February 18, 2003

C.U. Ecologists Examine Renewable Energy

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According to an analysis that appeared in the December 2002 edition of BioScience called “Renewable Energy: Current and Potential Issues,” if renewable energy sources were fully employed, they would only replace about one-half of the energy currently consumed by the United States.


Alternative energy sources reviewed included hydroelectric power; biomass, which consists of growing, harvesting and burning woody materials; wind power; photovoltaic cells, such as those used in solar power; hydrogen cells; biogases, burnable methane products; biofuels, such as ethanol and methanol; geothermal sources, such as geysers; and passive heating, which includes better insulation of windows.

Prof. David Pimentel Ph.D. ’51, entomology, who led the team of graduate students through the analysis of energy needs, noted that all of these sources had their own inherent problems.

“It’s not as bad as oil and coal, but they all have their problems,” he said. According to the analysis, alternative energy systems would occupy one-sixth of America’s land area if fully developed, among other problems.

For hydroelectric power, a major problem is the amount of space required.

“To provide electricity for a city of 100,000, you need 7,500 hectares [18,750 acres],” Pimentel said.

Similar space concerns exist for biomass and wind power as well. Pimentel noted that biomass had other hazards, including both pollutants produced by the biomass and the dangers inherent in harvesting.

“It is several times more hazardous to harvest wood than it is to harvest coal,” he said.

Pimentel, however, expressed more optimism for wind power.


“I think that it has a lot of potential,” he said. “At good sites it can be lower than [the current average price of] seven cents per kilowatt-hour. At bad sites, it can be a lot higher. We were optimistic in our estimations but realistic.”

Another positive aspect of wind power is the ability to use the land on which the windmills are located for growing limited farming plants that would not require large machines to harvest.

“I think it’s very good, and I think that we could produce a significant 10 to 15 percent of our electricity,” Pimentel said.

Another promising source is solar power.

“Photovoltaic cells took up the least amount of space,” Pimentel said. He added, though, that “it’s one of the more expensive ones right now, running about 21 cents per kilowatt-hour.”

Pimentel estimated that the price would become more reasonable over the course of 10 to 15 years.


Biogas and some biofuels also exhibited promise. Biogas relies largely on manure, biofuels on plants. Pimentel had some concerns about biofuels.

“I would not recommend using corn stalks and that sort of material,” he said. “We already have a serious problem with soil erosion. I am against using any crop residues for fuel. Producing ethanol requires more energy than it yields; about a gallon and a half of oil is used to get ethanol. The only reason to produce it is subsidies.”

Pimentel did note, however, that switch grass appears very promising. He said that it can have a good yield and can be harvested while keeping the land covered.

“Switch grass is absolutely worth looking into,” he said.

Pimentel also noted that hydrogen cells exhibited a great deal of promise.

“Hydrogen is probably going to be our future liquid fuel,” he said. “But hydrogen is a nasty material to handle and manipulate. You have to put it under about 1,000 pounds [of] pressure to keep it liquefied or keep it very cold. It’s going to be our future material, but it’s not free; it’s costly.”

Pimentel noted his motivation for the analysis.

“I would like to see more research on renewable sources before we run out of oil or get $10[-a-gallon] gas,” he said. “I’m trying to promote research so that we’ll have this when the time comes when we need them. I am concerned about the global climate change problem. I think it’s real and I think we ought to be doing something about it. This is where conservation helps.”

Not everyone is as optimistic about the general public’s willingness to adopt conservation methods.

“I don’t think anyone will truly adopt new power-generating ways until he is economically affected himself, which hasn’t happened yet,” said Matt Parry ’05.

Pimentel said that the biggest message of the analysis is that conservation will ultimately become essential, so it is a good idea to start working on it now.

Jim Muske ’03 agreed that ecological consideration is a necessity.

“One thing I remember from taking a course here, [RSOC 324: Environment and Society], was that we shouldn’t just expect science and technology to take care of all our problems. We also have to realize that supporting an eco-friendly position entails changing the way we live,” Muske said.

Muske added that conservation efforts should be given higher priority.

“If in addition to supporting renewable energy, we started using a lot less energy, the impact would be far greater. Most of conservation does pay you back in fairly good turn. I think our current administration is neglecting the importance of conservation.”

Archived article by David Hillis