Nuclear fusion could solve the world’s energy needs because hydrogen and deuterium are widely available as the constituents of seawater and so are relatively cheap and nearly inexhaustible.
Fusion does not emit carbon dioxide or other greenhouse gases into the atmosphere.
There is no radioactive waste with a fusion reaction. The major by-product is helium, an inert, non-toxic gas.
Fusing nuclei together in a controlled way releases four million times more energy per kg than a chemical reaction such as burning coal, oil or gas. This keeps transportation and mining costs low and reduces the associated hazards.
Nuclear fusion releases four times more energy per kg than a nuclear fission reaction.
Against nuclear fusion
The technological difficulties of fusion reactors are difficult to overcome.
Temperatures approaching the temperature of the sun (approximately 150,000,000 °C) are required for fusion to occur on Earth. Reaching this very high temperature and containing the reaction at it for a sufficiently long time is very difficult.
There are many difficulties to overcome before nuclear fusion provides electricity on a commercial scale and it may be another 50 years before that happens.
Nuclear fusion reactors will be expensive to build because of the technology required.
The system used to contain the nuclear fusion reaction will be expensive to operate because of the very high temperatures needed for the nuclei to fuse.