The trouble also looks like it comes from the fact that this is economically efficient, it's just environmentally damaging.
Is it though? I mean, sure, they are using less efficient modes of transportation, but outside of bulk-good raw materials (which for the most part are still carried on slower, more efficient means of transport), production energy is so much higher than transport energy.
Assuming it is able to cut down on waste or excess from overstock even a little, I strongly suspect it is at least close to equivalent. Any wasted material from overstock is a massive energy loss. On top of that are the costs of running warehouses; keeping them in adequate temperature ranges (for products and employees), lighting, construction & land use, managing all the stuff that goes into running it and so on. Without those other supply chain energy costs factored in, one can hardly make an analysis of JIT's energy cost compared to traditional supply chains, especially when the whole point is trading off one for the other.
Maybe so, but it's hard for me to believe.
It's not just less efficient modes, it's also much, much more frequent use of those modes. I think the rough comparison for the account that I work on (I'm on the air freight team shipping stuff for a company that produces audio equipment) is that when they move a part from shipping ocean by default to shipping by air, they will go from one ocean shipment every couple months to a flight every couple weeks. And there are some parts I see flown almost every week.
Those bulk transportation modes also consolidate more. There are dozens of parts in a speaker. Every part is produced by a different vendor. When shipping ocean, they will gather stuff from multiple vendors in the same region and then transport it all together. By air, cargo planes are normally filled to capacity regardless, but then every shipment is delivered by truck from the airport individually.
It also creates a lot of chaos that results in inefficiency, because there is no room for error. If there is a delay anywhere in the supply chain, drastic measures have to be taken to correct it. I've seen planes chartered to fly from the other side of the planet just to carry a handful of pieces of a single component, to prevent shut down of a production line. Just a couple months ago, this happened multiple times for one product before the situation could be brought back into routine.
I find it hard to believe that it could be more environmentally costly than all that for material to sit around for a while longer. They still continually have the JIT stuff on hand, so they must have storage facilities for it. The only difference is in the quantity and the rate at which that material cycles through.
And anyway, I didn't mean for this to turn into a debate about shipping methods. I was just agreeing with an earlier comment, and providing an example of the kind of stuff I wish environmentalists would focus on instead of marketing themselves on "blue sky" energy strategies and such.