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GHG emissions from beef and sheep production are a very significant source of GHGs from UK agriculture.

Of the UK’s total agricultural area (18,819 hectares) grassland contributes the largest proportion with approximately 11,345 hectares of land classified as rough grazing, temporary or permanent pasture in 2020. There is therefore clearly a role for beef and sheep production in the UK to utilise this substantial land area that is unsuitable for cropping. In regards to GHG emissions, reduced stocking rates would immediately reduce the farm’s overall GHG output and consequent CO2e footprint, but may not be the best approach for business security, land-use or habitat safeguarding. Furthermore, there must be consideration for the emission contribution from importing meat products which if are not produced in the UK must be sourced from elsewhere.

The majority of GHGs from beef and sheep are emitted as methane (CH₄) – this is a by product of the ruminant’s digestive process as it converts forage to useful energy. Another significant GHG emission is nitrous oxide (N₂0) which is emitted mainly as a result of fertiliser and manure applications in the process of producing food and bedding used as part of the wider livestock production process. Data collected by the FCT suggest that often the use of diesel, electricity and direct carbon dioxide (CO₂) emissions are less than 10% of a total farm carbon footprint, so in comparison to the afore mentioned emission sources are of lower priority.

Mitigation Strategies:

Improving Overall Efficiencies of the Flock/Herd:

This is the route recommended by the major industry organisations and, where possible to implement, will benefit the farm business as well as reducing farm GHG emissions.

The Scottish Agricultural College have put numbers to a couple of immediate efficiency indicators in beef production systems:

• Reducing calf mortality rates by 5% will reduce GHG emissions by 10% per kg carcass weight.
• Increasing the energy content of ensiled grass by 1MJ/kg DM will improve feed quality and DM intakes resulting in a reduction of GHGs by approximately 6% per kg of carcass weight.
• Teagasc, the Irish research and extension service, estimate that there are differences of over 3x between the ‘worst’ and the ‘best’ beef farms across the range of production systems. They calculate that an extension in the grazing period by two weeks either side of housing cattle can reduce GHG emissions by over 5% due primarily to the reduction of slurry stored and the higher digestibility of grazed grass compared to conserved forage resulting in better live weight gains. They are currently working on a ‘carbon navigator’ tool that will be used by extension workers to assess current KPIs and plot improved efficiency targets for farms to aim at that can be quantified.
• Improved health status, improved feed conversion efficiency and any management changes to increase live weight gain will have corresponding benefits to all aspects of the farm business.
• The opportunities for diet modification are far less than with dairy herds as nearly all beef and sheep are extensively reared with little concentrate inputs. However incorporating legumes (and where possible high sugar rye grasses to increase the feed value of the grass will also benefit both bottom lines.
• The area for greatest GHG reductions is around the application of manures and fertilisers. Any reduction in the use of fertilisers will have a significant effect as N₂O is the most potent of all GHGs. Careful application techniques for manures and careful timing of all applications to avoid putting on more nutrients than can be taken up by plant growth or taken into the soil organic matter will significantly reduce GHG emissions. It is equally important to not apply nutrients to waterlogged soils as N₂O emissions will be very high in these conditions – and you’re losing nearly all the Nitrogen that you’re putting on to feed the pasture.

Replacing Nitrogen Fertilisers with Legumes:

Legumes such as clover have the ability to fix nitrogen and can replace or reduce the need to apply artificial nitrogen. Introducing clovers, or other legumes, into established permanent pasture requires attention to detail but is relatively straightforward to achieve, and, once established they can produce similar amounts of forage to fertilized grass without the cost or GHG emissions.

Manure Storage:

There are a number of studies on how different storage techniques for solids and slurries affect GHG emissions with conflicting results.

Methane producing bacteria thrive in anaerobic conditions and higher temperatures therefore aerating slurry stores, regularly turning muck heaps and emptying the slurry/manure store before the summer will reduce CH₄ emissions. However ammonia and nitrous oxide losses are generally lower in aerated conditions – one study found losses of N₂O to be half from aerated slurry stores than un-aerated stores. It is agreed by all researchers that using a trailing shoe for slurry applications reduces GHG emissions (and nitrogen losses) as immediate soil contact reduces losses of ammonia with consequent reduction in N₂O emissions.

Mob stocking:

Mob stocking is a technique that is being developed in many countries as an alternative pasture management system for beef. It runs counter to the conventional grazing strategies which encourage regular and frequent grazing. In mob stocking the intervals between grazing are 2-3x as long, with the grass much more matured when grazed. The cattle are only on any area of grass for a few days maximum, at very high densities, and trample a significant proportion of the grass into the soil. This ‘wasted’ grass increases soil organic matter content with a corresponding sequestration of carbon. See soil sequestration section for more details.

