About us

D-mat is a company for our sustainable future, which employs experts in various fields. We aim to advance one planet lifestyles; a resource-wise and low-carbon life. D-mat is specialised in carbon and material footprint calculations as well as researching and mainstreaming sustainable lifestyles. Our services are suitable for companies, government agencies, research institutions and social enterprises, among others.



+358 40 541 2876 (FI)
+49 15 15040 2619 (DE)


Michael Lettenmeier

Research, consultancy, speeches

Michael (Doctor of Arts, M.Sc., Environmental Science and Policy) is the chief executive officer of D-mat ltd and one of the leading experts of resource efficiency and dematerialisation in Finland. His consultancy, training and research activities in Germany and Finland cover sustainable consumption and production, measuring and monitoring carbon and material footprints, eco-efficiency, ecological rucksack and MIPS, and the sustainability of companies, households, municipalities and transport systems. Michael has conducted and supervised sustainability assessments and footprint calculations for numerous companies, supervised dozens of master’s theses, and produced and edited a large variety of publications in the field of sustainability and eco-efficiency.




Viivi Toivio

Carbon and material footprints, consultancy

Viivi focuses on developing procedures and tools for the carbon and material footprint calculation of households and lifestyles, as well as for individual products and services. She is also consulting and training households, municipalities and companies in their transition towards one planet thinking. Viivi has developed several lifestyle carbon footprint tests and contributed to the development of the Climate Puzzle as well. She holds a Master's degree in Environmental Ecology, and also works as a consultant for D-mat at the Hot or Cool Institute.

Jari Kolehmainen



Jari Kolehmainen

Carbon footprint calculations, research

Jari's responsibilities include carbon footprint calculation, developing data models and data tools along with other data analysis. He is a Master of Social Sciences and a qualified software developer, whose multidisciplinary studies included environmental policy, atmospheric physics as well as data science. Previously, Jari has worked at the Finnish Environment Institute (SYKE) and at the Centre for Consumer Society Research at the University of Helsinki, where he conducted household intervention research that aimed to reduce energy consumption.




Ursula Rinta-Jouppi

Carbon footprint calculations, research, consulting

Ursula is working with carbon footprint calculations, calculators and data analysis especially with Jari. Ursula is also involved in helping to organise workshops and accelerators. Previously she has worked on projects such as My Carbon Action and the translation of the Climate Puzzle into Swedish. Ursula is studying Environmental and Food Economics at the University of Helsinki, with a minor in Mathematics and Computational Methods. In addition to her work at D-mat, Ursula also works as a teacher.


In addition, to get more deeply acquainted on the current topic or commission at hand, D-mat ltd employs other experts of relevant fields, consultants, educators and interns.