Emission module

This module contains functions that parametrise the emission components of the model.

The NIR method is based on National Inventory Report 2022 - (Published_April 2024) which is compatible with v2.6 of the SB-GAF tool and v11.1 of G-GAF tool from PICCC.

author: Young

AfoLogic.EmissionFunctions.f_crop_residue_n2o_nir(residue_dm, F, decay_before_burning)

Nitrous oxide and methane emissions from crop residues:

  1. the combined nitrification-denitrification process that occurs on the nitrogen returned to soil from residues.

  2. Burning of crop residues.

  3. runoff and leaching of nitrogen returned to soil from residues.

These parameters are hooked up to both the residue production at harvest (+ve) and consumption (-ve) decision variables. The AFO equation is a simplified version of the NIR formula below because the decision variables are already represented in dry matter and account for removal.

Mass of N in crop residues returned to soil: M = (P x Rag x (1- F - FFOD) x DM x NCag) +(P x Rag x Rbg x DM x NCbg)

  • P = annual production of crop

  • Rag = residue to crop ratio

  • Rbg = below ground-residue to above ground residue ratio

  • DM = dry matter content

  • NCa = nitrogen content of above-ground crop residue

  • NCb = nitrogen content of below-ground crop residue

  • F= fraction of crop residue that is burnt

  • FFOD = fraction of the crop residue that is removed

The mass of fuel burnt (M): M = P x R x S x DM x Z x F

  • P = annual production of crop

  • R = residue to crop ratio

  • S = fraction of crop residue remaining at burning

  • DM = dry matter content

  • Z = burning efficiency for residue from crop

  • F = fraction of the annual production of crop that is burnt

Nitrous oxide production from nitrification-denitrification process (E) E = M x EF x Cg

Nitrous oxide production from leaching and runoff (E) E = M x FracWET x FracLEACH x EF x Cg

Parameters:

  • residue_dm – dry matter mass of residue decision variable.

  • F – fraction of crop residue that is burnt (ha burnt/ha harvested).

  • decay_before_burning – fraction of crop residue that is decayed before burning time.

Returns:

Nitrous oxide production from nitrification-denitrification process and nitrous oxide production from leaching and runoff.

AfoLogic.EmissionFunctions.f_fert_emissions(fert_nitrogen_propn_k_n, fert_propn_urea_k_n)

Calculates GHG emissions linked to fertiliser applied to rotation activities, using the methods documented in the National Greenhouse Gas Inventory Report.

Emissions are from several exchanges:

  1. the combined nitrification-denitrification process that occurs on the nitrogen in soil.

  2. atmospheric deposition due to ammonia released from the volatilization of fert which increases nitrogen in the nitrogen cycle and therefore increase nitrogen deposition which produces some n2o when interacts with the earth.

  3. runoff and leaching of nitrogen.

  4. urea hydrolysis: Urea applied to the soil reacts with water and the soil enzyme urease and is rapidly converted to ammonium and bicarbonate.

  5. Liming hydrolysis: The lime dissolves to form calcium, bicarbonate, and hydroxide ions.

Returns:

emissions (kg co2e) per tonne of fert applied.

AfoLogic.EmissionFunctions.f_fuel_emissions(diesel_used)

co2, n2o and ch4 emissions from fuel combustion. Assumption in AFO is that all equipment is diesel.

For some reason in this function, ef also converts to co2e.

Parameters:

diesel_used – L of diesel used by one unit of a given decision variable.

Returns:

kg of co2e

AfoLogic.EmissionFunctions.f_n2o_atmospheric_deposition(N, ef, FracGASM)

Calculate the nitrous oxide production from atmospheric deposition due to ammonia released from volatilization which increases nitrogen in the nitrogen cycle and therefore increase nitrogen deposition which produces some n2o when interacts with the earth.

Nitrous oxide production from atmospheric deposition: N x FracGASM x EF x Cg

Parameters:

  • N – Nitrogen

  • ef – Emission factor (EF) (Gg N2O-N/GgN)

  • FracGasm – fraction of N volatilised

Returns:

AfoLogic.EmissionFunctions.f_n2o_leach_runoff(N, FracWET, FracLEACH)

Calculate the nitrous oxide production from leaching and runoff of nitrogen in dung and urine.

Nitrous oxide production from runoff and leaching (N): N = (F + U) x FracWET x FracLEACH x EF x Cg

Parameters:

  • N – Nitrogen

  • ef – Emission factor (EF) (Gg N2O-N/GgN)

  • FracWET – fraction of N available for leaching and runoff

  • FracLEACH – fraction of N lost through leaching and runoff

Returns:

AfoLogic.EmissionFunctions.f_pas_residue_n2o_nir(residue_dm, RBG_t, NCAG_t, NCBG_t)

Nitrous oxide emissions from pasture residues (green pasture senescence, dry pasture, nap):

  1. the combined nitrification-denitrification process that occurs on the nitrogen returned to soil from residues.

POC is not included atm (because not much poc). To hook it up would require making a new variable that is v_poc_slack and then making con_poc_available ==.

