Seaweeds are one of the world's most underrated biomass resources. They are part of the European Union's 'blue growth' strategy as an alternative resource to meet the growing demand for sustainable biomaterials. The application of the biorefinery concept allows obtaining products with high added value along with the biofuel. The cultivation and use of seaweeds in the Baltic region are in the early stage. In the Thesis, the potential applications of Baltic seaweeds are evaluated by applying the biorefinery concept. During the study, the author develops the research by proposing seaweeds as a feedstock, evaluates the products and technologies potentially applicable in the biorefinery. In order to improve the availability of feedstock, a seaweed cultivation laboratory stand is being set up. The aim of this work is to perform integrated research to evaluate the potential application of the biorefinery concept for seaweed species available in Latvia. More specific this Thesis is addressed to identify potential seaweed species, find out the possible amount of biomass and search for the direction for seaweed utilization so that it constitutes part of the national economy and become recognized as a significant type of the biomass. The Doctoral Thesis is based on seven thematically unified scientific publications published in various scientific journals and are available in scientific information repositories and international databases. The aim of these publications is to identify the seaweed species present in Latvia and to look for the direction for seaweed use. The introduction of the work introduces with the aim and set tasks, describes the structure of the work and provides an overview of the author's practical and scientific contribution. The first chapter provides an overview of the scientific literature, previous research and focuses on the properties of seaweed biomass. The obtained results and discussion are given in the third chapter. Conclusions are made at the end of the work.