Water and Energy Nexus: Nature Geoscience May edition

I have recently written a commentary for Nature Geoscience in which I and my co-authors discuss the tie between energy and water usage. For those who have a subscription to Nature, you can link to the article here. Alternatively, you can sign up for free and read the article OR just read my pasted text below:

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TEXT OF ARTICLE
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Water and solar energy enable trees and plants to grow today, just as hundreds of millions of years ago. Creation of the deposits of biomass that became fossil fuels depended on these two resources. The technological advances that have changed human life profoundly over the past decades and centuries have altered, but not resolved, this close coupling between water and energy. Current technologies for power generation, with some exceptions such as wind turbines and photovoltaic solar cells, rely heavily on the availability of large amounts of water. Primarily this water is needed for cooling thermoelectric plants and supplying fluid pressure and flow for hydroelectric power generation. But in a changing climate, it is not clear whether sufficient volumes of water will continue to be available where needed. And if, in an attempt to combat climate change, petrol is replaced by biofuels at a significant scale, more water will be needed for irrigation. Furthermore, clean fresh water is a basic necessity for human health and development. Large quantities of water can be provided — as long as sufficient energy supplies are available to reach deep aquifers, treat dirty water or desalinate the oceans. But a scarcity of energy implies a scarcity of water, just as constraints on water availability threaten the supply of energy, at least with the current infrastructure. Because of this interconnection (Fig. 1), water and energy cannot be treated in a disaggregated fashion, as is common today with both

markets and policy makers.

THE NEED FOR WATER IN POWER GENERATION

Large power plants present a strain on water resources. In the US in 2007, thermoelectric power generation, primarily comprising coal, natural gas and nuclear fuels, generated 91% (3,500 million MW h) of total electricity. These thermoelectric power plants require cooling by water, air or a combination of the two (Table 1), amounting to 40% of US freshwater withdrawals. Open-loop (or once-through) cooling withdraws large volumes of surface water, fresh and saline, for one-time use and returns nearly all the water to the source with little of the overall water being consumed by evaporation. While open-loop cooling is energy efficient and low in infrastructure and operational costs, the discharged water is warmer than ambient water, causing thermal pollution, which can kill fish and harm aquatic ecosystems. Thus, environmental agencies regulate discharge temperatures, taking into account a water body’s heat dissipation capacity. Closed-loop cooling requires less water withdrawal because the water is recirculated through use of cooling towers or evaporation ponds. However, because the cooling is essentially achieved through evaporation, closed-loop cooling results in higher water consumption (Table 1). The alternative, air-cooling, does not require water, but instead cools by using fans to blow air over a radiator similar to that in automobiles. The power efficiency of this is lower, up-front capital costs are higher and real-estate requirements are larger, making it a less attractive option economically.

Water is obviously central to power generation in hydroelectric dams. In the US in 2006, hydroelectric power plants generated approximately 7% (268 million MW h) of total electricity. Fifty-eight percent of US hydroelectricity is generated in California, Oregon and Washington alone, making the power supply vulnerable to regional changes in water availability. Though hydroelectric power is attractive for many reasons, it is least reliable during droughts when the need for water may take precedence over hydroelectricity.

THE NEED FOR ENERGY IN WATER PRODUCTION

The relationship goes the other way too, in that energy is necessary for producing and delivering fresh and potable water, just as water is necessary for generating energy. For example, energy is needed to convey, heat and treat fresh water and waste water. Heating water in homes and businesses for cooking, cleaning and other municipal and commercial uses consumes 3.6 quads, or 3.6%, of total US energy consumption. Thus, the need for hot water represents an important enduse for energy. Combined heat and power systems are efficient because they use otherwise wasted heat to do useful tasks.

Supply and conveyance of water is one of the most energy-intensive water processes, estimated to consume over 3% of total US electricity1,6. However, the energy use for supply and conveyance of water varies widely depending on the local infrastructure. Many gravity-fed systems require little energy, whereas long-haul systems, such as that in California, require vast energy investments to move water across the state and over mountain ranges. The average surface water treatment plant consumes over 370 kW h Ml–1. Tapping into groundwater sources also requires energy for pumping, which is dependent on aquifer depth: at a depth of 120 m, 530 kW h Ml–1 is required1,6.

Recent news articles illustrate these competition between water resources and power generation: the debate of whether to use water from a reservoir to serve municipal needs for drinking water versus generating hydroelectric power arose with Uruguay’s Salto Grande dam and the US Colorado River lakes; a natural gas power plant and private landowners argued over groundwater rights in Texas; and hydroelectric dams were taken offline in response to drought in Georgia, among others2–5.

