With the boom in renewable energy, many of the credits that trade hands merely represent a transfer of money from one profitable enterprise to another, critics say. …Companies looking to offset their emissions are buying credits in vast numbers that do little to help neutralize their carbon output. Pedro Martins Barata, a former executive board member of the U.N. program, known as CDM, says he is concerned the market lacks transparency, making it difficult for buyers to understand which projects would have happened without issuing credits. “No one should buy any of that stuff anymore,” said Mr. Martins, who is now at the Environmental Defense Fund. …Surging demand for credits is being driven by companies, often under pressure from investors, governments and customers, to reduce their net carbon footprint. More than 5,000 companies have signed a U.N. pledge to eliminate or offset their greenhouse-gas emissions by 2050. [to access the full story a WSJ subscription is required]