On-farm greenhouse gas emissions Tony van der Weerden AgResearch, - - PowerPoint PPT Presentation

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On-farm greenhouse gas emissions Tony van der Weerden AgResearch, - - PowerPoint PPT Presentation

Jan 27, 2023 866 likes •1.12k views

On-farm greenhouse gas emissions Tony van der Weerden AgResearch, Invermay Energy from Dairy Effluent workshop, 22 April 2015 NZs GHG profile Proportion from each sector (2012) Agriculture 7% 5% 46% Energy 42% Industrial

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On-farm greenhouse gas emissions

Tony van der Weerden AgResearch, Invermay ‘Energy from Dairy Effluent’ workshop, 22 April 2015

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NZ’s GHG profile

NZ: unique profile - agriculture dominant source Gross emissions: 70,000 Gg CO2-e Net emissions: 49,500 Gg CO2-e (due to CO2 removal by forests) (Ireland closest profile: ~33% from agriculture)

46% 42% 7% 5%

Proportion from each sector (2012)

Agriculture Energy Industrial processes Waste

Source: NZ’s GHG Inventory. MfE, 2014

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Not all greenhouse gases are equal...

Gas Global warming potential Carbon dioxide (CO2) 1 Methane (CH4) 25 Nitrous oxide (N2O) 298

One kg of methane is 25 times as potent as one kg of carbon dioxide, or 1 kg CH4 = 25 kg CO2 equivalents

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NZ’s GHG profile

NZ: unique profile - agriculture dominant source Gross emissions: 70,000 Gg CO2-e Net emissions: 49,500 Gg CO2-e (due to CO2 removal by forests) (Ireland closest profile: ~33% from agriculture)

46% 42% 7% 5%

Proportion from each sector (2012)

Agriculture Energy Industrial processes Waste

Source: NZ’s GHG Inventory. MfE, 2014

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SLIDE 5

GHG by sector

Source: NZ’s GHG Inventory. MfE, 2014

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Contribution of dairying: livestock numbers

Increasing dairy cattle, decreasing sheep & beef

Source: StatsNZ

2012: 50% of agricultural GHG emissions from dairying

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Dominant gases & sources:

Enteric 96% Dung 2% Effluent 2%

GHG emissions from dairying

Grazing 72% N fertiliser 25% Effluent to soil 3% Methane 65% Nitrous Oxide 35%

Methane (CH4) Nitrous oxide (N2O)

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Methane

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How is enteric fermentation methane produced?

Volatile Fatty Acids production FEED Hydrogen

Methane

Rumen microbes=methanogens

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AgResearch Grasslands, Palmerston North

Methane

How is enteric fermentation methane measured?

SF6 technology Respiration chambers

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Nitrous oxide

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How is nitrous oxide produced?

Nitrification Denitrification

N2O

N2O

Naturally occurring soil processes Soil bacteria and fungi convert nitrogen to N2O Enhanced by:

  • nitrogen inputs
  • wet or compacted soil conditions

Nitrate Animal urine Urea fertiliser Ammonium

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Sources of GHG on a ‘typical’ dairy farms in Waikato & Southland

Description Waikato Southland Effective farm area (ha) 180 300 Effluent block 27 65 Cows/ha 3.2 2.7 Kg MS/cow 420 350 Kg MS/ha 1344 945 N fertiliser kg N/ha 140 140

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Sources of GHG on average dairy farm e.g. Waikato, Southland

Sources of GHG on a ‘typical’ Waikato dairy farm

Source: Overseer

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Sources of GHG on average dairy farm e.g. Waikato, Southland

Sources of GHG on a ‘typical’ Southland dairy farm

Source: Overseer

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Comparing Waikato & Southland dairy farms

Source: Overseer

GHG intensity:

  • ratio of GHG emission and farm

annual MS production.

  • Good measure of a farm’s

efficiency. Waikato 8.4 kg CO2-e/ kg MS Southland 9.3 kg CO2-e/ kg MS

Waikato Southland

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  • Animal breeding – selection of low CH4 emitters
  • Diet manipulation (increased dietary fat, brassicas)
  • Rumen manipulation (biological control, inhibitors,

vaccines)

CH4 mitigation options

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SLIDE 18
  • Reducing dietary N (e.g. maize silage, tannins)
  • N urea fertiliser: reduced rate, better timing
  • Improve N conversion efficiency in rumen ( N in

excreta,  MS/cow)

  • Avoid grazing wet soils (feed-pads or housing)

N2O mitigation options

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Feed pads – 27% Stand-off pads – 22% Animal shelters – 2% Winter barns – <1%

Luo et al., 2013

Off-paddock facilities (slowly) on the rise….

2004: Approx. 6% of dairy excreta deposited off-paddock 2015: more, but data not available on how much more

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Drivers for increased use of off-paddock facilities

  • Avoid grazing wet soils → reduce N2O emissions*
  • Limiting N leaching → off-paddock an option.
  • Protect soil structure, pasture production.
  • Increasing dairy intensification - most common dairy

system: 10-20% of feed as supplements. More off-paddock facilities……but costly.

* Currently no incentive

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Pugging

increase moisture content

Compaction

SOIL MOISTURE: driver for treading damage and nitrous oxide emissions

increase nitrous oxide emissions

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When to stand-off?

N2O N2O N2O

Effluent ponds Effluent application Off-paddock facility

‘pollution swapping’

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Summary

  • Agriculture is largest source of NZ GHG; dairying

represents 50% of total ag emissions

  • Dairy farms: Methane from enteric fermentation and

Nitrous oxide from soils most important sources (~97% of total emissions)

  • Most promising short-term mitigation options:
  • reduced dietary N,
  • improve N conversion efficiency,
  • selection of low CH4 emitters