Non-CO₂ emissions from biomass burning

Methods 5.0

Emissions of non-CO₂ gases released from burning biomass.

Introduction

The emissions from biomass burning are proportional to the mass of fuel available for combustion in the land parcel. The method to estimate the mass of fuel \(M\) varies depending on the land use (cropland, perennial crop) and requires input data. CO₂ emissions from crop biomass burning are considered ephemeral (CO₂ is sequestered and released within < 1 year) and are not considered by this method.

Ariel photo of crop residue burning as a management tool. Photo: Univ. of Arkansas Agricultural Experiment Station.

Methods

The method in Fieldprint Calculator v4.2 has been updated for v5 with a revised method from Ogle et al. (2024). The method works in a similar manner but with the enhancement of greenhouse gas separation (CH₄ and N₂O) and allowing users to indicate the size of the area of the field that was set on fire (e.g., 50% of the field rather than the entire field).

The mass available for combustion is estimated by the following equations.

Crop residue biomass from croplands:

\[ M = [(Y_b \times HI^{-1}) - Y] \times DM \]

• \(Y\) = crop harvest or forage yield of the crop burned (kg ha^-1)
• \(HI\) = harvest index ratio of yield to above-ground biomass (kg yield [kg biomass]^-1)
• \(DM\) = dry matter content of harvested crop biomass or forage (kg dry matter [kg biomass]^-1)

\[ [GHG]^{burning}_{total} = AB \times M \times C_e \times EF \]

• \([GHG]^{burning}_{total}\) = the annual total GHG emissions (kg GHG)
• \(AB\) = area burned of the land parcel (ha)
• \(EF\) = the emission factor for each GHG based on land use category (g GHG kg^-1)
• \(C_e\) = combustion efficiency for each land use category (dimensionless)

Conversion of GHG emissions to CO₂e

Total, per area and per crop production units of GHG emissions can be converted to CO₂e by applying the corresponding global warming potential factor of each GHG.

\[ \begin{align} [CO_2\text{e}]^{burning}_{total} &= [GHG]^{burning}_{total} \times [GHG]^{gwp} \\ [CO_2\text{e}]^{burning}_{area} &= [GHG]^{area}_{total} \times [GHG]^{gwp} \\ [CO_2\text{e}]^{burning}_{prod} &= [GHG]^{prod}_{total} \times [GHG]^{gwp} \end{align} \] where:

• \([CO_2\text{e}]^{burning}_\cdot\) = total, per area and per crop production unit CO₂e emissions (kg CO₂e)
• \([GHG]^{burning}_\cdot\) = total, per area and per crop production unit GHG emissions (kg CO₂e)
• \([GHG]^{gwp}\) = global warming potential factor for each GHG

Example

The following is a sample of the results produced by the method. For illustration purposes, the scenario considered has the following characteristics:

• Setting: Corn field from Ripley (KS) under reduced tillage

• Field area: 40.5 ha

• Yield: 10607 kg corn / ha

• Area burned: 40% of the area with previous crop (wheat) residue

NoteResults

CO₂e emissions from non-CO₂ gases from biomass burning shown at the field level, per hectare, and per kg of crop

System Boundary	kg CO2e	kg CO2e / ha	kg CO2e / kg corn
On-Farm Non-Mechanical Sources and Sinks	9107	225	0.021

Constants and factors required for calculation

Carbon fraction of aboveground biomass.

Symbol	Name	Value	Units
F_c	carbon fraction of aboveground biomass	0.45	kg C/kg dry matter

Harvest indices and dry matter content

Harvest indices and dry matter contents for crops.

crop	DM	HI
Alfalfa	0.880	0.95
Barley	0.855	0.46
Chickpeas (garbanzos)	0.840	0.46
Corn (grain)	0.845	0.53
Corn (silage)	0.350	0.95
Cotton	0.920	0.40
Dry Beans	0.840	0.46
Dry Peas	0.840	0.46
Fava Beans	0.840	0.46
Lentils	0.840	0.46
Lupin	0.840	0.46
Peanuts	0.910	0.40
Potatoes	0.200	0.50
Rice	0.860	0.42
Rye	0.860	0.50
Sorghum	0.860	0.44
Soybeans	0.870	0.42
Sugar beets	0.150	0.40
Wheat (durum)	0.865	0.39
Wheat (spring)	0.865	0.39
Wheat (winter)	0.865	0.39
All other crops	0.860	0.39

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Combustion efficiency (\(C_e\)) factors

Combustion efficiency factors by crop.

Crop	Stage_of_burning	C_e
Alfalfa	Early season burn	0.74
Alfalfa	Mid-late season burn	0.77
Barley	NA	0.90
Chickpeas (garbanzos)	NA	0.80
Corn (grain)	NA	0.80
Corn (silage)	NA	0.80
Cotton	NA	0.80
Dry Beans	NA	0.80
Dry Peas	NA	0.80
Fava Beans	NA	0.80
Lentils	NA	0.80
Lupin	NA	0.80
Peanuts	NA	0.80
Potatoes	NA	0.80
Rice	NA	0.90
Rye	NA	0.90
Sorghum	NA	0.80
Soybeans	NA	0.80
Sugar beets	NA	0.80
Wheat (durum)	NA	0.90
Wheat (spring)	NA	0.90
Wheat (winter)	NA	0.90
All other crops	NA	0.90

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Global Warming Potentials

Global warming potentials for N2O and CH4 according to AR6 100-yr horizons.

Assessment Report (AR)	Time Horizon	Gas	Global Warming Potential
AR6	100-yr	CH4_biogenic	27
AR6	100-yr	N2O	273

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References

Ogle, Stephen M, Paul R Adler, Gary Bentrup, Justin Derner, Grant Domke, Stephen Del Grosso, Johannes Lehmann, Michele Reba, and Dominic Woolf. 2024. “Chapter 3: Quantifying Greenhouse Gas Sources and Sinks in Cropland and Grazing Land Systems.” In: Hanson, Wes L.; Itle, Cortney; Edquist, Kara, Eds. Quantifying Greenhouse Gas Fluxes in Agriculture and Forestry: Methods for Entity-Scale Inventory. Technical Bulletin Number 1939, 2nd Edition. Washington, DC: US Department of Agriculture, Office of the Chief Economist. 6-1-6-23. Chapter 3. 1939: 31.