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Homepage / What producing a carbon footprint from scratch has taught me: Perfection shouldn’t be the enemy of the good, but the devil’s in the detail!

What producing a carbon footprint from scratch has taught me: Perfection shouldn’t be the enemy of the good, but the devil’s in the detail!


My five-year-old often asks me – “Daddy, what do you do when you go to work?” – quickly followed by musings about whether I’m stronger than his friend Max’s Daddy, who arrests ‘baddies’ and if I will be home in time for Bluey (a brilliant Australian cartoon about a family of Blue Heeler dogs!).

It’s been nice, therefore, to be able to point to products on supermarket shelves and tell my son that I help to make sure the people who make them are treated fairly, whilst looking after our planet – something which has become easier to do lately, given the growing number of on-pack sustainability logos and claims.

Historically, sustainability messages on products were fairly limited, internationally certified and stayed away from things like ‘carbon footprints’, which were a bit of a niche for the technically minded. Praise, though, must be given to the likes of Tesco, who some of us may recall trialled carbon labelling of several own-brand products back in 2008.

These days a trip to the supermarket can be an overwhelming experience, while perusing the number of carbon claims on products, which can be either ‘carbon neutral’, ‘net zero’ or even ‘carbon negative’.

I recently completed a module as part of my Sustainability Masters at Cranfield, which has been both the most challenging, and insightful, module to date, as it included developing – from scratch – a carbon footprint for a good or service of our choice, without the ability to tap into a ‘ready-to-use’ database of emission factors. To support this project, and my ongoing work to establish a carbon reduction plan within Princes, I conducted an assessment of carbon footprint consultancies.

Many of these do a great job and clearly play an important role in helping organisations to understand their emissions and how to prioritise reducing these. What I’ve found, however, is that like all claims, the devil is in the detail and the detail is not that easy to find for a sustainability practitioner, let alone a consumer.

Having previously relied on the insights and recommendations given by our carbon data specialists, some reflections on what I’ve learned include:

  1. Carbon footprinting is complicated

If a carbon footprint is the ‘cradle to grave’ snapshot of a product or service from raw material through to disposal, it genuinely is a minefield in terms of assessing the various inputs, processes and outputs.

If we take olive oil as an example, it’s end consumption and therefore carbon impact can vary massively – from being used as a dip for bread, through to cooking potatoes for the weekly roast. How then can we reasonably and accurately measure the output processes?

Then there’s the potential waste and disposal of the oil to consider, alongside associated packaging and consumer recycle rates – all of which is challenging to measure.

  1. It’s time intensive

Accurately mapping and measuring a full carbon footprint system from scratch is, our lecturer advised, a multi-year project typically undertaken as part of doctoral theses – time many of us can ill afford when the 2030 SDG Goals feel like they’re around the corner.

  1. They might not be as accurate as we’d like to think

As a result, we are all relying on ‘guestimates’ or, to put it more scientifically, ‘proxies’, to provide an indication of a carbon footprint. This can mean using emissions data that is very old or specific to a certain production technique in a certain part of the world.

Even in the simple harvesting of olives for olive oil, there are inevitably so many variances in the number of trees per acre, annual yields, mechanical versus traditional harvesting approaches, where and how any agrichemicals may be applied and how they were sourced.

In summary…

I guess that brings us back to the age-old question: what is the best way to talk to consumers about sustainability messages on-pack? Have too many brands jumped on setting a net zero target without fully understanding what it means and how to get there?

If I were a consultant, I would insert my solution at this point, but the reality is that I’m just trying to navigate my way through this sea of data, claims and counter claims as I suspect many readers of this blog might be.

The recent focus from the Competition and Market Authority (CMA) on fashion brands’ sustainability claims1 and requirements around the Green Claims Code may lead to a clarity of sustainability claims, but it’s unlikely to see any significant alignment of approach.

All of this, of course, is on the back of calls along the same lines of a recent The Economist article, stating that Environmental, Social and Governance (ESG) criteria should be ‘boiled down’ into one simple measure: emissions2.  If only it were so simple, and we could reliably trust all the data at our fingertips.

In the absence of limited to no data, the use of proxies makes sense.  However, my challenge to readers and those involved in using carbon footprints would be to:

  • Check the sources of the data and their age. The latest Government emission factors for transport is likely to be accurate, as emissions from some vehicles are comparative – irrespective of location. However using emission factors developed ten years ago using a different production process isn’t going to give a very accurate picture. Where possible, use the supply base for primary data sources. You might be surprised at how carefully they are monitoring, for example, energy use in stages of production. That said, make sure you do a comparison to sense-check their calculations.
  • How complete is your dataset? Do you have values for most of the pertinent elements of your production lifecycle? I’m in the lucky position as part of my course to have access to the latest academic journals, but if you don’t, check what your database source has and how up-to-date it is.
  • Do a rough and ready estimate yourself of where you think most of the carbon emissions will be found within the supply chain. There are lots of guides out there to help, such as PAS 2050 as a starting point.
  • How complete is the footprint? I’ve seen countless measures of footprints resulting from a packaging element change (e.g. moving from glass to plastic can reduce the footprint by x amount) when actually they only meant to refer to the packaging element of the total lifecycle.  What about comparing the nutrient density of products, which is often overlooked when it comes to low carbon alternatives?
  • Remember to think about the impacts beyond the carbon ‘tunnel vision’. Whilst one product may have a favourable carbon footprint versus another, what about the water footprint, social impact or economic impact as a broader set of considerations?
  • Do some research into product losses and co-products produced from waste at different stages as these may all significantly lower the carbon footprint than just changing the packaging format of the finished SKU. For example, within olive oil, it’s common to find raw materials can be used for manufacturing bricks, cement paste and pharmaceutical products.
  • Beware the reliance on how carbon neutrality or net zero is being achieved. There is growing attention on the limitation of carbon off-sets, ‘phantom forests’3 and the like, so be sure to interrogate the entire plan – even if it’s set by 2040 or 2050.

None of us want perfection to be the enemy of the good and inhibit progress and communication on sustainability issues to consumers. I personally don’t believe that most brands intend to mislead consumers with their carbon footprint claims, however without knowing how and when to challenge claims and the plans to realise net zero goals, we mustn’t fall into the temptation of outsourcing the strategy to an external database which doesn’t paint a true picture of the issue.

At Princes, we’ve taken a steady approach to understanding and mapping out our footprint before making any net zero commitments, and we will continue to be transparent with our customers about the limitations as we find them.  We’re at the stage of mapping our value chains to understand largest greenhouse gas emitters by category and at some point by product, as part of our work in setting Science Based Targets and a net zero goal for our group  (and carbon neutrality for our manufacturing sites by 2030).

We believe in conveying the right messaging to consumers, but more importantly, ensuring we have the right level of due diligence, evidence and reassurance behind any product claims. Otherwise, how can we reliably point to products on shelves and say to our children with conviction that we trust them?


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Paul Williams, Cranfield University

Paul Williams

Written By: Lina Mitchell

Currently Global Head of Sustainability at international food and drink group Princes, Paul Williams leads the company’s environmental and social sustainability approach across its supply chains. Paul is a Board member and Director of the Ethical Trading Initiative and Food Network for Ethical Trade. He is also a Chartered Environmentalist, and Member of both the Chartered Institute of Procurement and Supply (CIPS) and Institute for Environmental Management & Assessment (IEMA). He is currently studying the Sustainability MSc.

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