Ethanol from willow trees – is it worth it?

The current obsession with ‘carbon neutral’ – in many ways a very good one – has meant that people are very keen to label things carbon neutral when in fact they are nothing of the sort. Biofuels is a prime example. If you look at it simply – you burn a tree and release carbon but, through photosynthesis, it took in that much carbon while it was growing. However, a whole lifecycle analysis is needed to understand how sustainable these crops are. This takes into account emissions from transportation, inputs such as fertiliser, and the disposal of waste products.

Cambridge scientists did this analysis for the production of bioethanol from willow in the UK. Their results showed that bioethanol from willow would produce over 80% less greenhouse gas than burning gasoline from fossil fuels. These savings are much greater than the ‘first-generation biofuels’ that have been grown in the US and come from crops such as corn. They make ethanol from willow seem like an appealing option.

A major advantage of willow over first-generation biofuels is that it can be grown on marginal land. It even improves the soil quality; willows are coppiced so only replanted every 30 years. The soil isn’t ploughed in this time so any carbon that the tree sequesters in the soil remains there.

However, it’s not yet economically viable. A high capital investment is needed, and the provision of the willows themselves and enzymes needed to make the ethanol are expensive. The study suggests that selective breeding can help change this. The significant genetic diversity of willows can be exploited through breeding to make them even more suitable for biofuels use. For example, a higher ratio of cellulose to lignin would increase the yield of ethanol.

A.L. Stephenson, P. Dupree, S.A. Scott and J.S. Dennis (2010) The environmental and economic sustainability of potential bioethanol from willow in the UK. Bioresource Technology 101, 9612-9623

I think this research again highlights the point that has come up in our discussion of GM crops – just because some of the earlier biofuels ideas using food crops turned out to be a bad idea, it doesn’t mean that there’s no potential for biofuels to reduce greenhouse gas emissions.


About Rebecca Nesbit

I am author of a popular science book 'Is that Fish in your Tomato?' exploring the fact and fiction of GM crops. In my work and leisure so far, I have trained bees to detect explosives, used a radar to study butterflies for my PhD, written a novel, taken the train from London to China, organised Biology Week, sold science jewellery on Etsy, and traveled to four continents with Nobel Laureates. Best off all, I've made lots of friends whose support I very much appreciate. Thank you! Please visit my website:
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6 Responses to Ethanol from willow trees – is it worth it?

  1. Michael says:

    And using gasoline is any less carbon neutral? The point is not that bio produced fuels are not carbon producers, but that they are better than the current fuels used.

  2. I agree – even if we haven’t found perfect solutions, they’re still better than what we have. Willows seem like a good option to me

  3. Judy says:

    And Willows will also provide habitats for insects etc – and attractive landscapes.

  4. Tom Monkhouse says:

    They also suck all groundwater from the land and wreck drainage systems, causing subsidence and blockages. They need to be grown on land either far from housing or next to a river.

    I never thought of trees as a fuel source like that before (apart from wood and coal I guess); what is it that gives willows an edge over others?

    • EmmaLouiseWright says:

      Willow’s good ‘cos it grows really fast. Basically. I think they also looked at other fast growing trees and decided that willow ad poplar produce the most biomass. Miscanthus grass is also used, apparently the giant grass produces 2.5 times as much ethanol as corn!!

  5. Winston C says:

    What is the fastest growing tree with a 75% plus cellulose content , high sugar content should attract ants……

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