Online purchasing, and hence e-commerce packaging production and use, have grown steadily in recent years, and so has their environmental impact as a result. This paper reviews the evolution of packaging over the last century through a compilation of scientific literature on e-commerce packaging focusing on its environmental side. The primary aims were to identify research gaps in e-commerce packaging and to propose new research lines aimed at reducing its environmental impact. A systematic search of abstracts was conducted to identify articles dealing with sustainability in e-commerce packaging in order to better understand changes in materials and formats, identify problems such as oversizing and allow prospective readers to become acquainted with the latest innovations in materials, sustainability and logistics. Based on existing research, packaging materials and technology evolved rapidly until the 1990s. Later, however, it has become increasingly difficult to further reduce their cost and environmental impact. Also, some packaging products continue to be made from non-renewable materials and thus restrict growth of e-commerce. Further research is needed with a view to producing new packages from renewable sources such as cellulose-containing materials, which are widely available in nature, or from recycled cellulose-based materials such as cartonboard. Improving distribution processes with new, more effective tools could additionally help alleviate the environmental impact of packaging. Similarly, new production processes such as additive manufacturing and 3D printing might help optimize package volume and shape, thereby facilitating more sustainable production through, for example, reduced CO 2 emissions. Currently available technology can be useful to rethink the whole e-commerce packaging paradigm, which has changed very little over the past few decades.

Vertical farming is emerging as an effective measure to grow food in buildings and can increase food production in urban areas in a more sustainable manner. This study presents a comprehensive environmental assessment of food production in an integrated rooftop greenhouse (i-RTG)-an innovative vertical farm consisting of a rooftop greenhouse connected to a building-and considers rainwater, residual heat (energy), residual air (CO 2) and food from an industrial ecology perspective. This synergistic connection preserves resources and improves conditions in the greenhouse and the building. The goal of the study is to show the feasibility of the system and to calculate the environmental impacts from its whole life cycle, from infrastructure to end of life, by comparing these impacts with those of conventional production. The results show that the system is feasible and produced 30.2 kg/m 2 of tomato over 15.5 months. The synergy with the building allows the cultivation of winter-fall crops without supplying heating and maintained an average temperature 8 °C higher than that outdoors. Moreover, rainwater was used to irrigate the crops, reducing consumption from the water supply network by 80-90%. The environmental assessment showed that the operation of the i-RTG has more impacts than the infrastructure due to the use of fertilisers, which account for 25% of the impacts in four of the six impact categories studied. Regarding the infrastructure, the greenhouse structure and rainwater harvesting system of the building have substantial environmental impacts (over 30% in four of the six impact categories). Comparison with a conventional greenhouse demonstrates that the i-RTG has a better environmental performance, showing between 50 and 75% lower impacts in five of the six impact categories (for instance, 0.58 kg of CO 2 equivalent per kg of tomato vs. 1.7 kg), mainly due to the reduced packaging and transport requirements. From this study, it was concluded that optimisation of the amount of infrastructure material and management of the operation could lead to even better environmental performance in future i-RTG projects.

A sustainable and secure food supply within a low-carbon and resilient infrastructure is encapsulated in several of The United Nations' 17 sustainable development goals. The integration of urban agriculture in buildings can offer improved efficiencies; in recognition of this, the first south European example of a fully integrated rooftop greenhouse (iRTG) was designed and incorporated into the ICTA-ICP building by the Autonomous University of Barcelona. This design seeks to interchange heat, CO2 and rainwater between the building and its rooftop greenhouse. Average air temperatures for 2015 in the iRTG were 16.5°C (winter) and 25.79°C (summer), making the iRTG an ideal growing environment. Using detailed thermophysical fabric properties, 2015 site-specific weather data, exact control strategies and dynamic soil temperatures, the iRTG was modelled in EnergyPlus to assess the performance of an equivalent 'freestanding' greenhouse. The validated result shows that the thermal interchange between the iRTG and the ICTA-ICP building has considerable moderating effects on the iRTG's indoor climate; since average hourly temperatures in an equivalent freestanding greenhouse would have been 4.1°C colder in winter and 4.4°C warmer in summer under the 2015 climatic conditions. The simulation results demonstrate that the iRTG case study recycled 43.78 MWh of thermal energy (or 341.93 kWh/m 2 /yr) from the main building in 2015. Assuming 100% energy conversion efficiency, compared to freestanding greenhouses heated with oil, gas or biomass systems, the iRTG delivered an equivalent carbon savings of 113.8, 82.4 or 5.5 kg.CO2(eq)/m 2 /yr, respectively, and economic savings of 19.63,15.88 or 17.33 €/m 2 /yr, respectively. Under 1 similar climatic conditions, this symbiosis between buildings and urban agriculture makes an iRTG an efficient resource-management model and supports the promotion of a new typology or concept of buildings with a nexus or symbiosis between energy efficiency and food production.

Defining sustainable cities is not straightforward. The main issues involved in urban sustainability are buildings, energy, food, green areas and landscape, mobility, urban planning, water and waste; and their improvement is promoted through different strategies. However, a quantitative method, such as life cycle thinking (LCT), is essential to evaluating these strategies. This paper reviews LCT studies related to urban issues to identify the main research gaps in the evaluation of these improvement strategies. The review identifies the main sustainability strategies associated with each urban issue and compiles articles that deal with these strategies through LCT, including environmental life cycle assessment (LCA), life cycle costing (LCC), social LCA (S-LCA) and life cycle sustainability assessment (LCSA), as well as integrated analyses with combined tools. Water, waste and buildings are the urban issues that accounted for a larger amount of studies. In contrast, a limited number of papers assessed urban planning and energy (excluding energy in buildings). Strong interrelations among urban issues were identified, most of them including water. In terms of methods, 79% of the studies exclusively applied life cycle tools (i.e., LCA, LCC, S-LCA or LCSA). Within this group, the environmental dimension was the focus of 84% of the papers. Single environmental indicators (e.g., global warming) were common in 20% of the analyses, highlighting the need to integrate more impact categories to prevent trade-offs. In the field of social and sustainability assessment, there is a need for methodological advances that foster their application in urban areas. Further research should cover the thematic and methodological gaps identified in this paper, such as developing models that assess complex urban issues, generating comprehensive LCT studies and promoting multi-indicators. Life cycle tools might benefit from revising the methodology with stakeholders to optimize the understanding and communication of life cycle results for policy-and decision-making processes.

a b s t r a c tThe Cradle to Cradle (C2C) certification has gained popularity amongst companies as a way to distinguish more environmentally friendly products. This article analyzes the C2C certification by determining how successful this eco-labeling scheme is in distinguishing environmentally preferable products in order to probe if the certification informs correctly to the consumer about the environmental performance of products. Furthermore, we identify for which product types the C2C certification really results in environmental impact reduction. First a review is done in order to detect the debilities, if any, of C2C. Secondly, the fact that C2C requirements do not tackle environmental aspects of products from a life cycle approach, and concentrates exclusively on raw materials and end of life phases, is further analyzed in depth. To do so, Life Cycle Assessment (LCA) already published results for different product categories are used to determine if the life-cycle stages considered under the C2C approach coincide with the most relevant stages in terms of life-cycle environmental impacts. This helps ascertain if and when C2C can be considered an appropriate ecolabel.It is concluded that for products with high-energy consumption during use, C2C does not guarantee relevant environmental improvements, since it does not account for a substantial part of the product's environmental impact. For these reasons, we argue that C2C is not always an appropriate scheme to distinguish environmentally preferable products.