Circular economy reconciles waste generation with energy efficiency

Today, the waste generated by our way of life is no longer just a by-product to be reprocessed but a resource that is more and more tapped into. What was until recently still a puzzle for local authorities could very well become an adjustment variable of energy policy. Here is an overview of the benefits of the various waste recovery methods and their potential contribution to energy efficiency.

Circular economy to foster sustainable development

In order to overcome the scarcity of natural resources, a genuine waste management industry has emerged echoing the suggestion made by the French chemist and philosopher A. Lavoisier in his dictum that “nothing is really lost or found; it’s all about transformation”. The circular economy is based on the principle of recycling: each product, once consumed, obsolete or broken, is entitled to a new life. Waste management takes inspiration from bio-mimicry, aiming not only at lowering production costs but also cutting consumption of raw materials.

Waste-to-energy schemes

Organic waste is sorted into green waste, bio-waste (also known as FFHW, fermentable fraction of household waste) and organic waste from crop production. FFHW can be re-used for two distinct purposes: compost and energy production (thanks to its calorific value).

Energy can be obtained through two different methods: methanation and incineration. The former consists in transforming FFHW into biogas which will in turn generate electricity, heat or fuel. In the latter, FFHW is directly burnt, without going through the “methanation chain”. Water heated over 300°C can then either drive a turbo-generator and produce electricity or be directly fed into surrounding building heating networks.

Although the methanation waste-to-energy scheme offers “limited environmental achievements compared with fossil fuels” according to the French Environment and Energy Management Agency (ADEME), incineration generates toxic household waste bottom ash, only 90% of which can be recovered.

waste, energy efficiency

Besides, some waste recovery units chose to resort to cogeneration, i.e. simultaneous production of heat and electricity. In such a scheme, very high-pressure steam (46 bars) drives a turbo-generator before being fed into a heating network.

Despite its particularly high cost, a study conducted by the ADEME proved the overall higher efficiency of this kind of non-renewable energy-based installation, due to the “combination of heat and electricity production”. However, it is to be noted that its environmental impact is not as positive in terms of air eutrophication*.  These complex installations benefit from incentive schemes, such as the French electricity law (n° 2000-108), which aims at promoting “renewable energy-based installations or installations relying on energy efficient technologies such as cogeneration”.

Room for expansion and improvement

Today, waste-to-energy schemes represent 31% of collected waste and account for about 6% of renewable energy generation, which itself makes up 15% of the French energy mix. Therefore, although there is a significant potential for waste-to-energy initiatives, the high cost of installations is the main hurdle to the sector’s expansion. Besides, such schemes create as many environmental problems as they solve, such as the recycling of household waste bottom ash.

Energy mix and renewable energy production in France in 2010 (primary energy):

waste, energy efficiency

Treatment of household and similar waste (rubble and backfill excepted):

waste, energy efficiency

Source: ADEME 2011, “Public waste collection service in France

*Eutrophication: excessive richness of nutrients in a lake or other body of water or air (Oxford dictionaries)

For more information:

  • Analysis of the life cycle of waste-to-energy schemes for biogas from methanation of separately collected fermentable fraction of household waste in France; ADEME presentation

Waste-to-energy schemes, vedura.fr

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