Of all the greenhouse gases, it is carbon dioxide that accounts for the bulk of climate change effects. This gas is emitted in the combustion of fuels that contain carbon – which is to say, most of the major fuels currently in commercial use. Climate change concerns have served to stimulate research and development activities in low-carbon energy sources. Renewable sources such as wind or solar energy are the most well known. These technologies tap into naturally occurring flows and convert them into electricity. Bioenergy – energy derived from vegetable matter – is another low-carbon resource. Bioenergy systems can be designed and operated sustainably so that the carbon dioxide emissions generated from burning the vegetable matter or its derivatives are offset by the carbon dioxide absorbed through photosynthesis during plant growth. Thus, bioenergy is regarded as CO2 neutral from a system-level standpoint.
Many biofuels can be derived from indigenous energy crops without the need for cutting-edge technology. Brazil, for example, has used sugarcane-derived bioethanol as a blending agent for gasoline for several decades now. Their highly successful ProAlcool stands as an example of a robust alternative energy program that has stood the test of time. Critics of bioenergy raise the "food versus fuel" issue, arguing that agricultural land is best used for food production rather than as energy farms. The resolution to this debate is as much a social, political and economic issue as it is a scientific and technological one. In any case, global trends have once again made alternative energy attractive enough to be seriously considered. An example is the recent effort by the Philippine government to develop bioethanol and biodiesel programs that utilize indigenous crops to produce substitutes for petroleum products. These measures are particularly timely, with recent oil price trends suggesting that gasoline prices may reach P40/liter by the end of 2005.
Despite the wide array of low-carbon energy technologies available at commercial or near-commercial levels of development, the bulk of the world’s energy is still derived from fossil fuels – natural gas, coal, and (especially for the transportation sector) oil. There is a certain pervasive technological inertia that makes it difficult to dislodge these dominant energy sources; economists refer to this effect as "network externalities." For example, most modern vehicles run on either gasoline or diesel oil. Many countries also have well-developed fuel supply chains to bring these fuels from refineries to depots and eventually to the end-users. The existence of established networks for producing and distributing these goods give an implicit advantage to the incumbent technologies, since new competitors must penetrate the market without the benefit of such supporting infrastructure. In the case of alternative motor vehicle fuels, for example, the most viable candidates are those that are sufficiently similar to gasoline or diesel to be used interchangeably, or mixed, with these conventional fuels.
Elsewhere in the world, major energy companies are investing heavily in retrofitting existing fossil fuel-fired plants to be more climate-friendly. Some of the concepts being tested are so exotic that they seem to border on science fiction – and yet huge sums of money are being invested in their development. One such technology is carbon sequestration, or, more precisely, carbon capture and storage (CCS). CCS techniques involve removal ("capture") of carbon dioxide gas from the exhaust of power plants, and then pumping the gas into some isolated reservoir ("storage"). Capture technologies include gas scrubbers that use chemical agents to isolate carbon dioxide from power plant stack gases. More innovative techniques include oxyfuel combustion – burning coal, oil or gas in pure oxygen to give an exhaust gas consisting mainly of carbon dioxide and water vapor – and precombustion capture through fuel gasification. Once the carbon dioxide gas is captured, it is compressed and prepared for storage. Candidate storage sites include impermeable underground geological formations – certainly seismic risk assessments are necessary to ensure long-term viability of the storage system. Deep-sea disposal is another option. At the extreme pressures found deep in the world’s oceans, carbon dioxide liquefies into a dense, oily liquid that sinks to the ocean floor to form pools that are – in principle, at least – isolated from the atmosphere. As fanciful as these schemes might appear, carbon dioxide storage is now being used commercially, for example, in conjunction with enhanced oil recovery (EOR) in petroleum reservoirs. Some experts estimate that CCS power plants can be in commercial operation before the end of the next decade.
It remains to be seen exactly what will become the dominant energy resource of the 21st century. Thermodynamic arguments point to renewable energy as the only viable option in the long run, particularly when we think in terms of centuries rather than decades. On the other hand, fossil energy definitely has the incumbent’s advantage of network externalities, and it will be necessary to make do with them for the foreseeable future. CCS may eventually turn out to be a viable and socially acceptable transition technology – or it may not. As for the futuristic concept of the "hydrogen economy," that will certainly bear some detailed discussion in another article.
Joel Q. Tanchuco is an assistant professor of the Economics Department of De La Salle University-Manila. He holds an M.A. in economics from the University of the Philippines-Diliman, and specializes in energy and natural resource economics. E-mail him at tanchucoj@dlsu.edu.ph.