Waste to Energy : All about EfW: ISWA White Book on Energy from Waste Technologies

A staggering 2,700 million tonnes of MSW were generated in 2019. It is expected that this figure will increase to 3 billion tonnes by 2030. According to the World Bank, almost two thirds end up in landfills and open dumps. Only 11.5 per cent of the total amount is disposed of in controlled landfills, 58 per cent in open dumps. The rest is destroyed in open burning.

Looking at the aspect of controlled waste management, 11 per cent goes to composting and anaerobic digestion, 20 per cent to recycling and 23 per cent of the waste is treated in waste to energy – or energy from waste (EfW), the sector’s preferred term, as stated in the recently published ISWA White Book on Energy-from-Waste Technologies. “The term EfW puts more emphasis on energy than waste to energy and is preferred to ‘incineration’, which originally did not have any energy recovery and is therefore no longer considered a viable option,” the authors write.

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In lower-income countries, the food and green fraction makes up the majority of MSW. This share decreases as the income level rises. This means that appropriate treatments must be developed for individual compositions.
The organic fraction in MSW generates large amounts of methane, especially if it is disposed of in open dumps and uncontrolled landfills, which in turn is a very high greenhouse gas (GHG) contributor.
Another effect of a high percentage of organic material in MSW is that the energy content is proportionately lower.

It is a fact that in many parts of the world there is no adequate waste management system, which results in environmental problems and health hazards. The UN recognised the problem by declaring sound waste management a human right.
Sanitary landfills are a huge step up from dumps and open burning and many NGOs such as the ISWA Closing the Dumpsites taskforce work towards closing dumpsites worldwide.
The authors of the ISWA White Book see ‘moving up the waste hierarchy’ as the next step, meaning reduction, reuse, recycling and separate collection of biowaste – as well as the implementation of EfW, according to the requirements of the local waste characteristics of course. “The preparation of a comprehensive and performance-based waste management practice is a prerequisite to such development.”

Read more on the topic: Waste-to-Energy in a Circular Economy: Friend or Foe?

EfW has established itself as the most viable option to treat residual household waste and the waste remaining after prevention, recycling and biowaste treatment.

The major advantages of EfW are:

• safe and clean treatment of residual waste, thanks to an efficient overall design, combustion process and flue gas cleaning, efficient operation, always in compliance with strict emission regulations and permits, with specific lower limits to be defined at local level
• it is the final destination for mixed, contaminated or degraded materials
• it allows recycling and material recovery by treating hazardous substances and preventing contamination of recyclable waste streams
• it facilitates the recovery of the energy contained in residual waste to provide local, non-intermittent, reliable, sustainable and mostly renewable energy, helping to reduce dependence on imported fossil fuels
• the recovery of metals and the use of bottom ash as construction aggregates
• it significantly reduces the amount of waste sent to landfill.

Of course, EfW does require significant funding capacities as well as long-term planning. Some countries started developing EfW decades ago and can now rely on the experiences and knowledge they have gained. Although a large number of alternative technologies such as pyrolysis and gasification have been tested in recent years, grate technologies are still the gold standard for EfW.

Read our interview with ISWA working group chair Johnny Stuen.

As an island – and a densely populated one to boot – Japan does not have much space for landfill. According to the World Bank, only 1 per cent of the almost 44 million tonnes of waste generated annually is landfilled. “The remainder is either recycled or converted to energy in state-of-the-art waste-to-energy facilities,” it said in a report, continuing: “The different treatments are considered as complementary to each other.”

In addition, all local governments are required to develop a local solid waste management plan that looks ahead about 10 years.

“The national government has published guidelines to assist local governments and ensure consistency. The national government also provides subsidies to support the development and improvement of waste treatment facilities.”

Japan’s efficient solid waste management is mainly due to effective cooperation between national and local governments. In 2005, Japan initiated the development and implementation of the 3R policy: Reduce, Reuse and Recycle resources.

As can be seen from the diagram (Figure 1), material recycling and EfW plants for residual waste go hand in hand in the treatment of MSW. With over a thousand small-scale facilities, EfW is relatively well developed in Japan.

More than 90 per cent of these plants are based on the grate combustion process. However, due to the policy of melting the slag to safely dispose of the ash (which cannot be used for road construction), Japan has also developed alternative technologies such as fluidised beds and gasification to facilitate ash vitrification, which was necessary to obtain government subsidies until 2005. Since 2010, the ash smelters have no longer needed to be operated, which has significantly reduced waste treatment costs

China’s economic growth has gone hand in hand with an urban growth rate, resulting in an ever-increasing number of fairly large cities. These inevitably generate a great amount of waste that needs to be treated safely. In China, EfW has therefore become an essential part of the waste treatment strategy as a key element of the circular economy law issued in 2008 (one of the first in the world). It has been put in place with very ambitious five-year plan objectives (especially in the 12th and 13th plans).

EfW plants were initially based on European technology with licence agreements. Now they are locally designed, built and operated. Coincidentally, China is the world’s largest market for the construction of new EfW facilities.

Figure 2 shows the development of new EfW plants across the country, many of them with a yearly capacity above 500 kt/year. After just 15 years of effort, China’s total installed EfW capacity has now surpassed that of Europe and is expected to double in the next 10 years. Thanks to this new infrastructure network, around 50 per cent of the municipal solid waste generated in China is already properly treated by the 400 EfW plants.

The summary table has been established from the perspective of residual MSW treatment in countries where EfW is not yet implemented. Here LCV usually ranges from 5 to 8 MJ/kg as compared to 8 to 10 MJ/kg in Western Europe. Considered are technologies that have at least one plant in commercial operation.

The table can be downloaded here.