Much of the energy discussion involves electricity: How should we replace the coal that is extremely polluting and rapidly driving climate change? Wind and solar power are great when it’s windy and sunny, when it’s not we need to do something else. This basically means burning something — using a part of the 0.1% of energy that is in the electrons of matter — or using some of the 99.9% of energy that is in the nuclei of atoms.

Today is the official day for going downhill with a sledge in Helsinki (photo by author)

But in the north, such as in Helsinki where I live, most of the energy is actually not spent as electricity but as heat for homes and other buildings. This also goes for emissions. More than half of all greenhouse emissions of our city — including traffic, electricity, industry and waste management — come from heating. As predictions for climate change look very bad, possibly showing a 4 degree rise in temperature by 2100, we need to combat this biggest source of emissions.

The good news is that almost all of our heat is produced centrally in big power plants and distributed to buildings through a district heating network. The bad news is that currently almost all of the heat is produced from fossil fuels, much of it by burning coal. Since wind or solar electricity is pretty much useless for heat generation the existing plans mostly call for burning something else instead of coal. The obvious choice for “something else” is wood. Millions of cubic meters of wood would need to be burned to get enough heat for Helsinki, which has around 1.2 million people in the metropolitan area.

While wood is renewable it is not without emissions. The international climate research panel IPCC has estimated the these total emissions for energy sources:

Total lifecycle greenhouse emissions compared (grams of CO2 per kWh, graph by author)

While biomass has less than a third of the emissions of coal, it is twenty times as polluting as wind or nuclear. The other problem with industrial use of biomass is that it involved cutting down large areas of forest. Forests are important for moderating the effects of climate change, and they have a lot of value in the biodiversity of their ecosystems. Increasing use of forests in Finland will have serious adverse effects on biodiversity according to researchers. And the wood that would be burned could be used in much more profitable ways as construction material or source of biochemicals.

As heating up the city with wind power is impossible, the other very low emission energy source, nuclear, seems like an obvious candidate for district heating. The problem is that nuclear has a negative image for a lot of people. The Chernobyl and Fukushima accidents scared many, even though the number of actual deaths was much smaller than some of the headlines, and the reactors were outdated models . And the ongoing construction of a new massive nuclear plant (by the French company Areva) in Finland has been a source of ridicule due to constant delays and cost overruns.

Fortunately there is a solution for these problems. The next generation of nuclear reactors will be small and serially produced in factory instead of a massive reactor being built individually, piece by piece on the construction site. They are also small and use new technologies to achieve new levels of safety. The use the concept of passive safety, which means that in the very unlikely worst case scenario cooling of the plant is not dependent on multiple redundant active cooling systems, but happens by itself without need for any electricity supply or actions from the operators of the plant.

Last year we had municipal elections in Finland, and I wanted to propose a better solution for reducing our emissions than burning of forests. I had an idea to make a statement with many candidates in the elections supporting an investigation into practical possibilities of using next generation small reactors for district heating. With lots of help from my friends in the Finnish Ecomodernist Society we managed to get more than a hundred candidates from many political parties supporting this initiative. Many of the supporters had a natural science or engineering background, which is not too common with political decision makers in Finland or elsewhere.

The election was a success for a few of those candidates, including me as the first representative of the Pirate Party in the Helsinki City Council. My first action was to make the investigation of small reactors a reality and I write a proposal on it with lots of help from Atte Harjanne, a climate researched in the Green Party. We needed 15 councillors (out of 85) to support it for the proposal to turn into an official investigation and spent months last year explaining the idea through talks, newspaper articles and social media. In November we reached the required support and I submitted the initiative to the city.

The idea in our initiative is to investigate the new models of small and modular reactors and different ways to place them around Helsinki. In principle such reactors could be placed safely inside bedrock quite close to areas of housing, but politically it’s easier to e.g. consider the area of an old coal power plant 50 km from Helsinki. By using such reactors it would be possible to reduce all the greenhouse emissions of the city by more than half. As a lot of the activities around climate change involved very marginal reductions (does changing lightbulbs to LEDs reduce the emissions by 1%?) this would mean finally doing something very effective for the greenhouse emissions.

Our initiative for nuclear district heating generated quite a lot of publicity. Last time nuclear district heating was seriously considered in Helsinki was probably in the 1970s, so it was surprising for many people. At the moment the formal investigation is being worked on in different parts of the city organization, such as the city-owned energy company and the board for city environment. We already got results from a study by the Technical Research Centre of Finland, which found that using small serially produced reactors is not only possible but also economically viable even for cities smaller than Helsinki.

The study by the Technical Research Centre used as an example a reactor by NuScale Power from United States. Their reactor produces 160 MW of heat and 50 MW of electricity, and has been recently certified as passively safe by the Nuclear Regulatory Commission in US. The first commercial plant is planned to be constructed in Idaho by 2025, with 12 reactors working together in a single plant to make 600 MW of electricity. WIth Idaho being warmer than Finland, the plan is to use heat from the reactors to purify water instead of district heating.

Another small reactor that is far in development is called the pebble bed reactor. It uses spheres the size of tennis balls as fuel elements and is going online in China for commercial power production this year. The pebble bed reactor is especially good for heat production, as the temperature of the output steam is higher than in commonly used water-cooled nuclear reactors. This means it can be connected to district heating systems with better efficiency and also used for heat production in industrial plants instead of fossil fuels.

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The initiative for nuclear district heating started before our municipal elections, and has now gathered considerable steam. After the investigation started in Helsinki three other Finnish cities and one major municipality have started one as well. There was clearly a lot of pent-up support for this idea, which makes a lot of sense when you consider the basic facts instead of the popular image of “scary” nuclear power. Some people see it as “engineers and scientists against misconceptions by humanists”, but I think everybody can understand why nuclear heating makes sense once the facts are explained clearly without many technical terms, numbers and abbreviations.

District heating itself is not very popular around the world. Iceland has around 95% of homes using it, and Finland around 90% of apartment blocks use it, while many northern countries have little or no district heating. Heating homes one-by-one is inherently much more polluting than producing power in a large, optimised plant.

To reduce carbon emissions from heating around the world, we need two things: A district heating network and an environmentally friendly way of producing the heat for the network. District heating with small, modular reactors is the only single solution that can reduce total emissions from cities like Helsinki by more than a half. Environmentally friendly electricity can be produced “on the side” by such plants, further reducing the emissions of the city.

I’m happy that Helsinki and other cities in Finland have now taken the lead in political progress towards climate-friendly heating. We hope to show the way to other northern cities and work together with them to try to avoid our winters ending up much colder or much warmer than they’ve been so far, depending on what we “win” from the climate change lottery.

A Russian translation of this post was originally published in the science section of Russian newspaper Nezavisimaya gazeta.