ch4 emission in agriculture, estimates and mitigation

p. 1Expert Group “Methane Emissions in Agriculture”s J.L. Peyraud 28 May 2021

CH4 emission in agriculture, estimates

and mitigation practices

J.L. Peyraud


General considerations

on methane emissions


On farm GHG emission of Livestock sector

Sectors % total

AgricultureLivestock

107

Industry* 38

Transport 21

Tertiary 12

* Including manufacture of mineral N fertilizerEuropean Environment Agency, 2019 - mean 2003-2018

Livestock emissions(Gt CO2-eq)

Europe 0.25

World 8.144

95

37

8

(FAO, 2019)

https://www.eea.europa.eu/data-and-maps/data/data-viewers/greenhouse-gases-viewer,

• Reducing agricultural GHG emissions would require as a priority diminishing enteric CH4 and soil N2O emissions.


Cattle number (Eu-15)

Evolution of on farm CH4 emission of EU livestock sector

Enteric + manure CH4 (Tg/an)

CH4 livestock (% CH4 total)

- 1.5 %/year

https://www.eea.europa.eu/data-and-maps/data/data-viewers/greenhouse-gases-viewer (2021)

https://www.eea.europa.eu/data-and-maps/data/data-viewers/greenhouse-gases-viewer


• The calculation of CO2-eq misrepresents the role of CH4 in global warming• Biogenic CH4 is part of a natural C cycle• CH4 is a short life (9±2 y) vs CO2 and N20 • CH4 do not accumulate in the atmosphere if

the rate of emission is constant• N2O still continue to accumulate even

though emissions are slowly being reduced

Rethinking CH4: livestock’s path to climate neutrality

• What consequences? • No additional warming if the rate of CH4 emission is constant or decrease !

• Reducing CH4 emissions will have a very important short-term effect (cooling effect ≈

storage of C as planting trees): an opportunity for the ruminant to reach climate neutrality

• Avoid any increase in emissions (and therefore in ruminant numbers)


Emissions sources in bovine farms

• Enteric CH4

• Manure management (CH4, N2O)• Feed production (N2O)• Machinery & energy (CO2)


Mitigation practices


Reduction of livestock production

• A rapid reduction of emissions according to the Tier 1 method

• But unintended effects may arise

• Increase in global CH4 emissions • Decrease in grassland area with subsequent soil C and biodiversity losses

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p. 9Autonomie en protéines pour l’élevage français : Quelles perspectives J.L. Peyraud

Enteric CH4: Feed additives

Mitigation(%/kg product)

Comments

PUFA (omega-3) • 15 to 20%, • Persistent effect

• Increase nutritional value of milk and meat• Distribution (extensive systems)?

Chemical inhibitors: (methyl) 3NOP (DSM)

• 20 to 30%, • Persistent effect

• Residues in animal products? • Not yet marketed• Distribution?

Tannins • 0 to < 20 % (trefoil) • Effects depends of the origin of tannins• Other unexpected effects on digestion (+/-)

Red algae • Up to 80% (Roque et al., 2021) • Need to be confirmed

• Consequences on the production cost, market valuation?

(adapted from Doreau et al, 2011; Patra et al, 2017)

p. 10Autonomie en protéines pour l’élevage français : Quelles perspectives J.L. Peyraud

Enteric CH4: Feeding practices


Comments

Use of forage legumes • 5% (Luscher et al., 2014)

• Persistent effect• Mitigation of N2O• Protein autonomy whatever the system

High proportion of starchy concentrate

• 0 to 10% (dairy) (INRAe, 2018)

• < 10% beef production• Feed vs food competition, cost • Acidosis

Precision livestock feeding

• 10% ? • Avoid overconsumption of feed• Intensive systems with confined animals

Modifying the microbial ecosystem

• ? • Need to be explored. First results areencouraging


Enteric CH4: Herd management


Comments

Low emitting animals • ? • Antagonism with the efficiency of digestion: The most efficient animals seem to have better cellulose digestibility and produce more CH4

(Renan et al., 2016 ; Mc Donnell et al., 2016)

Age at first calving (28-30 to 24 months)

• 5 : dairy sector • More difficult for beef sector (breed precocity)

Culling rate (35-40 to 25%) • 10% dairy sector • Very few possibilities for suckler cows

CH4/DMI

LWG/DMI


Manure CH4 : Ruminants and non ruminants

Mitigation(% manure emission)

Comments

Reduction of storage time • 10% • Reduction of NH3 emission

Rapid burial • < 10% • Reduction of NH3 emission

Biogas production • Huge potential : A production potential of primary energy close to French hydroelectric production (Elba, 2018).


Soil C sequestration

• C Sequestration represents compensation in a range of 20 to 60% of C footprint or 40 to 80% of enteric CH4

• Potential for additional sequestration

4P1000 study (Pellerin et al., 2019)

Direct seeding

Insertion of cover crops

Organic amendments

Crops rotation with grasslands

C sequestration (Mg C/ha/year)

0 0.2 0.4 0.6

• Livestock and grassland have strong potential for increasing soil C sequestration


- 50% GHG

(CH4)

N2O emissions

En & protein

autonomy

Bio-diversity

+ 25% Organic farming

National inventories

Reduction of ruminant production + 0/- + - + +

Methane inhibitors + 0 0 0 0 -

Use of forage legumes + + + + + -

Precision livestock farming + + + 0/+ 0 -

Age at first calving reduced culling rate + + + 0 + +

Smart use of manure + + + 0/+ + + (EF)

Biogas production + + + 0 0 +

Soil C sequestration + 0 0 0 0 +

Are there winning strategies between CH4 mitigation

practices and other objectives of the Green deal?


How to facilitate adoption of

mitigation practices?


Role of public policies and actors of the supply chains

Comments

Tax meat (GHG and health) • Mitigation of N2O not considered• Transfer to non ruminant meat (increase in feed vs food

competition) and/or to cheaper ultra-processed food

Tax GHG emissions • Tackle the 2 major GHG sources : livestock and mineral fertilizers• N2O tax > CH4 tax (long vs short live pollutant)

Certified emission reduction units, “C market”

• Positive approach, farmers are paid for progress• On farm implementation of mitigation projects (Hyland et al., 2017)

• PP: approbation of practices, certification of diagnostic tools• The interest will increase with the price of C

C labelling • Private actors can differentiate themselves

Rewarding grassland for the public goods they provide

• Soil C sequestration, preservation of biodiversity

(Peyraud and Mc Leod, 2021)


Take home messages


• CH4 mitigation options

• While intense research into enteric emission mitigation is conducted few commercially proven and cost-effective solution are yet available: from experiment to real live (lower mitigation…• Feed additive seems to be efficient• Precision livestock farming: need further evaluation beyond the proof of concept,• Low emitting animals, manipulation of microbial ecosystem: still prospective,

• Some win-win practices: use of legume forage, improved herd management (cow longevity and health), smart use of manure, production of green energy,

• Improving practices are generally easier to deploy in intensive systems than in extensive systems for which it is essential to account for the C sequestration in the inventories

• Most of the practices have additive effects.

• Public policies to stimulate the development of mitigation practices • Rethinking the role of CH4 in climate change: different policies could be set for CH4 and N2O,

• Developing, stimulating positive approaches for the farmer point of view vs new tax

• The different tools are not mutually exclusive,

• Implementation of practices well adapted to the local context (C market) make progress more

difficult to trace back in national inventories,

ch4 emission in agriculture, estimates and mitigation

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