Comment ▼ A hydrogen-fueled economy? admit it. I am not a technological pioneer. And I am not a particularly good prognosticator, either. I was the one who bought a Betamax rather than a VCR. It goes handin-hand with my penchant for buying high and selling low (economics wasn’t my game either). But now we find ourselves evaluating the prospect of employing that lightest of all gases—hydrogen—to bail us out of global warming and to provide a whole new energy system for the 21st century. Can it really work? For our part, ES&T has been covering the issue in news reports, research articles on policy analyses and the technology of recovering hydrogen from wastewater, and, just last month, a timely feature by Bruce Logan on extracting hydrogen from renewable resources (Environ. Sci. Technol. 2004, 38, 2281–2285; 2004, 38, 161A–167A). Hydrogen is not really an energy resource per se. We do not mine it from the Earth’s crust; rather we electrolyze it from water or extract it from hydrocarbons. It is an “energy carrier”. Hydrogen is produced only when we obtain it via other energy resources, such as renewable wind power or solar photovoltaics that generate electricity to split water (clean hydrogen), or from fossil fuel hydrocarbons (methane, methanol, gasoline) reformed into hydrogen. In addition, renewable biomass and/or waste products could be used to produce hydrogen directly through microbial fuel cells or indirectly through ethanol. In any case, it takes energy to make hydrogen, and life cycle assessments are required to ensure that you are, indeed, producing net energy and decreasing greenhouse gases compared with other methods. Storage of hydrogen is a huge hurdle. The small tank that powers my outdoor gas grill holds a nice amount of energy. With a steel shell just 1/8-inch thick, it holds liquefied propane at just a few atmospheres pressure and ambient temperature, enabling the storage of enough energy to “burn the meat” at least 40 times. However, hydrogen requires tremendous pressures and/or frigid temperatures (–241 oC) to liquefy. Thus, current hydrogen fueling stations in Munich, Reykjavik, and California use pressurized hydrogen gas (200 bar), which is still too voluminous to store onboard a vehicle for a 250-mile trip. So, researchers are turning their attention to solid-state storage systems (metal hydrides) at liquid densities or better. Perhaps in the future, liquid hydrocarbons (e.g., methanol or ethanol) will be used directly in first-generation fuel cell vehicles or reformed for use in a hydrogen fuel cell.
I
© 2004 American Chemical Society
The prospect of using hydrogen as an energy carrier to power our economy would not at all appear promising, if the alternatives were not so bleak. It is true that the world is facing declining oil and natural gas production. Even Saudi Arabia, the largest holder of proven oil reserves in the world, will face declining production within this decade. We will need a new energy system before we run out of oil, and certainly long before we exploit all coal reserves. It is not so much that we are running out of fossil fuels; rather, we are running out of places to put the exhaust gases and carbon dioxide. Already we have set in motion serious environmental and social/geopolitical consequences by our societal addiction to oil. And like any addict, it is difficult to admit the problem and to think logically about solutions. If you want to see the future, go to Iceland, where a fleet of 80 buses is being converted to hydrogen fuel cells (DaimlerChrysler) and pressurized hydrogen is being generated from hydropower via the electrolysis of water (Shell). Iceland has pledged to be the first country to be totally free of fossil fuels (granted, they have an advantage with unparalleled hydropower, geothermal resources, and sparse population). Germany has 15 buses at the Munich airport running with BMW hydrogen-fueled internal combustion engines and emitting pure water. Or travel to Japan, where the Honda FCX fuel cell car is coming soon and 70,000 homes have roofing tiles made of photovoltaics to electrolyze water to hydrogen, which is used in fuel cells to run all the home appliances and more. My prediction: In the next 20 years, we will vastly improve our energy efficiency, adopt wind and solar applications where they make sense, and manage carbon carefully. Hybrid cars, efficient appliances, carbon sequestration, and renewable energy sources will be the big winners. By 2020, we will begin to see a hydrogen economy emerging. You heard it here first (from the “Rodney Dangerfield” of all prognosticators). By the way, I just bought a hybrid electric vehicle. Shouldn’t you?
Jerald L. Schnoor Editor
[email protected] JUNE 1, 2004 / ENVIRONMENTAL SCIENCE & TECHNOLOGY ■ 191A
