Lake County News-Sun: When it comes to ecology, HSBC Holdings, the London-based global banking giant, is not just paying lip service. Its new North American headquarters in Mettawa, which opened in July, has become a showcase for the company’s ecological initiatives. The $100 million, 560,000-square-foot building collects roof water for flushing toilets, uses drought-resistant landscaping to reduce water usage, and buys electricity from non-carbon-emitting sources including wind farms. Wednesday, …