Aspen is the strongest substrate blend. It has the highest compressive strength. [(link to Aspen product page →)](https://grow.bio/collections/shop/products/aspen-mycelium-material?ref=sb)
Great! and on the other hand, if I want a material to support a lot of weight, what is the best substrate?
Indoors you can keep your mycelium chair for as long as you want. It will not decompose indoors. If/when you are ready to get rid of your chair, toss it outside (or in your compost pile). Once it comes in contact with soil and water, it will decompose naturally. :)