alt Hacker NewsThe Ocean Cleanup immediately comes to mind. I very much doubt that they're even slightly "sustainable" in a financial sense, but their engineering and logistics efforts seem to be serious, and outcomes meaningful.
And I've seen various cottage industries in the developing world grow out of/highlighted by Precious Plastic - ones who provide perhaps 5-30 jobs in poor and polluted areas of the world. A warehouse, some crude but effective machinery for processing the waste.
I will mention. Ocean Cleanup has a 55 million Euro budget. Precious Plastic is being criticized for having squandered a 100k donation. That 550 times less.
Ocean Cleanup claims to have removed 21,000 metric tons of plastic in its existence.
If we assume linear growth in budget, that's $330M Euro / 21k ton = 15,000 Euro per ton of garbage.
About 10 million tons of plastic end up in the ocean each year, so over their history, they've cleaned up 0.2% of the annual input.
I can't really comment if any of that good or bad, but I thought numbers (even if squishy estimates) would be helpful to inform the discussion.