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The Oireachtas committee on climate change, the chair of the Climate Change Advisory Council and Minister for Climate Action Richard Bruton have all recently endorsed Teagasc’s 2018 study on the greenhouse gas “marginal abatement cost curve” (MACC). This is scientific jargon for the answer to this question: how much greenhouse gas can we cut from agriculture, and how much would that cost?
Teagasc measured the potential of farming practices and technologies proven to lower emissions in Ireland over the next decade. During that period, Ireland has committed to bringing its combined greenhouse gases from agriculture, transport and heating 20% under 2005 levels. Researchers found 27 actions farmers can take to contribute to this target, but two are ruled out because they may fail EU sustainability criteria (growing crops to produce biodiesel and bioethanol fuels).
Implementing the remaining 25 would have a net cost of €34m/year, to be shared between farmers and government, and could cut farm emissions by over a third. Yet as production increases, agriculture would still not achieve a 20% cut by 2030.
Improved beef maternal traits
Better calf health and survival, lower feeding and calving interval improve sucklers’ footprint. This assumes a €1.67/year improvement in the maternal replacement index, returning €32m to farmers over 10 years.
Beef genetics: improved liveweight gain
Producing the same beef from fewer, more efficient cattle can cut emissions and increase profitability by €13m. BDGP’s €300m cost is not included in these two measures.
Dairy EBI
This measure assumes the average EBI will rise to €180 by 2025 and the average farm will produce 570,000l at almost 3.6% fat and 4.25% protein.
Extended grazing
Livestock out at grass have lower emissions from their rumen, from slurry and from machinery to make silage. The benefits would be greater than the cost of extra drainage work.
Nitrogen use efficiency
This measure assumes that 429,000ha, representing one-third of acidic soils, receive 7.5t/ha of lime, reducing the need for N fertiliser.
Improved animal health
Healthy cattle have higher productivity and lower wasted emissions. The worst offenders are Johne’s in dairy and BVD in beef. Another win-win.
Sexed semen
Restricting purebred dairy calves to females only would increase the number of beef cross calves out of dairy herds, reducing the suckler herd and its emissions.
Inclusion of clover in pasture swards
This measure assumes that 25% of beef farms and 15% of dairy farms broadcast clover seeds over existing grass swards, improving soil carbon and reducing nitrogen fertiliser requirements.
Fertiliser type
Switching 50% of CAN and all existing urea to protected urea holds the single largest potential to cut emissions in farming, at an additional cost of €4.2m/year.
Reduced crude protein in pig feed
Each 1% cut in crude protein content in pig rations reduces nitrous oxide emissions from their slurry by 10%. This measures assumes a 4% cut.
Draining wet mineral soils
Improving drainage reduces emissions from fertiliser and slurry, with increased grass growth partly offsetting the cost. This, however, should be avoided on organic soils (see below).
Slurry additives
Acids such as alum or ferric chloride costing €250-300/t reduce emissions of both greenhouse gases and ammonia from pig and cattle slurry during storage.
Adding lipids/fatty acids to dairy diets
A 3% dry matter (DM) fat supplementation acts on cattle digestion and reduces methane emissions by 10%. Milking gives dairy farmers a chance to feed oils to cows year-round.
Low-emission slurry spreading
Trailing hoses and shoes help reduce both ammonia and indirect nitrous oxide emissions. This measure targets 50% low-emission spreading, mostly by contractors.
Grassland management
Farmers can increase grass growth and the amount of carbon stored by grassland through fine-tuning of fertilising and reseeding, while limiting soil compaction and monitoring swards more closely.
Re-wetting soils
Drained organic soils release carbon dioxide. Re-wetting 40,000ha of such grassland, or converting 65,000ha of deep to shallow drained soils, would cut those emissions, but poorer grass growth would cost farmers nearly €5m in additional feed.
Forestry
This measure assumes a large increase in afforestation to 7,000ha each year, resulting in the single largest cut to greenhouse gases in the MACC as new trees continue to absorb carbon dioxide after 2030.
Tillage cover crops
Catch crops such as mustard not only reduce nitrate leaching, they also increase soil organic matter.
Ploughing in straw
This assumes 25% of the tillage area having straw incorporated, increasing soil organic carbon and sequestration of carbon dioxide from the atmosphere – but at a high cost.
Farm energy saving
Using plate coolers, heat exchangers and variable speed drives in milking parlours, and solar panels to produce some of their own power, farmers can replace fossil fuels while saving money.
Wood biomass for energy generation
The supply of pulpwood from forest thinnings and residues will boom in the coming decade, providing fuel to replace oil, gas or peat.
Short-rotation willow and miscanthus biomass for heat production
This measure assumes the conversion of 15,000ha of grassland to willow and miscanthus, with the new renewable heat scheme supporting demand, but warns that this business is “uncertain”.
Willow for electricity production
Willow chips are already co-fired at Edenderry power station and 9,000ha are assumed to be planted for this purpose, generating an estimated margin of €196/ha.
Anaerobic digestion
Biogas production can save emissions by replacing fossil fuels to produce electricity and heat, and improving slurry management. It would require large amounts of grass and a 14c/kWh tariff on top of the wholesale electricity price in this scenario.
Biomethane
This represents the upgrading of biogas from 50 anaerobic digestion plants to the standard required for injection into the national gas network, with large capital costs involved.
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