Water and Land: Bottlenecks of Green Energy

The entire premise of renewable energy is that it is supposed to be environmentally friendly and renewable. Yet as research continues into green energy, it is clear that most types are constrained by limited resources. The two most fundamental resources that play a vital role in the generation of green energy are water and land. Yet the extent of the impact that water and land limitations have on green energy is overlooked. Without the proper conservation of these two resources, green energy cannot be truly renewable.

Continued unregulated expansion of green energy is sure to strain these two limited resources. Land is an especially precious commodity, as many forms of green energy, especially solar and biomass, rely on huge tracts of land in order to be viable. Water is a just as important a commodity. All thermoelectric electricity generators, including solar, fossil, and nuclear, require water in some form, though it usually serves as a coolant.

It is important to note that current energy sources aren’t more efficient in terms of land and water use. Electricity generated from coal uses a lot of land and water. An above average size coal mine in the United States takes about 15,000 acres [1]. In addition, coal mining strips the land of its native vegetation, and causes deforestation. In the Jaintia Hills region of India, for example, the amount of forested area had dropped by 50% in 30 years by 2007, while the amount of land devoted to coal mining jumped 350% [2]. Current water use in thermoelectric plants that process fossil fuels can vary anywhere from 0.3-0.8 gallons per kilowatt-hour, but this is only for plants that have a re-circulating cooling system. For the once-through cooling systems that older plants use, the water usage can range anywhere from 7.5-50 gallons per kilowatt-hour. Currently, many plants are being upgraded so that they are more water efficient [3].

However, the problem here is that renewable energy also requires a large commitment of land and water resources, if not larger than traditional energy sources. One example is electricity generated from photovoltaic solar panels. Photovoltaic solar plants require vast amounts of land to operate. In addition, they must be built in specific regions in order to achieve maximum efficiency. The best area for these power plants is in the Southwest, as there is little to no cloud cover in the relatively arid region, so the greatest amount of solar radiation hits in that area for the greatest amount of time each year. However, large photovoltaic cell power plants use up to 180 acres [4]. The principle problem is that photovoltaic power plants are much less efficient than coal. While coal produces roughly 5,376,000 kWh per acre, the most efficient photovoltaic power plant to be built in the Mojave Desert, the AV Solar Ranch One, will only produce 285,714 kWh per acre. Therefore, in order for solar energy to completely replace coal energy as the primary source of electricity, solar energy will have to take up around 19 times the land area currently used for coal mining, and this is the best case scenario, when solar energy generation is most efficient. It’s also important that coal mining does up heave a lot of land, but the land can be reclaimed for other uses once the coal is extracted from the area [2]. Photovoltaic power plants will take up the land indefinitely, causing long term damage to the area.

Another type of solar energy power plant, the solar tower, has the same shortfalls as photovoltaic plants. They work by using mirrors to reflect sunlight onto one solar tower, which uses the heat generated to create steam from water, thus turning turbines. Solar towers must also be built in arid regions for maximum efficiency, which not only disturbs the land, but also drains the water from the region. Arid regions are already devoid of water, and the solar tower requires water to generate the steam power. Therefore, because of the scarcity of water in these regions, it must be brought in from other areas [4]. Water resources are already strained in the area, and groundwater is quickly disappearing. Although exact numbers for groundwater depletion have not been measured, the United States Geological Survey estimates that around the western border of the Mojave Desert, the primary location for solar plants, has experienced a 75 foot decline in groundwater levels since 1902. The eastern border is much worse off, with groundwater levels dropping roughly 150-200 feet since 1902 [5]. This causes a large amount of strain on water resources in the area, and the states bordering the Mojave Desert to the west and east, California and Colorado, are already facing a water crisis. The continued expansion of solar tower power plants is sure to cause a large amount of stress on water resources in the region in future years.

