Potentials and costs of carbon dioxide mitigation in the world's buildings
Introduction
A large body of literature suggests that the buildings sector is key for low-cost climate mitigation worldwide (IEA, 2006a; UNEP, 2007; IPCC, 2007). Above all, this sector is the second largest global carbon dioxide (CO2) emitter after industry, representing approximately 33% of the global total (Price et al., 2006). At the same time, buildings are often considered as a “goldmine” of greenhouse gas (GHG) mitigation (Turmes, 2005) due to the large cost-effective opportunities as well as the broad variety of co-benefits. A wide range of best practices and cases demonstrate energy savings in buildings as high as 80% at little or no extra cost (Harvey, 2006; Öhlinger, 2006).
While many experts report such generous opportunities to conserve energy and to mitigate GHG emissions within the buildings of many countries, these opportunities are often not taken advantage of and not covered well by existing policies (Lechtenböhmer and Thomas, 2003). The reasons for this include the widespread and fragmented nature of the efficiency potential among buildings and among end-users (Novikova et al., 2006), combined with the especially high number and strong barriers to adopting efficient building technologies and practices (IEA, 2006a; IPCC, 2007; Golove and Eto, 1996). However, a large number of policy success stories and much experience, including the Energy Star endorsement program in the United States and the appliance labelling scheme in the European Union, have demonstrated that with well-designed policies aimed at saving energy major reductions in GHG emissions are possible (Ürge-Vorsatz et al., 2007a, Ürge-Vorsatz et al., 2007b).
Therefore, if targeted by well-tailored policies, a significant portion of GHG emissions associated with buildings can be cut in a cost-effective way. However, how large is this potential and how much will it cost to capture it? How much can the world's buildings contribute to global mitigation efforts? How much will it cost to achieve a certain reduction target, or, vice versa, how much emissions can we reduce at an affordable cost? How do buildings compare to other sectors? What kind of mitigation options are of the highest priority and how do these priorities vary among different world regions? According to the knowledge of the authors and of a broad circle of experts in the energy efficiency community, an in-depth global bottom-up assessment of the global GHG mitigation potential in buildings has not been made recently. Besides three pieces of work covering several countries or regions (ADB, 1998; Halsnæs, 1999; Shukla, 1995), the authors, after an extensive search, have located only one study (AIM, 2004) in the public domain that provides a global estimate, which, however, covered a limited number of technological options.
Section snippets
Aim, significance and structure of the paper
This paper aims to address the gap in knowledge outlined in the introduction by presenting the results of a research effort that appraises the global potential for CO2 mitigation in the world's building sector. The research relied on existing national and regional bottom-up assessments, summarising their results in a global framework with a focus on CO2 mitigation. The goals of the paper are to (i) provide an estimate for the global potential of CO2 mitigation in the world's building sector;
The methodological framework
This section discusses the major methods applied and assumptions made to enable a comparative assessment of studies evaluating buildings-related CO2 mitigation opportunities around the world and to construct the global estimate of CO2 reduction potential in the world's buildings, along with associated costs. First, the section describes how studies with different analytical approaches and assumptions were selected. Since each study uses its own methodology, different parameters and ways to
Results: comparative analysis of CO2 reduction potential in buildings in selected countries
As shown in the previous section, various approaches have been used to estimate the costs of CO2 mitigation in buildings. In many cases, the results of different studies even for the same country vary considerably, depending on assumptions regarding base-case conditions; the diversity of the building stock and operating practices; the rate of technology diffusion; the shapes of cost, price, and learning curves; and the discount rate adopted for evaluating the various options. Despite these
5.1. International comparison of the cost dynamics for CO2 limitation: supply curves of CO2 mitigation
Fig. 1 illustrates the potential for CO2 abatement as a function of costs for eight selected recent detailed studies from different world regions. The steepness of the curves, i.e. the rate at which the costs of the measures increase as more of the potential is captured, varies substantially by country and by study. Despite the concern about different assumptions made by different studies, the figure clearly demonstrates the wide range of opportunities for cost-effective and low-cost CO2
Estimates of CO2 mitigation potential in the World's buildings
While there are methodological challenges in aggregating figures of the discussed studies based on differing assumptions, an estimate for the global potential in the buildings sector was developed correcting for as many of the differing assumptions as possible, as described in the methodology section (Section 3) above in detail. The results of the calculations suggest that by 2020, globally, approximately 29% of the projected baseline emissions can be avoided cost effectively through mitigation
Conclusion
This paper investigated the potential for CO2 emission mitigation and associated costs in the world's buildings. The main conclusion is that substantial low cost reductions can be achieved over the coming years in energy-related CO2 emissions in the buildings sector. If this potential is realised, the building-related CO2 emissions would stay constant over 2004–2030. These stabilisation levels (if achieved by all other sectors) would cancel about 3°C temperature increase.
For the countries
Acknowledgments
We are thankful to the Central European University and the International Policy Fellowship, who supported the research work for the authors’ contribution to the IPCC report, and the present publication. Our special gratitude goes to Mark Levine (Lawrence Berkeley National Laboratory), who provided invaluable ideas and contributions to the paper.
We are thankful to experts who helped us locate studies used for the research. These include Sebastian Mirasgedis (National Observatory of Athens),
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