Waste-to-energy is the process of generating energy from waste. Generally, this is done by combusting recycled municipal solid waste and industrial waste in grate incinerators or fluidized bed incinerators. Waste-to-energy plants and EfW facilities turn pre-processed waste into heat and electricity, which are directed to heating networks and electricity grids for communities and businesses to use. The main sources of energy are municipal solid waste and industrial waste. This mixed waste naturally contains various components of different sizes and with variable energy content. Sorting valuable metals and other nonflammable materials out before combustion increases the calorific value of the waste fuel and the WtE plant's energy production. Another key factor in the waste-to-energy process is the homogeneity of the waste fuel: particles that are the right size catch fire at the right time, burn steadily and produce the maximum amount of energy. Optimally shredded waste provides the continuous material flow that is needed for stable and efficient combustion. As a result, for example, there is less variation in emissions, meaning that the impurities can be filtered more effectively.