If the deal goes through, Cargill would have nine Brazilian soy crushing plants.

U.S. grain trader Cargill will seek antitrust approval in Brazil for a binding offer to acquire three soy crushing plants in a bid to boost biodiesel production and expand operations in the world's biggest soy producer.

In a statement on Monday, Cargill said the deal involves crushing and biodiesel plants in the cities of Anapolis, Porto Nacional and Cachoeira do Sul, in addition to four warehouses. They all belonged to Granol, a privately owned soy crusher.

If the deal goes through, Cargill would have nine Brazilian soy crushing plants, equaling Bunge, according to data from oilseed lobby Abiove.

Cargill's move is a sign of likely consolidation in the local soy crushing industry at a time of cheap soybean supplies after a bumper crop. Some 68% of Brazil's biodiesel is produced from soybeans, according to Abiove, which projects this year's national output of the biofuel at 7 billion liters.

Granol's biodiesel production capacity is 887 million liters annually at the three plants Cargill is buying, according to the seller's website.

In June, Cargill expressed an interest in bidding for the assets of another privately owned crusher, Imcopa, which is in bankruptcy.

Cargill and Granol declined to disclose the deal's value, citing confidentiality related to the antitrust approval process.

Paula Cadette, daughter of one of Granol's founders and the firm's director-superintendent, said by telephone that the age of the company's owners and large working capital requirements were key factors in the decision to sell 100% of Granol's biodiesel business to Cargill.

Granol is keeping two soy processing plants in Sao Paulo state that make soyoil and soymeal, including one that has an ongoing toll manufacturing agreement with Cargill in the town of Bebedouro, Cadette said.

The possible renewal of the toll agreement with Cargill is still under discussion, Cadette added.

After the sale to Cargill, which Cadette said took "some years" to negotiate, Granol was left with 30% of its original soy crushing capacity at two plants in Sao Paulo state.

(Reporting by Ana Mano in Sao Paulo; Editing by Sharon Singleton, Will Dunham and Matthew Lewis)