An unmanaged shutdown of the Secuda coal-to-liquids plant operated by South African energy company Sasol could wipe $550 million off the country’s $400 billion economy and cost nearly 25,000 jobs, researchers said. The facility, the world’s largest single-site greenhouse gas emitter, supplies nearly a third of domestic fuel, making it a strategic company woven into the nation’s fabric as both an economic powerhouse and environmental headache.Nei…