Technical possibilities

Experience shows that the best outcomes for recycling and the environment are attained through segregated collections. Keeping waste fractions separate at source and collecting them separately is the first step towards the recovery of secondary resources. Plastics, glass, paper, metals, organic waste and minerals can best be reused if they are clean and unmixed.

Recyclable materials can be reclaimed from waste by separate collection or by using sorting and separation technologies. For efficient and effective recycling, each material requires a different set of processes: separately collected glass, for example, is sorted, cleaned and crushed before being made into new products in a glassworks. Paper, plastic and metals need sorting into grades and types and recycling in paper mills, plastics processing plants and metal foundries. The processing of mixed municipal waste is rather more complex.

Separately collected organic waste is treated biologically and is suitable for material recovery. Depending on its composition it can be composted or used to generate biogas in fermentation plants. Appropriate processing turns the fermentation residues into a valuable soil improver and fertiliser, much like compost, for agricultural and horticultural use. Liquid fermentation residues can be used as agricultural fertiliser in a similar way to liquid manure.

As well as being burnt in incinerators, mixed residual waste can also be treated in mechanical-biological treatment (MBT) facilities. A series of treatment stages extracts recyclable materials such as metals and produces quality-assured refuse-derived fuel (RDF) for energy recovery.

In ‘waste-to-energy’ processes energy is recovered from waste in various ways: by generating electricity and heat in waste incineration plants or RDF-fuelled combined heat and power (CHP) plants; by using processed waste as refuse-derived fuel in industrial processes – mostly in cement works and coal-fired power stations; and by using organic waste to generate biogas.

The Waste-to-Energy discussion can be difficult to follow due to the high complexity of the different technologies involved. Political decision makers especially in developing and emerging countries are often confronted with international advisors that promote the idea of WtE as a silver bullet to solve both, the municipal solid waste and energy problems. However, framework conditions in most developing and merging countries are different to those that have seen the rise of WtE projects in industrialized countries. The bigger picture must be taken into account to decide upon the applicability and the suitability in a given context. Advice must go beyond mere technical aspects.

This guide is intended to bridge the knowledge gap between technical experts and political decision makers and assist the latter in following the discussion and in appropriate decision making. The guide was developed by the Deutsche Gesellschaft für Internationale Zusammenarbeit GmbH (GIZ) on behalf of the German Federal Ministry for Economic Cooperation and Development (BMZ) in cooperation with the University of Applied Sciences and Arts Northwestern Switzerland (FHNW).

GIZ Waste to Energy Guideline 2017

Properly managed, environment-friendly landfills are indispensable and will remain so for the long term in some countries. A landfill should be thought of as a built structure which safely encloses otherwise unusable waste, preventing it from escaping into the soil, water or air, and which limits the emissions arising in the landfill body (landfill gas), or recovers them for energy use. At some time in the future, when resource and energy prices are higher and residues that are unusable today become resources in their own right, landfills may themselves become exploitable deposits (landfill mining).