51

*Activity data at the district scale was entered into SECTOR.

Figure 5. GHG emissions in Thai Binh Province from rice in the spring season calculated using different emission factors, namely the IPCC default value and empirical data from Tariq et al. [24] for continuous flooding (CF), single aeration (1xAe) and double aeration (2xAe).

Figure 6. GHG emissions in Thai Binh Province from rice in the summer season calculated using different emission factors, namely the IPCC default value and empirical data from Tariq et al. [24] for continuous flooding (CF), single aeration (1xAe) and double aeration (2xAe).

Tariq A, Vu Q D, Jensen LS, de Tourdonnet S, Sander BO, Wassmann R, de Neergaard A. Mitigating CH4 and N2O emissions from intensive rice production systems in northern Vietnam: efficiency of drainage patterns in combination with rice residue incorporation. Agriculture, Ecosystems & Environment 249, 101–111 (2017). doi:10.1016/jagee201708011.

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