Carbon flow and management in regional rice production in Thailand

Figures & data

Figure 1. Spatial boundary and scope of the study.

Table 1. Transfer coefficients of biomass processing plant.

Process	Output TC description	TC value	References
Composting	Compost product Off-gas Leachate	TCcompost = 0.61 ± 0.09 TCoff-gas = 0.36 ± 0.05 TCleachate = 0.03 ± 0.004	[10]
Pyrolysis and Gas Engine	Bio-char Off-gas	TCChar_pyro = 0.15 ± 0.02 TCoff-gas Pyrolysis = 0.85 ± 0.13 Electrical efficiency 14 ± 5%	[11, 13, 15]
Gasification and Gas Engine	Bio-char Off-gas	TCChar_Gasi = 0.05 ± 0.007 TCoff-gas_Gasify = 0.95 ± 0.14 Electrical efficiency 24 ± 5%	[11, 12, 14, 16]

Table 2. Improvement scenarios of alternative management of rice straw and application of by-product to soil.

Scenario	Description of the scenario
1 Compost	Collect 75% of all rice straw to co-compost with animal manure and apply all compost to soil in the area Return 25% of rice straw plowed back to soil farmers apply all compost product to the soil in the area
2 Pyrolysis and Gas Engine	Collect 75% of all rice straw to pyrolysis plant to produce electricity and bio-char Return 25% of rice straw plowed back to soil Sell electricity to regional grid Sell bio-char back to farmers who apply it to the soil in the area
3 Gasification and Gas Engine	Collect 75% of all rice straw to gasification plant to produce electricity and bio-char Return 25% of rice straw plowed back to soil Sell electricity to regional grid Sell bio-char back to farmers who apply it to the soil in the area

Table 3. The multiplication factors for C sequestration in different products and by-products.

Type	Potential sequestration (proportion of applied C sequestered for 100 years)	References
Compost	0.15 ± 0.03	[18–20]
Bio-Char	0.8 ± 0.24	[21,22]

Figure 2. C Flow in the system in the base case (tonne/y).

Table 4. Energy and environmental benefit from the scenarios.

Item	Base case	Scenario 1	Scenario 2	Scenario 3
CH4 emission (tonne CH4/y)	54,249	19,424	18,703	18,605
CH4 reduction from base case (tonne CH4/y)	–	34,825	35,545	35,644
CH4 reduction from base case (tonne CO2 eq/y)	–	870,628	888,636	891,094
Annual C budget (stock) in the soil (tonne C /y)	99,082	195,120	108,002	91,712
Type of by-product returned to soil		Compost	Bio-char	Bio-char
C in by-product returned to soil (tonne /y)	–	117,099	24,583	8,194
Potential C sequestration (proportion of applied C sequestered for 100 years( (tonne)	–	17,565	19,666	6,555
Electricity produced (MWh/y)	NA	NA	50,400,000	216,000,000
CO2 offset (from electricity production from biomass) (tonne CO2 eq/y)	NA	NA	29,298*	125,561*

* Calculated from emission factor of electricity production from Thai grid mix in 2010 (0.5813 kgCO₂ eq/kWh).

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