A large gripper transports residual waste through a hall.
2024-04-01 VDE dialog

Waste to energy: Extracting the best

It will never be possible to completely avoid residual waste. Companies and municipalities benefit from the energy produced by waste incineration. But what sounds like a clean solution can also be an obstacle to the circular economy.

By Eva Augsten

A mass of gray rolls slowly through the bunker. Blue garbage bags float on the surface, providing splashes of color. In places where the flimsy matter has sunk down a little, pale strips of plastic run between the clumps of garbage like strings of chewing gum. More than a million tons of garbage are produced each year in Hamburg. Around half of it is residual waste, which is incinerated in the municipal waste recycling plants. One such plant – the first on the European continent – went into operation in the city in 1896, because space has always been scarce here.

For some time now, the focus has no longer been on simply reducing the mountains of waste. Today, the energy produced during incineration at Hamburg’s three large sites is in high demand. In the east of the city, the Borsigstrasse waste recycling plant burns 320,000 metric tons of household and similar waste each year, generating around 785,000 megawatt hours of district heating – enough to supply almost 4,000 households. A new heat pump, utilizing a further 350,000 megawatt hours of heat from the flue gas, went into operation as recently as the end of 2023. The waste incinerator at Rugenberger Damm, south of the River Elbe, is on a similar scale. To date, it has been supplying a nearby industrial park with energy. A new connection under the Elbe will soon allow heat from the incinerator to be transferred to the municipal district heating grid. And it’s a model that’s set to stay: in the north-west of Hamburg, the city sanitation department is currently building its new “Center for Resources and Energy” (ZRE). As of 2025, this will also collect 323,000 metric tons of garbage each year, 145,000 metric tons of which is residual waste. The city sanitation department plans to use a modern sorting plant to save almost another 10,000 metric tons of metal, paper, glass and certain plastics from the furnace. The rest will be incinerated. In summer, the energy will primarily be used to generate power, and in winter for district heating.

Waste is an essential source of energy for municipalities and companies

Hamburg is far from the only large city to favor waste as a fuel source in its energy supply. According to the German Environment Agency, more than 25,000 million metric tons of waste was incinerated in thermal waste treatment plants in 2021. Around half of this total is household waste. There is also a large quantity of waste that can be processed to produce what are known as substitute fuels. These have a clearly defined energy value, for example, and are often produced in the form of briquettes or pellets, so that they can be burned in a highly controlled manner and produce fewer harmful substances. Sewage sludge and hazardous waste such as oils and chemicals are also incinerated.

The Verband Kommunaler Unternehmen (VKU, German Association of Local Public Utilities) estimates that a further 24 million metric tons of waste and substitute fuels are combusted in facilities operated by industrial firms to generate energy for their own requirements. This is of particular interest in energy-intensive sectors such as the paper and cement industry. The combusted waste may be generated in the company itself, or be bought in. “In total, then, almost 50 million metric tons of waste is incinerated in Germany each year,” says Patrick Hasenkamp, VKU Vice President and Head of AWM, the city of Münster’s waste management company.

Incineration is better than landfill

There’s no question that, once waste has been produced, it must be got rid of. Local authorities have a legal responsibility to ensure this happens. And anything that can be incinerated can’t simply be dumped. This principle has also been anchored in law for almost 20 years, because incineration, or “thermal waste management” in waste management jargon, is definitely a better option than landfill. Incineration not only saves space, it also destroys many harmful substances, as well as viruses and bacteria. Toxic substances that remain in the condensed incineration residues are far easier to store safely than entire waste mountains.

A bird’s eye view of the Rugenberger Damm waste recycling plant, Hamburg

The garbage recycling plant at Rugenberger Damm is one of two in Hamburg. Waste from more than one million households and from trade and industry is recycled here. No residual waste ends up in landfill; 100% of it is burned.

| stock.adobe.com/aufwind-luftbilder

And then there are the benefits for the energy supply. Ultimately, energy providers, industrial firms and heat grid operators all need to reduce their consumption of oil, coal and gas. Waste is a very welcome alternative. Energy from waste is available on demand around the clock, whatever the time of year. That makes it popular among district heating providers, and not just in Hamburg. Energy providers need to be able to deliver heat even in the middle of a cold, windless winter night – conditions in which the efficiency of heat pumps drops through the floor and energy prices go through the roof. Because waste has to be disposed of throughout the year no matter what, in municipal heat planning the heat generated from waste and substitute fuels is regarded as “unavoidable waste heat”. Provided it is residual waste being incinerated, around half of it is biomass anyway. That's also good news when it comes to the renewable energy requirements.

