D-mat is a company for our sustainable future, which employs experts in various fields. Our services include consultancy, education, footprint calculations and research. D-mat is specialised in carbon and material footprint calculations as well as sustainable lifestyles.


Michael Lettenmeier

Michael Lettenmeier (Doctor of Arts, M.Sc., Environmental Science and Policy) is the managing director of D-mat ltd. Michael is one of the leading experts of resource efficiency and dematerialisation in Finland. His consultancy, training and research activities cover sustainable consumption and production, measuring and monitoring material flows, eco-efficiency, material footprint and MIPS, and the sustainability of companies, households, municipalities and transport systems. Michael has analysed and evaluated the sustainability and the material footprint of numerous companies, tutored tens of master’s theses, and produced a huge variety of publications in the field of sustainability and eco-efficiency.

Viivi Toivio

Viivi Toivio is footprint analyst at D-mat ltd, focusing on developing procedures and tools for the material and carbon footprint calculation of households and lifestyles, as well as for individual products. She is consulting and training the transition of private households, municipalities and business towards one-planet thinking. Viivi holds a master’s degree in Environmental Ecology and has also worked in ecological field and laboratory work and in environmental education with different authorities and municipalities.


Sanna-Liisa “Sannis” Sihto-Nissilä

Sanna-Liisa “Sannis” Sihto-Nissilä has a PhD degree in atmospheric physics and large experience in climate change related research and education. Her PhD research was about aerosols’ climate effects. In D-mat Sanna-Liisa is responsible for carbon footprint calculations and development of the tools for it. Besides D-mat, she teaches climate change course at Aalto University and participates to the national Climate University project.

Jari Kolehmainen

Jari Kolehmainen works as a Chief Data Officer at D-Mat ltd. He is a Master of Social Sciences and a qualified software developer. His multidisciplinary studies includes environmental policy, atmospheric physics as well as data science. Jari’s responsibilities include carbon footprinting, developing data models and data tools along with other data analysis. Previously, Jari has worked at the Finnish Environment Institute (SYKE) and at the Centre for Consumer Society Research of the University of Helsinki, where he was conducting household intervention research that aimed to reduce their energy consumption.


Salla Lahtinen

Salla Lahtinen works as a chief project coordinator at D-mat Ltd, where she focuses on the coordination and realization of workshops and experiments of the international Sustainable Lifestyles Accelerator (SLA) project. Salla has her background in fine arts and has previously worked in communication in international sustainability projects. Salla is studying in the Creative Sustainability Master's program at Aalto University.

Sonja Nielsen

Sonja Nielsen works as a service designer and researcher at D-mat Ltd. Sonja’s expertise lies in combining service design methods with sustainability science, especially related to climate change mitigation and circular economy. Sonja has worked as an environmental consultant and service designer in several consultancies, as well as a communications lead for citizen movements. She has also developed an educational design game for promoting 1.5-degree lifestyles, which has been widely used in educational and municipal contexts in Finland and abroad. Sonja holds a Master’s degree in Creative Sustainability from Aalto University.

Annastina Saari D-mat

Annastina Saari

Annastina Saari works as a junior consultant at D-mat ltd and her main focus is in carbon and material footprint calculations. She is soon-to-be MSc in Economics and Business Administration from Aalto University with a focus in information systems science. In her master’s thesis she studied the potential of a carbon footprint calculator in changing users’ lifestyles into a more sustainable direction. In addition, she has a minor in strategy and experience design, and besides work she is studying Forest Sciences at University of Helsinki.


In addition, D-mat ltd. employs experts of relevant fields to acquire deeper knowledge on the topic at hand.