Ulva’s Kelp Industry Seaweed plays an important role in the history of Ulva. It was burned to produce kelp, a product in great demand in the early 19th Century for making glass and soap. Being a labour-intensive process (it took 20 tons of seaweed to produce 1 ton of kelp) Ulva’s population grew to meet the demands of cutting, carrying and burning enough seaweed for an average output of 23 tons of kelp per year. In 1785 Ulva was purchased by a pioneer of the kelp burning industry and his son, Staffa MacDonald was reputed to have ‘trebled his income and doubled his population by careful attention to his kelp shores’.