One Dollar Coin: What’s the Footprint?
Ask Pablo: Do $1 Coins Have A Smaller Footprint Than $1 Bills?
Dear Pablo: Does the one dollar coin have a smaller footprint than $1 bills and what is the environmental impact of the $1 coins that the US Mint is supposedly stockpiling?
On the one hand paper money is lighter and cheaper to make but, on the other hand, coins last a lot longer. Let’s find out which has a lower footprint. We’ll also learn what’s behind the Mint’s stockpile of the unwanted one dollar coin.
National Public Radio (NPR) has recently reported on the Federal Reserve’s $1 Billion stash of $1 coins that nobody wants. NPR reports that “the coins are the wasteful byproducts of a third failed congressional effort to get Americans to use one-dollar coins in everyday commerce.” The current incarnation of the one dollar coin features presidential portraits, George Washington through Ulysses S. Grant so far, and 20% of US coins are required to carry the image of Sacagawea.
US $1 coins weigh 8.1 grams are made from copper (88.5%) with a manganese brass cladding (6% zinc, 3.5% manganese, and 2% nickel).
So the $1 billion in coins contain:
7,168.5 metric tons of copper, worth at least $63.2 million dollars at today’s prices,
486 metric tons of zinc, worth $1 million,
283.5 metric tons of manganese, worth $1 million, and
162 metric tons of nickel, worth $3.5 million.
A formal Life Cycle Assessment (LCA) on the $1 coin and banknote was performed back in 2007 by students at Michigan State University, before the current stockpile was minted. Their study was intended to answer “which is better, coin or paper?” and looks at the entire life-cycle of coins and paper money, from resource extraction all the way through to recycling/disposal.
What Is The Impact Of Making The Coins?
The impact of making the coins extends far beyond the US Mint. The impact begins with resource extraction, namely mining. Mining can result in erosion, siltation of streams, contamination from leachates and processing chemicals, and many other impacts, not to mention the human impact. One of the easiest impacts to quantify is the impact on climate change through emissions of greenhouse gasses (GHG) associated with each material. The GHG emissions from the copper alone can be estimated at around 14,840 metric tonnes of CO2-equivalents, or the equivalent of 2,700 average US passenger vehicles.
What Is The Impact Of Making Dollar Bills
A US $1 banknote weighs only 0.917 grams and is not actually made from paper pulp but rather from 75% cotton and 25% linen (the fibers from a flax plant). The environmental impacts of growing cotton are well known; herbicide/pesticide use, heavy water use, and the use of defoliant chemicals. While coins tend to last many years or even decades, the average dollar is replaced after 42 months of circulation due to wear. After this it is partially recycled into roofing material but mostly sent to the landfill. On the other hand, dollar coins remain in circulation about 17 times longer and are fully recyclable in the end.
The GHG emissions associated with the materials in a US dollar can be estimated at around 3 grams of CO2-equivalents, so the emissions are about one fifth that of the coins. When you take into account the longer lifespan of the coins though, the benefits of coins become clear. The coins cause only one third the greenhouse gas emissions as the equivalent US Dollar bills.
What Is The Impact Of Coin Weight?
When the $1 coins are finally released their heavier weight will have a small incremental, yet potentially significant impact on transportation emissions. This is not only the case when coins are transported from the US Mint to Reserve Banks and individual retail banks, but also in the weight that they add to our own transportation footprint. The emissions from air travel, for example, are highly dependent on the weight being transported. This may seem trivial but just imagine if every American commercial air travel passenger carried just one $1 coin over the 500 million passenger-miles traveled last year. If some airline have considered urging passengers to empty their bladders prior to departure then a couple of grams per customer in excess coinage must also have an impact. In aggregate, this would result in an estimated 1,350 kilograms of extra GHG emissions! Ok, so that’s only one quarter of the emissions of the average US passenger vehicle, so the US Dollar coin is still environmentally preferable.
The bottom line is that few people want heavy coins weighing down their pockets and purses, as is evidenced by the growing stockpile of unwanted coins in the US Mint’s vaults. But one organization is working to change that. The Dollar Coin Alliance is trying to promote the use of dollar coins for their environmental and economic advantages. But today less and less people are using cash anyway. Maybe we should be asking “what’s better for the environment, paper cash, the one dollar coin, or credit?” Maybe we will answer that question next time…
Pablo Päster is a weekly columnist for TreeHugger.com and Principal Environmental Consultant at Hara Software.