Fuel cell-powered vehicles that employ hydrogen as fuel are the acknowledged future hope for passenger-vehicle transportation. Hydrogen is billed as the ultimate non-polluting energy source. Burning hydrogen means no emissions, save water vapor, and as the earth's simplest element, it appears to be in huge supply.
The trouble is, hydrogen isn't there just for the taking; it must be separated from other naturally occurring compounds. As always, it takes energy to make energy, and manufacturing hydrogen is no exception.
As world governments and global automakers tout the utopian benefits of hydrogen as a fuel, and new partnerships are formed to enter other potential hydrogen markets such as heavy-duty trucks and homes, it will become increasingly important to discern "clean" hydrogen from "dirty" hydrogen.
A recent study conducted by Canada's Pembina Institute for Appropriate Development, along with the DavidFoundation, takes a look at greenhouse-gas emissions produced by the hydrogen fuel cell vehicle and the "process" of making its fuel.
Although fuel-cell vehicles (FCVs) themselves emit no greenhouse gases, the manufacture, shipping and storage of hydrogen does, the study shows.
Climate-Friendly Hydrogen Fuel: A Comparison of Life-Cycle Greenhouse Gas Emissions for Selected Fuel Cell Vehicle Hydrogen Production Systems compares the five most feasible hydrogen production/delivery systems from "cradle-to-grave" with a current internal combustion engine vehicle (ICEV) - in this case, the Mercedes-Benz A-Class.
Environmental benefits of FCVs are contingent on the amount of carbon dioxide (CO2), methane (CH4) and nitrous oxide (NO2) emitted during the hydrogen-producing process and subsequent storage and delivery processes. The study examines five of these life cycles: onboard methanol reformulated gasoline, onboard methanol reformulation, centralized natural gas, decentralized natural gas and decentralized electrolysis.
These five processing systems represent those which, due to current cost, availability and infrastructure, are the furthest ahead in the near term.
Some "green" or renewable energy processes are not considered in the study for various reasons. Centralized electrolysis, for example, currently is unavailable to maintain the expected near-term hydrogen demand and would take a significant infrastructure overhaul to meet and supply those expected demands.
Also, electrolysis performed with electricity generated from nuclear power plants is considered an unacceptable environmental alternative. Onboard ethanol reformation also is not expected to meet demand anytime soon. These and other systems are not considered in the research.
The study quantified the amount of greenhouse gases produced by a vehicle over 621 miles (1,000 km) - with a range of 373 miles (600 km). Each "refueling" process was assessed in addition to its hydrogen-producing method.
The Pembina Institute studies greenhouse gases from a "cradle-to-grave" view, taking existing data, running it through complex computer life-cycle programs, and then analyzing the data. Scholars from Princeton University worked with scientists from Ottawa. Engineers from the Society of Automotive Engineers (SAE) fed off information from researchers at the California Air Resources Board (CARB).
Researchers admit the study is limited in scope. The report does not track other non-greenhouse-gas air pollutants, water effluents or solid waste.
Matt McCulloch, eco-efficiency analyst and co-author of the report, tells WAW: "We're not going to come down and put our stamp on anything." Mr. McCulloch adds that much more research needs to be done.
So, what did researchers conclude?
The gasoline ICEV emits the most greenhouse gasses (or greenhouse gas-equivalents) - 248 kg for every 1,000 km (546 lbs./621.4 miles) traveled - with a yearly average of 6,200 kg (13,640 lbs.) emitted, based on Canada's national driving average of 25,000 km (15,500 miles).
Surprisingly, decentralized electrolysis, separating hydrogen from water at smaller facilities, such as service stations using electricity from generators fueled by natural gas, is a close second to the ICEV, producing 237 kg (521 lbs.) of CO2-equivalent emissions over the same distance, equating to 5,925 kg/25,000km (13,035 lbs./15,534 miles). This exemplifies the core of the study - some hydrogen-producing processes are just not that "green" when tallying emissions produced in the total manufacture, storage, transport and refueling process.
On the other hand, given today's technologies and infrastructure, centralized natural gas reforming emits only 70 kg per 1,000 km (154 lbs./621.4 miles) of like-CO2 gasses, which equals a mere 1,750 kg (3,850 lbs.) annually.
The study notes that small natural gas reformers easily could be added to the existing infrastructure. One could fill up at home, the office or local gas station, all ofwhich would be equipped with smaller reformers, with natural gas being shipped via diesel truck and pipeline. This process is not dependent on a massive overhaul of natural gas pipelines to be fortified for hydrogen transport.