This past week my colleague Michael Webber presented some preliminary results (currently under review for publication at Environmental Science and Technology) at the 2008 annual meeting of the American Association for the Advancement of Science. A journalist from the Toronto Star reported about the results of our work. And Gordon Quaiattini, the president of the Canadian Renewable Fuels Association (CRFA), put in his 2 Canadian cents worth of comment to the Star editor.
First, our work on this is under review so I won't comment too much on the methodology until it is accepted and published, but I can clarify some aspects of the table in the Toronto Star article as well as the comment by Mr. Quaiattini.
As far as Mr. Quaiattini is concerned, let me assure him that neither me nor Michael are against biofuels. What we are for is understanding the impacts of all fuels. That is why we presented information that compares a variety of fuels, and future work can focus on additional biofuels and alternative fuels.
Mr. Quaiattini claims that 85% of U.S. corn is non-irrigated. This is fairly consistent value as in 1998 we show approximately 1.9 billion bushels irrigated (see http://www.nass.usda.gov/census/census97/fris/fris.htm Table 22) out of about 9.8 billion bushels of US corn grain (see http://www.nass.usda.gov/ and select 'US corn grain' stats for 1998 in the pull down menu) - this gives 15.6% irrigated. He also states the numbers of 3 gallons of water to process the corn into a gallon of ethanol, and this is at the lower end of the range of values we used.
The data presented in the aside in the Star article lists ethanol water 'use' (note in this case consumption and withdrawal are roughly equivalent) as 40-130 gallons per mile driven on E85. This is close, but not quite accurate as noted. We calculate 12-136 gallons per mile driven on E85 derived from irrigated corn in the U.S. The range exists because not all regions that grow corn need the same amount of irrigation. Obviously some regions get more rain than others. We have made no claim (yet!) on the total water consumed and withdrawn for travel in light duty vehicles in the US.
NOTE: when considering ethanol derived from non-irrigated corn, the values for consumption and withdrawal are less than 0.5 gallons/mile. This shows you that the vast majority of the water of concern is for irrigation.
IMPORTANT:
Does this mean we should not use biofuels? ABSOLUTELY NOT!!!
What it does mean is that we need to understand the limits of our water resources while considering the tradeoffs that that the "biofuels vs. fossil fuels" debate entails. Fossil fuels are essentially really old biomass as nature has done a lot of work for us in growing the plants and storing them in the ground (over 100s of millions of years) for us to now use. Biofuels are essentially really young fossil fuels.
When planning for growing crops either for food or fuel, we need to use both the land and water resources responsibly. I applaud the efforts of the Canadian Renewable Fuels Association and other similar organizations that are helping promote alternatives to fossil fuels for transportation or stationary applications. I believe we can avoid a water conundrum, and our work is providing information to help society do just that.
Wednesday, February 20, 2008
Water for Transportation - publication on "electric miles"
A paper of mine has been published online today in the journal Environmental Science and Technology. The paper describes how much water is used, that means consumed and withdrawn (which are two different concepts) for driving a vehicle on electricity as "fuel". This pertains to electric vehicles (EV) or plug-in hybrid electric vehicles (PHEV) while they travel on battery power alone.
First, two basic definitions:
water withdrawal is that water which is taken from a source, run through a process, and returned to the source or some other source.
water consumption is water that is withdrawn but not returned to the source due to evaporation (for example - in cooling processes for steam power plants) or evapotranspiration (evaporation from through plants).
Due to water consumed and withdrawn for cooling steam electric power plants (coal, nuclear, geothermal, solar concentrated power, and most natural gas), we can associate that water usage with the electricity generated from the plant. Assuming that an EV or PHEV is charged with electricity from the generic U.S. grid, each mile driven by a average light duty vehicle (a car, pickup truck, or SUV) will consume 0.2-0.3 gallons of water and withdraw 8 gallons of water. This is approximately 2-3X more water consumption and 12X more water withdrawal than when driving a light duty vehicle on petroleum gasoline.
Does this mean we should not pursue EV and PHEV technology? ABSOLUTELY NOT.
There are many benefits to the integration of EV/PHEV vehicles which include the ability to use a diversity of fuels sources - anything that can end up generating electricity (burning stuff to produce steam, nuclear power, wind power, photovoltaic solar, etc.). The ability to use a variety of transportation fuels by way of the electric grid is very powerful and important.
While the water consumption and withdrawal is higher than using petroleum gasoline, we can easily plan and accommodate for the increase in water usage per mile. The use of EV/PHEVs will occur gradually, and water resources will not be the limiting factor for their adoption. Full speed ahead for electric cars.
First, two basic definitions:
water withdrawal is that water which is taken from a source, run through a process, and returned to the source or some other source.
water consumption is water that is withdrawn but not returned to the source due to evaporation (for example - in cooling processes for steam power plants) or evapotranspiration (evaporation from through plants).
Due to water consumed and withdrawn for cooling steam electric power plants (coal, nuclear, geothermal, solar concentrated power, and most natural gas), we can associate that water usage with the electricity generated from the plant. Assuming that an EV or PHEV is charged with electricity from the generic U.S. grid, each mile driven by a average light duty vehicle (a car, pickup truck, or SUV) will consume 0.2-0.3 gallons of water and withdraw 8 gallons of water. This is approximately 2-3X more water consumption and 12X more water withdrawal than when driving a light duty vehicle on petroleum gasoline.
Does this mean we should not pursue EV and PHEV technology? ABSOLUTELY NOT.
There are many benefits to the integration of EV/PHEV vehicles which include the ability to use a diversity of fuels sources - anything that can end up generating electricity (burning stuff to produce steam, nuclear power, wind power, photovoltaic solar, etc.). The ability to use a variety of transportation fuels by way of the electric grid is very powerful and important.
While the water consumption and withdrawal is higher than using petroleum gasoline, we can easily plan and accommodate for the increase in water usage per mile. The use of EV/PHEVs will occur gradually, and water resources will not be the limiting factor for their adoption. Full speed ahead for electric cars.
Friday, February 1, 2008
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 ...
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 ...
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