As freshwater supplies become strained, many have turned to water sources once considered unusable, including brackish ground water and sea water. Although use of these water sources mitigates constraints on drinking-water supplies, treatment of brackish ground water and sea water requires as much as 10–12 times the energy use of standard drinking-water treatment. However, usually, untreated saline water can be used to cool the thermoelectric power plant that may be required for desalination.

Partly because of the high energy requirements, proposed desalination water treatment plants in Carlsbad, California, and Chennai, Tamil Nadu India have been opposed7,8.

Wastewater treatment also requires large amounts of energy, which will increase as discharge regulations in the US become stricter, requiring increasingly energy-intensive treatment technologies.

Estimates range from 250 kW h Ml–1 for trickling filter treatment, which uses a biologically active substrate for aerobic treatment, to 350 kW h Ml–1 for diff used aeration as part of activated sludge processing, and 400–500 kW h Ml–1 for advanced wastewater treatment that uses filtration and the option of nitrification6. Sludge treatment and processing alone can consume energy in the range of 30–80% of the total energy used in a wastewater plant; other physical and chemical treatment processes use much of the remaining percentage.

A THIRST FOR TRANSPORTATION FUELS

Two of the earliest fuels were wood and dung. They are still the major primary energy fuels for many regions of the world, providing 8.5% of the primary energy globally10. Trees require water for growth, as do the animals that supply dung. But modern liquid fuels such as gasoline, ethanol and diesel also require water for their extraction, farming, processing and refining. This ‘embodied water’ is not directly used in a vehicle, but rather indirectly required to make the fuel.

Water use for transportation can be considered in a similar fashion as for power generation in the form of withdrawal — that is, the amount of water that is necessary, but may eventually be returned to the system — and consumption, for example, through evaporation. However, in the context of transportation, consumption can additionally be associated with irrigated farming and as a feedstock. Generally, while driving light duty vehicles using current petroleum-based gasoline (assuming an average fuel economy of 20.5 miles per gallon (mpg) = 8.7 km l–1) and diesel (28.2 mpg = 12.0 km l–1), embodied water is withdrawn and consumed from nature at rates of up to 1.5 l km–1 and 0.3 l km–1, respectively.

Using liquids converted from other fossil fuels (coal, oil shale and tar sands) means that the rates of water consumption and withdrawal are 2–4 times and 1–2 times higher, respectively, and they are much more concentrated in regions where the fossil fuel resources exist.

Propelling vehicles using hydrogen and electricity also has substantial water impacts when drawing from the average US electric grid (owing to water used for power plant cooling as discussed earlier). Under these assumptions, driving ‘electric’ miles using a fuel-cell vehicle with hydrogen via electrolysis and a plug-in hybrid electric vehicle (PHEV) or electric vehicle (EV) consumes water at 0.9 and 0.5 l km–1 while withdrawing 27 and 17 l km–1, respectively11,12. Using wind and photovoltaic solar power to supply required electricity for transportation makes water intensity negligible. However, even if every US light duty vehicle mile were driven via US electric power with current technologies, US water demand would only increase by 0.9% (3.4 billion litres per day). Most of the fuels under consideration to replace petroleum are more water intensive, with biofuels residing at the top of the list. Only for fuel crops that are not irrigated is the water intensity comparable to petroleum fuels. But many fuel crops are irrigated, and accounting for irrigation can cause water consumption rates to be 2–3 orders of magnitude higher than without irrigation. Although only 15–20% of US corn and 5–10% of US soybean bushels are irrigated to any degree, there was still a substantial water contribution to biofuel crop farming at nearly 5,700 gigalitres (3.5% of US water consumption) in 2005 for the production of ethanol alone. Given that agricultural irrigation is the most water-consumptive sector of the US economy, high water usage is not surprising. But by switching to biofuels, this water consumption is likely to grow.

Additionally, competing water demands oft en make the siting of ethanol plants difficult because they require large amounts of water. Ethanol processing plants consume water for cooling processes, including the exothermic fermentation reaction, requiring 1–3 million litres per day to produce 250,000–750,000 litres per day of ethanol13,14.

LOOKING TO THE FUTURE

We see trends towards more water- intensive liquid fuels, more energy-intensive water sources and a growing population that will require more of both. These challenges will be exacerbated by climate change, which may cause geographic and temporal changes in the amount, annual distribution and form of precipitation (for example, as rain or snow). Because cities and their infrastructure are built on the basis of past precipitation patterns, such climatic changes may require substantial adjustments. In regions where water becomes scarcer, people must weigh the pros and cons between moving the people to the water and moving the water to the people (the latter of which requires continuous additional energy).

