Waste-to-Energy
Waste-to-energy refers to processes that extract the residual energy from any sort of waste and convert it either into heat or ultimately electricity. It is estimated that if the U.S. reduced landfill by 65% and converted that into energy, it could provide 2% of the nation's electricity. It would also reduce the emission of green house gasses.
The Waste Hierarchy
Waste-to-energy sits almost at the bottom of the waste hierarchy.This hierarchy shows the different stages of waste, helping to minimize waste ending up in landfill, which is both energetically and economically ineffective.
Before waste is collected and managed by municipalities, waste should be avoided (e.g. supermarkets stop packaging vegetables). If it can't be avoided, waste should be reduced (e.g. size of packaging). Once it's been produced, it may be re-used. For instance, plastic carrier bags. Another example would be up-cycling in fashion where leftovers from manufacturies are sewn together to create new clothes.
Once products are no longer used and disposed of by the consumer, they become waste and enter a waste management cycle of recycling and recovery (waste-to-energy). Ideally, only waste that cannot be recylced or converted into energy should end up on landfill.
Waste that has been delivered by trucks will be sorted, automatically as well as manually, as some types of waste may require pre-treatment.
In the gas plant, the waste is heated, but not necessarily burnt, and converted into a high-calorifc gas. Here, oxygen may be added.
The gas is buffered in tanks to ensure all-time availability, and can be delivered to the gas turbine as needed.
Market
We consider waste to be a renewable source of energy, particularly since the production is growing. Global waste production in 2012 was 1.3bn tons, which is expected to grow to 2.59bn by 2030 and 3.4bn tons by 2050.
The amount of waste produced per capita increases with income but also with degree of urbanization. Yet, what to do with waste is a problem everywhere in the world, as landfills are filling up and recycling alone cannot fill the gap.
As can be seen in the diagram on the right, in order to reduce landfill to almost zero, countries like Singapore or Denmark make use of both technologies recycling and waste-to-energy. Hence, there is a huge potential for waste recovery (waste-to-energy) now and in future.
There are 2,200 waste incineration plants worldwide, consuming 225 million tons of waste per annum.
