Scientific Article for Students

Introduction Have you ever heard of shale gas? It’s a type of natural gas found deep underground. It was impossible to access 20 years ago, but now it’s a big part of liquefied natural gas (LNG) production. LNG is an important energy source, used all over the world. The U.S. has become the world’s largest exporter of LNG. But what makes it different from other energy sources? Many researchers consider it a cleaner alternative to coal. This is because it produces less carbon dioxide (CO₂) when burned. But we have to consider how people make and transport LNG, too. First, we need to extract shale gas (Fig. 1). Then, we need to cool it to super-low temperatures to turn it into liquid. This makes it easier to transport in big ships. Yet the process of extracting, liquefying, and moving LNG releases harmful greenhouse gases. These include methane and CO₂. Methane is especially dangerous for the environment. This is because each molecule traps a lot more heat than CO₂. So is LNG a better option than coal for the environment? Or does it have a larger carbon footprint? This is what we wanted to find out! Methods [150-200 words] We wanted to measure the total carbon footprint of liquefied natural gas (LNG). So, we looked at each step in its production process: from getting the shale gas out of the ground to making energy out of it. The steps include: Shale gas extraction – Drilling deep into the earth and injecting huge volumes of water (“fracking”) pushes the shale gas up to the surface. Methane leaks out during the drilling process and from pipelines used to transport the gas. Liquefaction – Cooling the gas to turn it into liquid uses a lot of energy. This creates CO₂ emissions. And since shale gas is burned for this energy, even more methane is leaked. Shipping LNG – Giant ships transport LNG around the world. Some of these ships release methane through “boil-off”. This happens when the liquid gas heats up slightly and turns back into a gas. Depending on the ship’s technology, more methane is emitted. Many ships burn the boil-off for their fuel, but then some unburned methane comes out in their exhaust. End-use combustion – When the LNG is finally burned to make electricity, it releases CO₂ into the air. We measured and compared these emissions to those of coal. This allowed us to see how good (or bad!) LNG really is for the environment. Results The results were surprising! Liquefied natural gas (LNG) has a much larger greenhouse gas footprint than people might expect. It does release less CO₂ than coal when burned. But methane emissions during production and transportation make things worse. We discovered that the overall footprint of LNG is 33% worse than coal (Fig. 2). Here’s what adds to LNG’s total emissions: Methane leaks and emissions during gas extraction account for almost 40% of the total emissions. Liquefying the gas into liquid form adds around 9%. Depending on the type of ship, the transportation of LNG adds another 4-8% to the total emissions. When the final consumer uses the gas, it produces CO₂. This makes up around 34% of the total emissions. A surprising result showed that newer, supposedly more efficient ships often leak more methane than older ships. This is because of the methane that escapes in their exhaust. This means the ships don’t burn their fuel (methane) fully. Discussion Our study found that liquefied natural gas (LNG) is not as eco-friendly as it seems. Yes, LNG releases less CO₂ than coal when burned. But it has a hidden problem: methane leaks. Methane is a greenhouse gas that traps much more heat than CO₂. This makes it a big concern for climate change. Methane leaks happen at several stages. When we first extract shale gas for LNG production, some methane escapes. Then, more methane can leak out when turning it into liquid and shipping it across the ocean. This is especially true with newer, more efficient LNG ships. These ships use fuel better, but they also have more methane slip. This means methane escapes in their exhaust. Because methane is so powerful at trapping heat, these leaks make LNG’s greenhouse gas footprint larger than expected. To really make LNG a cleaner choice, companies need to find ways to stop these methane leaks. Reducing emissions at each stage might lower LNG’s impact on the planet, but it is very difficult and expensive to do so. Conclusion Every energy source affects the environment, even those that seem greener. But our use of fossil fuels is by far the great problem for the climate, and LNG is worse than any other fossil fuel. Luckily, renewable energy sources such as solar and wind are becoming less expensive and more available every day! What can you do as an individual? Remember to reduce, reuse, and recycle to cut down on waste. Choose public transportation, biking, or carpooling to lower emissions. Conserve water by taking shorter showers and fixing leaks. Each step we take helps reduce greenhouse gas emissions. Which means you’re contributing to a healthier planet!