These parameters are hooked up to both the pasture growth and consumption decision variables. The AFO equation is a simplified version of the NIR formula below because the decision variables are already represented in dry matter and account for removal.

M = Aikl x FracRenewal x (Yk / 1000) x (1 - FFODik) x NC AGk) + (Aikl x FracRenewal x (Yk / 1000) x RBGk x NC BGk)

  • M = mass of N in pasture residues

  • Aikl = area of pasture (ha)

  • FracRENEWAL = fraction of pasture renewed = 1/ X where X is the average renewal period in years: 10 years for intensive systems and 30 years for other systems

  • Yk = average yield (t DM/ha)

  • RBGk = below ground-residue: above-ground residue ratio

  • NCAGk = N content of above-ground residue

  • NCBGk = N content of below-ground residue

  • FFODik = fraction of pasture yield that is removed

Nitrous oxide production from nitrification-denitrification process (E) E = M x EF x Cg

Parameters:

  • residue_dm – dry matter mass of residue decision variable.

  • RBG – below ground-residue to above ground residue ratio.

  • NCAG – nitrogen content of above-ground crop residue.

  • NCBG – nitrogen content of below-ground crop residue.

Returns:

Nitrous oxide production from nitrification-denitrification process and nitrous oxide production from leaching and runoff.

AfoLogic.EmissionFunctions.f_stock_ch4_animal_bc(ch, intake_f, intake_s, md_solid, level)

Animal component of the Blaxter and Clapperton method for CH4 production - linked to the animal DVs. This is best linked to the animal DVs because the value varies with the level of feeding which is not known if it were connected to the feed-stuff. However, it does require an estimate of the M/D of the feed being consumed which is an optimised variable. However, a reasonable approximation is available from the M/D of the feed that generated the animal profile.

Note, in Blaxter and Clapperton 1965 there is an error in table 5 (it should be b=2.37-0.05D (required to make figure 3 work)) and there is an error CH4 equation derived from table 4 and 5. It should be CH4 (kcal/100kcal feed) = 1.30 + 0.112D + L (2.37 -0.05D). In the 2012 tech paper these error were fixed. This is the equation used below.

Note 2: When they are lactating the ewes intake doubles (or more) and there is a corresponding increase in the energy expended on producing milk. So should the extra intake be counted as higher L and therefore reduce emissions per unit of intake. Or if there is no change in weight are they still considered to be at maintenance and hence high emissions per unit of intake? This is not mentioned in B&C. Currently assuming that level of feeding is relative to energy used for maintenance functions and doesn’t include the energy used for milk production.

Parameters:

  • ch – methane parameters

  • intake_f – herb intake (kg)

  • intake_s – supplement intake (kg)

  • md_solid –

  • level – the amount of feed consumed divided by the amount required when energy retention is zero, that is the amount required at maintenance (level=0 at maint).

Returns:

kg of methane produced per day - animal component

AfoLogic.EmissionFunctions.f_stock_ch4_animal_nir()

Calculates the component of livestock methane emissions linked to stock activities, using the methods documented in the National Greenhouse Gas Inventory Report.

livestock produce methane from both enteric fermentation and anaerobic digestion of manure. The amount of emissions are effected by both livestock factors (e.g. age, relative size, EBG) and feed factors (e.g. quality, protein content, intake). Thus, in AFO the NIR equations are split between livestock and feed activities for improve accuracy.

The NIR equations for livestock methane emissions are as follows:

  • Methane production from enteric fermentation (M): M = I x 0.0188 + 0.00158

  • Methane production from manure (M): M = I x (1 - DMD) x EFT

At the moment milk consumption does not contribute to methane from either enteric fermentation or manure decomposition (likely not a big issue since it would be of a small magnitude).

Returns:

methane production kg/d that is linked to the livestock decision variable.

AfoLogic.EmissionFunctions.f_stock_ch4_feed_bc(intake, md)

Feed component of the Blaxter and Clapperton method for CH4 production - linked to the feed-stuff DVs. This is best linked to the feed-stuff DVs because the value varies with M/D and this is only an estimate when emissions are calculated for the animal component of the emissions.

Note, in Blaxter and Clapperton 1965 there is an error in table 5 (it should be b=2.37-0.05D (required to make figure 3 work)) and there is an error CH4 equation derived from table 4 and 5. It should be CH4 (kcal/100kcal feed) = 1.30 + 0.112D + L (2.37 -0.05D). In the 2012 tech paper these error were fixed. This is the equation used below.

Parameters:

  • intake – dry matter intake of the feed-stuff decision variable (kg).

  • md –

Returns:

kg of methane produced per x intake - feed component

AfoLogic.EmissionFunctions.f_stock_ch4_feed_nir(intake, dmd)

Calculates the component of livestock methane emissions linked to feed activities, using the methods documented in the National Greenhouse Gas Inventory Report.

livestock produce methane from both enteric fermentation and anaerobic digestion of manure. The amount of emissions are effected by both livestock factors (e.g. age, relative size, EBG) and feed factors (e.g. quality, protein content, intake). Thus, in AFO the NIR equations are split between livestock and feed activities for improve accuracy.

