(Adds background on RAW, Alvean; adds consultants' comments)
SAO PAULO, March 21 (Reuters) - RAW and Alvean, two joint ventures that originate and export sugar, accounted for almost 40 percent of Brazil's exports of the sweetener in 2017, according to data from maritime company Williams compiled by Reuters.
The world's No. 1 exporter, Brazil shipped 24.89 million tonnes of sugar last year, the data showed.
RAW, a joint venture of Wilmar International Ltd and the Raízen group - formed by Cosan SA and Royal Dutch Shell Plc - accounted for 21.1 percent of Brazil's sugar exports, or 5.26 million tonnes.
Alvean, formed by Brazil's Copersucar and U.S.-based Cargill Inc, exported 4.43 million tonnes, or 17.8 percent of the total out of the South American country last year, Williams data showed.
Brazil's center-south, the world's biggest sugarcane producing region, processed 35 million tonnes of sugar in the 2017/18 crop cycle, trade group Unica said.
Julio Borges, founding partner of JOB, an ethanol and sugar consultancy, said concentration in the sugar business is a global trend.
He added that while supply-side concentration facilitates global trade of the commodity, it makes sugarcane mills "subject to the oligopoly of the big players."
Arnaldo Luiz Corrêa of Archer Consulting said concentration exists in the industry but does not impose barriers on new entrants.
RAW and Alvean did not have an immediate comment. (Reporting by José Roberto Gomes; writing by Ana Mano; editing by Jonathan Oatis)