You don't understand what is meant by the phrase:...

You don't understand what is meant by the phrase: environmentally sustainable.

It refers to the impact on the environment your production has not the effect the environment might have on your production.

Spodumene Production:
I am no expert but I imagine open pit mining is hugely detrimental to the environment and requires significant energy. Then there is conversion:

Table I. Material and energy inputs for the production of 1 tonne of lithium carbonate from Spodumene
Materials Amount Units
Spodumene (Li2OÆAl2O3Æ4SiO2) 1.34 tonnes
Sulfuric acid (H2SO4) 0.48 tonnes
Soda ash (Na2CO3) 0.52 tonnes
Water (H2O) 24.00 tonnes
Utilities Natural gas 1.66 GJ
Electricity* 1.01 GJ


Brine Production:
Relies essentially on the sun to do most of the work.

"The extraction of lithium carbonate (Li2CO3) from Salars generates sodium chloride (NaCl) as a byproduct. Each tonne of lithium carbonate (Li2CO3) requires 1.8 tonnes of sodium carbonate (Na2CO3) and approximately between 12.53 and 18.80 GJ/m2 of solar radiation."

Sure there are transport costs for both processes, however the sheer volume of spodumene required for transport and the additional materials needed and distance (ship to China then after conversion to customers all over the world, compared to Brines who can ship direct to the customer) will leave a much larger carbon footprint than brines.

We all believe the lithium story where demand (EV, Home power storage etc..) will created due to the fact current energy production is not environmentally sustainable maybe it is best we produce lithium in a way that follows that ideal. I'd be intrigued what Elon Musk had to say.

Source: Peiro L, Mendez G & Ayres R 2013. Lithium: Sources, Production, Uses, and Recovery Outlook. University of Barcelona