Kelp harvesting began in the 1950s, to produce algin, used industrially as an emulsifier. In 1954 the CSIRO estimated a potential yield of about 40,000 tons of dry Macrocystis per year, and a commercial license was granted in 1958 to Chegwiddon, Button and Kearns, and in 1961 transferred to the Alginates (Australia) Company. Harvesting began in 1963, with an alginate processing operation based at Triabunna. Kelp was harvested three times a year to a depth of three feet by barges fitted with cutting blades, but a maximum of 493 tons (dry weight) a year was harvested, and some beds yielded only one crop per year. In 1971 Alginates applied for an extension of their lease area and permission to include bull kelp (Durvillaea potatorum). Early in 1973, bull kelp was processed for the first time. But dwindling supplies of kelp and low prices meant the Alginates factory closed later that year.
Meanwhile, Peter Luck employed industrial chemist Ralph Bayer to develop a method of using the bull kelp on Luck's Trefoil Island. With assistance from researchers at the University of Tasmania's Agricultural Science Department and the Australian National University in Canberra, Bayer developed the liquid garden fertiliser, Seasol. The first commercial quantities were sold in 1979 to Greece and Israel where seaweed fertiliser had long been used. Overseas sales continued, but Australian sales were slow for years until eventually Seasol was publicised on television gardening programs. Sales boomed, and Seasol is now the leading liquid seaweed product in Australia. Bayer sold the company in 1984 but Seasol is still made in Invermay, Launceston, sourcing nearly all of its seaweed from King Island and Marrawah.
In 2004 there was no direct harvesting of kelp due to its ecological importance to marine ecosystems and fisheries resources. However, beach-cast kelp supplies about 5 percent of world production. From the 1970s beach-cast bull kelp has been harvested on King Island, and milled for export to Scotland. Introduced Japanese sea kelp is harvested (Undaria pinnatifida) on the east coast, and beach-cast seaweeds and seagrasses are collected locally in several areas, for use as garden mulch.
In 2001 the Heres family who farmed near Circular Head noticed that their cows enjoyed licking kelp. Analysis of the kelp found it rich in trace elements and the Heres added it to their pastures. Their cows' health improved so much that in 2001 they started marketing a liquid kelp fertiliser, Marrawah Gold, made from beach-cast kelp.
Further reading: www.kelpwatch.tas.gov.au; J Cassidy, 'Inventing Northern Tasmania', LHSPP 2005; Sunday Tasmanian, 19 November 2006.
Alison Alexander and Jill Cassidy