Incineration inevitably leads to CO2

On balance, then, energy from waste plays an important role for the provision of public services, argues the VKU in a position paper that is also backed by other municipal and industry associations. Energy recovery is the “most sustainable way of handling residual waste,” the association concludes. So does using waste as fuel make a meaningful contribution to climate neutrality?

The answer may not be so straightforward after all. Because when waste and substitute fuels are burned, CO2 emissions inevitably enter the atmosphere. Roughly speaking, one ton of CO2 is released for every ton of waste. So even assuming that the biomass in this equation is completely carbon-neutral, the emissions are still considerable.

Since the start of 2024, therefore, carbon emissions from waste incineration have been covered by Germany's Fuel Emissions Trading Act (BEHG). The basic principle: where emissions cost money, they will fall. The operators of waste incineration plants are not fans of this idea. Both the VKU and Germany’s largest private waste incineration company, EEW Energy from Waste, warn that the legislation is causing waste charges to skyrocket and encouraging the export of waste.

Instead of restricting incineration, EEW is looking for new ways to phase out the fossil-based share of CO2. “This fossil-based share can naturally be isolated and used for other industrial processes,” says Bernard M. Kemper, CEO of EEW in an interview. The first plant, which is designed to isolate 270,000 metric tons of CO2 annually, is currently in the approval stage (as of summer 2023). He puts the investment required “in the triple-digit millions.”

The chicken and the egg: how unavoidable is garbage?

The second point of criticism is the logic of unavoidability. Once the residual waste has arrived at the dump, incineration is in fact the most environmentally friendly alternative. It is largely undisputed that there will always be a few components, such as infectious waste for example, for which incineration is the only option. The term “zero waste” that’s currently on everyone’s lips is therefore often misinterpreted, concedes Professor Henning Wilts, Head of the Circular Economy Department at the Wuppertal Institute. It really means ‘no wastefulness’ rather than ‘no garbage’.” In figures: according to Statista, 160 kilograms of waste per person were disposed of as residual waste in 2020. For a Zero Waste label, a municipality must fall below 50 kilograms per head. This is an ambitious target. However, there are pilot projects that seem to indicate it is achievable. In one large Berlin residential complex, residual waste was reduced from 230 to 84 kilograms per person in a three-year period thanks to a combination of a new fee structure, targeted waste management advice and the cleaning of collection points.

Conveyor belt in a waste recycling plant

Fuel from waste: The material mix consisting of paper, card, wood, plastic films, rubber and textiles is conveyed on a belt to the furnace for incineration.

| stock.adobe.com/martin mecnarowski

If garbage is regarded not as a problem but as a source of energy, these efforts pose something of a dilemma: if waste suddenly becomes avoidable after all, combined heat and power stations lose their source of fuel. An analysis conducted by the German conservation union Nabu indicates that this is not merely a hypothetical problem. According to the organization’s assessment, an average of 204 kilograms of residual waste is generated per person in major cities with garbage incineration plants. The figure is far lower in cities without their own garbage incineration facilities, at 173 kilograms.

Planning on waste that ideally shouldn’t exist

Even if every drink bottle and yogurt pot were to end up in the designated recycling bins, there is little prospect of turning them all into new plastics. Material combinations, color pigments, additives and composite materials make recycling a futile undertaking for many products. “Many of today’s packaging solutions and products are in fact practically unrecyclable. If we want to have a genuine circular economy, we therefore need to start with product design,” says Wilts. The EU’s Green Deal has laid a lot of groundwork for this in some respects in recent years. The focus here is less on waste avoidance and more on raw materials. After all, at the start of their life, today’s waste products took high levels of energy and carbon consumption to make. Many were imported from far away. The new regulations will cover not only recyclable products but also minimum amounts of recycled material. The implementation deadlines are long and extend well into the 2030s. However, if the plan is successful, it will mean that there is automatically less waste from which power and district heating can be obtained.

On balance, therefore, waste-to-energy is a complex “if-then” relationship. With the design and construction of every waste incineration plant, operators are betting on a certain volume of waste. If the plant they design is too small, they cannot fulfill their disposal obligations. If it is too large, they have to hope for garbage that ideally shouldn’t exist.

Eva Augsten is a freelance journalist in Hamburg, Germany, who specializes in renewable energy.

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