1 Introduction

Higher education institutions objectives include education, research, and community service. HEI contribute to the development of the society leaders and show a good example of positive and responsible practices in the community. HEIs have important influence through education to shape the mindsets and values of people in relation to sustainability (Horan and O’Regan 2021). According to Žalėnienė and Pereira (2021), HEI are driving force for implementing sustainability, as well as are considered as a change agent and a catalyst to achieve sustainability. HEI provides required knowledge, skills and values to empower students to contribute to sustainable development ( Dec 2021). The university has a role to create the knowledge, integrating sustainable education and research programs, and promoting environmental issues to the public (Lourrinx and Budihardjo 2019). A sustainable university would show the following principles (Wright 2002; Lourrinx and Budihardjo 2019): Integrate social, ethical and environmental aspects, commitment to graduate attribute of critical systems thinking, encourage research, outreach and campus planning and create policies and practices to achieve equality and diversity.

The Higher Education Sustainability Initiative (HESI) for Rio + 20 was established in 2012 by a group of UN partners as a platform to collaboratively champion education, research and actions for sustainable development in the Higher Education Institutions. Summary of Progress was reported by HESI in UNESCO World Conference on Education for Sustainable Development, Aichi-Nagoya 2014. Concerning education, it reported that most universities trying to integrate sustainability in their curricula, at least by introducing one standalone course. In research some universities highlighted sustainability research and publications by their students and faculty. In operation most of universities-initiated activities to green the campus including recycling initiatives, planting trees, encouraging bike services. In outreach a large number stated awareness programs to the public and hosted conferences and workshops on sustainability (Rio + 20 Higher Education Sustainability Initiative 2014).

UI GreenMetric is a university ranking system that was developed by University of Indonesia in 2010 for assessment and comparison of campus sustainability efforts. GM tool included six categories and forty indicators, Greening Universities Toolkit (Toolkit) is a United Nations Environment Program UNEP focusing on “transforming universities into green and sustainable campuses”. The toolkit includes four elements and 12 indicators (UNEP Toolkit 2013). Fisher et al. (2015) remarked that new tools are evolved in different regions of the world, and then they reviewed and compared different assessment sustainability tools and pointed out to the need for systematization of tools to allow for comparison. Objective of the assessment tool according to STAR tool (AASHE 2019) is to establish a framework for sustainability in all HEI. Enable comparisons over time and between universities. Give incentives for continuous improvement of sustainability. Simplify information sharing between HEI sustainability implementation. Develop a powerful, and wide university sustainability community. Lourrinx and Budihardjo (2019) in his paper determined how the UI GreenMetric is implemented at Diponegoro University in addition they gave recommendations for indicator that has not been fulfilled. Dziminska et al. (2020) propose a conceptual model that shows how universities could work as culture change agents for sustainable development. The paper gives the interrelations between university main operations of education, research and societal engagement in the context of sustainability. Horan and O’Regan (2021) assessed the utilization of sustainability indicator for HEI, and then they critical assessed 12 sustainability assessment tools SATs to develop a set of indicators, weighing method, and scoring to get the score for each criteria. Then they implemented this SAT in the Ireland’s higher education sector. Omazic et al. (2021) in their review on sustainability of HEI found out that the path of the HEI toward sustainability is not clear and they identified key concepts and research themes for sustainability and SD in HEI along with the research gaps. More research as case studies, projects, and methods sustainability and SD in HEIs is still needed. A holistic approach is needed that involving all areas of action and all stakeholders. According to many researchers (Findler et al 2019; Horan and O’Regan 2021; Lourrinx and Budihardjo 2019; Yawei et al. 2021) greening of education would include education curriculum, governance structures, campus operations, research focus, and outreach activities. Hence greening will cover all aspects of the HEI activities and areas. Indicators and tools to assess each of above areas have been developed. Various evaluation and ranking systems for the HEI sustainability have been developed and reviewed by researchers.

2 Proposed Greening System for Higher Education in Palestine

Based on review of the tools used worldwide and taken into consideration knowledge of local geographical, political, land, local resources, as well as social, economic, and educational system Table 1 shows the suggested categories and proposed indicators for greening of higher education institutions in Palestine. Meanwhile, the table gives the weights of categories and indicators as evaluated by local experts’ team. The percentage of each category from the total score of the weights is shown in Fig. 1 while the percentage of each indicator from the total scores is shown in Fig. 2.

