Sweetgreen Inc was valued at $5.53 billion after shares skyrocketed 86 percent in their New York debut on Thursday, as investors embrace companies that focus on healthy and environment-friendly food. Much of the demand is being fueled by millennials and generation Z consumers, who are more than willing to spend on sustainable products that are also healthy. Sweetgreen’s shares opened at $52, compared to the IPO price of $28 a share, which was well above its targeted price range of between $23 and $25. The Los Angeles, California-based company raised $364 million on Wednesday, selling 13 million shares in an upsized initial public offering, compared with its original plan of 12.5 million. Founded by three college graduates in 2007, Sweetgreen operates 140 restaurants in 13 states in the United States. It offers “earth-friendly” meals made with seasonal and locally-sourced ingredients. The company’s revenue rose to $243.4 million in the nine …