Regional climate projections will be needed to inform planning and policy. When siting new power plants, governments and power generators need to consider water availability over the plants’ lifetimes, normally on the order of several decades. Policy for energy and water resources should be integrated to consider less-water-intensive options in agriculture, such as forestry, and in electricity generation, such as wind, photovoltaic solar and air-cooling technologies. In the fuel sector, water consumption and withdrawal need to be included in environmental impact analyses such as those dictated by the Energy Independence and Security Act of 2007, which requires life-cycle analysis for understanding the greenhouse-gas impacts of renewable fuels. Like diversified long-term financial investment strategies, future water and energy infrastructure should also be diverse and multiscaled in order to create resilience in an uncertain climate and energy future. For example, Ghana has had highly fluctuating reliability of electricity supply owing to heavy dependence upon hydropower or other single energy sources, without extensive electric grids to help transport electricity in tough times.

Distributed energy systems provide smaller-scale systems and add resilience to electric grids dominated by large centralized power plants, but they are usually considered more expensive owing to conventional financial and appraisal systems that account for capital but not operating expenses. For new power plants at greenfield sites in the US, open-loop cooling has been outlawed for all practical purposes by the environmental constraints on water intake velocity. The trend since the 1980s has been towards closed-loop cooling. However, closed-loop cooling makes the use of sea water more difficult, because evaporating water with high proportions of dissolved solids can create foul-up problems. Nevertheless using sea water, waste water and other low quality water for cooling should be encouraged where possible.

We also need policy that allows the operating costs and energy consumption of buildings and homes to be integrated into the construction, sales and finance phases of development. More energy efficient buildings within larger cities require less bulk city services. We must ask ourselves why we require no energy return on investment for crown moulding yet claim photovoltaics do not pay back fast enough. Fortunately sustainable concepts such as LEED (Leadership in Energy and Environmental Design) and projects such as the China EcoBlock18 guide and demonstrate integrated water and energy infrastructure via whole system design.

Water and energy cannot be separated. With an unlimited supply of available energy, we would be able to supply as much clean water as the world needs. In the real world of resource constraints, we need to simultaneously conserve water and energy. Thankfully, water conservation and energy conservation are synonymous with each other, so we have the opportunity for swift progress.

Leaving fossil fuels in the ground vs. using them all up now

I wrote a think piece for Worldchanging playing off one of the basic arguments against climate mitigation (we'll be richer in the future and more capable of dealing with any effects) with the idea of leaving fossil fuels in the ground (will we also be more capable of using fossil fuels in the future, and should we strive to leave some?).

One thing that did not get into the article in time (but came the day after I submitted it!) was the fact that the Saudi King himself made reference toward specifically leaving some of their new found reserves for future generations! How is that for some new thinking!

Visit the site to read the commentary (http://www.worldchanging.com/archives/007962.html), or see below.

NOTE: As one of the early bloggers notes, nuclear energy has a wide range of possibilities (over carbon-based fossil fuels), and those were too much to go into for one article, aside from the fact that I am definitely not an expert on nuclear materials, for fission or fusion (always 50 years away!).

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Success is Winding Up with Oil in the Ground

Will we always be more capable in the future?

One basic economic argument against substantial climate change mitigation investments often centers on the concept that, because of monetary discount rates and historically-proven continuous economic and technological growth, society will be both ‘richer’ and more capable of dealing with possible negative effects in the future. Proponents of this argument often use it to reason that mitigation is simply too economically costly to pursue.

Can the same argument hold for production of fossil fuels? That is to say, if we are going to be richer and more capable in the future, won’t we have a better use for all energy sources, including fossil fuels? And will part of our ability to deal with societal issues, such as those caused by climate change, be predicated upon having available energy? If the answer to these questions is “yes”, then we should keep our fossil fuels in the ground.

The reason that the idea of preserving fossil fuels and ecosystems for future generations is not widely held is that the pattern since the industrial revolution of the 1800s shows us that energy consumption is highly correlated to economic growth, and thus the ability to become ‘richer’ (Figure 1). But recently Ecuadorian officials have proposed that the international community pay approximately half of the assumed value an oil deposit that lies beneath the Yasuni Amazon ecological reserve in order not to extract the oil [1]. Is this a beginning to question the present value of fossil fuels?

