Ellie O’Byrne


Let’s get on the biogas bus and use eco-friendly fuel

Biomethane can be harvested from slurry or food waste and be compressed for use as an eco-friendly fuel, such as to power our buses, writes Ellie O’Byrne

Let’s get on the biogas bus and use eco-friendly fuel

Biomethane can be harvested from slurry or food waste and be compressed for use as an eco-friendly fuel, such as to power our buses, writes Ellie O’Byrne

Biomethane could be used as as a fuel for Ireland’s bus fleet, says Professor Jerry Murphy, the director of UCC’s Centre for Marine and Renewable Energy (MaREI).

Biomethane, or ‘green gas’, can be harvested from methane-producing sources like slurry and food waste. In a compressed form, it’s then fit for use to power public transport.

Ireland is both frittering away a valuable natural resource and allowing unnecessary greenhouse gas emissions by not harnessing all this gas power, he says.

“Ireland has 8% of the cattle of Europe and 1% of the human population,” he says.

We’ve loads of slurry; around 20m tonnes produced per year. Agriculture creates a third of all greenhouse gases emitted in Ireland. The least we can do is cover the slurry tanks for anaerobic digestion and the gas can power buses.

In countries that already use this technology, like Denmark, farmers make a supplementary income from supplying the gas, and end up with a digested fertiliser, which they use instead of spreading raw slurry (the latter has a knock-on impact on water quality).

Also, “methane gas has a warming factor of 28, meaning it has 28 times the global warming impact of carbon dioxide,” he says. “When a bus burns the methane as fuel, it does release carbon dioxide. But that’s 28 times better than letting it escape into the atmosphere as methane,” Prof Murphy says.

In March, Prof Murphy was on hand for the first-ever biomethane bus journey in Cork: a trial spin to Ringaskiddy in a biogas-fuelled bus.

Having studied the use of biogas worldwide for over two decades, Prof Murphy says it’s beyond time for the Government to roll out biogas infrastructure.

of MaREI, Prof Brian O’Gallachoir and Prof Jerry Murphy.
of MaREI, Prof Brian O’Gallachoir and Prof Jerry Murphy.

The clock is ticking: under the National Development Plan, diesel-fuelled buses will no longer be purchased from July. However, last year it was reported that the National Transport Authority (NTA) had bought 200 new diesel buses for delivery in 2018 and 2019, a rate that’s pretty much business-as-usual: the NTA normally procures 100 new buses per year.

Prof Murphy says the move was disappointing. “It made no sense,” he says. “If you buy a new bus, you want to get 10 years out of it. So, in 2029, we’re still going to have diesel buses in the national fleet. All the buses in Cork could run on the gas produced by our food waste alone. But we export food waste for disposal and use diesel.”

The main challenge in making sure that every bus in Cork is biomethane-powered is setting up the infrastructure to capture, store, and dispense the fuel, whereas gas-fuelled buses are widely commercially available and already used in countries around the globe.

With 10,000 jobs expected for Cork within the next five years, and the much-discussed boundary extension due at the end of the month, Kieran Lettice, of industry group Energy Cork, says Cork is an ideal model city for low-carbon transport options.

“Cork has an order of magnitude that’s helpful for trialling an early roll-out of these technologies, particularly when it comes to buses, but also electric vehicles,” Mr Lettice says. “Buses hold the key to successful public transport in Cork, whereas, in Dublin, there’s an understandable emphasis on light rail.”

Of course, people only take the bus when services are regular, reliable and easily accessed; for personal transport options, there are many ways to go low-carbon and they’re not all Shanks mare.

Electric cars are growing in popularity, due in part to a grant-aid scheme from the Sustainable Energy Authority (SEAI), which offers up to €5,000 to a private purchaser.

ESB’s rapid charge network is quickly making more charge-points available, (with 1,100 nationwide), and their e-cars app lets drivers know which power points are free nearby, so they don’t get caught short. Electric scooters are rarely seen in Cork, unlike in Dublin, where they are a frequent sight. This could be down to the greater distances for Dublin’s commuters, or possibly the cost: an adult’s new electric scooter is upwards of €400. They have a top speed of 25km per hour, can be used in bike lanes, and don’t need a licence.

However, the carbon benefits of all electric vehicles depend on how the power to charge them is generated in the first place.

“Electric vehicles are zero emissions at the point-of-use,” Mr Lettice says, “but what generates the electricity is important.

There are misconceptions that electric vehicles still produce a lot of emissions, but that’s not true.

“Even in the most carbon-intensive countries, like Poland, where a lot of power still comes from coal plants, an electric car still makes a saving of about 50% on emissions.”

Cycling is, of course, a truly emission-free form of transport. With 10 new Coke Zero Bike rental stations due for Cork in 2019, and over a million journeys clocked on the rental bikes in the first four years of operation, they’ve become a city transport institution that’s here to stay. Cork, for all its hills, is a friendly-sized city for pedal-power, as well as for innovative new approaches to low-carbon transport.

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