Living on Earth: CURWOOD: And now from diesel to natural gas. As Congress considers sweeping changes to our energy system, natural gas suppliers are hoping to win a bigger piece of the pie. Citing newly found sources of gas, they trumpet its low carbon potential for transportation, and say it’s a cleaner alternative to high carbon coal for generating power. But others say not so fast. Living on Earth’s Jeff Young reports. YOUNG: This August marks 150 years since the birth of the American …