However, the renewable energy source that relies most heavily on land and water is biomass. Biomass is usually generated from either the same land as that used in agriculture, or competes with it. The problem with biomass energy comes from the vast amounts of land that it requires, and the competing interests that it poses. Land use in biomass energy has been extensively studied, especially in small regions such as Hawaii. The problem presented by the production of biomass energy is amplified in small regions, as there must be a careful balance maintained between land used for biomass energy, for agriculture, and for natural biospheres such as forests or swamps [6]. For example, the federal ethanol subsidies enacted in the United States created a complex tradeoff where farmers had to divide their limited land for corn production into corn used for ethanol and corn used for food. This division of land led to an increase in food prices of roughly 5% for wheat and 7% for corn [7]. Competing interests because of limited land causes catastrophic results for the vast majority of citizens, who rely on low food prices every day for sustenance. Agriculture already uses most of the land that can be used for biomass energy, so an increase in the biomass energy demand must result in an expansion of land use. Unfortunately, this results in either deforestation or wetland draining, as these are the main methods through which land is reclaimed [8]. These actions result in a huge loss of biodiversity, as well as loss of some of the most important carbon sinks left in the world. Conversion of forests or wetlands into farm land on a global scale contributes a yearly net increase of about 1.6 gigatons of carbon dioxide into the atmosphere, which is roughly a fourth of the carbon dioxide generated from fossil fuel combustion each year [8]. It is also clear that any expansion of biomass production requires a greater use of water. Agriculture already accounts for 33% of the water use in the United States [9], and increasing biomass production means increasing water use. This is a huge problem, as areas such as California and Colorado are experiencing a water crisis, where their water reservoirs are quickly drying up. In these areas, attempting to devote more land to agriculture means a greater strain on water supplies, which is ultimately unsustainable [5].

With the limitations of renewable energy clear, there is imminent need for a solution. Land and water use is intrinsically tied with the development of all of these forms of renewable energy. The solution, then, becomes controlling the development of each renewable energy source so a balance is struck between reducing greenhouse gas emissions and protecting vital resources.

The first issue to tackle is the impending water crisis. While an overarching plan of water distribution must come on a national level, conserving existing water supplies is incredibly important. A vital imperative for both local and national governments is to ensure that water delivery methods do not leak and are in good repair. Although this may sound rather banal and obvious, the fact remains that several billion gallons of drinking water are lost each day because of leaky pipes in America alone [1]. It is imperative that this most basic of problems in the water supply is fixed.

Yet the growing scarcity of water requires further action beyond fixing local water pipes. There must be a greater focus on management of water resources. One easy way to force greater oversight of water resources is to simply raise its price. This would force greater water conservation. Total water usage in the United States amounts to 410,000 million gallons per day, with about 49% being used for thermoelectric power and 33% for agriculture [9]. A boom in the use of solar power or in biomass production would result in a greater demand for already scarce water in America. This boom must be controlled, at the very least by forcing companies to conserve more water as they expand their business.

The land usage crisis poses a separate yet equally as important issue. The amount of potential land for renewable energy development is extremely limited, and much of this land is federally owned. The federal government owns a total of 650 million acres of land, but less than half of it is even suitable for renewable energy development, and development is only commercially viable on only a quarter of federal lands [10]. The first step is to temporarily freeze any further land reclamation activity, or at least severely limit it. The next step is to create a tax on land reclamation, similar to a carbon tax. This tax would be calculated based on the net increase in carbon dioxide emissions, the loss of biodiversity, and possibly other factors as well. This would create an economic disincentive for increased land use. Although this might have the effect of severely limiting the expansion of some forms of renewable energy such as biomass, it would also force companies to focus their efforts on discovering more land-friendly forms of biomass energy. This is an extremely daunting task, but wasteful land usage will only spell disaster for renewable energy.

The limitations of renewable energy are still omnipresent, and as the nation moves to embrace renewable energy, the growing scarcity of water and land are important issues that must be considered. Although alternative energy is being marketed as a sort of panacea for the problems of climate change and energy dependence, an idealistic view of alternative energy will only lead to neglect of the conservation of resources.  By then, it may already be too late.

