Emergy Synthesis of Urban Agriculture in Rio de Janeiro, Brazil

Cities are increasingly challenged in sustaining their growing populations with food. As fossil energy reserves are depleted, the sustainability of food production is highly dependent on the ability to yield more food relative to resource use. In preparing cities for peak oil, urban food systems are therefore needed that make better use of local and renewable resources, as opposed to imported and non-renewable resources. Emerging partly as a response to escalating food and energy prices, urban agriculture may contribute food while using significantly less fossil fuels and other non-renewable resources, hence reducing greenhouse gas emissions as well as pressure put on dwindling fossil fuel reserves. To examine the feasibility of urban agriculture, an emergy evaluation was performed, based on a participatory case study in central Rio de Janeiro, Brazil. On a yearly basis, the studied system yielded 5.96 kg of vegetables per m 2 . The Emergy Yield Ratio (EYR) calculated was 8.63, and the Emergy Sustainability Index 35.43, which indicate very high and sustainable yield if compared to most conventional agricultural production. Put together, these results indicate urban agriculture offers several opportunities for more sustainable food production; such as more appropriate use of local renewable resources, recycling of urban waste and decreased dependence on imported and nonrenewable resources. If incorporated in policies for sustainable development, urban agriculture may thus facilitate transition to a more energy efficient food system, as well as decreased fossil fuel use and greenhouse gas emissions at aggregate levels of society.