In the United States before the industrial revolution, the labor of 95 out of 100 people were required to feed the population of 5 million. Today, the less than 3 out of 100 are required to feed the US population of over 300 million - with food to spare for export. How is this possible? Fossil fuels provide high energy density storage sources that literally take the place of labor, and since their large scale use, we have used them to accumulate knowledge in how to further reduce physical labor. The huge reduction in farming labor over the last 200 years has resulted in “extra” hours for people to get paid to do things like drive around taking photos of celebrities for gossip magazines.

Because fossil fuels are limited and have provided us with the luxury of excess time, a major goal of society should be to break the causation between increasing fossil fuel consumption and increasing human development. I say human development and not economic growth, because the social aspect of economics is only a part of human development [2]. Extracting more fossil resources by consuming more fossil energy only buys more time to learn how to design and implement sustainable energy systems.

The laws of diminishing returns for fossil fuels cannot be avoided on the time scale of human civilization. Human civilization operated on a 100% sustainable energy a few hundred years ago, and after fossil fuels become completely uneconomical in hundreds of years more, we’ll again operate on a 100% sustainable energy system. The question is: what is that next 100% sustainable system going to look like?

Will it not be a success if human society finds an acceptable sustainable arrangement where we have excess fossil fuel reserves still lying in the ground? That is to say, we could define success as solving the energy and development problem before running out of economical fossil energy resources. Why consume the last of fossil energy reserves? Since reserves are partially defined by the economics of extraction, they are also partially a measure of our culture in how we value things, including energy resources, food, and social goods. If we want future human civilization to live in a manner better than the time before fossil fuels, that demands using our fossil fuels today such that we learn not to need them in the future.

Today we can’t make a photovoltaic solar panel without fossil-powered electricity manufacturing plant. We couldn’t build a hydroelectric dam without fossil-powered vehicles and cement plants. We can’t make and install a wind turbine without fossil-powered steel factories and transport systems. We need to track the progress, or lack thereof, of the ability of renewable energy systems to make themselves.

We didn’t need Nobel Prize Chemist Richard Smalley to tell us that the sun is the only source of energy for a sustainable human society. What we do need is everyone focused on the issue of both cultural and technological adjustments to make the most of solar direct (sunlight) and indirect (wind, waves, crops) energy.

Carey King, PhD, works at the University of Texas at Austin's Bureau of Economic Geology. This is his first contribution to Worldchanging.

notes:

[1] Pearson, Natalie O. Ecuador Plans to Nix Exploitation of 1B Bbl Oil Deposit. Dow Jones Newswires. March 03, 2008. Available at: http://www.rigzone.com/news/article.asp?a_id=57679.
[2] Sen, Amartya. Development as Freedom. First Anchor Books, 1999.

Offshoring Energy and Emissions - Coming back from Developing to Developed Countries

A recent study in the journal in Environmental Science and Technology discusses the 'embodied carbon' in global trade. The concept of embodied effects in global trade has been noted by scientists and engineers by estimating such aspects as the energy embodied in a product when it is made in one place and shipped to another.

Somewhat by definition, making a product in China (say a Barbie doll) and shipping it to the United States takes more energy than making it in the United States and keeping it here. Just think of the energy used to create the infrastructure (tankers) and fuel the cargo ships (low grade petroleum used in ships). You don't need these if you don't travel the globe, but both systems require intra-continental infrastructure.

As peak oil and gas come on, businesses will be forced (albeit in some views 'rightly so') to better account for the energy used to make a particular product or provide a particular service. Products from China don't cost less in the U.S. because it actually costs less to make from an engineering sense; it just costs less based upon how much you value a person's time and labor. Essentially the time of farmer converted to factory worker in China has less value than the average Joe/Jane in the U.S. The 100s of millions of workers in China available to work cheap is the main reason why products have gotten cheaper in the U.S.

Essentially, the CO2 being shipped from abroad to the U.S. (and generally from developing to developed countries) is a proxy measure for energy. As suggested in the synopsis (linked above), the solution is likely to factor the cost into the consumer of the product and not necessarily its producer.

And we should quit shipping electronic 'waste' to China, as someday we'll likely wish we kept it to make use of it via recycling, but that's another story ...

New Energy Bill

The US Congress passed an energy bill yesterday and Bush signed it into law. It is both a step backward and forward for energy policy. See this CS Monitor article for a synopsis.

Creating a higher CAFE standard to get to 35 mpg by 2020 is certainly a good step forward, and it has been a long time coming. The biofuels mandate is a marginally good idea. The emphasis on corn ethanol is not the greatest due to the environmentally unfriendly aspects of using a tremendous amount of irrigated water (200-2,500 gallons of water for every gallon of ethanol) consumed and fertilizer runoff into the Gulf of Mexico. To most engineers who study the problem, I would say they believe biofuels must be non-irrigated and farmed in a way that sustains the nitrogen cycle, and not only the carbon cycle we hear so much about.

