Tuesday, May 15, 2012
Is Clean Energy Truly More Spatially Compact than Fossil Fuels?
Living more compactly to leave more space for nature means shifting to renewable, clean forms of energy, I argue so far in this blog. We need to settle once and for all whether clean energy is indeed more spatially parsimonious than fossil fuels. The footprint for wind energy is fairly small, but solar energy requires substantial amounts of space. When we account for the probable spatial impacts of climate change induced by continued fossil fuel use, is it the case fossil fuels will absorb more space than a shift to clean energy, especially to solar?
Global warming alters our spatial landscape through two primary mechanisms: sea-level rise and shifts in vegetation zones. As the earth’s climate warms, oceans expand and rise by absorbing more heat from the atmosphere and more water from retreating glaciers and melting ice sheets. Rising oceans rip away at beaches, inundate coastal wetlands, invade low-lying cities, and take over agricultural lands in river deltas. Climatic warming also leads to upward shifts of vegetation zones both in latitude and altitude. Hot-weather zones such as deserts expand their coverage at low latitudes, while cold-weather zones such as tundra with permafrost shrink at high latitudes. In mountainous landscapes, prairies and warm-weather forests march upward to higher elevations while subalpine zones retreat and contract with no place to go.
One area of the world much affected by desert expansion is the Sahel, a band of land up to a thousand kilometers wide just below the Sahara desert stretching across Africa from the Atlantic Ocean to the Red Sea. The Sahel is a 3 million square kilometer transition zone between Sahara desert to the north and less arid savannah and tropical forests to the south. The Sahel is mostly grassland with scattered acacia trees, and was once home to large populations of grazing mammals, some of whom have gone extinct in the face of overhunting and competition with livestock. On its seasonal wetlands, the Sahel also hosts millions of migratory birds moving along the African-Eurasian flyways.
The countries of the Sahel are home to more than 90 million residents who in the last fifty years have suffered from increasing incidences of drought, crop failures, and periodic famines due to subnormal rainfall. These countries, including Chad, Mali, Mauritania, Niger, and Sudan, are among the poorest in the world. The Sahel is vulnerable to declining vegetation cover and desertification not just because of drought, but as a consequence overpopulation, overgrazing, and excessive cropping, all of which add to the area’s poverty. Improvements in agricultural practices that reduce erosion and economize on scarce water resources have begun to raise living standards for some in the Sahel, but the future will be increasingly difficult for most if global warming continues at its current pace. As recently as 2010, the Sahel suffered a serious drought placing 350,000 in danger of starvation and 1.2 million under the risk of famine. The Intergovernmental Panel on Climate Change (IPCC) predicts that under current climate trends the proportion of the global landscape subject to extreme drought will increase from the current 1 percent to about 30 percent by the 2090s. If this occurs, a southward push of the Sahara desert boundary into the Sahel will likely continue as will the suffering of its residents.
While low-latitude hot deserts are predicted to expand due to continued climate warming, the actual average annual temperature increases on a global scale will be greatest at higher latitudes. Arctic tundra, a major high-latitude vegetation zone, is already exhibiting symptoms of stress from rising temperatures. Arctic tundra covers a huge, sparsely populated area of 11.5 million square kilometers extending across the northern edge of the North American and Eurasian continents just above expansive stretches of boreal forest. Tundra landscapes feature long, very cold winters, short summers, desert-like precipitation, high winds that blow across a flat topography, and huge volumes of permafrost (permanently frozen soil) just below the biologically active surface soils. Because of a short growing season and harsh winter conditions, only ground-hugging shrubs and low-stature grasses, wildflowers, mosses, and lichens can survive in the tundra, not trees, and even shrubs disappear in the northern-most reaches. In the short summers, the tundra teems with grazing caribou and musk oxen and millions of waterfowl attracted by marshes, bogs, and lakes created by the melting of the upper permafrost layers. Historically, human intrusion in the Arctic tundra was limited to aboriginal populations that survived mainly through hunting and fishing, but recently the North Slope of Alaska and other locations have become prime territory for oil production. The Arctic tundra remains one of the least directly disturbed natural habitats in the world.
