Keeping track of the CO2 in the air

CO2 sensors

Small sensors with a big effect

Switzerland will be installing a dense CO2 measuring system, one which is unique globally. 300 sensors routinely collect up-to-date measurements for scientific purposes. These form the basis for Empa’s atmospheric dispersion models.

Text: Michael Lieberherr, images: Swisscom,

By signing the Paris Agreement in 2015, the international community has agreed to reduce worldwide emissions of greenhouse gases. More than 190 states have now ratified the agreement. However, there are certain cities that have set themselves even more ambitious targets. What is currently still needed, however, are the right tools to measure the progress we are making – for example, tools based on up-to-date measurements of the CO2 concentration.

The Carbosense project is creating new opportunities to do this. There will soon be 300 CO2 sensors distributed across the country, and they will be transmitting their data in real time using the Internet of Things. In the past, there were only a few locations around Switzerland where CO2 could be measured. This dense sensor network – unique globally – records the CO2 concentration in the atmosphere and how it changes in different places and over time. Lukas Emmenegger, Project Manager at Empa, says: “The CO2 sensor network will provide a valuable foundation, allowing a better understanding to be gained of the natural and man-made sources of CO2, and the CO2 sinks, in Switzerland.”

An X-ray machine for CO2

For the city of Zurich, where there are plans for a particularly dense sensor network, Empa has developed a model that can simulate the CO2 concentration from ten different sources (see figure). These sources of emission include different modes of transport, industry and home heating systems. Empa will link the sensor data to its model simulations, which will allow an initial estimate of the emissions to be made. Lukas Emmenegger says: “This will gives us measurements with a sufficient density to keep track of the city of Zurich’s CO2 emissions more or less in real time. The measurements will also provide valuable information about the dispersal of other harmful airborne substances”. The scientific and technical applications based on the sensor data collected from around Switzerland will, in turn, offer points of reference for traffic planning, preventive healthcare and developments in relation to smart cities, while also providing a better understanding of the way CO2 is exchanged between the atmosphere and vegetation.

Swisscom will install the CO2 sensors at antenna sites. The 300 battery-powered sensors transmit their measurements to the data centres operated by the Swiss Data Science Center in the ETH department by means of Swisscom’s Low Power Network. The Low Power Network only offers a narrow bandwidth. All the same, it has a large range, does not use a lot of energy for transmission and reduces networking costs. This makes it ideal for networking environmental sensors, car parks, containers or other communal infrastructure.

The sensor network not only offers benefits for science, but for the Low Power Network itself: The sensors distributed all across Switzerland provide a good way of testing the network quality on an ongoing basis.

Distribution of CO2 concentration (not including the background value of approx. 400 ppm) in the city of Zurich, averaged over the years 2013–2014.

The figure shows the simulation of an atmospheric dispersion model based on the emission inventory of the city of Zurich. In future, these types of model calculations will be linked to the measurements from the sensor network in order to use them to derive a better estimate of urban emissions.

Project Carbosense

Carbosense is a collaboration between Empa, the Swiss Data Science Center (SDSC), Decentlab and Swisscom. The project was jointly initiated by Empa and Swisscom. It is also being financed by

In January 2017, Swisscom opened an LPN Experience Center in Zurich. Those interested can obtain an insight into the opportunities and applications that the Low Power Network can provide.

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