OTTER is a H2020-funded project aimed at enhancing the understanding of methods and pedagogies surrounding Education Outside the Classroom (EOC) and how those can effectively support the acquisition of scientific knowledge and transferable skills amongst students, specifically in the field of environmental sustainability and the reduction of plastic waste. It also strives to increase interest in scientific topics among young people, while contributing to a range of innovative educational projects, further establishing scientific citizenship within the EU. Moreover, OTTER aims to strengthen education outside-the-classroom (EOC) networks within Europe, connecting experts from four different regions within the continent (Finland, Hungary, Ireland and Spain). The strengthened networks will be utilised to carry out a programme of EOC pilot schemes, further analysing their impact on student performance, including their levels of sophisticated consumption and scientific citizenship, ultimately building a clearer understanding of the effects of Education Outside the Classroom (EOC) on EU citizens. The pilot schemes will share a common theme revolving around issues of plastic waste and recycling, building on the existing momentum of joint efforts focusing on tackling related global educational, social, and environmental issues, as well as creating a more engaging learning environment outside of the classroom.