Defining Sustainability is a question all but rhetorical in nature. It pertains to an almost spiritual relationship between people, animals and the land, unique to each locality, born of the climate, the geography and the culture. Where local tradition and religion once set the boundaries for these relationships, global institutions now grapple with the granularity of these issues.

Miles Middleton: Nuffield Farming Scholar 2022.

Emerging in the nineties as an indicator of environmental sustainability, the carbon footprint has become widely recognised by the public, and in many instances, adopted by the media, commercial entities and by government, as the key metric of environmental sustainability (Laurent & Owsianiak, 2017). 

Fundamentally carbon footprints represent a metric of efficiency, describing the ‘carbon input’ required to produce a standardised unit of output.

The biological complexity of ruminant production systems which encompass multiple outputs as well as the use of co-product inputs, create opportunity for choices and methodological divergence between authors when calculating carbon footprints, to result in significantly differing figures despite comparable source material.(Dalgaard et al., 2014)

Pertaining to the dairy sector, the key factor above all others that drives the carbon footprint of milk is enteric methane, often making up more than half of the carbon footprint (Mc Geough et al., 2012)[fig 1]. This is most commonly calculated using Tier 2 methodology set out by the IPCC (2006) and bases this figure as a direct product of gross energy intake. In light of this, it is clear why feed efficiency is a key determinant of the carbon footprint of milk. It is therefore unsurprising that the correlation between the carbon footprint and profitability is strong (O’Brien et al., 2015).

For farmers seeking to reduce the carbon footprint of milk, the key focus should be to improve overall feed efficiency.

However, while efficiency and sustainability may not be concepts diametrically opposed, the two should not be conflated; Sustainability, is a far broader concept.


Figure 1. Relative proportion of greenhouse gas emissions from the lactating animals over the 6-yr cycle.(Mc Geough et al., 2012)


When asked to define sustainability within the dairy sector, expert stakeholders, largely converged of a set of overarching themes that should characterise a resilient and sustainable dairy sector.

These themes describe a self-perpetuating industry, that can continue in perpetuity, without eroding the natural or social capital upon which the industry, and wider communities, depend upon to function.

Natural capital has been described and defined as encompassing soil health, clean water and biodiversity (Goodland, 1997).

The protection of natural capital is key to the resilience of our food production systems in the face of a changing climate, safeguarding the ability to deliver food while preserving the integrity of the land for future generations (Rockström et al., 2009).

While Livestock systems can play an integral role in restoring and maintaining natural capital (Mcclellan Maaz et al., 2023), what is frequently perceived as the highly intensive nature of dairy farming can create barriers to this and present risk of environmental damage.

The ever-accelerating pursuit of perceived efficiency has had a profound effect on the shape of the dairy sector, consolidating the industry into ever fewer farms, using ever less land but with ever greater dependency on purchased feed, agri-chemical inputs and debt.

The high fixed cost structure of many dairy farms drives the pursuit marginal output. In general terms, nutrient use efficiency follows a law of diminishing returns. Low input, low output systems represented a more efficient use of external nutrient inputs, leading to lower risk of nutrient losses into the environment and lower environmental pressure. (Dentler et al., 2020)

Excessive loss of nutrients into the environment is directly linked to terrestrial and freshwater eutrophication and biodiversity loss.(EU Nitrogen Expert Panel, 2015) 

The use of carbon foot printing as a primary environmental KPI fortifies the drive for efficiency leading to high levels of capitalisation and intensification. As a gauge of sustainability, it has profound limitations.

It is the custodianship of natural capital, not the dependency on purchased inputs that will sustain agriculture and society through a changing climate and a turbulent future.

Dalgaard, R., Schmidt, J., & Flysjö, A. (2014). Generic model for calculating carbon footprint of milk using four different life cycle assessment modelling approaches. Journal of Cleaner Production, 73, 146–153. Click here for more information

Dentler, J., Kiefer, L., Hummler, T., Bahrs, E., & Elsaesser, M. (2020). The Impact of Low-input grass-based and high-input confinement-based dairy systemson food production, environmental protection and reasource use. Agroecology and Sustainable Food Systems, 10.

EU Nitrogen Expert Panel. (2015). (PDF) Nitrogen Use Efficiency (NUE) - an indicator for the utilization of nitrogen in agriculture and food systems Prepared by the EU Nitrogen Expert Panel. Click here for more informaion

Goodland, R. (1997). Environmental sustainability in agriculture: diet matters. Ecological Economics, 23, 189–200.

IPCC. (2006). Chapter 10 Emissions From Livestock and Manure Management. In Forestry and Agriculture (Vol 4).

Laurent, A., & Owsianiak, M. (2017). Potentials and limitations of footprints for gauging environmental sustainability. Current Opinion in Environmental Sustainability, 25, 20–27.Click here for more information

Mc Geough, E., Little, S., Janzen, H., McAllister, T., McGinn, S., & Beauchemin, K. (2012). Life-cycle assessment of greenhouse gas emissions from dairy production in Eastern Canada: A case study. Journal of Dairy Science, 95, 5164–5175. Click here for more information

Mcclellan Maaz, T., Heck, R. H., Glazer, C. T., Loo, M. K., Rivera Zayas, J., Krenz, A., Beckstrom, T., Crow, S. E., & Deenik, J. L. (2023). Measuring the immeasurable: A structural equation modeling approach to assessing soil health. Click here for more information

O’Brien, D., Hennessy, T., Moran, B., & Shalloo, L. (2015). Relating the carbon footprint of milk from Irish dairy farms to economic performance. Journal of Dairy Science, 98(10), 7394–7407. Click here for more information

Rockström, J., Steffen, W., Noone, K., Persson, Å., Chapin, F. S., Lambin, E., Lenton, T. M., Scheffer, M., Folke, C., Schellnhuber, H. J., Nykvist, B., de Wit, C. A., Hughes, T., van der Leeuw, S., Rodhe, H., Sörlin, S., Snyder, P. K., Costanza, R., Svedin, U., … Foley, J. (2009). Planetary Boundaries:Exploring the Safe Operating Space for Humainty [Article]. Ecology and Society, 14(2), 32. Click here for more information

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