Further reading:

To find out how to account for sheep in your enterprise head here.

Areas to focus on when improving the efficiency of pork production.

Pig Rearing, Fattening and Breeding

Production of pork produces approximately half the GHGs per kilo of meat compared to beef or lamb since pigs are monogastric and produce only a fraction of the methane of ruminants. However the majority of UK beef and lamb are fed from land that is not suitable for any other agricultural cropping and which is sequestering carbon, while extensive and especially intensive pork production utilises arable crops to produce food with far less efficiency than the direct consumption of those crops. Traditionally pig production was an efficient means of converting inedible waste food and bi-products into food, with current legislation on swill feed meaning that this is not at present possible.

GHG emissions from pig rearing systems are primarily nitrous oxide (N₂O) which in most studies accounts for about half of all GHG emissions with the remainder being equal between methane (CH₄) and carbon dioxide (CO₂).

Emissions from pig production occur from two main sources, the underlying enteric emissions produced when food is broken down during the rearing process (11% GHG contribution) and during manure management. For pig production 20% of the total GHG contribution is from nitrous oxide and a further 69% from methane released from manure.

Feeding

Approximately 50 – 70 % of all GHG emissions are from the growing (and to a lesser extent any processing and transporting) of feedstuffs, this is partly from the production and application of nitrogen fertilisers and partly from the soil processes and GHG emissions inherent in most crop husbandry systems. If the ration contains soya grown overseas is can have much higher emissions associated with its production.

Ensuring optimum feed conversion efficiency is a key aim for all pig farmers along with achieving the optimum productivity from your production system. So attention to feed analysis and diet, minimizing waste and attention to factors that may reduce feed conversion efficiency are standard husbandry practices.

However as the majority (60–70 %) of emissions are from N₂O, reducing the amount of crude protein (CP) in the ration formulation can also have a positive effect on reducing N₂O emissions. In pig rearing approximately 25–40% of all the nitrogen (N) contained in feed rations is converted into proteins and used in animal growth, the other 60–75% is excreted. The higher the levels of N in the manure, the greater the potential there is for ammonia (NH₃) emissions, which can be oxidised to N₂O and therefore subsequent N₂O emissions. A diet with lower levels of CP will potentially result in lower N₂O emissions. There have been a number of studies that have shown that reducing the CP level of the diet by 3% – a 17% CP down to a diet with 14% CP – and supplementing with appropriate amino acids (to ensure sufficient levels of essential amino acids for achieving full growth potential), can result in a reduction of 30% less N excreted, by the animal and up to 40% reduction in N₂O emissions from the manures as slurry or solids.

Manures

There are a variety of strategies that can be employed to reduce the amount of N₂O and CH₄ emissions associated with manure storage and application. The proportion of GHG emissions from each stage will depend very much on the system adopted and the weather and so can be very different between farms and in each year.

Storage

Ensuring that there is adequate slurry storage and land for spreading on so that applications can be best matched to crop growth and nutrient requirements is fundamental.

During storage it is possible to reduce losses of CH₄ and N₂O through specific management of the slurry store and muck heaps, but the amounts of emissions that can be reduced are not clear. Bacterial activity is responsible for the production of CH₄ and ammonia (NH₃) – which is then available to be oxidised to N₂O – and is dependent on a range of factors especially, pH, temperature and the degree of aeration of the store.

The composition of manure heaps, the moisture content and the amount of airflow over the storage will also affect rates of emissions. Covering the surface of a slurry store/muck heap with a plastic sheet has shown to reduce emissions (covering with chopped straw or woodchip doesn’t). Acidifying the slurry store reduces the bacterial activity and has been shown to significantly reduce NH₃ and CH₄ production. Cooler temperatures and regular turning of manure heaps also reduces emissions.

Muck spreading

Best practice during application is generally considered to be always cost effective as it makes maximum use of the nutrients in the manures with minimum GHG losses. Matching nutrients in the slurry to the crop requirements (only spreading slurry in the growing season), not spreading on water logged soils, using a trailing shoe to place the slurry next to the soil rather than spreading onto of land/grass will all significantly reduce N₂O emissions.

Anaerobic digestion

Because pig slurry is higher in undigested feedstuff than cattle slurry, it is more suited to anaerobic digesters. Using the slurry in an AD plant gives a triple win as not only are GHG emissions from slurry storage cut to almost zero, the resulting digestate releases less N₂O on application than slurry or FYM, however applied, and also the carbon in the slurry is used to produce methane which is then captured in the AD plant and used as a renewable source of energy.