Climatic changes are already afoot in the Arctic. Weather reporting stations throughout the area show an upward trend in both temperature and precipitation over the last fifty years. Permafrost temperatures measured from bore-hole samples taken for the past 20 years show a distinct upward trend. The end of snowmelt in recent decades is occurring at progressively earlier dates in the spring, resulting in longer summer growing seasons and lengthier periods of permafrost melting. Glaciers in nearby mountains have shrunk substantially since the 1950s, showing evidence of a long-term warming trend. In response to a lengthening growing season and more moderate temperatures, shrubs are expanding northward into previously shrub-free areas where only grasses and other ground-hugging vegetation survived historically. At the southern boundary of the tundra, the boreal forest appears to be marching northward as temperatures moderate with younger trees successfully establishing themselves farther and farther north over time. Within the tundra, more and more depressions, called thermokarst, can be observed where ice-rich permafrost has melted and caused subsidence of the soil layer above.
One could easily think that tundra warming and the advance of forests into the tundra really doesn’t matter that much because so few people live there. The caribou, arctic foxes, musk oxen and waterfowl that make the tundra home would of course disagree, but there is another good reason to worry about the health of the tundra biome. Under normal conditions, tundra accumulates huge amounts of carbon. Each year plants grow and die in the summer season, but the organic matter they create doesn’t get a chance to fully break down before the winter freeze, and a portion of this organic matter gets locked up in the permafrost. The accumulation of permafrost over time has created a huge carbon reservoir. As the arctic tundra warms and increasing amounts of permafrost melt, organic matter freed from the ice is broken down by bacteria and carbon is released back to the atmosphere. Where oxygen is available, this release takes place in the form of CO2, but in the many arctic bogs lacking oxygen, the release occurs as methane which is a much more powerful and dangerous greenhouse gas than CO2. Through this mechanism, permafrost melting leads to more greenhouse gas emissions, increased climatic warming, and yet more permafrost melting to complete a not so virtuous circle. Although potentially substantial because of the Arctic tundra’s size, the final quantitative effects of permafrost melting on climate change remains unknown. Why take a chance? Destructive impacts of global warming on big landscapes like the Sahel and Arctic tundra can be avoided by moving quickly to a clean energy economy that will itself possess a modest spatial footprint. To see this, let’s focus our attention on one of the potentially most disturbing of all climate change impacts, the inundation of coastal lands by a rise in the sea level.
Until recently, scientists were predicting up to a 1 meter rise in sea level by the end of this century, but now some have changed their tune. The melt rates for the Greenland and Antarctic Ice sheets are greater than recently thought, increasing sea-level rise estimates to 1-3 meters by 2100 with the possibility of a 5 meter rise if ice-sheet breakups takes place. The effects of a 1-meter rise are substantial and a 5-meter rise could be catastrophic. I refer you to a recent report, “The Impact of Sea Level Rise on Developing Countries: A Comparative Analysis,” from the World Bank for a fascinating analysis and description of the sea-level rise problem.
As one can imagine, those countries that suffer the greatest effects from sea-level rise are low-lying, such as the Bahamas, and possess extensive river deltas, such as Viet Nam, Egypt, and Bangladesh. These countries will suffer from population displacement, declines in gross domestic product, and a general loss of land area that will include inundations of croplands, urban landscapes, and wetlands. The country likely to be hardest hit from a 1-meter sea-level rise is Viet Nam with projected inundation of 5 percent of its total land area, 7 percent of its agricultural lands, 11 percent of its urban extent, and nearly 30 percent of its wetlands. Of all the world’s ecosystems, wetland loss is potentially the most devastating from sea-level increases because so much has already disappeared due to past human intrusions. At the global level, a 1-meter sea-level rise will impact nearly 2 percent of remaining wetlands, while a 5-meter rise will raise that number to 7 percent.
Because of both geography and a lack of resources for coastal landscape defenses, it is the developing countries of the world that will suffer the most from sea-level rise. Ironically, attacking climate change through clean energy development will not only avoid such harms, but for some countries, such as Egypt, it will create significant economic opportunities. Egypt, is second only to Viet Nam in projected potential damage from sea level increases. While Egypt won’t loose much of its 1,000,000 square kilometer surface area, because its population and arable lands are so heavily concentrated in the Nile Delta, even a meter sea-level rise will be devastating. From such an increase, Egypt will see some 13 percent of its 40,000 square kilometers of cropland inundated and as much as 9 percent of its population will suffer displacement. A 5-meter sea-level rise would increase the cropland loss to 35 percent.
