Sustainability issues, as unwanted results of not fully respecting natural cycles, are widely recognized as wicked problems, which should not be thought of as problems to be solved, but rather as "conditions" to be managed, as if they were a chronic disease (Seager et al., 2011). Thee exists a general agreement on the need to reform scientific expertise by developing new ways of knowledge production and decision-making able to cope with the challenges sustainability poses. In this sense, transdisciplinary aspects of sustainability are acknowledged as a transformational stream of sustainability science. Transdisciplinarity is considered a competence for sustainability in technological curriculums. Nevertheless, engineering education professionals tread on unfamiliar ground when entering transdisciplinarity approach, as it includes social sciences and humanities perspectives. Advancing sustainable engineering science requires creating new long-term, participatory, solution-oriented programs as platforms to recognize and engage with the macro-ethical, adaptive and cross-disciplinary challenges embedded in professional issues. Meanwhile, individual university professors and researchers take a step forward to try out innovative experiences in their classrooms to deal with complexity and reach holism in fostering knowledge in different ways. This paper analyses first what is being done and how is it being focused, and second, What are the strategies for and purposes of implementing transdisciplinary experiences in engineering higher education. Assuming that distinct patterns of definition of transdisciplinary exists, the authors collated transdisciplinary initiatives in engineering education for sustainability from Thompson Klein (2004) discourses on transdisciplinarity: transcendence, problem solving and transgression. The also explored how practical constraints imposed by a classroom context, highlighted the limits of transdisciplinarity, and offered suggestions on improvements, which could be implemented. Balsiger (2015) proposes four varieties of transdisciplinarity (soft, hard, inclusive and reflexive) to identify ways for moving from one type to another as circumstances change, in terms of stakeholder's collaboration and knowledge integration possibilities. The methodology consisted in literature review of articles published in relevant journals in the field of sustainability, which focussed on transdisciplinarity approaches in engineering education. We have analysed how the different initiatives fit in Klein's discourses on transdisciplinarity. Moreover, an affinity analysis has been performed to cluster transdisciplinarity initiatives in engineering education for sustainability in homogeneous groups. Finally, in the varieties of transdisciplinarity framework, the experiences identified when reviewing the literature have been spread over the range among Balsiger's taxonomy. The investigation indicates that most transdisciplinary initiatives in technological education for sustainability fit in the problem solving discourse, where co-production of knowledge and method-driven aspects are relevant. Additionally, they fit in the scheme of broad collaboration and deep integration understood as hard transdisciplinarity. Within such discourse, experiences related to "innovation" fit in the reflexive transdisciplinarity area, which depends more on the efforts of education entities. It is relevant that none of the experiences analysed seems to fit under the transgression discourse paradigm, linked to human rights and emotional intelligence. We conclude that, if engineering programs are to challenge transdisciplinarity, in order to assure the acquisition of competences and worldviews needed to cope with complexity, a new brand of engineer should be trained, one that thinks critically about the co-construction of public welfare and the technological systems in which he or she works. This analysis is a starting point to analyse transdisciplinarity in engineering education for sustainability and to construct the education framework (curriculum structure, faculty competences, pedagogical approaches, etc.) that best facilitates the practice of transdisciplinarity in engineering education. (C) 2017 Elsevier Ltd. All rights reserved.