The removal of the renewable energy production tax credits for wind, solar, etc. is disappointing, but it has lapsed and been restarted three times already in its brief history. What we really need is a PTC scheme that sets it at a medium to high level (note: it was 1.9 cents/kWh) and has it steadily decrease in a set manner which cannot be changed. This gives businesses the ability to know the future of this kind of incentive such that they can invest in infrastructure that must be amortized over several decades.

The CS monitor article mentioned above does point out one thing that I think is good: energy policy might now be, as it should, a perennial subject. That doesn't mean that energy policies should change every year, it just means they should be evaluated every year.

Some elements of a proper energy policy

A proper Energy Policy in the United States would promote (1) clarity of purpose, (2) diversification of use of energy resources, and (3) more transparent and accurate pricing of energy such that the market (consumers and energy companies) can properly make both short and long term decisions.

How to promote each item above:

(1) CLARITY – State, through actions and rules in the Energy Bill, that the U.S., being the largest energy consumer in the world, and the largest energy user per capita, must always consider the tradeoffs of such a large amount of energy. These tradeoffs are environmental stewardship, security/accessibility of energy resources, and costs that don’t cause disruptive economic conditions (but that if changing slowly over time in the right direction can work to our benefit). For example: The fact that private banks will not underwrite new nuclear facilities is testament to how high they perceive the risk. Does this mean that the U.S. should have no new nuclear facilities? Not necessarily, BUT if the taxpayers underwrite (through government loan guarantees) the high infrastructure costs (for nuclear plants and disposal), then the taxpayers should also reap the economic benefits of this underwriting. I don’t want a “national energy company” (i.e. U.S. government running a nuclear facility), but I might rather have that than the U.S. citizens taking the risk of a nuclear facility without directly benefiting from the cheaper operational costs of generating electricity from nuclear facilities.

(2) DIVERSIFICATION – The oil shocks of the 1970’s took petroleum out of the mix (almost, but not entirely) of electricity generation. We are benefiting from this decoupling today with higher oil prices. Consumers will generally benefit when there are multiple competing sources of fuels/energy for various applications ranging from heating/cooling homes to fueling cars. The market is NOT SET UP to take into account these concerns, so it is the responsibility of the government to set up the rules such that various companies end up filling the need for a diverse energy supply that includes ALL fuels renewable, fossil fuels, and nuclear. THE MOST IMPORTANT thing to do regarding this concept, and energy policy in general, is to promote higher CAFE fuel standards for cars AND LIGHT TRUCKS AND SUVS. We, the United States, can do this, and should. More fuel efficient cars are being made, and can be made. Also, the more fuel efficient a car is, the further it can go ON ANY FUEL (electricity, hydrogen, gasoline, diesel, etc.). AND, higher fuel standards do not mean people will buy less cars, so I’ve never been sure why automakers are so concerned about this issue as long as the time for transition is appropriate.

(3) TRANSPARENT PRICING – Every energy usage today is subsidized in some way by the government at both the state and federal levels. This is not inherently bad as the governments have concerns and perspectives that the players in the economic market do not have. The U.S. has established over long time scales that it is willing to promote and fund expansion of fuels that are BOTH NEW (wind, solar) AND WELL-ESTABLISHED (coal, petroleum exploration). Arguments abound such as (1) fossil exploration is “new” and R&D is needed, or (2) wind energy is starting at a disadvantage and needs R&D to compete as well as new transmission lines and rules, (3) etc. on other energy resources. All of this is generally true, and people are just bickering over who is not getting their fair share. Everyone has an argument because the coupling between energy subsidies and subsidies in other areas of the economy are sufficiently blurry. There are some areas where U.S. investment can have a more direct effect upon pricing than others. For example, the U.S. is only one player in indirectly dictating (by consumption, production, and intervention in oil-rich areas) the price of oil. But investing in resources that exist within the U.S. (renewables, coal) a more direct effect will be had upon how much citizens spend on energy. We can make a start to people understanding this by making some basic information available in a simple and straightforward manner: 1. Government dollars given to promote each fuel (wind, oil, coal, etc.) 2. Amount of energy consumed from each fuel (absolute values and percentages) 3. Dollars per energy consumed 4. List of externalities that are and are not accounted for in prices of energy. Examples include SO2 is not sufficiently internalized for coal plants (due to technology for scrubbing) and nuclear waste disposal is not sufficiently internalized for nuclear power.