Wikipedia shows that seaweed has 3 uses:
1. Food
2. Medicine
3. Fertilizers
2 & 3 may be harder to get into. But 1 is not that hard to start on your own.
Go here:
http://www.macrobiotics.co.uk/seavegetables.htm
Order that book.
Try creating some recipes.
And sell the dish to restaurants and delis.