Environmental Problems, Their Causes, and Sustainability 1

Producing Hydrogen from Green Algae FoundIn a few decadeswe may be able touse large-scalecultures of greenSPOTLIGHT algae to producehydrogen gas.This simple plant grows almosteverywhere and is commonly foundin pond scum.When living in air and sunlight,green algae carry out photosynthesislike other plants and producecarbohydrates and oxygen gas.However, in 2000, Tasios Melis, aresearcher at the University ofCalifornia at Berkeley, found a wayto modify the photosynthesisprocess to make these algae producebubbles of hydrogen ratherthan oxygen.First, he grew cultures of hundredsof billions of the algae in thenormal way with plenty of sunlight,nutrients, and water. Then he cut offtheir supply of two key nutrients:sulfur and oxygen. Within 20 hours,the plant cells underwent a metabolicchange and switched from anoxygen-producing to a hydrogenproducingmetabolism, allowingthe researcher to collect hydrogengas bubbling from the culture.Melis believes he can increasethe efficiency of this hydrogen---producing process 10-fold. If so,sometime in the future a biologicalhydrogen plant might cycle a mixtureof algae and water through a systemof clear tubes exposed to sunlightto produce hydrogen. Thegene responsible for producingthe hydrogen might even be transferredto other plants to producehydrogen.Critical ThinkingWhat might be some ecologicalproblems related to the widespreaduse of this method for producinghydrogen?While we are working to develop a renewableenergyhydrogen revolution, energy analysts call forus to focus on two more immediate and important priorities.One is to begin sharply reducing our dependenceon carbon-containing fossil fuels—especially oiland coal, which emit large quantities of carbon dioxide.The other is the related challenge of sharplyreducing our emissions of carbon dioxide and othergreenhouse gases to help slow global warming and climatechange. Analysts suggest that we do this by■ Greatly improving fuel-efficiency standards formotor vehicles through a combination of mandatorygovernment standards and much higher taxes ongasoline and diesel fuels, coupled with a correspondingreduction in income and payroll taxes. This couldbe done within 10 years. Some energy analysts accusecar companies of misleading the public by saying thatwe do not need to increase government (CAFE) fuelefficiencystandards because we can depend onhydrogen.■ Providing large tax breaks for people and businessesusing fuel-efficient cars, buildings, heatingsystems, and household appliances and keeping suchbreaks in place for at least 25 years■ Investing much more in public transit running onless polluting natural gas as an alternative to the carand using at least half of the money collected by gasolinetaxes to promote this change■ Greatly increasing research and development subsidiesfor development and phasing in of renewableenergytechnologies, such as wind power, solar cells,biomass, and geothermal energy, and providing suchsubsidies for at least 25 years. Such non-carbon energytechnologies will be needed to produce hydrogen.■ Providing very large tax breaks for people andbusinesses using renewable-energy technologies andkeeping such breaks in place for at least 25 years.It will take large amounts of fossil fuel energy andmoney to phase in the use of hydrogen during the lasttwo-thirds of this century. If we do not conserve fossilfuels their prices might rise to the point where wecould not afford to use them to help us make the transitionto a renewable-energy hydrogen economy by theend of this century. Also, failing to reduce the threat ofclimate change is likely to divert huge amounts ofmoney from hydrogen to help us deal with the harmfuleffects of climate change.xHOW WOULD YOU VOTE? Do the advantages of burninghydrogen as a source of energy outweigh the disadvantages?Cast your vote online at http://biology.brookscole.com/miller14.18-9 ENTERING THE AGEOF DECENTRALIZED MICROPOWERWhat Is Micropower? Think Smalland DispersedEnergy analysts expect dispersed, small-scaleenergy-generating units to replace centralized,large-scale power plants over the next fewdecades.According to Chuck Linderman, director of energy supplypolicy for the Edison Electric Institute, the era of bigcentral power plant systems is coming to a close. He andother energy analysts believe the chief feature of electricityproduction over the next few decades will be404 CHAPTER 18 Energy Efficiency and Renewable Energy