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With world resources finite, and increasing public awareness of the harmful effects of our ‘throwaway culture’, a move towards what’s known as a circular economy seems a sensible option. In short, this means making products last longer, and recovering materials or other benefits from them when they can’t be fixed.
In an ideal world all waste would be reusable or recyclable (or we wouldn't generate it in the first place), but in reality we do generate waste that it is impossible to recycle. The next best thing to do with this waste is to use it to generate energy.
Energy-from-Waste (EfW), also known as Waste-to-Energy (WtE), is widely recognised as a technology that can help mitigate climate change. This is because the waste combusted at a WtE facility doesn’t generate methane, as it would at a landfill and the electricity generated offsets the greenhouse gases that would otherwise have been generated from coal and natural gas plants. WTE facilities are the only form of energy generation that actually reduces greenhouse gases.
How Does It Work?
Traditionally, EfW has been associated with incineration. Yet, the term is much broader, embracing various waste treatment processes generating energy (for instance, in the form of electricity and/or heat or producing a waste-derived fuel).
How truly ‘green’ waste-to-energy is depends on the efficiency of the plant turning the waste into energy, and the proportion of the waste that is biodegradable. This affects whether the approach is considered to be ‘recovery’ or simply ‘disposal’ of waste.
Combustion. This is where heat produced by burning waste produces heat, driving a turbine to generate electricity. This indirect approach to generation currently has an efficiency of around 15-27%, albeit with a lot of potential for improvements. Whether any approach to generating energy from waste can be considered sustainable depends on the ‘net calorific value’ of the waste going into the process.
Gasification, rather than being the business of driving turbines directly, is about the production of gas from waste. Our everyday rubbish, consisting of product packaging, grass clippings, furniture, clothing, bottles, appliances and so on, is not a fuel as much as the feed for chemical conversion at very high temperature. The rubbish is combined with oxygen and/or steam to produce ‘syngas’ – synthesised gas which can then be used to make numerous useful products, from transport fuels to fertilisers or turned into electricity.
Pyrolysis. Where pyrolysis is different from other methods listed so far is that decomposition of various solid wastes takes place at high temperature, but without oxygen or in an atmosphere of inert gases. This means the process requires lower temperatures, and has lower emissions of some of the air pollutants associated with combustion.
Anaerobic digestion can be used to generate energy from organic waste like food and animal products. In an oxygen-free tank, this material is broken down to biogas and fertiliser.
Is it the best solution?
A report released 16 July 2020 by UK think tank Policy Connect, entitled ‘No time to waste: Resources, recovery and the road to net-zero’, which was supported by 13 cross-party MPs, claims that EfW technology is the ‘safest, cheapest and most environmentally responsible solution to the UK’s residual waste problem’.
But they recognise that ‘EfW is not the perfect long-term solution for residual waste. But accompanied by a drive to increase heat use and to decarbonise EfW further, it is the best available technology, and is an essential part of the net-zero transition ahead of us.’
At present, it is the best solution for non-recyclable materials, and one that we utilise here at J&B Recycling as part of our waste management solution for non-recyclable materials.