Harms of this kind can be avoided with a shift to clean sources of energy over the next forty years. A recent pear-reviewed study by DESERTEC, a foundation that advocates for desert-based solar thermal energy, points the way to a clean energy future with a minimal impact on global land use (See “Clean Power from Deserts: The DESERTEC Concept for Energy, Water and Climate Security”). The world’s hot desert cover 36 million square kilometers on which a huge volume of solar energy falls each year, so much that only about 1 percent of desert surface area would be needed to replace present-day global fossil fuel energy. Primary global energy consumption from fossil fuels currently equals 107,000 Terrawatt hours (TWh) a year, and a kilometer of hot desert receives 2.2 TWh of solar energy annually, of which 0.33 TWh can be captured at a presently attainable 15 percent electricity conversion rate. Even if total fossil fuel energy demand ultimately doubles, which exceeds current projections for the next half-century, no more than 2 percent of desert landscapes would be needed for solar energy production under the radical assumption that all of our fossil-fuel replacing energy comes from deserts. As opposed to photovoltaics, which generate electricity only when the sun shines, solar thermal technology uses mirrors which focus the suns energy on towers containing molten salt that store heat for powering steam driven electric generators 24 hours a day. Some desert landscapes, such as the Sonoran and Mohave deserts in the U.S., contain threatened species, but avoiding the destruction of rare desert habitat seems reasonable under a solar energy regime through careful placement of solar thermal facilities given the amount of desert landscape available worldwide. In sensitive habitats, photovoltaic panels may be the better technology to apply because it needn't be installed in the more disturbing large scale facilities typical of solar thermal. Solar panels can be tucked in along exists roads and power lines without doing much damage. At some point in the future we will most likely be using daytime solar energy to produce hydrogen through electrolysis that can in turn be employed in fuel cells that convert hydrogen back into electric energy for any number of applications including running motor vehicles or supplying electricity on demand.
Countries like Egypt and Tunisia can play a huge role in supplying solar energy, not only for North Africa and the Middle East, but the European Union as well. As noted in an earlier post, a thermal solar project is already planned for Tunisia that will deliver 2,000 megawatts of energy to the Italian electrical grid through a direct current high energy line under the Mediterranean. If Egypt devoted 2 percent of its deserts to thermal solar energy production as its share of a doubled global fossil fuel-replacement total, it would absorb only about 18,000 square kilometers of its 1,000,000 square kilometers of surface area. Solar energy development of this magnitude on Egypt’s deserts would be a small price to pay for avoiding inundation of 13 percent of its Nile valley agricultural lands and displacement of 9 percent of its population due to a fossil-fuel induced sea-level increase.
Given the opportunities for both wind and solar energy production in northern climates, some of which are already being utilized, deserts will never have to supply anywhere near a 100 percent of the worlds fossil-fuel replacing energy needs. Nevertheless, DESERTEC predicts a substantial clean energy role for North Africa and the Middle East in the future, with upwards of 700 Terrawatt hours per year imported from the region’s deserts by Europe in 2050. Even though the volume of investment over the next 40 years to achieve this much solar capacity would be huge, the final cost per kilowatt hour would be an affordable 0.05 Euros. The amount of desert surface area needed for this much energy production would be a bit more than 2,100 square kilometers, with perhaps half being located in Egypt. Needless to say, the volume of investment flowing into North Africa to develop enough solar capacity to supply 700 Terrawatt hours for export as well as meet local energy demand would significantly boost the region’s pace of economic development. DESERTEC forecasts a total investment in North African and Middle East thermal solar power of 350 billion Euros plus another 45 billion in high voltage direct current transmission lines by 2050.
The point is simple: solar energy is a much more spatially compact and benign route to take than the fossil fuel/climate change path we are now on with its probable harms to coastal landscapes from sea level increases. If we stick with fossil fuels and climatic warming, major vegetation zones will suffer damage and loss as well, such as the Sahel from drought and desertification and the Arctic tundra from permafrost melting and the northward march of boreal forests.