Practices to reduce emissions

Dairy Australia and partners have been working hard to understand the abatement options for reducing farm emissions. Some ‘possibilities’ have been highlighted within this Toolkit, but Government policies and individual farm situations will influence these options. It is recommended that dairy farmers should focus on current efficiency and profitability rather than directly targeting emissions reductions in the first instance.

At present the best advice to dairy farmers is to follow current best practice for soil, pasture, fertiliser and herd management as this will minimise greenhouse gas emissions per litre of milk.

Existing best practice tools like the Dairy Self-Assessment Tool (Dairy SAT), the Australian Dairy Carbon Calculator and Fert$mart are available to dairy farmers to identify and explore strategies that can be applied to reduce emissions on-farm.

Dairy SAT is an environmental self-assessment and action planning tool for Australian dairy farmers. It covers 10 key topic areas: Soils, Fertilisers, Effluent Management, Irrigation, Greenhouse Gas Emissions, Biodiversity, Energy and Water in the Dairy, Pests and Weeds, Chemicals, and Farm Waste.

The Australian Dairy Carbon Calculator allows farm managers and other users to calculate the impact of adopting different abatement strategies on their total farm GHG emissions and GHG emissions intensity and can help them work out the strategies best suited to their farming system.

Abatement strategies modelled by the calculator fall into four categories; herd management, feeding management, soil management and farm intensification. Modelling shows that any farm efficiency improvement will lower GHG emissions/t MS.

Some suggested practices for reducing emissions have been provided below.

  • Methane

    At this point there is limited opportunity to establish ‘forestry plantings’ with the intent of gaining a credit for the sequestered carbon. Dairy farms are usually small, intensively managed properties with little of the land class where Government modelling indicates that forestry plantings for carbon sequestration may be economic – i.e. marginal and lowly productive farmland.

    On the other hand, many dairy farms have small areas, including riparian zones, where revegetation for conservation purposes is already encouraged and common, and where an additional benefit from carbon sequestration may be available for existing or new plantings.

  • Reproduction efficiency
    SOURCE: PDCCF fact sheets on 'Getting herd and breeding management right' - underpinning science and farmer case study.

    Applying best practice management to improve herd longevity, fertility, transition cow management and health can have major effects on lifetime cow productivity, and therefore profitability and farm emissions intensity.

    Cow in field  Video: Using genetics to reduce greenhouse gas emissions 
    Understanding the Australian Breeding Value for feed conversion
    Cows feeding  Video: Taking care of cows 
    Keeping your cows healthy for welfare, profit and emissions mgt

    Key points

    • Heifers and unproductive animals cost money to maintain, and continue to produce greenhouse gas emissions during their unproductive periods

    • Reducing the amount of time that cows are unproductive will reduce farm emissions

    • The key ways to reduce unproductive periods are through timely mating, fertility, reducing replacement rates and increasing lifetime cow production.

    Suggested practices for maximising reproduction efficiency (‘herd management’)

    • Improve longevity, fertility, time to first calf, transition cow management and herd health to reduce replacement rates, increase lifetime animal productivity and profitability, and reduce emissions intensity

      • Reduce herd size to minimise total emissions

      • Reduce the number of unproductive animals to increase efficiency

      • Extended lactations reduces the number of dry cows

      • Extended longevity in the herd reduces replacement rates

    • Improve feed conversion efficiency to reduce input costs and emissions (per litre of milk)

    • Animal breeding for lower emissions

    • Balanced crude protein in the diet to reduce urinary N and nitrous oxide emissions

    • Rumen manipulation to reduce the abundance of methane producing microbes.

  • Feed efficiency
    SOURCE: PDCCF fact sheets on 'Getting the diet right' - underpinning science and farmer case study.

    Greenhouse gas emissions are highest per kg of milk solids when cows are fed poor quality diets. High quality, high digestibility feed will maximise milk production and minimise greenhouse gas emissions per kg of milk solids.

