Yeah sorry i was joking....it might be hard to find something eco friendly that doesn't bio-degrade. You could always use the land fill angle....this geo tex is made by melting down plastic sacks that would be buried in a big nasty landfill. Or if needed you could resort to explaining how plastic soda rings picked up off beaches are used to make geo tex.I am seeking soil stabilization properties, also prevention of migration of soils...and you know this.
Natural vegetable fibers could be used....something along the lines of burlap even--not very cheap, but customers big into the green thing would not mind the price difference.
Problems: Whereas it would offer great tensile strengthe initially, in a matter of maybe three years it would be gone.
As is bio-degrades, it becomes worse than if you had used no stabilizer at all...you have organic matter down there degrading into gas and dust--shifting soils.