Life Cycle Assessments

On a daily basis, it is hard to escape the noise of carbon commentaries. Discussions on still largely hypothetical topics like “net zero” and “carbon capture” are frequent. The food we consume, the transport options we choose, the energy we use to heat our homes and offices are all subject to an ongoing dialogue that few understand in depth; all too often we are victims of corporate greenwashing. 

While writing our most recent series “How vets reduce carbon footprints”(currently available on our LinkedIn or Facebook pages) it became increasingly clear that the devil is always in the detail and that the level of detail required is sometimes daunting! How can we know for sure that ‘product x’ has had its carbon footprint recently reduced by 15%?

In the centre of this melee of carbon claim and counter claim lie “life cycle assessments” (LCA’s), a system that attempts to accurately measure the sources and consumption of carbon along a production chain. It is of course quite possible to theoretically model any system but such a methodology will necessarily rely on assumptions and generalisations. Modelling, such as that undertaken by Zhang et al [1] will provide a useful overview of carbon consumption in, for example, food produced from farm animals. But in the real world every farm is different, every geographical region will introduce variations. Standardised models are necessarily inflexible.

Life Cycle Assessments provide a technique for “assessing the environmental aspects and potential impacts associated with a product system or device.” They are subject to ISO standards [2] and are produced from real world data, by carefully measuring the carbon inputs and emissions along a food production system. This is a complex analysis which must first be carefully designed and which is sometimes compromised by the poor availability of quality data. Take for example, milk production on a dairy farm. The production system begins with inputs that produce grass, which will probably include fertilisers, agrochemicals, diesel and farm machinery. There will be energy inputs for milk harvesting, hygiene and cooling, there may be additional inputs for irrigation or housing systems. Additional feed may be imported, either locally or from distant shores, and numerous other inputs will be required before the milk is transported from the farm. This may be a convenient place to draw a boundary line, “at the farm gate”, but if we are examining a particular food product, yoghurt for example, our analysis will have to include subsequent transportation, processing and packaging, as well as aspects of consumption and disposal. It is clear that any LCA must carefully define the categories and limits of its analysis before the detailed data can be collected. 

The data itself can vary in quality and ease of collection. There may be practical considerations which will limit its availability but it is likely that the final figure, which in the case of a dairy farm might be expressed as Kg of CO₂e (carbon dioxide equivalents) per Kg of milk solids, will provide a more realistic representation of the real world situation than a purely theoretical model. 

Once accurately established the data generated by a detailed LCA is still open to debate. As the recent publication by the Sustainable Food Trust, “Grazing Livestock - It’s not the cow but the how” pointed out, any LCA has a necessarily narrow focus which cannot measure other important sustainability aspects such as biodiversity or social implications. And of course the ongoing debate about how best to measure emissions such as methane, rears its ugly head yet again! But a well designed LCA does provide a basis upon which changes in production systems can be developed and progress towards reducing carbon emissions made. In the second part of this article I will present a summary of the detailed work undertaken by AgResearch in New Zealand who have been extensively involved in the LCA of New Zealand dairy production.

Keep an eye out for this article which will be available through our social media channels and website next week.