> Is it possible to be light weight, relatively comfortable, and still green?
In some ways, sure; in others it will be difficult. [It’s certainly interesting to note how much “disposable” stuff there is in our current lifestyle “across the board”, not just in backpacking!]
#1 BEST TIP – Treat your gear gently, and take good care of it.
Sleeping bag/quilt: Buy a top-quality item, take good care of it, and keep it for a long time. Will you have THE lightest, newest, most trendy one out there? No, but you’ll have a good, light-enough piece of gear (think 10-yr-old WM – still great!). Ironically, down would be a better choice than synthetic, because it retains its loft through many, many more cycles of compression than a synthetic will. For example, I have a quality winter sleeping bag from 1999 that is as good now as when I bought it. I believe it’ll last at least another decade or two, especially with infrequent/seasonal use.
Tent: Cuben might be too “disposable” for greenness, as it’s more fragile and folks have said that, when it gets old, its water-proofing deteriorates. Perhaps a silpoly or silnylon of medium-light weight would last the longest (and could be re-treated as needed for water-proofing). If your tent has a slightly higher-denier floor, and you’re careful about site selection/cleaning, you would not need a footprint at all. Keep the zippers out off the ground, and gently clean the tent regularly to prevent deterioration from dirt/dust.
Backpack: Again, a more durable, wear&tear-resistant fabric, and treat it gently. Perhaps a metal frame (like Seek Outside) that could last (nearly) forever.
Some items that will be more challenging:
Electronics (GPS/Phone/Headlamp/external battery) — maybe a solar charger (I like my Suntactics 5), but many of these devices will have planned obsolescence.
Clothing — Think nylon! Nylon is generally more abrasion resistant, and doesn’t develop “perma-stink” like polyester, so you can keep it for a long time. I have old nylon clothes from the late 1990s that look virtually new, even though I’ve hiked in them a ton – and they’re “reasonably light”. Merino wool “sounds” green, but in reality often wears out fairly quickly (esp. compared to nylon).
Toiletries — Get a bamboo toothbrush (light and more sustainable). Don’t buy mini-sized products; instead pour your lotions & potions into little containers that you reuse (love my old eye drops bottles for all kinds of on-trail products). Use a “trail bidet” and avoid toilet paper.
Poisons — Don’t use bug spray. Instead, cover up with nylon clothing and a head net. Instead of sun block, try (as much as possible) to cover up instead.
Food — As much as possible, make your own “pre-portioned” snacks, re-use the ziplocks when practical, and cook in your pot (my 30 year-old titanium pot is still rockin’!), rather than doing freezer bag cooking.
In conclusion, if you’re trying to be truly “UL” base weight under 10lbs, you’ll have to make some compromises to greenness. If you’re going SUL, you may have to throw most of it out the window! ;~)