 Can you name some fuels that can be burned to generate energy? Coal, oil and gas are probably the first that come to mind. In this video we're going to look at another special type, biofuels. We have fossil fuels to thank for providing us with energy, that has been used for many huge advances in society. However, they also have some serious disadvantages. Burning fossil fuels releases carbon dioxide, which is a major contributor to global warming. Sulfur dioxide gas is also released, which makes acid rain, damaging the habitats of organisms. And oxides of nitrogen are produced, which can cause lots of breathing problems, especially for people who suffer with asthma. Without growing global population of 7.5 billion, we have ever increasing energy demands. We need more environmentally friendly, cleaner, renewable alternatives. So what are biofuels? Biofuels are produced from living matter. They have many advantages, but some disadvantages over burning fossil fuels. Biofuels are said to be carbon neutral. The amount of carbon dioxide released when they are burnt is the same amount of carbon dioxide used to make the fuel in the first place. However, some people argue that biofuels are using valuable land that could otherwise be used to provide food for the 800 million undernourished people around the world. So what are examples of biofuels? Simply burning wood counts as a biofuel. As we've been burning wood for 600,000 years, there's not much I can say about it, that you don't already know. So we're going to focus on a more complicated biofuel, instead, biogas. It's a surprisingly simple process to make biogas. Inside a sealed tank, bacteria and other microorganisms anaerobically digest different feedstocks in the absence of oxygen to produce biogas. This biogas can then be used for energy. The tanks, known as digesters, are just like big stomachs, with lots of microorganisms inside to help with digestion. Like a stomach, the digesters need feeding. One of the clever things is that the food can be plant-based material, like energy crops, especially grown for generating energy. Or farm waste materials, like cattle slurry. Or it can even be food waste, waste water and sewage sludge. We can make a renewable energy from all these useless waste materials. How amazing is that? In go the feedstocks and the microorganisms digest away and do their magic. The temperature inside the tank is either about 35 degrees Celsius, or it's hotter between 50 and 60 degrees. This depends on the type of microorganism inside the tank. Just like in your digestive system, the feedstock is stirred around inside the digestive tanks to ensure the microorganisms are reaching the undigested material. The anaerobic digestion process takes somewhere between 14 and 40 days to complete, and results in biogas being produced, which is collected from the top of the digestive tanks. Biogas is about 60% methane and 40% carbon dioxide, with some other trace contaminants. The biogas can then be used to generate electricity, or even better, it can be cleaned up, compressed and injected into the gas grid as bio-nethane. Inside the tanks we're left with a waste product called digestate. Another fantastic thing about this process is that the waste digestate is a great fertilizer, it can be used instead of petrochemical fertilizers, so not only has renewable gas been produced but an organic fertilizer is made. Bioethanol is another example of biofuel. It's made by allowing yeast to ferment sugar. The sugar source can come from sugarcane and also fuel crops like maize, wheat and some grasses. The ethanol product can be mixed with an alkaline fuel like petrol or diesel and used to fuel cars. These mixed fuels can be 85% bioethanol and only 15% fossil fuel. Whilst fossil fuels are still being burned, significantly less fossil fuels are burned overall. This process works best in countries where lots of the raw material, sugar, is grown like Brazil. So there you have it, biofuels are a useful alternative to fossil fuels, they're not a perfect alternative but they certainly have some advantages. If you like the video give it a thumbs up and don't forget to subscribe, comment below if you have any questions, why not check out our Fuse School app as well. Until next time.