    Pasture and sky  Video: High quality feed 
    The importance of quality feed for digestion and reducing emissions
    Calf in field  Video: Forage crops for dairy 
    Overview of the results from using forage beet in WA
    Pasture and nitrogen  Video: Green seeker - Fert$mart nitrogen 
    How to source accurate plant nitrogen measurements
    Cows near trees  Video: Pasture digestibility 
    Growing quality rye grass for milk production and reducing emissions

    Suggested practices for feed efficiency (‘feeding management’):

      Monitor and supplement diets to ensure nutritional requirements are met when pasture quality is low

    • Use low protein, high energy supplements when pastures are high in nitrogen to improve milk production efficiency, avoid excessive dietary nitrogen and minimise nitrous oxide emissions

    • Include fats and oils as feed supplements to increase milk production if dietary fat levels are below 2-3%, to reduce methane emissions

    • Maximise diet digestibility to reduce methane production*

    • Balance energy and protein contents to minimise nitrous oxide emissions from urine

    • Pasture breeding** may offer improvements in feed quality and in rumen methane or urinary N production.

    Note there is already an Emissions Reductions Fund Method - Feeding dietary fats and oils.

    *Note, however, that while improvements in diet quality can reduce methane emissions per litre of milk produced, they often act to increase total farm methane emissions. This is because milk production per cow increases, but cow numbers often go up to take advantage of the higher quantity and quality of feed. Thus, making changes to reduce emissions would require analysis of the impacts on productivity and profit.

    **Traditionally, pasture breeding has focussed on increasing dry matter yields and the longevity of sown pastures. These are still vital traits, but now that the ability to manipulate plant genes has dramatically increased, plant breeders in Australia are working on mechanisms that significantly increase the digestibility of pasture species. Though many years away, increasing the digestibility of ryegrass is being investigated, with studies on fescue and C4 grasses to follow.

  • Nitrogen management
    SOURCE: PDCCF fact sheets on 'Getting nitrogen fertiliser right' - underpinning science and farmer case study.

    Nitrogen fertiliser use is essential in most dairy systems but the low efficiency of its use means that more than 60% of nitrogen added to pasture systems is lost to the environment.

    With nitrogen efficiency often below optimum in dairy systems, there are a number of practical ways farmers can better match their nitrogen fertiliser applications with pasture demand, other inputs and prevailing conditions – and therefore reduce input costs.

    Pasture and sky  Video: High quality kikuyu pastures 
    Secrets to growing high quality kikuyu pastures
    Crop off drain Video: Drainage planning - wet areas on dairy farms 
    Managing wet areas through drainage

    Practical advice on soil and fertiliser management is available via Fert$mart website.

    Key points:

    • Poor nitrogen fertiliser management increases greenhouse gas emissions and wastes money

    • Strategic use of nitrogen – when plants will respond and when extra feed is needed – saves money, time and emissions

    • Poor irrigation and soil management practices will lead to loss of nitrogen from the system, including some as nitrous oxide.

    Suggested practices for nutrient management:

    • Use best practice nitrogen fertiliser management to reduce nitrogen loss, and improve nitrogen use efficiency and therefore profitability of nitrogen use

    • Avoid high rates of nitrogen fertiliser, especially when soils are warm and close to field capacity

    • Use best practice soil and irrigation management practices (irrigation and drainage) to make the best use of water, reduce soil inundation and minimise loss of nitrogen from the soil

    • Reduce grazing on wet soils when urine patches will be most likely to emit nitrous oxide

    • Nitrification inhibitors (on fertiliser, fed to cows, or applied to pastures as a spray) can reduce soil N loss as nitrous oxide.

  • Effluent management
    SOURCE: PDCCF fact sheets on 'Getting effluent right' - underpinning science and farmer case study.

    Although effluent management comprises typically only 8% of total farm greenhouse gas emissions, managing effluent storage and re-use to minimise emissions can provide broader benefits for on-farm efficiency, profitability and the environment. By viewing effluent as a valuable source of nutrients rather than a waste product there are opportunities to save money on fertiliser, improve soil fertility and condition, and minimise the risk of water pollution, as well as reduce emissions.

    Dairy farmers in dairy Video: Fert$mart effluent - Effluent as fertiliser
    Information on good management of effluent on dairy farms
    Digging dirt cows Video: Keep it low - managing manure
    How to minimise emissions from the effluent pond

    See also Effluent and manure management database for the Australian dairy industry, Fert$mart website and RIRDC report on Creating energy from effluent.

