City-Integrated Bioenergy for Low Carbon Urban Development

Cities are a major contributor to the global energy demand and carbon emissions (e.g., approximately 65%), and therefore they are key players in developing climate change management strategies. Alternative, city-integrated... [ view full abstract ]

Cities are a major contributor to the global energy demand and carbon emissions (e.g., approximately 65%), and therefore they are key players in developing climate change management strategies. Alternative, city-integrated renewable energy systems are considered as a sustainable solution to meet the high-energy demands of growing urban areas in an environmentally responsible manner. In OECD countries, the total primary energy supply from renewable sources almost doubled between 1990-2015, from 271 to 510 Mtoe, at an average annual growth rate of 2.6%. Bioenergy (i.e., biofuels and waste), was the biggest contributor to the 2015 renewable primary energy supply in the OCED at approximately 55.1%, of which, shares of solid, liquid biofuels and biogas were respectively 37.4%, 10.6%, and 4.2%. While the majority of growth of renewable energy has taken place in final consumption sectors (residential, commercial, industry and most significantly transport sectors), the highest growth rate belonged to liquid biofuels with an average increase of about 44% per annum since 1990.

The aim of this study was to assess the current and potential contributions of bioenergy systems, particularly from biomass and renewables wastes, to low carbon and climate resilient urban planning in global cities. In addition, we evaluated some of the most recent and promising technological advancements in bioenergy systems that could help urban areas become sustainable and livable cities. We discuss the use of bioenergy systems for thermal and electricity and fuel generation in four broad sectors: transportation, residential, commercial, and industrial. Owing to the energy storage capacity and a greater reliability of biomass, compared to wind and solar, bioenergy has been gaining increasing attention in hybrid renewable energy systems. In urban areas, local bioenergy produced from biowaste has proven particularly effective for creating carbon offsets through displacing fossil fuel sources.

The results show that bioenergy is expected to make a larger contribution to urban energy generation in the next decade. However, there seems to be a big shift in bioenergy feedstock from edible biomass feedstock (e.g., crops, vegetable oils, and animal fats) to biowaste sources. Furthermore, the use of non-edible vegetable oils is increasingly becoming a topic of controversy because of an inappropriate implementation of land, water, and energy resources vital for human food production. Alternatively, bioenergy from the biowaste - a ubiquitous and low-cost feedstock - will be expected to play a key contribution to the sustainable urban energy and emissions planning. Meanwhile, the role of biogas and liquid biofuels in urban transportation is a growing interest for city decision makers that highlight the need for implementing an integrated approach to urban transportation and waste management. Therefore, designing an incentive-based regulatory approach which facilitates the use of liquid biofuel/biogas (e.g., derived from the biodegradable municipal wastes) in public and private urban transportation can be very helpful. Although relying on biowaste feedstock can address some of the issues concerning the sustainable bioenergy generation (e.g., impacts on land, water, and biodiversity), biomass low energy density and conversion efficiency are among the key factors hindering the widespread implementation of urban bioenergy.