**6. Conclusions**

The material and energy flow perspective of diagnosing our cities and setting goals of transforming them into more sustainable forms captures the essence of many of the global and local environmental challenges we face while it provides insights about the economic and social sustainability of what we do with the material and energy. The dominant and narrow notion of less-is-better falls short of optimal solutions as it cultivates different levels of burden shifting and suboptimization. Conventional analysis and the actions it derives only move the problem of one environmental medium into a problem of different medium. Cities have been pushing contemporary waste problems into future problems by, for example, landfilling divertible wastes. Plastic wastes from our cities and other parts of the economy have been shipped to China for so many years to the extent that it has assumed as a nonissue locally until this year when China banned the import of plastic waste from other countries including Europe and North America. The practice has been shifting the problem geographically. When the world successfully phased of chemicals that depleted the ozone layer, some of the replacements were later found to be highly potent greenhouse gases. Solving the ozone layer depletion problem was followed by unwelcome development of negatively impacting another global problem.

The consequences of the suboptimal vicious circle of solving one problem by creating another problem or parking problems for tomorrow or pushing issues spatially can be avoided at best or reduced at least by having enough level of life cycle literacy that can inform the public-level and corporate-level decisions that seek to replace old systems with new alternatives. Moving toward a thorough and comprehensive consideration of the important parts of the life cycle of material and energy used in cities, all the environmental, social, and economic aspects associated with that use within a well-defined temporal and spatial system boundary are important. Retraining current cohorts of technical and managerial staff of our cities and educating new generation of decision-makers with the skill of crafting life cycle goals and communicating to relevant stakeholders will energize such full systems-level accounting.

It is not practical or necessary to have a detailed quantitative calculation for every part of the material and energy aspects of our urban areas. Continuing with a piecemeal approach that in the long run and from a broader perspective is not cost-effective, and a disservice to the people, the planet and broad-based profit is not an option.