References

  1. http://www.infrastructurereportcard.org/sites/default/files/RC2009_full_report.pdf.
  2. Sarma, K, Kushwaha, S.P.S. “Coal Mining Impact on Land Use/Land Cover in Jaintia Hills District of Meghalaya, India Using Remote Sensing and Gis Technique.” Guru Gobind Singh Indraprastha University School of Environment Management. 2005.
  3. The Energy Foundation. “The Last Straw: Water Use by Power Plants in the Arid West.” 2003.
  4. Ren21. “Renewables: Global Status Report 2009 Update.” 2009.
  5. Konikow L, Kendy E. “Groundwater depletion: A global problem.” Hydrogeology Journal. 2005 American Society of Civil Engineers. “2009 Report Card for America’s Infrastructure.” 2009.
  6. G. G. Marten, o. Babar, L. Christanty, P. Kasturi, O. Lewis, C. Mulcock and I. Willington, “Environmental considerations for biomass energy development: Hawaii case study”, East-West Environment and Policy Institute Report No 9, HI, USA, 1981.
  7. Mitchell, Donald. “A Note on Rising Food Prices.” The World Bank.
  8. Watson, Robert T, et al. IPCC Special Report on Land Use, Land-Use Change And Forestry. IPCC. 2000.
  9. Kenny, J.F., Barber, N.L., Hutson, S.S., Linsey, K.S., Lovelace, J.K., and Maupin, M.A., 2009, Estimated use of water in the United States in 2005: U.S. Geological Survey Circular 1344, 52 p.
  10. U.S. Department of Energy, U.S. Department of the Interior. “Assessing the Potential for Renewable Energy on Public Lands”. 2003.

Allan is a first-year at the University of Chicago.

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  • John Hoffner

    Good paper on water and land issues associated with renewable energy systems. However, where the arguement falls apart regarding photovoltaics and land use is that the technology is flexible and can be installed on many of the vast rooftops of commercial and residential buildings throughout the U.S. (and world) Tapping rooftops utilizes a distributed resource that is otherwise wasted energy – roofs baking out in the environment. The advantage of PV is that it can be installed on rooftops and unused land areas – unlike coal or gas plants that must be large, centralized systems which require open or closed cooling systems. PV also requires no water for cooling and in most cases very little for panel washing. This should be included in your analysis of PV. There have been many papers that examine the contribution that PV can make if only a small percentage of our roofs are fitted with PV systems.

    John Hoffner
    PV Progam Manager

  • Thank you for your comment John! We would love to get more feedback from you on this article, particularly because it is in your area of expertise

  • Allan Zhang

    Ah the idea of PV cells on rooftops is definitely one element of their usage that I overlooked, and perhaps the scope of my topic might have gotten a bit broad.

    While PV cells on rooftops can certainly make an impact on energy, there is the question of just how efficient they will be at generating the amount of power needed to sustain our every day lives. I have read several papers on this idea of “Energy Payback” on PV cells on rooftops, and from what I can tell, it’s an issue with no clear consensus.

    The more general problem with PV systems on rooftops is that in general they will never be as efficient as PV plants out in the desert for example. Over most cities and suburban areas, cloud cover is a serious concern for most of the year, leading to decreased yields for PV cells installed on rooftops. This in essence leads to the energy payback issue mentioned earlier, where there’s a certain amount of time that a PV panel must be installed before it can even generate the amount of energy used to create it in the first place. I’ve seen numbers go as high as 10 to 15 years for the amount of time that the PV panel must be installed before it can pay back the energy usage that it took to build it in the first place, which means that it effectively hasn’t contributed to reducing energy usage for 1/3 to 1/2 of its overall lifetime, since most PV panels have a 25-30 year lifespan, which is definitely an issue.

    However, you are correct in that this is a topic that I should have considered in my article, although I suppose that in terms of land and water usage, the question would have to be weighed in terms of whether PV cells on rooftops could effectively replace a sufficient number of energy producing plants that do use up land space.

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