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News Article

New research methodology shows significant reduction in carbon footprint of British pig farms

All environmental impacts reduced, with 37% and 35% reductions for indoor and outdoor bred pigs, respectively

According to a new study published in Agricultural Systems, the carbon footprint of British pig farming has fallen by almost 40% over the last 20 years. The study, led by the Institute for Global Food Security (IGFS) at Queen’s University Belfast, used new methodology to conduct the analysis.

Historic data on livestock systems across England, Scotland and Wales were used in the study. The sparse data available on agricultural inputs led to the development of a new research methodology in which outputs were used to retrospectively estimate inputs, a process known as ‘inverted modelling’. Although Northern Ireland was not included in the study, there are plans to extend the methodology to NI in the near future.

Agricultural systems worldwide are under pressure to reduce their carbon footprint, with the UK government setting a target of ‘carbon neutral’ farming by 2050.

Calculating the carbon footprint of a farming system is a complex metric involving a large number of indicators including the kind of fuel used on the farm, the manner in which soil is cultivated, the style of land management and the types of animals and crops farmed.

Despite the fact that the environmental impact contribution per unit of meat from pig systems is relatively low, pig meat is the meat type most produced and consumed globally thereby contributing significantly to several forms of environmental impacts. In 2013 it was estimated that the total contribution of pig systems to greenhouse gas (GHG) emissions was 668 million tonnes CO2 , about 10% of GHG emissions produced by livestock systems overall.

Pig farming is considered to be a major contributor to the acidification and eutrophication of the environment due to nitrogen and phosphorus emissions from manure storage and spreading.

In this latest study, an overall fall in carbon footprint was observed across the pig farming sector, breaking down, for indoor and outdoor-bred pigs respectively, to reductions of 37.0% and 35.4% for Global Warming Potential (commonly known as carbon footprint); 21.2% and 16.4% for Terrestrial Acidification Potential; 22.5% and 22.3% for Freshwater Eutrophication Potential; and 15.8% and 16.8% for Agricultural Land Use.

Animal feed was found to be central to the environmental impact of pig farms – accounting for 75-80% of the carbon footprint. Changes to feed ingredients, therefore, had the potential to significantly alter the carbon rating of pig farms and the industry as a whole. Specifically, the increasing trend of replacing soya imported from South America (which has a high environmental footprint associated with deforestation) with home-grown crops such as rapeseed and sunflower meal to feed pigs was found to have a significant mitigating effect on environmental outputs.

Advances in animal nutrition and availability of feedstuff were also found to have had a beneficial effect, particularly the increased availability of synthetic amino acids and enzymes, the price of which decreased over the time period in question. When added to domestic feedstuffs like rapeseed, these supplementary ingredients increased nutrient availability and improved feed balance, which was found to have reduced nutrient excretion in manure whilst boosting animal productivity by as much as 30%.

The study also found that such supplements in animal feed helped lower levels of phosphorous in run-off from pig manure by more than 20%, reducing the contribution of pig systems to freshwater pollution.

Changes in performance due to breeding for leaner and faster growing pigs, increases in number of piglets born per sow per litter and reductions in overall mortality were also found to have contributed significantly to the reduced environmental impact. Advances in breeding leaner and faster-growing pigs alone was found to lower carbon footprint by 20%.

The study was led by Professor Ilias Kyriazakis from IGFS in collaboration with other UK institutions, interrogating publicly available Agriculture and Horticulture Development Board (AHDB) data from Great Britain from 2000-2020. He believes it is the first time inverted modelling has been used to investigate the environmental impact of any livestock system.

According to Professor Kyriazakis, the research findings are significant because they show an area of livestock farming where carbon footprint has been reducing over the past 20 years, almost ‘under the radar’. He said that more attention is currently focussed on ruminant food systems in view of their higher GHG emissions. He believes that there are important lessons to be learned from this study, not only for better environmental management as it relates to pig farming, but potentially for all livestock systems. Some of the improvements identified in this study could, he said potentially be applied to other animal systems, which would ultimately help move current collective agriculture systems towards a carbon-neutral model.

Ottosen M, Mackenzie SG, Filipe JAN, Misiura MM, Kyriazakis I. Changes in the environmental impacts of pig production systems in Great Britain over the last 18 years. Agricultural Systems (2021) 189: 103063,

Article details

  • Date
  • 10 March 2021
  • Source
  • Institute for Global Food Security (QUB)
  • Subject(s)
  • Animal breeding and genetics
  • Animal nutrition