Sunday, June 27, 2010

Is there enough Lithium on earth to make all cars run on batteries?

I've now heard this from several people: "While electric cars like the Tesla are a great idea, there's not enough lithium on earth to replace all gasoline driven cars with electric ones."

Not Quite Enough
I spent some time investigating this and found this paper: "The Trouble with Lithium". It argues that while there is enough lithium in the earth's crust to make all cars run on lithium ion batteries, not enough of it is extractable:
  • The world automotive fleet is 1 billion vehicles worldwide.
  • A battery electric vehicle needs at least a 30 kWh battery to be usable (30 kWh will go for 120 miles or around 190 kilometers).
  • A lithium-ion battery requires between 1.4 and 1.5kg of lithium carbonate (Li2CO3) per kWh of capacity. That's between 42 or 45 kg of lithium carbonate per car.
  • To equip all cars in the world with lithium batteries, we will need (conservatively) 42 billion kg of lithium carbonate. That's 42 megatons ("MT") of Li2CO3.
  • The paper estimates the global reserve base - the total amount of known lithium in the earth's crust - of lithium carbonate to be 58 MT, which would cover it. 
  • Of these 58 MT of Li2CO3, we currently know how to extract about 27 MT. That's not enough to turn all cars into all-electric vehicles.
However, keep in mind that all these numbers stem from a time before the discovery of vast mineral riches in Afghanistan. But I couldn't dig up numbers about how much lithium was discovered. This USGS report from 2007 lists out detailed megaton estimates for most metals that were discovered, but provides no estimate for lithium.

Leaving aside Afghanistan, South American countries hold about 80% of the world's lithium reserve base. If the world was to switch from oil to lithium-ion batteries, it's possible that South America could turn into the next Middle East. Bolivia, the country with the most reserves, is one of the poorest and least developed countries in South America, and not a close ally of the US. Since China has plenty of lithium deposits in Tibet, "the USA would again become dependent on external sources of supply of a strategic mineral while China would have a certain degree of self sufficiency."

Lithium ion batteries are light and have high energy densities. But they're not the only alternative. For example, zinc-air batteries are relatively light but hard to recharge. You need 39 MT of zinc to equip the world's cars with a 30 kWh battery. Contrast those 39 MT with the global reserve base of zinc, which clocks in at 1.4 BT - there's plenty of to go around. However, zinc-air batteries are a little harder than lithium-ion batteries to recharge, and only allow for 500 recharges. Yet they're much cheaper to manufacture, which may be their ultimate reason to succeed.

Thus, while we may not be able to mine enough lithium to make all cars run on lithium-ion batteries, it's entirely conceivable to replace all the world's gasoline-guzzling cars with vehicles powered by batteries of some kind.