Shipping uses basically no energy. The ocean is, functionally, dead level. When the cargo gets to its destination it has gained no potential energy. This is why ocean freight is by far the least carbon-intensive way of moving material. You should not be concerned about whether anything was shipped from overseas, in the global scheme of energy inefficiency.
I don't know why you are being downvoted, because it's true...
See page 92 of David MacKay's wonderful "Sustainable Energy Without the Hot Air" [1]. Figure 15.8 compares the energy intensity of different transport methods in kilo Watt hours per net ton kilometer. Shipping and rail are basically 1/10 to 1/20 of roadfreight. His conclusion is "Transporting freight by ship is surprisingly energy efficient".
Anyone with rational concerns about transportation costs for materiel should be advocating to dismantle and depopulate Denver. Moving mass a short distance up by truck costs more than moving it half way around the planet by ship. Inland navigation is similarly negligible, which is why the whole Minnesota-Ohio-Pennsylvania steel complex works so well.
Because shipping enables us to source products from much more distant locations; this can cancel out a chunk of that per-KM advantage. It might still be true that in many instances shipping is better for the environment than local production plus rail transport. However since we’ve elected to misprice carbon externalities, there’s no reason to believe we’re getting this right.
~10 gallons of diesel per cubic meter container crossing the pacific. And the majority of that is high sulfur, which is prohibited almost everywhere except high seas due to environmental impact.
Are you agreeing with me or not? With 10 gallons of fuel a truck would carry a cubic meter of steel, which is a hell of a lot of mass, maybe 100 miles on level ground, with an expert driver and a tailwind.
I disagree that people should be dismissive of the environmental impact of shipping in general. It alone contributes 3% of global greenhouse gasses, not to mention all the water pollution.
I also disagree with your comparing an average per-cubic meter rate of a cargo shipment to a truck carrying a single 1m^3 steel cube. It is so far from being logical I can’t really respond at all.
I also disagree with your complete dismissal of the heightened impact of the sulfur used in high seas shipping.
