There's no provision for a player character to acquire this skill.
To be fair, the same problem cropped up with the Naval Architect skill needed for designing starship classes (the 1% fee associated with new designs). How did CT solve it? By giving NAVAL Architect skill to SCOUTS ... because editors forgot to put it into LBB5.80 extended character generation for the NAVY.
S-Flow's approach seems to be to see which existing skills (broadly defined) could be used here instead of creating an entirely new skill. It's a different way of looking at the problem, but it's not being narrow-minded.
Extend what already exists, rather than create new out of whole cloth.
from an economic point of view, regenerative life support shouldn't be less expensive (including externalties such as the opportunity cost of the required equipment space) in the long run than the standard life support consumables. If it were, it would be the default and the R.A.W. system would be an optional alternative!
I don't think of this as an either/or type of judgement in the direction of good/bad. Instead, it's more a matter of economic pressure and the time horizon for a return on investment.
Think of it this way.
In CT, consumable life support reserves "weigh in" at 150 person/weeks per 1 ton costing Cr150,000 per ton.
Over the (presumably 40 year) operational lifetime of a starship, a single crew member working 48 weeks per year is going to require 1920 person/weeks of life support over that 40 year lifetime of the starship. If you bought that "all up front" at the beginning (during starship construction) and stuffed it into the cargo hold, it would cost 12.8 tons of cargo space and MCr1.92 in initial outlays for a 40 year supply of life support consumables per crew member.
If you assume crews work 50 weeks per year (with 2 weeks off/vacation during annual overhaul maintenance) this consumables equivalent climbs to 2000 person/weeks of life support over 40 years costing 13.333 tons and MCr2 per crew member.
No matter how you slice it, that's a pretty significant chunk of credits to spend over a 40 year (intended) lifespan for a starship.
But that's only if you buy it "all at once" ... up front ... and you do it with the life support consumables path.
However if you do it in "installments" (replenishing your life support consumables every 2 weeks) ... you'll still pay the same amount in cash (Cr1000 per person/week) but you won't need to spend the tonnage on the stockpile of reserves. You'll still have to pay MCr1.9 to MCr2 per person over 40 years in (consumable) life support overhead expenses, but with a limited reserve (4 weeks per stateroom?) you get to save ~13 tons for cargo ticket capacity, which represents a real savings!
You just need to go places that won't price gouge you for life support replenishment costs, that's all.
But ...
If you do a regenerative biome life support system for your starship, you'll be paying close to MCr0.3 per ton for laboratory space and hull metal and will need to allocate additional staterooms (and hull metal) for extra crew to manage the life support system (kind of like how high passengers require extra crew to accommodate them). Needing a larger crew, relative to the alternative, limits the practicality of such life support systems relative to the "alternative minimum" due to the loss of tonnage available for the purposes of generating revenue (cargo hold, low berths, passenger staterooms, you know the drill).
However, the biggest difference between consumables and regenerative life support alternatives shows up in the economics of subsidization.
That's because a subsidized starship has the construction cost "paid for" by the subsidizing government. However, the subsidizing government gets to take a 50% share of any revenues (not profits, revenues!) generated from ticket sales (passengers and freight) to amortize the expense involved in the construction of the starship.
But the real kicker is that the starship operator is 100% liable for all expenses incurred. That means annual overhaul maintenance, fuel, berthing fees, crew salaries, and of course ... life support overhead.
Well, if you can shift the lifetime cost of life support from the "operational overhead expenses" column (that the operator is 100% responsible for) into the "construction cost expenses" column (that the subsidizing government is 100% responsible for) ... you wind up with a starship that is
slightly more expensive to construct and buy ... but "cheaper to operate" to the tune of (a little bit under) Cr50,000 per year, per person aboard in recurring operational overhead expenses (which can add up quickly with crew and high/mid passengers).
For anyone familiar with the concept of double bookkeeping (not to mention "cooking the books") this kind of "shell game" with the operational expenses for starship operations shouldn't come as that much of a surprise. The REAL question is ... do you have ENOUGH "spare tonnage" in a starship's design to be able to take advantage of this opportunity and still keep the starship class (as a whole) profitable in merchant operations ... or does it "cost too much" in tonnage to be able to make the investment pay off over the 40 year lifespan of a starship?
There's no singular best answer for the full spectrum of possibilities here.
A J1 Free Trader COULD invest in this kind of regenerative biome life support upgrade, but there would be considerable costs (in tonnage) associated with doing so. A
Type: V-c laboratory setup would require 2 tons per person (so call it 20 tons for 10 people, crew+high/mid passengers). As a matter of practicality, you'd probably also want to install a TL=9 fuel purification plant into a stock Free Trader ... and at that point you're already -29 tons lost from your cargo hold capacity, a pretty SERIOUS downgrade relative to the stock Free Trader.
You don't have to pay for starport fuel (usually) and you can now waive your overhead expenses for life support, making it MUCH easier to make ends meet on the balance sheet when tallying of profit margins ... but you also have a dramatically reduced cargo capacity to mobilize speculative goods for arbitrage (which is where the REAL PROFITS are to be made!) ... so there are tradeoffs.
So in general, I'm thinking that the "really small" ACS (200- tons) are kind of "too rinky dink" to make best use of a regenerative biome life support system, mainly because such "small" starships don't have a whole lot of room to spare. Bigger starships (300+ tons) are where regenerative biome life support starts becoming a compelling option, because the tonnage needed for it becomes a smaller fraction of the overall starship displacement (the hull gets bigger faster than the life support system does).
Your mileage may vary, of course.