Season 5 - Biogas trains

Episode 2 - Is it really good for the planet?

Okay, so we may have screwed up a bit on the weather forecast for this early summer. But either way, replacing flowery board shorts and Havaianas flip flops with a waterproof poncho and rain boots is not a good sign for the planet (style-wise though, it's a win). This flux in the weather is just one of the complex consequences of climate change. Because, contrary to what some people think, cold and rainy weather doesn’t contradict the analysis and evidence from thousands of scientists across the globe. The fact that you’re spending your early summer playing board games instead of sunbathing won’t stop us from pondering the ecological pluses of biogas trains.

As we saw last week, biogas-fuelled trains could help decarbonise even just a small part of the part of the rail sector which still runs on diesel. But this solution can only be temporary, for obvious structural reasons. Indeed, as detailed by Ademe, the French agency for green transitioning, biogas is made from a methanisation process, i.e. “technology based on the degradation by microorganisms of organic matter, under controlled conditions and in the absence of oxygen, therefore in an anaerobic environment, unlike composting which is an aerobic reaction.” To put it more simply, the process consists of taking organic waste — plant or animal — and fermenting it in a large tank. This results in two products: biogas, which is used as fuel, and digestate (we’ll come back to that later).  

The benefits of this production method are numerous. First of all, making biogas doesn’t require fracturing the ground, or plunging gigantic machines into the bowels of the Earth. Multinationals needn’t take control of national resources in obscure geopolitico-economic contexts to make it happen either. Which, actually, gives it a hefty advantage over fossil fuels, like extracted gas and oil. What’s more, as the World Wildlife Fund (WWF) explains on its website, this methanisation process captures some of the monstrous quantities of animal manure and food waste that contribute heavily to nitrogen pollution of soil. Ditto for wastewater, which causes significant ecological problems if released into nature. It drastically reduces the methanisation that would have taken place anyway in landfills or manure deposits. As explained by the WWF, using biogas as fuel converts methane into CO2 so, like gasoline or diesel, it releases greenhouse gases when burned. Except that… methane is thirty-four times more problematic than carbon dioxide.

So — let’s talk problems. As mentioned, the combustion of biogas also produces CO2. Its ecological credentials therefore lie in the fact that the CO2 it produces when burned is less problematic than the products eliminated to manufacture it. It's a bit technical, but you get the idea — the benefits of this fuel are also its drawbacks. To produce biogas, you need waste. And lots of it. However, as we move towards global decarbonisation, this day-to-day human and agricultural waste will be reduced. Surely, it’s absolutely unthinkable to create a world in which we emit more waste in order to be able to produce more biogas. This doesn’t negate the ecological benefits of biogas, but does reduce its use to purely transitory. In one engine, what we reduce and consume is equivalent to the 5.2 tonnes of waste produced each year by each person living in the EU.

Finally, there’s another issue with the production of biogas: the digestate. Described by Ademe as “a moist product, rich in partially stabilised organic matter,” it is very often spread on fields as a fertiliser. And therein lies the problem — we’d be recycling polluting waste to produce a fuel equivalent to its fossil counterparts, and using what’s lying around to fertilise the fields that will produce the famous waste. And so it rolls on. Despite scant literature on the topic, it seems that digestate could cause real issues. As the excellent French site Reporterre explains in an investigation, the digestate is “full of pathogens” which seep into the groundwater. The same groundwater from which we take our drinking water. Not great, is it? Admittedly, there are methods to purify digestate. But as well as not being widely used, they’re often not up to the job.

Taking a day or night train is much more environmentally friendly than taking a plane or a car. And yes, running these trains on biogas would be more environmentally friendly than running on diesel. That’s impossible to deny. But, it’s far from the perfect solution. All that being said, as long as we produce enough waste to get rid of, it still makes a lot of sense.

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