The nutritional value of meat must be considered when comparing carbon footprints, researchers have said in a new scientific paper.
It focused on different lamb production systems, from low-input pastoral systems to higher-input systems for the latter ‘finishing’ period.
To date, no studies have explored the effect of finishing diet on the carbon footprint of lamb meat on a nutritional basis.
Lamb can be a valuable source of polyunsaturated fatty acids (PUFAs), such as omega-3 and omega-6 fatty acids, which play an important part in human health.
Data was collected from 33 farms that finished lambs on one of four distinct diets: forage crops, grass, concentrates, or grass and concentrates.
This data was then used to estimate the carbon footprint of lamb produced from each system.
The level of PUFAs in two important cuts of lamb were then monitored, to determine the carbon footprint per unit of omega-3 PUFA.
When a conventional mass-based functional unit was employed, lambs finished on grass diets had on average the highest carbon footprint.
However, when omega-3 PUFA content was accounted for, the grass diet had the lowest carbon footprint for cuts from the loin.
The research, published in the journal Frontiers in Sustainable Food Systems, used data from the Welsh Lamb Meat Quality project.
The study was undertaken by Hybu Cig Cymru – Meat Promotion Wales (HCC), Queen’s University, Bangor University and the Agri-Food and Biosciences Institute (AFBI).
Dr Eleri Thomas, who co-wrote the paper and is HCC's policy development executive, said the results were great news for the sector.
"We know that lamb production systems are under increasing pressure to reduce their environmental footprint, particularly emissions of greenhouse gases (GHGs).
"However, current metrics used to express the carbon footprint of lamb seldom consider its nutritional density and contribution to balanced diets in humans.”
Elizabeth Swancott, research officer for HCC, explained that typically, carbon footprint assessment of farms used mass-based units, which can be useful for comparing efficiencies of different farming systems.
"However, they do not reflect how farming systems impact the nutritional differences of the final product," she said.
"This study demonstrates the importance of considering nutrition when expressing and comparing the carbon footprints of nutrient-dense foods such as lamb.
"This approach will help inform discussions around the optimal diets for lamb production systems from both a human nutrition and environmental sustainability perspective."