Reducing CO₂ emissions and energy savings

The more intensive the production system, the higher the direct energy requirements, the larger the % of GHG emissions as CO₂ and the greater the potential to save money and GHG emissions from energy efficiency measures.

Heating and ventilation are responsible for most energy used in intensive systems. An energy audit will show how much energy is used, where, how your unit compares to similar farms, the areas where efficiencies can be put into place and likely costs and saving from such works. Good insulation, regular equipment maintenance, monitoring actual energy use against expected use and use of energy saving technologies such as heat exchange systems can all help with reducing energy usage and lowering GHG emissions. Whenever significant investment is being planned, looking at the smart ways to reduce GHG emissions, through the redesign of the system along with reducing energy consumption will be a valuable investment and should be a priority in any forward planning.

More information on available strategies to reduce the GHG emissions associated with dairy production.

Dairy farming is responsible for a significant release of GHGs from various aspects throughout the production process. Most of these emissions are from the biological processes that underpin the daily rhythms of the cow, such as feeding and dunging and are inherent in the production of milk. However, as with most complex biological processes, there are a range of factors that influence the scale of these emissions and many of them are open to management changes and improvements.

The most significant emission is from ‘enteric fermentation’ from the cows themselves as the microflora in their rumens breakdown the forage, with the subsequent release of methane (CH4) which is then emitted out by the cow.

Sources of Emissions

According to DairyCo a cow can produce up to 650 litres of methane a day. Researchers at Scottish Agricultural Colleges carried out an assessment from their own farms over 7 years to ascertain levels of methane emissions and found that that almost emissions associated with dairying were due to the release of methane from enteric fermentation with only minor differences between higher and lower forage based systems.

The other major source of GHG emissions is from animal manures and how they are managed prior to eventual incorporation into the soil organic matter. These losses occur as nitrous oxide (N20), methane and ammonia (NH4) and are dependent on how manures are collected and stored and returned to the land. These emissions account for 20–30 % of all GHG emissions.

The remainder of the emissions associated with dairying are from emissions associated from using nitrogen fertilizers, the import of feed and concentrates (and the emissions associated with their production) and the direct use of energy on the farm. Depending on how much nitrogen fertilizer is used, it can account for anything from under 5% to over 30% of all GHG emissions from the farm.

Emissions associated with imported feedstuffs on to farms are around 10% and can be higher depending on the providence of the raw materials – the farther away they have come from the higher the emissions.

GHG emissions from power and fuel use, mainly as carbon dioxide (CO2) are generally around 10% of a dairy farm’s total, see the Energy sections of the Toolkit for more.

Strategies for Reducing Losses from Enteric Fermentation

Approximately 75% of all the energy contained in feedstuffs that the cow eats is converted into CH4 emissions. Methanogenic micro-flora in the rumen use carbon dioxide to soak up the excess hydrogen produced from the breakdown of the forage to produce CH4 in the rumen and hindgut. Research is being carried out on this at present in the UK and overseas to try and get more accurate data and a better understanding of possible mitigation strategies.

It is important to be clear about reduced emissions per animal versus reduction per unit of productivity (milk/live weight gain) as some strategies may increase the total amount of methane produced per animal but reduce the amount produced per litre.

Feed Efficiency

The current advice from organisations such as DairyCo is to concentrate in the first instance on improving the efficiency of milk production through improved feed efficiency which will benefit the bottom line and also effectively reduce GHG emissions per unit of production. The higher the feed intake the more methane is produced but a diet that is optimised to production will mean that relatively less methane is emitted just for internal body maintenance.

DairyCo also recommends paying increased attention to improving overall herd health so as to reduce calf mortality and increase early year growth rates, and improving fertility with a consequent reduction in culling, and clearly all improvements in the herd health status will result in increased levels of milk production.

Feed Mixtures

The other possible opportunity for reducing methane production per animal and per unit of production is through diet alteration either by adding supplements or changing the forage mix.

There are a range of studies that have shown positive results from increasing the legume content of the forage (the tannins and saponins in certain legumes (and other plants such as garlic) appear to have an anti-methanogenic effect), replacing maize with grass forage and increasing the oil content of the feed.

Because methane production is linked to saturated fatty acid synthesis, feed compounds which affect these pathways also influence levels of methane production as fats can also combine with the excess hydrogen in the guts. This area is currently being further researched by both academic institutes and commercial feed manufactures.

Individual cows within the herd will produce significant differences in volume of methane produced for each cow; at lower feed intake levels there can be a difference between animals of 3 times, though this tends to flatten out at higher feed levels. This may present an opportunity to selectively breed for lower emission cows in the future as it is possible to estimate the individual output per cow from a milk analysis.

