The Japanese town turning cowpats into hydrogen fuel

 

In Japan, a foul-smelling waste product is being reimagined as a potential clean fuel of the future, with applications in powering cars and tractors.

As we approach, we are eyed suspiciously by dozens of cows whose breath fogs dramatically from their nostrils. It's a brisk morning in snowy Hokkaido, an island in northern Japan. The chilly air carries the unmistakable scent of cow manure—a smelly yet familiar byproduct of the region's thriving dairy industry. Covering 20% of the country's landmass, Hokkaido is Japan's second-largest island, home to over a million cows that produce more than half of the nation's milk and dairy products.

We are visiting one farm in Hokkaido that aims to transform this pungent aroma into something valuable: they are converting cattle manure into hydrogen. 

When burned, hydrogen does not emit carbon, making it an attractive alternative to fossil fuels. There are widespread hopes that it could serve as a sustainable fuel to heat homes and power cars, trains, aircraft, and ships in the future.

The most common method of producing hydrogen today involves using methane, a fossil fuel extracted from deep underground. This process is still associated with significant carbon emissions. Another method to produce hydrogen is through electrolysis, which splits water using electricity; however, this can be expensive and is only low carbon if renewable energy sources are utilized.

The Shikaoi Hydrogen Farm in Hokkaido, Japan, adopts a different approach by using a waste product that is abundant in the region. Approximately 20 million tonnes of cow manure are generated annually in Hokkaido. If not managed properly, this waste can pose environmental challenges, leading to considerable methane emissions and negatively impacting water quality if it leaks into local streams and rivers. The question then arises: Can this waste be transformed into a sustainable energy source?

"This project to produce hydrogen from livestock manure originated in Japan and is unique to this location," says Maiko Abe from Air Water, one of the companies involved in the hydrogen farm initiative. During our visit to the Shikaoi facility, part of an upcoming episode of the BBC's TechXplore focusing on Japan, Abe explains, "Shikaoi accounts for 30% of Hokkaido's cow waste and urine, which provides significant potential for renewable energy."

Launched in 2015 by Japan's Ministry of the Environment, the project aims to convert agricultural by-products into hydrogen for the local community, creating a circular economy. Cow excrement and urine are collected from local dairy farms and processed in an anaerobic digester at a central facility. Here, bacteria break down the organic waste to produce biogas and liquid fertilizer. The biogas is then purified into methane, which is used to manufacture hydrogen.

Currently, the plant has a hydrogen production capacity of 70 cubic meters (about 18,500 gallons) and features an on-site fueling station that can fill approximately 28 hydrogen fuel cell vehicles daily. Although the hydrogen can fuel cars, the station has been specially designed to accommodate agricultural vehicles like tractors and forklifts, which are challenging to electrify with batteries due to their size and the nature of their work. The hydrogen-powered vehicles are utilized on the farm, reducing emissions that would otherwise result from traditional fuel sources. Additionally, the hydrogen produced is stored in canisters and transported to provide power and heat to other facilities in the area, including a local sturgeon fish farm and the nearby Obihiro Zoo.

While producing and storing hydrogen at scale requires substantial energy and infrastructure, there are challenges associated with hydrogen itself. It must be stored as a gas in high-pressure tanks, and its low molecular weight can lead to leakage. Furthermore, hydrogen can cause metal storage containers to become brittle, necessitating additional safety measures when handling it. 

Hydrogen can also be stored in liquid form by cooling it to cryogenic temperatures below -253°C (-423°F), but this process is energy-intensive and requires significant infrastructure. While hydrogen has nearly three times the energy content of petrol (gasoline) by mass, its low molecular weight means that, by volume, a liter of liquid hydrogen contains only a quarter of the energy found in a liter of petrol. Since hydrogen is the lightest gas in the universe, it occupies more space kilogram-for-kilogram than petrol, requiring more storage space compared to fossil fuels like petrol, diesel, and natural gas. This adds to the challenges of producing and storing hydrogen at a large scale.

The hydrogen farm project in Hokkaido also faces climate-specific challenges, particularly during the subzero winters, which necessitate new technologies to produce hydrogen steadily without the small amounts of water vapor in the methane freezing.

Using agricultural waste as a methane source for hydrogen production is relatively uncommon, but it relies on the same process as producing hydrogen from natural gas: steam reforming. In this process, steam heated to 800°C (1,472°F) reacts with methane to produce hydrogen, along with the by-products carbon monoxide and carbon dioxide (CO2).

According to Abe, the project remains sustainable since the carbon produced originates from the grass the cows grazed on: "Since it was originally in the atmosphere, it is considered carbon neutral." Moreover, the project helps prevent the methane that would otherwise be emitted from the manure from entering the atmosphere, where it acts as a potent greenhouse gas. The leftover slurry from the manure, after the biogas has been extracted, is used as fertilizer on nearby fields.