Agence France-Presse: Nigeria, tipped to be the world’s next natural gas powerhouse, is on the frontline for climate change as it is ranked Africa’s largest producer of greenhouse gases. Experts meeting in the country last week said the west African powerhouse, which has the seventh largest proven natural gas reserves in the world at 187 trillion cubic feet, could become a key player in the international gas market. But the gas is mainly found in the Niger Delta — an oil-producing area of swamps …