Competition-based learning, as the name implies, involves competition between learners as the context of learning. This competition is usually rewarded, condition which is necessary to create competition between players, which indirectly increases motivation and engagement in learning. The reward of a competition can be something physical, such as a medal, a monetary award, or can be something abstract, in the form of a bonus in the grade.

Active learning is important in the classroom, and classroom competitions are one of the best ways to engage students in active learning. Typically, when the problem that is the subject of the competition falls into the hands of the students, they become much more likely to ask questions to the teacher, in comparison to a typical classroom homework assignment, and some students even try to learn beyond the established curriculum in order to win the competition.

To introduce concern for the environment and the fulfillment of the sustainable development objectives in the classroom, it is advisable to carry out concrete actions that increase motivation and awaken the attention of students.

Thus, in this work a green competition-based learning didactic proposal is described. Students must build a miniature prototype boat that is capable of collecting floating trash in bodies of water such as lakes and rivers with little current. The project focuses on the physical phenomena behind the operation of a boat and the assembly of the prototype, so the disciplines most notably addressed are science, technology and engineering.

As a first step students conduct an on-line search for information to find viable methods of floating and propelling the boat, as well as garbage collection. Then they make the 3D design from the sketch using Tinkercad as a tool. After this, the students agree with the teacher on the materials needed and assemble the prototype in class using the tools available. In this step the teacher promotes the use of recycled materials in the interest of sustainability. Finally, the class move to a nearby body of water or, alternatively, a portable pool is used to test the operation of the prototype boat by carrying out a time trial competition to collect objects.

The proposal is organized based on learning objectives, key materials, skills, time schedule, and an evaluation to optimize its impact.

Keywords: Competition-based learning, STEM project, teamwork, student motivation.