Growing and feeding high sugar content grasses can also help to both reduce CH4 emissions and reduce N2O losses as the higher sugar content of the diet results in reduced methanogenic activity and allows for better uptake of nitrogen (N) – with less N therefore excreted by the cow and available for N2O emissions.

There is on-going work on breeding clovers with lower protein contents, this is potentially useful for some reduction in N2O emissions as between 50-75% of all N ingested by a cow is excreted in the urine and liable to subsequent conversion through NH3 to N2O and emitted into the atmosphere.

Reducing GHG Emissions from Manure Management

Emissions occur as CH4 and N2O – the most significant being as N2O because of its much higher effect on climate change (‘Global Warming Potential’).

There is limited research to demonstrate the levels of mitigation that can be achieved by different manure management systems and some actions may have opposite effects on the different GHGs.

Storing wastes in a solid form rather than slurry will result in less CH4 but possibly greater N₂O losses and covering any store reduces the amount of CH4 released and possibly N2O as well (by reducing ammonia losses). Therefore from an emissions standpoint it is better to store wastes as solids.

The application of manures to fields can make significant differences to N2O losses. Slurry applied in the spring can result in up to 50% less N2O being emitted. By using a trailing shoe or injecting, further reductions will be obtained as the slurry is placed directly onto the soil, unlike traditional spreading. As with all fertiliser applications, matching the amount of nitrogen required by the crop in the next couple of weeks, to the amount applied, will reduce nutrient losses and improve margins as well as emissions.

As with all fertilizer applications, matching the amount of nitrogen required by the crop in the next couple of weeks, to the amount applied, will reduce nutrient losses and improve margins as well as emissions.

Anaerobic digestion is a triple win for dairy farmers as normal manure storage and application losses are reduced by a third and all the methane is turned into a renewable energy source – see Energy Generation section of the Toolkit.

Reductions through Fertiliser Application / Use of Legumes

The use of nitrogen based fertilizers can be the second or even the largest source of GHG emissions on dairy farms. This is due to the emissions of N2O which, depending on the temperature, moisture content of the soil, rainfall, soil organic matter and grass/crop growth rates can be very high and are very variable. As described in the Fertility section of the Toolkit these losses can be reduced by good management which will also improve the efficient use of the fertilizers and therefore gross margins.

Grassland farmers have a great advantage over arable farmers for making very significant savings on fertilizers by using legumes, primarily clovers, to replace much or all fertilizer use, as demonstrated by organic dairy farmers who are regularly achieving high levels of production of forage without any fertilizers. As fertilizer use accounts for around 20% (and could be much higher or lower) of all GHG emissions from conventional farms, incorporating legumes into grazing swards and using red clover, lucerne or sainfoin for cutting will make a very significant difference to a farms GHG emissions and with careful management will also improve margins as less or no nitrogen based fertilizers are required.

Reductions through imports of feedstuffs

Emissions from imported feeds are generally the fourth greatest cause of emissions on dairy farms at around 10%. These are ‘indirect emissions’ to your farm as they have been generated in the growing of the crops on another farm and also include all emissions associated with the processing and transportation to your farm.

This will be greater on farms that have a lower home grown component to the diet and will be significantly greater if the feedstuffs are grown overseas on land that has been recently converted from pasture or semi natural vegetation to cultivated land, such as some soya. Looking for alternatives to these feedstuffs should be a priority for all farmers concerned about GHGs.

Power and Electrical Efficiencies

CO2 emissions directly from diesel and electricity use are the easiest to quantify accurately and are usually the smallest of all the dairy emissions at around 10%.  Any savings and efficiencies that can be made here will automatically benefit the bottom line and if cost effective should be implemented as a priority.

Machinery operation is covered in the Buildings and Operations section of the Toolkit.

On dairy farms the use of electricity for tank cooling can be greatly reduced with a plate cooler and the heat released from bulk tank cooling of the milk can be reused to heat the hot water for washing round via a heat exchange unit. Both items are easily retrofitted to a parlour and most dairy farmers now have one or the other or even both. Using solar thermal panels to heat the water for the wash round can also now be cost efficient, and more so with either a grant or through the Renewable Heat Incentive scheme. Find out more in the Energy Generation section of the Toolkit.

Further opportunities

All livestock farms have a significant opportunity to sequester carbon in the soil – see the Soil and Sequestration sections of the toolkit.

Summary

There are numerous opportunities for saving emissions and money. There is lots of overlap with operations and energy generation and efficiency, so don’t forget to read those sections too, and of course the opportunities from sequestration.