The NIR equations for livestock methane emissions are as follows:

  • Methane production from enteric fermentation (M): M = I x 0.0188 + 0.00158

  • Methane production from manure (M): M = I x (1 - DMD) x EFT

Parameters:

  • intake – dry matter intake

  • dmd –

Returns:

AfoLogic.EmissionFunctions.f_stock_n2o_animal_nir(cl, d_cfw, relsize, srw, ebg, mp=0, mc=0)

Calculates the component of livestock nitrous oxide emissions linked to animal activities, using the methods documented in the National Greenhouse Gas Inventory Report.

livestock produce nitrous oxide emissions from several exchanges:

  1. the combined nitrification-denitrification process that occurs on the nitrogen in manure.

  2. atmospheric deposition due to ammonia released from the volatilization of dung/urine which increases nitrogen in the nitrogen cycle and therefore increase nitrogen deposition which produces some n2o when interacts with the earth.

  3. runoff and leaching of nitrogen in dung and urine.

The amount of emissions are effected by both livestock factors (e.g. age, relative size, EBG) and feed factors (e.g. quality, protein content, intake). Thus, in AFO the NIR equations are split between livestock and feed activities for improve accuracy.

The NIR equations for livestock nitrous oxide emissions are as follows:

  • Nitrogen retained in the body(NR): NR = {(0.045 x MP) + (WP x 0.84) + {[(212 - 4 x {[(EBG x 1000) / (4 x SRW ^ 0.75)] - 1}) - (140 - 4 x {[(EBG x 1000) / (4 x SRW ^ 0.75)] - 1}) / {1 + exp(-6 x(Z - 0.4))}] x EBG} / 1000 / 6.25

  • Nitrogen excreted in faeces (F): F = {0.3 x (CPI x (1 - [(DMD + 10) / 100])) + 0.105 x (ME x I x 0.008) + 0.08 x (0.045 x MC) + 0.0152 x I} / 6.25

  • Nitrogen excreted in urine (U): U = (CPI / 6.25) - NR - F

  • Nitrous oxide production from animal waste (N): N = ((F x EFf x Cg) + (U x EFu x Cg))

  • Nitrous oxide production from atmospheric deposition (N): N = (F + U) x FracGASM x EF x Cg

  • Nitrous oxide production from runoff and leaching (N): N = (F + U) x FracWET x FracLEACH x EF x Cg

Note: Freer 2007: Crude protein, being total N × 6.25

Parameters:

  • d_cfw – daily growth of clean fleece

  • mp – milk production i.e mp2_dams

  • mc – milk consumption i.e mp2_yatf

  • relsize – relative size of animal

  • srw – standard reference weight of animal

  • ebg – daily empty body gain

Returns:

kilograms of n2o emissions per day linked to the animal activity

AfoLogic.EmissionFunctions.f_stock_n2o_feed_nir(intake, dmd, cp)

Calculates the component of livestock nitrous oxide emissions linked to feed activities, using the methods documented in the National Greenhouse Gas Inventory Report.

livestock produce nitrous oxide emissions from several exchanges:

  1. the combined nitrification-denitrification process that occurs on the nitrogen in manure.

  2. atmospheric deposition due to ammonia released from the volatilization of dung/urine which increases nitrogen in the nitrogen cycle and therefore increase nitrogen deposition which produces some n2o when interacts with the earth.

  3. runoff and leaching of nitrogen in dung and urine.

The amount of emissions are effected by both livestock factors (e.g. age, relative size, EBG) and feed factors (e.g. quality, protein content, intake). Thus, in AFO the NIR equations are split between livestock and feed activities for improve accuracy.

The NIR equations for livestock nitrous oxide emissions are as follows:

  • Nitrogen retained in the body(NR): NR = {(0.045 x MP) + (WP x 0.84) + {[(212 - 4 x {[(EBG x 1000) / (4 x SRW ^ 0.75)] - 1}) - (140 - 4 x {[(EBG x 1000) / (4 x SRW ^ 0.75)] - 1}) / {1 + exp(-6 x(Z - 0.4))}] x EBG} / 1000 / 6.25

  • Nitrogen excreted in faeces (F): F = {0.3 x (CPI x (1 - [(DMD + 10) / 100])) + 0.105 x (ME x I x 0.008) + 0.08 x (0.045 x MC) + 0.0152 x I} / 6.25

  • Nitrogen excreted in urine (U): U = (CPI / 6.25) - NR - F

  • Nitrous oxide production from animal waste (N): N = ((F x EFf x Cg) + (U x EFu x Cg))

  • Nitrous oxide production from atmospheric deposition (N): N = (F + U) x FracGASM x EF x Cg

  • Nitrous oxide production from runoff and leaching (N): N = (F + U) x FracWET x FracLEACH x EF x Cg

Note: Freer 2007: Crude protein, being total N × 6.25

Parameters:

  • intake –

  • dmd –

  • cp –

Returns:

kilograms of n2o emissions linked to the consumption of x amount of feed - feed component of equation