Ethical living: could felled ash trees be a source of green power?

Ash tree canker, Lawthorn Wood, North Ayrshire...
Ash tree canker, Lawthorn Wood, North Ayrshire, Scotland. (Photo credit: Wikipedia)

Can’t the environmental disaster of diseased ash trees be turned into clean power? Across the country the trees could be felled and burned to be used as a free source of zero-carbon power? The Guardian reports

This carbon cycle diagram shows the storage an...
This carbon cycle diagram shows the storage and annual exchange of carbon between the atmosphere, hydrosphere and geosphere in gigatons – or billions of tons – of Carbon (GtC). Burning fossil fuels by people adds about 5.5 GtC of carbon per year into the atmosphere. (Photo credit: Wikipedia)

Your ecological multitasking is impressive. Given that the UK has 80m ash trees, turning the tragic infestation of the Chalara fraxinea virus into zero-carbon biopower could keep a couple of biopower stations in business for some time. Despite the fact that Swedish researchers argue the trees should be allowed to develop resistance to this latest invasive pest, the Forestry Commission‘s principal pathologist is in favour of culling diseased trees by burning them, so your practical solution would provide some clarity and purpose.

But not so fast, because first we must consider the idea that burning trees is somehow carbon neutral. Indeed this is a concept that has made biogenic power (biopower) the hottest thing since, well, fire. Trees grow, extracting carbon dioxide from the atmosphere via photosynthesis and making them spectacular carbon sinks. The idea beloved by biopower prospectors is that when you cut the trees down and burn them you neutralise the carbon released by this process by replanting the trees. It’s the type of carbon cycle that means biopower plants burning wood can attract renewable energy subsidies.

Except it transpires that burning trees is hardly a quick fix. For starters, research shows that since newly cut wood is almost half water by weight, burning it emits 40% more carbon pollution than burning coal to produce an equivalent amount of energy.

Meanwhile new trees are not a carbon fix either. It will take a tree at least 10 years to be an effective carbon sink. Indeed, a US study by the National Resources Defence Council, Forests or Fuel, charts an acre managed for biofuel and shows that this land needs a quarter of a century to regrow to its full carbon density. That’s some heavy carbon accounting that must be carried across decades.

In the interim the biogenic emissions from burning have been kicked out into the atmosphere and the carbon sink that once dealt with emissions has been lost – it’s an ecological double whammy.

The loss of some ash trees now seems inevitable – pathogens permitting, I agree it would make sense to derive some benefit by burning these for fuel. But as for creating a dash for ash in the name of a sustainable fuel source? Let’s not go there.

Green crush of the week

In an old airfield at Shrivenham, Oxfordshire, community shares in a solar farm have sold out in just six weeks. According to the 1,650 investors,Westmill is the world’s largest co-operatively owned solar farm and can generate enough power to keep 1,500 homes in electricity. Power to the people.



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