    Key points:

    • Effluent should be viewed as a valuable source of nutrients which can be recycled into the system to offset fertiliser inputs, save money and reduce emissions

    • Reducing effluent volume will significantly reduce methane emissions from ponds

    • Methane capture technologies are highly effective at reducing emissions from effluent, but aren’t currently economically feasible in typical, grazing-based Australian dairy systems

    • Management of effluent beyond the pond system will influence nitrous oxide and ammonia emissions and environmental pollution.

    Key recommendations:

    • Use effluent and soil tests to match re-use applications with soil fertility deficits and plant requirements

    • Spread effluent regularly, over large areas of the farm to allow better utilisation of nutrients, and minimise the likelihood of nutrient overload and nutrient rich runoff

    • Apply best-practice nitrogen management to effluent re-use to minimise nitrous oxide and ammonia emissions and other forms of nitrogen pollution.

    Visit Dairying for Tomorrow for detailed information on effluent management, including short video clips and fact sheets on the following topics:

    • Making the most of effluent

    • Avoiding problems with effluent management

    • The value of effluent

    • Effluent system design

    • Minimising effluent volumes

    • Managing storage levels

    • Planning a new pond

    • Constructing a pond – soil testing

    • Pond de-sludging

    • Managing manure.

  • Managing heat stress
    Cool Cows is full of suggestions to help cows cope in hot weather.

    Many people are surprised to hear it doesn’t take really high temperatures to trigger heat stress in dairy cows. They start to feel uncomfortable once temperatures hit 23 degrees Celsius, which means heat stress is an issue in all Australian dairying regions.

    Heat stress is not just about daily maximum temperature either - the length or severity of hot conditions and humidity also contribute to the effect. It can cause a drop in milk production, reduced herd fertility and lower milk protein and fat tests. It can also trigger live weight losses and create animal health problems.

    Some heat stress strategies are simple, quick and cheap to put in place, while others are longer term, involving more cost and effort.

    Cows under trees  Video: Keeping cows cool 
    Three different approaches to managing heat stress

    Suggested practices for keeping cows cool:

    • Provision of shade and evaporative cooling

    • Minimise distance cows walk for milking/feed/shade

    • Hot season strategies

    • Monitor how the herd is coping with the heat.

    Dairy Australia is conducting a study into latest international science on heat stress and appropriate management strategies in 2016/17.

  • Storing carbon in trees

    At this point there is limited opportunity to establish ‘forestry plantings’ with the intent of gaining a credit for the sequestered carbon. Dairy farms are usually small, intensively managed properties with little of the land class where Government modelling indicates that forestry plantings for carbon sequestration may be economic – i.e. marginal and lowly productive farmland.

    On the other hand, many dairy farms have small areas, including riparian zones, where revegetation for conservation purposes is already encouraged and common, and where an additional benefit from carbon sequestration may be available for existing or new plantings.

  • Storing carbon in the soil
    What is soil carbon sequestration?

    Soil carbon sequestration is the process of transferring carbon from atmospheric carbon dioxide into plant material, some of which is added to the soil carbon store as dead plant material or animal waste.

    Soil is a complex mixture of organic compounds at different stages of decomposition. Soil organic carbon is divided into different ‘pools’ that are classified according to their rate of decomposition – as shown in Figure below.

    The amount of carbon in the soil depends on:

    • The climate and soil fertility: fertile soils in high rainfall zones (or with irrigation) can support high levels of plant growth and therefore have the potential to return large amounts of organic matter to the soil. The proportion of organic matter returned to the soil that is used for respiration by soil organisms depends on the soil temperature (higher temperatures, more respiration) and soil water content. The climate and soil therefore set the upper limit for soil carbon sequestration.

    • The agricultural production system: more carbon tends to build up under pastures than under crops.

    • Management: When soils are ploughed or otherwise disturbed, soil carbon previously protected from microbial action is decomposed rapidly. Systems that encourage the addition of plant litter to the soil (eg stubble retention or lax grazing) have some potential increase the soil organic matter pool and eventually the soil carbon content but the rates of change are slow (see below).

    McKenzie 2010

    Figure: A simplified illustration of the carbon cycle in soil. Source: McKenzie 2010.

    Dairy farmers have no control over their climate, little effective control over their soil fertility (most dairy soils are already highly fertile) and have a production system based on grazed pastures. Management is therefore the only significant option if dairy farmers wish to increase soil carbon.

