Huge potential to lower emissions, claims AFBI scientist

The beef sector is the predominant source of greenhouse gas emissions within the ruminant animal sector in NI, but there are huge opportunities to lower emissions going forward, AFBI director Dr Elizabeth Magowan has claimed.

Giving a presentation during the third in a series of four webinars looking at the sustainability of the NI beef industry, Magowan said that the event should be seen as a “call to action around accelerated adoption of known technologies” to reduce emissions on farms.

Those “known technologies” principally relate to good practice, such as correcting soil pH using lime, calving heifers at two years and rotational grazing of swards.

Ultimately the aim is to increase efficiency and reduce emissions per kg of beef produced.

Methane

The main greenhouse gas from beef production is methane produced as a result of the rumination process, and from manure management. It accounts for over half of beef emissions.

Nitrous oxide, mainly released after spreading inorganic nitrogen or organic manure is next at just under 25%, followed by carbon dioxide which accounts for around 22%.

Longer-term, there are also scientific advances that will help to lower emissions, said Magowan. They include novel and alternative feeds which reduce the output of methane from ruminants, new technology that will detect sickness in animals earlier, and new inorganic fertiliser formulations that reduce nitrous oxide emissions.

But she also acknowledged that getting to low or net zero carbon emissions will be a significant challenge for the beef sector as a whole.

Legislation

That fact is recognised in the proposed DAERA climate change legislation currently with MLAs at Stormont, which would set a 2050 target for NI to reduce emissions by at least 82% compared to 1990 levels. In 2050, remaining emissions would almost exclusively be from agriculture, and methane in particular.

However, the alternative private member’s bill taken forward by Green party leader Clare Bailey sets a net zero emissions target by 2045, and to achieve that, various experts have warned that NI beef, sheep and dairy numbers would need to be drastically cut.

The latest DAREA statistics show that from 1990 to 2019, NI greenhouse gas emissions are down 18%. The biggest reductions have been in energy supply and waste management sectors. However, while most are falling, agriculture is up 7%, mainly due to an expanding dairy herd over the period.

That expansion in dairy numbers has perhaps contributed to a general nervousness within local policy makers when considering new ways of accounting for the Global Warming Potential (GWP) of various greenhouse gases.

It is widely acknowledged that the current GWP100 system does not accurately account for the short atmospheric life span of methane, which breaks down in the atmosphere after 12 years, as compared with carbon dioxide from fossil fuel burning which remains for centuries.

The alternative of GWP* considers methane’s different global warming effect when compared to other greenhouse gases. In simple terms, methane released by cattle today is replacing methane released 12 years ago, so if herd numbers are stable, there is no additional global warming effect.

But where cattle numbers are rising, more methane is being added than being lost, and the global warming impact of this additional methane is significant.

“There is a lot of new evidence coming out, and there are positives and negatives for it [GWP*]. It has a positive impact from a calculation perspective, but only when methane emissions are falling,” noted Elizabeth Magowan.

Land can be a sink for carbon

Under the current government system of accounting for carbon emissions, figures are broken down by sector, with agriculture separate to that known as “land use, land use change, and forestry” (LULUCF).

It means that in official data, carbon sequestered in soils, hedges or trees does not directly offset emissions from farming.

“To be fair, at governmental level, they look at everything in the round, and they do appreciate that it is agricultural practices that are managing the land. It is not missed that agriculture plays a significant part in the LULUCF sector,” maintained Dr Elizabeth Magowan.

However, the latest DAERA statistics suggest that LULUCF in NI is not actually bringing in more carbon than it emits, principally due to carbon being lost from cropland and from wetlands (eg when it is drained, or when peat is extracted).

“It is an area we need to work on to make it a net sink going forward,” said Magowan.

Big range in carbon calculators

Various companies now offer calculators to work out the carbon footprint on farms and there is a wide range of calculators in development, Dr Elizabeth Magowan told attendees at last Thursday’s webinar.

“Calculators can vary in their quality. Some will be better than others. All of them need to be continuously worked on to improve accuracy. There is a need for harmonisation and government are looking at that,” she said.

At present, CAFRE is using Agrecalc, a carbon footprint tool developed in Scotland by SAC Consulting together with SRUC researchers.

According to Aleathea Brown from CAFRE, it was chosen because it measures whole farm emissions, not just from one enterprise.

Soils and hedgerows

However, while it does account for carbon sequestered by woodland, it does not as yet, account for carbon sequestered by soils or hedgerows.

“They are getting launched early next year,” confirmed Brown.

Carbon benchmarking is currently offered to farmers in the environmental Business Development Group (BDG) programme as part of a pilot, but will be rolled out to other BDG groups “hopefully in the near future,” she added.

Carbon-efficient is good business sense

Of the beef farmers participating in the environmental Business Development Group (BDG) programme who have already completed a carbon benchmark, over 50% of emissions are due to methane released either directly by ruminants, or from manure management.

Explaining the data, CAFRE’s Phelim Connolly confirmed that the remaining emissions were mainly from nitrous oxide released when fertiliser or slurry is spread, and carbon dioxide either from when fuel is burned, or associated with inputs brought on to the farm.

He said that there are a number of areas farmers can focus on to reduce methane and nitrous oxide emissions per kg of beef produced, and in particular, better nutrient and livestock management.

“They are win-wins for farmers in terms of increasing profitability while simultaneously reducing carbon emissions,” said Connolly.

Top of his list is soil pH, with analysis of over 6,000 soil samples taken by BDG farmers showing that only 7% were at the optimum level for soil fertility (pH, P and K). A total of 43% of grassland in NI (excluding rough grazing) requires lime.

At a pH of 5 to 5.5, over 30% of chemical fertiliser is effectively wasted, and where pH is 5.5 to 6, this figure sits at 21%. In addition, clover has an important role in reducing reliance on fertiliser, but requires pH to be at 6.3.

Slurry

When it comes to reducing nitrous oxide emissions, Connolly said that slurry should ideally be spread in cooler and duller weather in the spring, and applied using low-emission spreading equipment.

Farmers should also consider a switch from CAN to protected urea, as it has an inhibitor which significantly lowers nitrous oxide losses.

Grazing

In terms of grassland management, to make the most out of farm inputs, Connolly said that farmers should switch to rotational grazing.

“Up to 50% of NI farmers still operate set stocked systems. However, AFBI research shows that dry matter per hectare can be increased from 6 to 10t without any additional inputs,” said Connolly.

He also highlighted the importance of making good quality silage and targeting this at the most productive stock.

“Reducing concentrate use will have a positive impact on carbon emissions,” he added.

In suckler herds, Connolly emphasised the importance of good fertility and removing problem cows.

He said that the farms that consistently have better carbon efficiency have more calves per cow per year, lower mortality rates, calve heifers at two years old, higher weight gains and high health status.

“Being carbon efficient is good business sense. Carbon footprinting highlights the waste in a system and allows you to do something about it,” he concluded.

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