The Photosynthetic City

The potential to grow energy and provide food and materials locally will become part of urban infrastructure. Photosynthetic processes in cities will reduce their ecological impact through replacing fossil fuels and can bring substantial ecological benefits through their emphasis on natural systems. There has been a positive trend in planning in the direction of an expanded notion of urban infrastructure to include the idea of “green infrastructure” using photosynthetic processes.  Green infrastructure refers to the many green and ecological features and systems, from wetlands to urban forests, that provide a host of benefits to cities and urban residents —clean water, storm water collection and management, climate moderation and cleansing of urban air, among others.  This understanding of green infrastructure as part of the working landscape of cities and metropolitan areas could also extend to include the photosynthetic sources of renewable energy, local food and fibre, as potential green infrastructure. Renewable energy can be tapped from the sun and wind and geothermal sources as a small scale decentralized technology as described in the previous section. However renewable energy can also be grown through biofuels. The transition to growing fuels will need to be tailored to new crops and forests that can feed into new ways of fuelling our buildings and vehicles. Farms and landscapes, open areas around cities could develop as the source of renewable energy, especially the production of bio-fuels. However they can also be produced as part of a city’s urban environment. This will mean more intensive greening of the lower density parts of a city and its peri-urban regions with intensive food growing, renewable energy crops and forests, but also greening the high density parts of cities as well. The City of Växjä in Sweden has developed a locally based renewable energy strategy that takes full advantage of its working landscapes, in its case the abundant forests that exist within close proximity of the city.  Växjä’s main power plant, formerly fueled by oil, has been converted to biomass, almost entirely now from wood chips, most of which are a byproduct of the commercial logging in the region.  The wood, more specifically, comes from the branches, bark and tops of trees, and is derived from within a 100 km distance of the power plant.  This combined heat and power plant (Sandvik II) provides all the town’s heating needs and much of its electricity needs, and its conversion to biomass as a fuel has been a key element in the city’s aspiration to become an oil-free city.  Clearly each city can develop its own mix of local renewable sources but Vaxja has demonstrated that it can transition from an oil-based power system to a completely renewable system without losing its economic edge. Indeed cities that develop such resiliency early are likely to have an edge as oil resources decline. The metropolitan landscape can be viewed as the pallet for a creative mix of solar design and renewable energy projects, and every city and region will have its own special opportunities and resources and in doing so will help integrate the green and brown agendas. One of the most important potential bio-fuel sources of the future will be blue-green algae that can be grown intensively on roof tops. Blue green algae can photosynthesize so all they need is sun, water and nutrients. The output from blue-green algae is ten times faster than most other biomass sources so it can be continuously cropped and fed into a process for producing bio-fuels or small scale electricity. Most importantly city buildings can all utilize their roofs to tap solar energy and use it for local purposes without the distribution or transport losses so apparent in our cities today. Bill McDonough says that ‘every roof should be photosynthetic’; by this he means either a green roof for biodiversity/ water collection/landscape, or for PV collectors or for biofuel algal collectors. This can become a solar ordinance set by town planners as policy by local governments. Few cities and few municipal governments have done much to take stock of their photosynthetic energy potential.  Municipal comprehensive plans typically inventory and describe a host of natural and economic resources found within the boundaries of a city—from mineral sites to historic buildings to biodiversity—but estimating incoming renewable energy (sun, wind, wave, biomass or geothermal) is usually not included here.  In advancing the renewable energy agenda in Barcelona, the city took the interesting step of calculating incoming solar gain.  As former sustainable city counsellor Josep Puig notes, this amounts to “10 times more than the energy the city consumes or 28 times more than the electricity the city is consuming”. The issue now is how to tap into this across the city. As well as renewable fuel, cities can incorporate food in this more holistic solar and post-oil view for the future. Food, in the globalized marketplace increasingly travels great distances—apples from New Zealand, grapes from Chile, wine from South Australia, vegetables from China.  ‘Food Miles’ are rising everywhere and already food in the US travels a distance of between 1,500-2,500 miles from where it is grown to where it is consumed.  Any exotic sources of food come at a high-energy cost. Thomas Starrs refers to modern food as “The SUV in Our Pantry,” in an article in Solar Today magazine:

