The Buses of Tomorrow Will Run on Sewage

Renewable Natural Gas, Matt Tomich, Energy Vision

How We Get To Next

Daisy Malt | February 24, 2016

Maybe you haven’t heard of biogas, but it has the potential to replace a quarter of the United States’ annual diesel use. Originating as organic waste, the fuel is not only environmentally efficient, but also proves that one man’s trash really is another’s treasure.

Here’s how it works. Decomposing organic materials like food, crops, animal manure, and even human sewage release methane and carbon dioxide through a process called anaerobic digestion. It’s similar to what goes on in your gut after a meal. When carrying out that process in dedicated tanks, you also end up with digestate, a sludge that’s full of nutrients and can be used as a fertilizer. The gases can be collected at landfills, too.

The biogas is refined to almost pure methane and compressed or liquefied so it can be used as a vehicle fuel that’s resource-efficient and low in emissions. Compared with petroleum-based fuels, combustion of biogas is less polluting. In fact, a report commissioned by the California Air Resources Board (CARB) suggests that, over its entire lifecycle, biogas made from food waste can actually result in net-negative carbon emissions — if it’s assumed that any greenhouse gases produced during the process are reabsorbed when new plants grow. That said, it does contribute to air pollution: Like fossil fuels, it produces nitrogen oxidessulfur oxides, and health-impacting particulates, although at lower levels. Upgrading the gas to almost pure methane also needs additional water and energy resources.

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Refined biogas is called biomethane and is chemically identical to the natural gas we use for cooking, heating, and transport. That makes it an easy win as a fuel — it can go in any vehicle that already runs on gas, so it’s a proven technology. A bus in Reading, England—powered by biomethane (made from cow manure)—set a land-speed record in 2015 for a service bus when it topped out at 77 m.p.h.

In Indiana, one dairy farm is using its herd’s waste to fuel the 42 trucks that transport its milk across America. Fair Oaks Farm specifically wanted to reduce its environmental impact, and can now produce the equivalent of 1.5 million gallons of diesel every year. Waste power is becoming more popular, according to President of Energy Vision Matt Tomich. He told me, “In 2015, close to 90 million gasoline gallon equivalents of renewable natural gas were produced (mostly from large landfills) for vehicle fuel. In 2012, this volume was effectively zero. [In 2016] that number is expected to approach 150 million.”

More examples can be found across the United States. The Persigo wastewater treatment facility in Grand Junction, Colorado, is the first in the state to operate a biogas-to-vehicle-fuel project. It creates enough biogas to fuel 38 of the city’s municipal vehicles, including dump trucks, pick-ups, and four regional buses. This cuts the requirement for gasoline and diesel by around 168,000 gallons per year. In Sacramento, commercial and household food waste is treated and goes back into fueling the very same trucks it is collected in, creating a perfect closed-loop system.

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