Table 1. Weights of categories and indicators in the proposed Greening of HEI
Fig. 1.
figure 1

The percentage for each category of the total scores and category priority from 100

Academic experts valuated all six categories almost equally important with 15–18%. The study included ten experts; six of which are engineering university professors, two are business administration professors and two are technical engineers working in HE. They are asked to give each indicator a grade out of ten according to their experience.

Figure 2 clearly demonstrates that water indicators have the highest weights among all indicators stressing importance of water resources and its sacristy in Palestine. Indicators relevant to emissions such as GHG emissions, and transportation indicators are viewed as lower priority.

The total grades given by all experts for each indicator have been summed and the indicator’s weight has been estimated as a percentage of the whole sum. The percentage of each category is estimated from the sum of its corresponding indicators and the weight of the category is taken as a percentage of all categories.

Fig. 2.
figure 2

The fraction for each normalized indicator of the total score

3 Elasticity and Plasticity of Sustainability Behaviour

Just like the behviour of metals in solid mechanics, humans’ behaviour towards sustainability can either be elastic or plastic. Elasticity and plasticity of sustainability behaviour in higher education institutions as a function of institutional ecological changes is shown in Fig. 3. University community response to sustainability ecological changes is governed by the linear curve in the elasticity region, institutional changes lead to creating new sustainability behaviour. The slope (rate of change) of the line in the elastic region measures the rapidity of green response of the community to institutional changes, this slope reads:

$$ Rate of\; change = slope = \frac{{Sustainability \;behaviour\; \left( {SB} \right)}}{{Institutional \;changes \;\left( {IC} \right)}} $$

The inclination of the curve indicates the speed of university community response to ecological changes; high slope means that the university will reach the required sustainable level sooner than low slope curve universities. In the elasticity region, there is always risk that the community returns back to zero point because the situation didn’t reach to settling level. When the university reaches to the required level of implementing green requirements this is called the settling level and this remains constant no matter what institutional changes occur; this situation is called plasticity region because the sustainable behaviour remains stable. Before reaching plastic region the society passes through transition region where the sustainability social behaviour fluctuates till settling and this is normal because of the dynamic influences of each university community.

Fig. 3.
figure 3

Elasticity of change and plasticity of behaviour in higher education institutions

4 Sustainable Go-Green Model of Higher Education

The resources of any higher education institutions are mainly classified to two main clusters; knowledge and materials. Knowledge includes educational resources of books and electronic scientific sources besides to instructors and students who hold this knowledge and transfer it. The second cluster includes all materials used to assist the teaching and learning process involving labs, equipment, devices, buildings and infrastructure. These two clusters are supported by water and energy which is considered the two main ecological sources needed for any society or institution. These clusters and supporters are the inputs to the sustainability model of higher education institution shown in Fig. 4. Institutional elements in higher education institutions are divided to three categories; indoor buildings, outdoor areas, and university society. These elements are the variables that can be changed in the abscissa of Fig. 3 against which sustainability behavior is measured. An elasticity-plasticity curve can be drawn for each one of these variables. Inside buildings sustainability can be increased by turning the Heating, Ventilation and Air-conditioning systems (HVAC) and other electric appliances to green ones by increasing their electric efficiency and using renewable energy sources to function them. Lighting inside and outside buildings can be turned to green by using energy conserving LED lights and by using solar Photovoltaic (PV) panels to supply them with electricity. The outdoor areas in the higher education institution can be guided to be green harvesting rain water in special wells, this collected water can be used for the irrigation of trees and plants that in turn should be increased and encouraged in the campus area. Waste water should be treated and also used for irrigation or for flush in bathrooms. Irrigation either from harvested rain water or from treated waste water can be powered by renewable solar PV panels.

Fig. 4.
figure 4

Sustainable model of higher education

5 Conclusions

The foregoing research aims at discussing the principle and methodology to turn higher education institutions in Palestine to sustainable and green ones. The first step was done by selecting specific key performance indicators based on reviewed literature. The indicators were prioritized by higher education experts then based on these priorities the weights, and the percentage of these weights have been calculated relative to the categories and relative to the total sum. This kind of calculation helped in taking the decision about the most important indicator to be concentrated on during the way to go green. The implementation of each indicator can be tested using elasticity and plasticity theorem where there is a specific level to be reached before settling situation. A sustainable model is presented in this paper showing all required indicator-related activities to be done in order to obtain a green model for a specific university. All indicators and activities should be related to the three sustainability pillars; social, environmental and economic to make sure that the institution goes well with the international sustainability development goals.