It takes about 10 fossil fuel calories to produce each food calorie in the average American diet. So if your daily food intake is 2,000 calories, then it took about 20,000 calories to grow that food and get it to you. In more familiar units, this means that growing, processing and delivering the food consumed by a family of four each year requires the equivalent of almost 34,000 kilowatt-hours of energy, or more than 930 gallons of gasoline. (For comparison, the average U.S. household annually consumes about 10,800 kilowatt-hours of electricity, or about 1,070 gallons of gasoline.) In other words, we use about as much energy to grow our food as to power our homes or fuel our cars.

There are now good examples of new neighborhoods and development projects that design-in from the beginning, spaces for community gardens and that attempt to satisfy a considerable portion of food needs on-site or nearby. Growing food within cities and urban (and suburban) environments can take any number of forms.  Community gardens, urban farms, and edible landscaping are all promising urban options. Prominent and compelling examples of edible urban landscaping have shown that it is possible to trade hardscape environments for fruit trees and edible perennials.  In the downtown Vancouver neighborhood of Mole Hill, for instance, a conventional alleyway has been converted to a green and luxurious network of edible plants and raised-bed gardens, in a pedestrianised community space, where the occasional automobile now seems out of place. New urban development can include places (rooftops, sideyards, backyards) where residents can directly grow food.  This has been a trend in developed cities, as new urban ecological neighborhoods have included community gardens as a central design element (e.g. Viikki, in Helsinki, South False Creek in Vancouver, Troy Gardens in Madison) but is perhaps most famous in Cuban cities over the past few decades in response to being cut-off from oil imports. Cities need to find creative ways to promote urban farming where it is feasible and not in tension with the need to redevelop for reduced car dependence. This may mean that a city can utilize the many vacant lots for commercial and community farms in areas that have been blighted (e.g. estimated 70,000 vacant lots in Chicago alone). However if these areas are well served with good transit and other infrastructure then such uses should be seen as temporary and indeed can be part of the rehabilitation of an area leading to the redevelopment of eco-villages that are car free and models of solar building as in Vauban.  Many cities have embarked on some form of effort to examine community food security and to promote more sustainable local and regional food production.  These can be integrated into ecologically sustainable urban and regional rehabilitation projects and can utilize the intensive possibilities of urban spaces such as in urban permaculture. In Madison, Wisconsin, a model urban garden called Troy Gardens has emerged from excess land owned by a state-owned mental hospital. Dubbed the Accidental Eco-village by those involved in its transformation, the land was being sold in 1995 when the community who used it as a garden and park stepped in and formed an association to try and buy the land. Through partnerships with other NGOs and the University of Madison Department of Urban and Regional Planning, the Friends of Troy Gardens was able to create a diversity of uses that enabled the money to be found. Thus on the site now is a mixed income co-housing project involving 30 housing units, a community garden with 320 allotments, an intensive urban farm using traditional Hmong agricultural techniques for a community supported agriculture enterprise, and a prairie restoration scheme which is regenerating local biodiversity. Progress in moving away from fossil fuels will also require serious localizing and local sourcing of building materials and this in turn provides new opportunities to build more photosynthetic-economies.  The value of emphasizing the local is many-fold and the essential benefits are usually clear.  Dramatic reductions in the energy consumed of these materials is, of course the primary benefit. It is also of course about strengthening local economies and helping them to become more resilient in the face of global economic forces and it is also about re-forming lost connections to place. At the Bed ZED project in London, more than half of the building materials for the project came from within a 35-mile radius, and the wood used in construction, as well as a fuel in the neighborhood’s CHP plant, derives from local council forests. A photosynthetic approach to urban use of fibre will mean an added reduction in fibre miles as well as potential to help re-grow bioregions. What do you think? Leave us a comment. ———- Peter NewmanPeter Newman is Professor of Sustainability at Curtin University in Perth, Australia. He is the co-author of Cities as Sustainable Ecosystems, Green Urbanism Down Under, and Resilient Cities: Responding to Peak Oil and Climate Change.