Miles that inputs to the production of tennis balls used at Wimbledon are transported (source: The Guardian)

The tennis balls used at Wimbledon were made locally up until 10 years ago (in Barnsley) but are now made in Bataan in the Phillipines. According to Dr Mark Johnson from Warwick Business School, the inputs required to manufacture them come from 11 countries and collectively travel 50,000 miles (80,000 km).

This is yet another example of the complex globalisation of supply chains. It’s also another illustration of how different places specialise in the production of certain goods. New Zealand, for example, is extraordinarily good at producing high quality wool, but it seems Stroud in the UK is better at turning it into the felt used in premium tennis balls.

According to business environment website EdieWaste, it’s also another instance of how the environmental impact associated with globalisation is ignored. It says “Wimbledon tennis balls serve up (a) vast carbon footprint”.

Environment writer for The Guardian, Damien Carrington, echoes the environmental risk:

The problem here is a simple one. Monetary cost has been minimised but, with such a vast footprint, it seems very unlikely that the environmental cost has been even close to minimised. It is a striking example of how failing to ensure that manufacturers pay the true cost of their environmental impact can lead to extraordinary supply chains in a globalised world.

The New Zealand wool is shipped 11,815 miles to Stroud. It’s turned into felt and then shipped 6,720 miles to the factory in Bataan. When they’re finished, the tennis balls are shipped 6,660 miles to Wimbledon.

I don’t know anything specific about the manufacture of tennis balls, but this sort of argument is familiar from the “food miles” debate. We’re urged to buy food locally to avoid the enormous carbon emissions supposedly associated with very long supply chains. For example, researchers found food travels 2,500 miles on average in the US before it’s purchased.

However as I’ve discussed before (e.g. see here and here), there are a number of reasons why buying locally is on average probably the least reliable guide to buying food on a sustainable basis.

Bulk shipping is remarkably efficient in terms of emissions per kilogram. According to one estimate, it takes a tablespoon of diesel fuel to move one pound of freight 3,000 miles by rail. Sea travel is even more efficient, with emissions per tonne km up to 30 times less than trucks.

The vast bulk of emissions associated with agriculture occur on farms and in factories. Transport is a relatively small component – around 4% – of the total carbon emissions from agriculture.

Most food can’t be grown in most places without resorting to potentially environmentally damaging practices like excessive application of fertiliser, irrigation or artificial heating of greenhouses. Locations that have some comparative advantage for a particular foodstuff are likely to be environmentally more efficient.

This article cites a British study which found that because British tomatoes are grown in heated greenhouses, they emit 2.4 metric tons of carbon dioxide per ton grown whereas Spanish tomatoes emit 0.6 tons. Further:

Another study found that cold storage of British apples produced more carbon dioxide than shipping New Zealand apples by sea to London. In addition, U.K. dairy farmers use twice as much energy to produce a metric ton of milk solids than do New Zealand farmers.

Marxist writer and activist Greg Sharzer points out in his new book No Local that Kenyan rose growers produce less carbon dioxide than Dutch growers. Large scale container and rail shipping means importing frozen fish to the UK emits less carbon than growing fresh fish locally. He says “the distance between farm and market isn’t an accurate gauge of environmental costs.”

I expect there’re strong parallels between food and the manufacture of goods. In fact the inputs required for tennis balls – like clay and wool – might well be cheaper to ship than food as they require less demanding environmental controls.

Also, the reason clay used to make tennis balls is cheaper to import might be because clay in the USA is cleaner and easier to extract than it is in the UK (or Bataan). If so, that could mean it requires less energy to collect and process.

The “50,000 miles” figure is misleading. Adding all the miles for tennis ball inputs together without weighting them by the relative quantities involved doesn’t provide an accurate figure. For example, some of the quantities (Magnesium carbonate?) might be quite small. Wool and felt account for 37% of that 50,000 miles yet their respective contributions by weight to the manufacture of a tennis ball isn’t explained.

Damien Carrington appears to have equated distance with emissions. I can’t say if that is or isn’t true in the specific case of the tennis balls produced for Wimbledon, but as a general rule simply adding the raw miles together overlooks a lot of other considerations.

As with food, the bulk of emissions associated with goods are likely to come, on average, from manufacturing rather than from transportation. And it should be borne in mind that the key source of emission associated with Wimbledon isn’t tennis balls or scones, but rather all those patrons travelling within and to the UK for the event.

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It’s neither here nor there really, but if it’s assumed the input source countries remain the same, it appears from the exhibit that there are fewer (unweighted) miles associated with manufacturing tennis balls in Bataan than in Barnsley. Differences in environmental regulation might be a more significant factor.