Material and energy cycles

The city is the major habitat of the human species – it is both a physical and a functional space. The circular nature of the urban metabolism (flows of food, raw materials, energy, water and people in motion) in this dynamic ecosystem must be taken into account in order to reduce emissions and their negative impacts.

Material and energy cycles
    Many aspects of urban planning have to date been considered on a sectoral basis, with no dialogue between them. A holistic approach which studies the city based on the constantly moving and transforming flows of materials, energy and organisms would be useful.

    We live in a time of transition towards a more sustainable urban model. The consumption of fossil fuels, technological development and the growth of mobility infrastructures have created urban models with strong environmental impacts and disproportionate levels of energy consumption, which seriously damage the territory and human health. The city needs to be considered as a dynamic ecosystem which contains many more systems. Based on this overall perspective, ecology and the laws of nature must be restored to the logics of town planning in order to build the city.
    While urban planning should improve the way people live, urban planning in the future must outline the conditions necessary to restore green infrastructure, minimise environmental impacts, and foster a resilient system that is adaptable to climate change.

    Better use of energy resources is needed in view of the emergence of centralised generation and large energy transportation networks. The linearity of urban processes must end, and waste flows must be used and recovered in a circular, renewable and recyclable way. In short, it is necessary to move towards a more broad-based and adaptable approach, in which the complexity of the territory as an ecosystem is managed differently depending on the type of action and its scale of application.
The infrastructure and technical services must be coordinated with the other uses in order to be optimised, and planning of the land reserves updated to meet new needs is necessary and the shortcomings of the current urban planning must be overcome for this reason. All aspects must be simultaneously taken into account in order to overcome the uncoordinated sectoral perspective.

Only 39% of the land allocated to technical services is currently in use, and 210 hectares have yet to be used. Meanwhile, 71% of the existing service infrastructures are located on land classified as for systems or installations.

    It is difficult to pinpoint the demand for material resources (food, raw materials and other consumer goods) in the metropolitan area, since, unlike energy and water, their flows are not accounted for systematically.

    Nevertheless, we know that the logistics of material flows require spaces suitable for fostering a more circular economy and a more restricted mobility of goods. Specialised economic activity areas in contact with residential fabrics play a strategic role in this respect.
    It should be borne in mind that by 2025, 70% of the waste generated will have to be recycled, which is a long way from the figure of 50% currently processed. On the other hand, positive trends are apparent in the increase in establishments engaged in activities related to the circular economy, and particularly in economic activity areas integrated into the urban fabric, where they now account for more than 20% of the total.

    The demand for water was 283 hm3 in the metropolitan area of Barcelona in 2017, which is 40% of Catalonia's total domestic consumption. This demand is mainly met by surface water captured in the Llobregat and Ter rivers, although the aquifers in the metropolitan territory also play a significant role as the source of 20% of the water supplied. Other less important sources are the sea water treated at the desalination plant, the water reclaimed at water reclamation plants (WRP), and bottled water from various sources.

    The metropolitan water cycle still has a long way to go in terms of becoming less dependent on the outside world, with the benefits that this would bring.

    The use of aquifers, reclaimed water and grey water, which are currently far below their potential levels, must be encouraged. 50% of the water supply could be covered by resources in the metropolitan area.

    The current annual demand for energy in the metropolitan area is estimated at 44,786 GWh, which is equivalent to 30% of Catalonia's consumption. This energy is mostly consumed in the form of combustible liquids and electricity, although natural gas also plays a major role. On the other hand, liquefied petroleum gases (mainly butane and propane) account for a much smaller proportion. The metropolitan area of Barcelona generated 38.6% of the electricity consumed within its territory in 2014 while 6.4% of its electricity came from renewable energy sources or was recovered by cogeneration.

    The energy cycle must undergo a transition in the coming years, as a result of the current climate crisis. One of the possible areas for improvement is that the metropolitan region has enough potential to cover up to 30% of the energy it currently needs using local renewable sources, because 30% of its urban land has a high potential for capturing solar energy. This land is mainly located in specialised areas of economic activity.

    Finally, work must be done towards the territorial integration of the infrastructures that guarantee energy supply. Taking into account the current and planned infrastructures, five strategic areas have been identified for addressing environmental and landscape integration in the metropolitan region and there are 13 others where the potential risks should be considered.

The diagnosis of the metropolitan region's material and energy cycles presents challenges that planning must address according to its general objectives and its capacity for action.

After the evaluation and final selection of the various alternatives has been completed, the PDU will be able to address the challenges and outline its proposals.

These proposals are defined in the specific terms of a preliminary document, in the objectives, section, which is divided into four broad categories of content: the structural elements, the agroforestry mosaic, the urban fabrics and the areas of action.
This map is based on map ‘I.17 Metropolitan service networks', which is part of the graphic material of the Preliminary Document.

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