How Malmö leads the world on waste recycling

November 18, 2009
  • Malmö meets most of heating needs through burning waste
  • Ash is recyled into road materials
  • Plans to turn unwanted food into vehicle fuel
  • Experiments help increase domestic recycling rates

Most people see the things they throw away as ‘waste’ they want removed. The citizens of Malmö, by contrast, see resources. When it comes to recycling, they are world leaders, as Open Knowledge discovered.

They heat homes by burning garbage, pave the streets with recycled ash, and turn food scraps into biogas that fuels buses.

An industrial hub that declined in the 1980s, Malmö reinvented itself around services, IT, and education, embracing environmental sustainability in the process. Malmö gets 40% of its electricity from wind power. It is also Sweden’s leading solar city. According to environment magazine ‘Grist’, their city is the fourth greenest city in the world.

“The great thing is that they do lots of experiments,” says Prof Jes la Cour Jansen of the University of Lund. “They are leading Sweden because they are very innovative and when they do things, they do them well.”

One thing Malmö has done brilliantly is transform its 1950s oil and coal-fired district-heating infrastructure into a model waste-to-energy system.

“About 65% of the city’s heat demand is met by waste incineration,” Trevor Graham, head of Malmö’s Sustainable Development Unit, told Open Knowledge. “We can envisage heating the entire city from waste, and perhaps providing 10% of its electricity too.”

Household and industrial waste is sent to a combined heat-and-power (CHP) incineration plant operated by waste management company Sysav AB.

“We burn it, which heats a water boiler which produces steam that powers a turbine to produce electricity,” explains Gunilla Carson, Sysav's communications manager. “It is then passed through a condenser where it warms the water which is circulated within the district heating system,” says Carson. Incineration produces its own waste. Some people don’t separate their garbage properly so contaminants like glass and plastics get into the incinerator, turning about 20% of the incinerator fuel into ‘bottom ash’.

But Sysav recycles that too. “We use the ash to make gravel for parking places, road construction, and barriers,” Carson says. “Nothing goes to landfill.” In addition, because garbage, not oil or coal, powers the plant, Sysav saves 430,000 kilotons of CO2 equivalent every year.

But incineration has its drawbacks. It produces CO2 and other pollutants, it consumes too much unsorted waste, and it is expensive.

Much of the unsorted garbage that ends up in the incinerator is food waste, which is neither good for the incinerator—it is too moist to burn efficiently—nor the best use of organic material.

Much better would be to feed the waste to biodigestors, where the decomposing food generates methane gas that can be used to generate electricity and fuel. “That is very much the direction we are going,” says Trevor Graham.

Biogas could also power the city’s buses and cars—currently, buses use a 50-50 mix of natural gas and biogas. Sysav plans its own biogas facility to turn food waste into biogas, and biofertilizer. 

Burning or gasifying waste to extract energy is arguably the easy part of waste management. Trickier problems are waste separation, recycling, and collection.

Malmö is helped by national laws that oblige the makers of plastics, glass, electronics, and packaging to recover and recycle their products. Swedes are used to separating these products into special bins.

Even so, the overall recycling rate in the city is still only about 35% and the vast majority of food waste is still incinerated - getting into the habit of recycling everything, it seems, is still beyond many.

And so the city is experimenting, installing bins for kitchen scraps in municipally owned apartments, and providing community composting machines. In the district of Augustenborg attitudes have changed since the construction of 13 buildings containing bins for everything from cardboard to batteries and food scraps. The recycling rate is now over 70%.

In the Western Harbour district, two systems are being tested; food waste grinders in individual kitchen sinks and centralized vacuum chutes.

The grinders churn food waste that is collected from a central tank and sent for biogas production. The outdoor vacuum chutes, meanwhile, suck the waste through underground pipes to the outskirts of the area where it is picked up by refuse trucks.

A perfect recycling system is perhaps out of reach. There will always be those who don’t sort their waste, and there will always be some landfill.

But Malmö’s dynamic, imaginative example nevertheless offers a critical lesson: waste management and recycling are not unpleasant, necessary evils but potential sources of energy. 

James Tulloch

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