Brazil, once the world's largest importer of slaves from Africa, has taken the lead in fighting 21st century slavery with a raft of innovative laws aimed at stamping it out. However, slave labour continues to thrive in the South American country - especially in the age-old practice of charcoal burning. The dirty and dangerous business is relied on by many international companies as one of the early stages in the manufacturing of pig iron. Brazilian pig iron is shipped to some of the world's biggest companies, including household name car manufacturers - who use it to forge steel. But the charcoal burning stage is sometimes done by forced labourers, including men from the poverty-stricken north of Brazil who are lured with false promises to remote camps. They are forced into working and living in appalling conditions, and often tricked into amassing massive debts that are impossible to meet in order to pay for their accommodation and even work equipment.