The company linked up with a water processing plant in Fukuoka, Japan, to source sewage sludge for energy. The sludge, which would otherwise go to landfill, is converted into biogas with the help of microorganisms. This environmentally-friendly process creates a key element that is used in the car’s fuel cell to produce electricity.
Sixty percent of the resulting biogas is methane, and 40 percent carbon dioxide. Without getting too technical, by isolating the methane and combining it with water vapor, hydrogen gas is produced.
The hydrogen that is recovered eventually finds its way into a Mirai’s fuel tank. And electricity is produced when hydrogen is combined with oxygen in the vehicle’s fuel cell, which powers the car’s electric motor.
The typical way hydrogen is commercially produced is by extracting methane from natural gas. This means that while fuel cell vehicles are zero-emissions at the point of use, they're not necessarily, or even typically, fossil-fuel free. Conversely, processing sewage to produce hydrogen avoids the use of fossil fuels, while at the same time reducing landfill waste. And since sewage waste produces biogas anyway, harnessing this byproduct effectively means there is no environmental downside to producing hydrogen in this way.
The idea isn’t new, but the fact that Toyota is backing it is important, as the car company is one of only a few that has a fuel cell vehicle available to the public today. Though the auto industry has experimented with fuel cell vehicles for a long time, the ramp-up to adoption remains slow. This is in part because fuel cells continue to be an expensive technology but also because there are very few filling stations where you can pump hydrogen. It’s a bit of a “chicken-and-egg” problem.
By demonstrating the concept of turning sewage into fuel, Toyota’s program not only illustrates a sustainable way of producing hydrogen, but also points to a future where every city might be able to capitalize on what is a naturally-distributed means of production. After all, every sizable population center has a wastewater treatment plant.
Indeed, turning sewage waste into a transportation fuel is already happening in California. This, again, is important because in the United States, if fuel cell vehicles catch on, early adoption will certainly take place in California.
FuelCell Energy, Inc. ran a demonstration project extracting hydrogen from human waste in Fountain Valley, California, a suburb of Los Angeles. Here, hydrogen was not only produced as a transportation fuel, but also to generate electricity for industrial applications.
The plant was able to produce enough hydrogen -- 100 kilograms daily -- to power around 50 cars a day, Scientific American reported. That isn't many, but the project was designed as a proof of concept, not as a commercial operation. Scientific American detailed that commercial viability would kick in at around 600 kilograms a day. But the catch is: Though this would power 300 cars a day, at that level of supply, it actually outstripped demand as a transportation fuel.
Likewise, Toyota’s project in Fukuoka is a relatively small operation, only producing enough hydrogen to power 65 Mirai vehicles. However, the company thinks the process could be scaled up to power as many as 600 cars a day if all of the wastewater plant’s biogas was converted to hydrogen.
So, the big question is: Will fuel cell vehicles eventually catch on? Navigant Research projects global demand could reach 228,000 vehicles a year by 2024, including both cars and buses. Hydrogen from sewage waste would struggle to meet demand at that level of course. But imagine if all the world’s big cities treated sewage for hydrogen production; that would constitute a significant level of production from an otherwise waste product.
For now, getting behind the wheel of a Toyota Mirai in California will cost you $57,500 to buy, or $349 a month to lease. But the customer, happily, will receive three years of complimentary fuel -- good news if you happen to live close to one of the 40 hydrogen filling stations California plans to have by the end of 2016. No guarantees the hydrogen from those pumps comes from sewage waste though.
image courtesy of the author, taken at the 2014 San Francisco Auto Show
Phil Covington holds an MBA in Sustainable Management from Presidio Graduate School. In the past, he spent 16 years in the freight transportation and logistics industry. Today, Phil's writing focuses on transportation, forestry, technology and matters of sustainability in business.
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