and how do the operators know which logs are usable?

 "It's all done by our instruments.  The good logs are identifiable by their frequency response to ultrasound; the computer displays it all in false colours - look in this headset."  he fastens some goggles to your head.  At first it's just a confusing array of near horizontal shapes and colours, blue red and green outlines with moving white vertical arms.
Sebastiao suggests that you move your head around and suddenly your brain clicks into 3-D recognition; head movement changes your apparent position of view and you can now see the outlines of trees and branches stacked in a heap.  The white tool with the glowing red tip is obviously the cutting blade; it moves through the logs inexorably working in tandem with a couple of clamping tools.  Your smile must have given away your awareness.
"The green ones are the ironwoods.  That's what we are looking for.  Occasionally we get some ebony and that shows up yellow.  If you were seated on the stage where the girls are, you would also feel the vibrations caused by the tools working - also another useful sensory feedback.."

It seems so graceful, like ballet

"indeed", agrees Sebastiao "underwater is an ideal environment to handle timber.  Those trees are huge and would weigh over 50 tons on land, but underwater they're only about 3 tons and we can manipulate them easily.  Furthermore they cut like butter, although once the wood dries out it is almost impossible to even mark it.  The shippers try to keep it wet until it hits the factories.  There they have learned how to handle it… I know because my uncle owns one." he adds assuredly.

You emerge from the goggles and look cautiously around; the room does not move.

"Want to see the end product?"

The Captain of the SL interrupts, "I think, Sebastiao, that we should be on our way, unless there are any last questions?"
There are many things that you would like to ask, but one major item is still unclear.

How do you move this huge vessel?

"Easy!  We are always attached to the bottom via the stingers; while drilling there are at least three stingers engaged and by varying the pressure on these we can adjust our depth and attitude. To move, we retract all but one end stinger and rotate about it.  Inserting the other end stinger allows us to swivel the opposite way.  A bit like the front end of a giant tortoise. Crude but effective!"  He smiles and offers his hand.  "but I see you need to be off.  Nice to meet you".

On the way out we call in at the Office to check and sign the loading papers, but soon we are back on board the SL.  There have been some changes in our absence.  The SL is now attached to a huge floating sausage, grey-green with an orange stripe down the side. It is a  'Towed Inflatable Reservoir' (TIR), normally referred to as a 'blimp'.
"The orange stripe means medium pressure methane - all the 6's written down the stripe refer to the pressure rating: 6 barG ." advises the Captain. "The Natural Gas Liquids (NGL) has been loaded onto tanks on board, and that, of course, is 80,000 tons of wood flakes".  He points at the hold which is full of what looks like grey-black building blocks in a towering heap.

Where did all that come from?

"The TIRs were ready loaded - we just swapped them for empty ones.  The wood skips are floated into the rear docking bay.  We dropped off a return skip with an empty TIR and also a tank of LPG for transport use.  Turnround time is less than one hour."
This time the Service Lighter eases away from the jetty with her strange cargo trailing behind her and heads off at an acute angle.  "We have to head up wind until we reach full speed.  Always got to keep the blimps downwind of us".
Gradually the speed rises and the sausage, which had been bouncing around a bit, stabilises nicely.

What size is the TIR?

"That's our standard 50m diameter by 400m long.  It holds about 4½ Million Standard Cubic Metres of methane.  The skin is 50mm thick carbon fibre reinforced polypropylene. When deflated it is 50m dia by 100m long and fits neatly into an empty skip"

But isn't methane lighter than air?

"Well, yes, at atmospheric pressure that's right.  However that blimp is compressed to 6 bar, which means the methane in it is four times the density of air.  The Hydrogen blimps normally need a bit of water ballast though, especially if the weather is a bit bumpy."
After this pronouncement, the captain goes silent.  The figures certainly need some digesting.  The captain suggests lunch.  For you it is a chance to ask some more questions.

So how many miners are there altogether?

"There are currently ten wood miners and about xxx gas miners.  Four more Gas Miners are commissioned every year, so the whole operation is continually expanding.  Currently we are at 60% of expected peak production.", he replies, "the target is to remove all 'surface methane' from the Amazon basin in 50 years, then continue to mine the wood as long as we need the material.  There are wood reserves there for about two thousand years "