Helsinki Region Environmental Services (HSY) monitors carbon stocks in the Helsinki metropolitan area using its in-house expertise. To establish the foundation for this work, HSY drew on the experience of the Natural Resources Institute Finland (Luke) in national and regional carbon balance accounting. HSY has published the results of the first assessment round in August 2026.
The cities of Helsinki, Espoo, Vantaa and Kauniainen have an ambitious goal of emission reduction. Achieving this goal requires not only reducing carbon dioxide emissions, but also closely monitoring regional carbon stocks in vegetation and soils and the carbon balance, that is, the changes in carbon stocks caused for example by land use. This will enable the identification of carbon sinks and emission sources across the region.
The cities commissioned their first carbon balance assessment in 2014, followed by a second in 2020. In 2025, the joint municipal authority HSY took on the task with its own experts. The team focused on carbon stocks and the carbon balance for the year 2024.
“Our aim is to reproduce the carbon balance calculations on a regular basis in a comparable way" says HSY’s Lassi Sarlos. As a GIS (Geographic Information Systems) specialist, he was already familiar with some of the programs and tools used in the calculations.
“Even so, we started almost from scratch. We needed to understand how our earlier studies had been calculated, how methods have evolved since then, and how to ensure comparability going forward. We also had to choose from dozens of open data sources those that would best serve the calculations.”
When selecting the methodology, Sarlos and his colleagues took the Finnish national greenhouse gas inventory as their starting point. This inventory is compiled annually by Luke, which was one of the reasons why HSY chose Luke as a partner for its calculation work.
HSY commissioned a service from Luke that was flexibly defined as around one week of expert input. Next, HSY divided the project into sections and worked with the most suitable Luke expert as an adviser for each one.
For example, in matters related to forest biomass and soils, Sarlos was supported by researcher Jukka-Pekka Myllykangas, who has worked on the same topics for the national greenhouse gas inventory and in many carbon balance calculations delivered to clients. Sarlos and Myllykangas met twice a week for an hour for about a month.
“Lassi was so well prepared for each meeting that we could get straight to the core issues, without any wasted time,” Myllykangas says.
“At each stage, we discussed exactly what I was working on and what kind of support I needed for that particular task. I received confirmation, for example, on the selection of input data and on assessing the quality and overall scale of the results. Talking things through with experts helped me build a much deeper understanding of carbon balance accounting as a whole,” Sarlos says.
HSY plans to publish the results of its carbon balance accounting in spring 2026 as an open geospatial dataset. The dataset will also be available in an open map service. The service already provides a wide range of other geospatial data on the Helsinki metropolitan area.
Sarlos expects the carbon balance data to be of particular interest to land-use planners.
“We produced the data at such a level of detail that planners can use it even when making detailed local plans.”
HSY (Helsinki Region Environmental Services), which provides municipal water supply and waste management services, as well as information on the metropolitan area and the environment. The regional and environmental information produced by HSY includes up‑to‑date data on air quality, greenhouse gas emissions, and geospatial information for the Helsinki metropolitan area.
HSY plans to calculate carbon stocks and carbon balances for the Helsinki metropolitan area independently and on a regular basis. HSY’s experts wanted support for the basic approach defined during the first assessment round.
HSY engaged three Luke experts through the “Hire a Genius” expert service. The roughly week-long assignment was divided into short meetings over several months. This allowed HSY’s experts to address issues that had arisen during the various stages of development work.
HSY established a solid foundation for carbon stock and carbon balance accounting that is well suited to the region’s environment and available data sources, and enables comparable monitoring in the coming years. In this way, the calculations support regional climate work.
100% HSY
“Luke’s experts were absolutely essential in helping us confirm both the overall approach and the details of the calculations – and, more generally, in making sure we were on the right track.”
– Lassi Sarlos, GIS Specialist, HSY
