 that the exhaust gases from your car during a journey are squashed into a bottle and weighed compared with the weight of petrol used how much do you think the exhaust gases will weigh much lighter about the same or much heavier than the petrol pause the video till you've thought of your answer well the answer is that they will be much heavier because you have added oxygen to the petrol releasing carbon dioxide into the atmosphere when we burn any fossil fuel we always put extra carbon dioxide into the air because the fuels contain carbon the principal element making up living things so here's another question like all other animals we breathe out carbon dioxide from the respiration of our food but why does this carbon dioxide not add to the carbon dioxide in the atmosphere pause the video till you've thought of your answer the answer is that this carbon dioxide is part of the natural carbon cycle it came from your food say bread which got its carbon from the atmosphere when it was growing as a wheat plant let's see where the people of the world get their energy 200 years ago we got our energy from biofuels traditional energy sources that are driven directly or indirectly by the daytime energy from the Sun firewood burning in air to heat our homes and cook our food grass and air for animals to respire gaining energy to pull our plows and carriages our own food which we joined with oxygen to give us energy to use our muscles nowadays burning these fossil fuels with oxygen has freed half the world from being limited by solar energy but there are still many people who live only with biofuels wood for cooking and heating and muscle power for farming and transport we use fossil fuels about equally for generation of electricity mostly coal transport mostly oil and heating and industrial uses mostly natural gas to reduce our carbon dioxide emissions we must burn fossil fuels more efficiently and try to replace them with alternatives efficiency filament light bulbs use a hundred units of electricity to produce just three units of light we should replace them either by fluorescent bulbs which use only six units or LEDs which transform almost a hundred percent of the electricity into light using only three units of electricity to produce the three units of light trains and trams can generate electricity as they break instead of wasting the kinetic energy as heat when they stop for motor vehicles we can continue to improve the number of kilometers driven per liter and we can drive more slowly and carefully with less use of the brakes our homes should be well insulated especially the roof so we waste less fuel in the winter in hot countries houses should be built so that they are naturally cool to save on air conditioning better still is to replace fossil fuels with alternatives many countries already use hydroelectricity which is generated from falling water and therefore solar powered and we are seeing wind turbines and solar panels beginning to make an impact on electricity supply research into energy from the tides and waves is producing useful results too and there is nuclear energy France generates 85 percent of its electricity this way which does not release carbon dioxide but we do have to consider the problem of safe disposal of nuclear waste if we replace coal which is almost pure carbon by natural gas which is methane ch4 has a fuel for electricity generation half the oxygen used will join with the hydrogen rather than carbon so our emissions of carbon dioxide will be halved this is the argument given for developing so-called fracking for natural gas which would replace coal in power stations and we can use our muscles more walking and riding a bike for short journeys so to summarize in order to reduce the amount of carbon dioxide we release into the atmosphere we need to reduce our reliance on fossil fuels by making our processes more efficient and by replacing the fossil fuel with alternative energy sources by generating electricity from the wind waves water from the wind