    In conclusion:

    • Well managed dairy pastures are generally regarded to be close to their physical storage capacity - so significant permanent addition is unlikely.

    • Australian soils are relatively dry and warm – this significantly limits the ability to build carbon content in the soil.

    • Soil carbon can be increased by growing additional dry matter - or for already highly producing pastures by allowing more pasture to decompose. Adding carbon (e.g. biochar) is also possible but that would be a cost to dairy farmers (not a source of income).

    • Raising soil carbon in the top 10cm of soil by 1% over 5 years would require adding to the soil more than 10 t DM/Ha above current levels – this is clearly impossible even for dairy pastures.

    • The potential price of carbon would need to be very high (over $200/t) to deliver a better return as soil carbon compared to using it for feed in milk production.

    • Building soil carbon requires significant nutrient inputs (especially N, P, S). If these have to be applied to raise soil carbon the fertiliser cost must be taken into account in any analysis.

    • Under certain climate conditions soil carbon increases could lead to higher emissions of nitrous oxide (another powerful greenhouse gas). This could see greenhouse emissions from participating farms increase.

    • It is expensive to accurately measure soil carbon with current technology and if the farmer has to pay for this ‘verification’ then cheaper methods would need to be developed.

    • Soil carbon can change significantly with changes in weather, soil moisture, land use etc. This raises the question of what is the risk for farmers claiming credits at one point in time if they are audited later under different climate/land use and have to repay.

    • The requirement to retain claimed carbon in soil for at least 100 years has implications for long term land use options, the value of land, and the passing of obligations across generations. For example, a shift from perennial pasture to annual cropping in response to other factors such as water availability, temperature, markets etc can reduce soil carbon and hence may lead to an obligation on farmers to re-purchase carbon permits for “claimed carbon credits” that are subsequently “lost”.

    Management practices that might increase soil carbon on dairy farms

    The magnitude and rate of soil organic carbon decomposition and sequestration depends on a range of soil and environmental factors.

    To boost organic carbon concentrations in soil, two main options are available: reduce the decomposition and/or improve the rate of addition of organic materials.

    In theory any management practice that increases pasture production should lead to increased soil carbon because of the associated increase in plant material (roots and litter) and animal dung. Practices such as fertiliser application, improved rotational grazing, irrigation, and improved pasture species all have the potential to increase pasture production and thus soil carbon – though the impacts can be small and slow (see text box about the long term P experiment). Application of dairy effluent and sludge to pasture will also provide additional carbon inputs to the system.

    These activities are already ‘best practice’ on most Australian dairy farms because of the impact that increasing soil fertility and pasture production has on farm profit. Therefore while some farmers may have the option of implementing these management practices, for most the opportunities to significantly boost soil carbon will be limited and if they are already considered good or best practice, such sequestration does not meet the requirement for ‘additionality’.

    For those dairy farmers who grow crops and make silage, minimum tillage systems will reduce the rate of soil carbon decline in cropping paddocks - again minimum tillage is already best practice for most soil types.

    What about Bio-Char?

    Bio-char is a charcoal like material produced by the pyrolysis (heating to between 350-600°C under limited oxygen) of organic matter. This converts easily-decomposable organic matter into a highly stable (i.e. biologically and chemically stable) form of carbon that potentially has both soil improvement and carbon sequestration benefits.

    Biochar is the solid by-product resulting from bioenergy production (Figure below). The pyrolysis conditions can be optimised for bioenergy or biochar production.

    CSIRO 2009

    Figure: Biochar, especially when combined with bioenergy production, can result in net removal of carbon from the atmosphere. Source: CSIRO 2009.

    Biomass (‘feedstock’) for biochar production can comprise most urban, agricultural and forestry biomass such as wood chips, saw dust, tree bark, corn stover, rice or peanut hulls, paper mill sludge, animal manure and biosolids.

    There are many issues and challenges to overcome before the production of bio-char becomes a practical carbon sequestration option for dairy farmers. However, some large dairy farms and feedlots may produce sufficient manure from dairy effluent to make biogas generation from methane an option. For more information on biogas in dairy systems download the Fact sheet: Biogas feasibility.

    See also Emissions Reductions Fund method - Destruction of methane generated from dairy manure in covered anaerobic ponds.

  • References

    The full series of PDCCF fact sheets are available on Reports page.

    Other references: