In a study published in the journal Nature Communications researchers from the Technical University of Munich calculated the environmental impact of various foodstuffs based on greenhouse gas emissions.
For beef and lamb, organic and conventional production resulted in similar climate impact, the study found. Organic chicken was slightly worse for the climate and organic pork slightly better than their conventional counterparts, it added.
Conventional livestock’s emissions come from manure and the release of methane. Animal feed crops can also be associated with high emissions, such as soy from South America. Organic livestock are not given imported industrial feed and instead are fed more climate friendly organic fodder. They also tend to be grass-fed, which leads to the preservation of CO2 sinks, which absorb carbon dioxide from the atmosphere.
However, the study said this means organic livestock produce less meat – meaning more animals must be raised to meet demand -- and grows more slowly, and therefore spend more time emitting greenhouse gasses before slaughter.
The researchers concluded that organic regulations prescribe “a certain amount of land per animal, which is higher compared to average conventional production, as well as a higher living age and lower productivity of organically produced feed and raised animals… This counterbalances or even reverses the described positive aspects of organic animal farming.”
But the Soil Association, the UK’s largest organic certification body, claimed the study establishes that organic products have lower emissions in the three categories considered (animal, dairy, and plant foods) compared to conventional, partly because organic generates living, carbon-rich soils that do not require the application fossil fuel fertilisers.
"The study notes that conventional meat and dairy have a carbon footprint associated with imported feed, which is absent in organic systems, and the authors conclude that organic farming has lower emissions per kilogram of foodstuff. The authors emphasise that the yield difference between organic and conventional means that organic requires a greater land area, and this carries a potential carbon cost, hence the need for dietary change," Rob Percival, Head of Policy, Soil Association, told FoodNavigator.
He added that the study highlights the many benefits of organic farming.“Look beyond the headlines, and this study actually adds to the case for organic. It looks at policy measures that might close the gap between current market prices and the true environmental costs of food – and it emphatically recognises the benefits of organic. The authors point to the positive impact a shift towards organic plant-based foods would have on health and well-being, as well as outlining the wider benefits of a transition to organic farming for ecosystems and the long-term productivity of land. We already knew an organic farming system would require a move towards less and better meat, and this report emphasises that organic plant foods have the lowest greenhouse gas emissions of any food category.
The study, he added, also underlines that “soil degradation resulting from conventional systems would slow down or could even be reversed by changing to organic farming”, noting organic farming’s lower soil-borne greenhouse emissions and higher rates of carbon sequestration. Far from being a dismissal of organic, this paper highlights the many benefits of organic farming, and the potential for pricing mechanisms to deliver a fair deal for farmers and citizens in an organic future.”
Richard Young, policy director at the Sustainable Food Trust, told FoodNavigator that the method used in the German study to assess methane emissions gives a ‘distorted picture’. He complained the researchers relied on GWP100 rather than GWP* methodology to assess the impact of methane emissions. (The time period usually used for calculating GWPs, or global warming potential, is 100 years. GWP*, an alternative application of GWPs where the CO2-equivalence of short-lived climate pollutant emissions is predominantly determined by changes in their emission rate.)
“In doing so, they ignore the significance of methane’s short atmospheric lifetime in comparison with the long (over 100 years) lifetime of nitrous oxide emissions and the indefinite lifetime of CO2 emissions.”
This, he said, overestimates the actual warming impact of methane three-fold when emissions are broadly stable (as is the case in the EU). “As a result, systems like organic farming, which include a significant proportion of grazing livestock as part of their fertility building phase, inevitably appear to have a higher carbon footprint than conventional equivalents, when in practice the opposite will be the case.”
Young pointed to research by Professor Myles Allen and colleagues at Oxford University which has claimed that GWP* gives by far the most accurate indication of the actual warming impact of methane emissions and that, while a herd of cattle which remains the same size over 20 years produces a constant level of warming, it does not increase global warming in any significant way.
Young added: “A further criticism of the study is that, like many other similar studies, the researchers fail to take account of historic soil carbon losses associated with all-arable farming systems, which are very much higher than those on organic farms where soil carbon levels are generally maintained and sometimes actually increased.”