You have the solar panels protecting the lower ponds of azolla which don't like direct sun. The solar panels provide excess electricity and power any machinery used to harvest the azolla. The azolla grows over TEN TIMES as fast as grass or any other plants, so you are cycling it rapidly producing truckloads of green biomass on a monthly basis.
A lot of grown azolla is eaten by organisms in the pond, which can also contaminate the feed. It spoils quickly, so best fed onsite. Biochar requires dehydration, which isn't easy for wet biomass that quickly starts to rot.
Yea it would need to be squeezed and dried for cakes. Thankfully you'd have a bunch of solar electricity to do that.
Dehydration can be done with vacuum, perhaps?