The main research area of Stig Irving Olsen is environmental assessment of products and systems. This is for example assessments of how a product impacts the environment in relation to e.g. climate changes, toxicity and acid rain throughout the whole life cycle of the product. The life cycle of a product begins at the extraction of raw materials for example in mining and it ends when the product is worn out and ends its life at a landfill or in an incineration plant - or even better is refurbished or recycled. Assessments of systems are alike but in stead of a product the object of assessment is a system like e.g. waste treatment systems or energy production systems. The latest years his focus has been on environmental assessment of different technologies starting with micro/nano production. Products manufactured by micro/nano production are special because they are so small and therefore they often entails particular impacts like the use of scarce metals or the health and environmental risks associated with nano particles. Other technologies, even if intuitively sustainable, may also have unforeseen impacts.