Comparison between material and energy recovery of municipal waste from an energy perspective: A study of two Swedish municipalities

The aim of this study is to compare material recovery to waste incineration with energy recovery from the criteria of energy efficiency. Material recovery saves virgin material and also energy since production processes using recovered material are less energy intensive than processes using virgin material, whereas energy recovery saves other fuels that differ among various energy systems. Optimisations are made for the district heating systems in two Swedish municipalities, showing that it is profitable for the energy utilities in the municipalities to invest in plants using waste as a fuel for electricity and heat production. The fuels replaced by the waste differ between the municipalities. For one it is mostly wood chips, and for the other, a lot of biomass is replaced, but the largest saving is in oil. Energy savings by material recycling of the waste are calculated. Non-combustible waste, such as metals and glass save energy in various extensions when material recycled, but give no heat contribution when incinerated. It is more complicated to compare material and energy recovery of combustible waste fractions, such as cardboard, paper, plastics and biodegradable waste since they can be recycled in both fashions. For these fractions it is important to consider the configuration of the energy system. The conclusions from the two municipalities are that even if there is a district heating system able to utilise the heat, from the energy-efficiency view point; paper and hard plastics should preferably be material recovered, whereas cardboard and biodegradable waste is more suited for energy recovery through waste incineration. These calculations are done with the assumption that biomass should be regarded as a limited resource and when saved eventually eliminates fossile fuel combustion in other facilities.