The limits of biomass

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A simple thought experiment. What if instead of building the 3.2 GW Hinkley C nuclear power station, the UK built a biomass plant instead? We would need to do two things: build the power plant and gather up the biomass for the plant. The first is not a major problem. The latter on the other hand is a problem, and not a mild one.

As Vaclav Smil points out:

Even with an intensively cultivated plantation of fast-growing trees, a wood-burning electricity generation plant would not have power densities higher than 0.6 W/m2, and for most operations the rate would be below 0.5 W/m²

Wind farms have a power density of roughly 2.5 W/m², or about 5 times greater than biomass. As I showed in an earlier post an offshore wind farm would have to be something close to 1,200 km² to provide as much power as Hinkley C.. So, a back of the envelope calculation would indicate that our biomass plant would need to be about 6,000 km², or more accurately 5,200 km² assuming a power density of 0.5 W/m². The United Kingdom has a surface area of 243,610 km², so this would already be taking up slightly over 2% of the UK’s land surface, and this is to provide only about 7% of the UK’s electricity.

What if we expanded biomass to provide all of the UK’s electricity? UK electricity demand averages about 40.6 GW throughout the year (source). To meet this we would need biomass plantations to cover about 81,000 km², essentially one third of the UK (or more likely somewhere else)). To put this in perspective only 12% of the UK is currently forested. The island of Ireland has a total surface area of just over 81,000 square km², so the map below will give you a good idea of just how much land is needed to supply all of the UK’s electricity from biomass. So, it is quite clear that there are some sharp limits on how much electricity you can get from biomass.

ireland - Google Maps


13 thoughts on “The limits of biomass

    Samuel said:
    March 25, 2013 at 5:48 pm

    Typo: You should write “or more accurately 6,200 km² assuming a power density of 0.5 W/m²” and not 5200.


      Robert Wilson said:
      March 25, 2013 at 5:53 pm


      I’m pretty sure what I have written is correct. The nuclear power plant will average about 2.6 GW, so if biomass is 0.5 W/m^2 then it will be about 5,200 km^2.


        Samuel said:
        March 25, 2013 at 5:56 pm

        Apologies, my calculations were wrong.


        Robert Wilson said:
        March 25, 2013 at 5:58 pm

        No worries


    Brian said:
    March 25, 2013 at 7:26 pm

    I’m disappointed. The proper unit for measuring this sort of thing is Wales, nor Ireland. As in ‘an area the size of Wales is lost in the Amazon jungle every year’. In fact, the only reason Wales exists is to be a unit of measure.


    Reiner Grundmann @ReinerGrundmann said:
    March 25, 2013 at 8:52 pm

    David MacKay has a nice illustration of the required land mass here:


    tuomasvanhanen said:
    March 26, 2013 at 11:50 am

    I’ll try my best to be specific here:

    You’re talking about growing biomass to fire the power plant that would create the same amount of electricity and heat as the nuclear power plant. The only option taken into consideration is growing trees or similar product for the biomass need.

    I know it’s hard to find these figures, but my question is: What if the left overs (biomass) from forest industry, and certain bio-based industrial residues (from the food industry etc) would be taken into account? What kind of percentage of the needed biomass could these accumulate to?

    In Finland (where the industry is totally different, of course) the wood residue based energy production covers about one fifth of the annual demand. Still advancements are to be made. The amount of forest residues of the whole renewable energy production is determined by the finnish government to be 19 % in 2020 (primary energy). The amount of biofuels will cover about 5 % of the whole renewable energy share.


      Robert Wilson said:
      March 26, 2013 at 12:19 pm


      There are two facts which make clear that Finland is a very poor guide for the potential of industrial residues to produce electricity: it has a very low population density and it has a very high forest coverage.
      So, compared to the UK: population density is 15 times higher, while percentage of land that is forested is 6 times higher (74% versus 12%). The conditions in Finland are very unique. Most countries are either much more densely populated or have much lower forest coverage, which significantly limits the sustainability of biomass.

      Another more fundamental problem is the energy return you get. Some biofuels (such as corn ethanol) more or less require as much energy put in to growing them as comes out the other end. I suspect this is also true of industrial residues in Finland, though maybe you can correct me on that.

      Overall, I don’t think the equation favours biomass or biofuels, except on rare occasions.


        tuomasvanhanen said:
        March 26, 2013 at 8:17 pm

        Cheers for your fine and well founded answer! Still I’d like to make one point.

        The whole point of using residues is that you produce something more valuable (such as paper in Finland) and you get the residual part (in this case black liquor) – that would otherwise be wasted. At this point it is more or less irrelevant whether the return on energy investment is positive or negative. It is nevertheless profitable to utilize that waste.

        The same goes with food industry – I guess in this we make a more useful example for you. Here’s a bio ethanol producing concept that you might find interesting.

        In the end I must emphasise that we have loads to learn from the UK in especially wind production. Hope to read more of that soon, even though we have limits for that as well. Still the best places will be built.


    AES said:
    April 9, 2013 at 3:17 pm

    Its great to see it expanding geographically too. I myself have seen a great increase in Kent, UK, which aptly fits with the garden of England title. So good to see this great energy source being put to such use on a global scale. It’s only natural to see that places such as the states are the foremost pioneers of implementing biomass as an alternative, renewable energy source, but it’s great to see biomass really taking off. Renewable energy sources are becoming more and more important in this world of mass consumption.

    Keep up the good work


    tuomasvanhanen said:
    April 11, 2013 at 4:14 pm

    I think this suits here perfectly.

    “London’s cooking waste to fuel power station … The prospect of easing the financial and logistical problems of pouring £1m a month into clearing the drains of 40,000 fat-caused blockages a year is being hailed by the companies as a “win-win” project … enough to provide more than half the fuel the power plant will need to run. The rest of its fuel will come from waste vegetable oil and tallow (animal fats) … The plant will produce 130 Gigawatt hours (GWh) a year of renewable electricity – enough to run just under 40,000 average-sized homes, say the planners.”


      Samuel said:
      April 11, 2013 at 9:40 pm

      You do realise that 130 GWh is less than 0.7% of the energy that will be produced by the Hinklex C NP ?

      Sure this is a good idea anyway if this energy could be produced at a reasonable price when factoring the positive externalities of getting rid of waste. But waste that I suspect was burned anyway so I’m not even sure the 130GWh are a net gain but rather an absolute value bigger than the efficiency of the classic incinerators burning it today.

      But I hardly see how this is a counter point to Robert’s rationale ? How many London do you have in England to produce 20TWh of electricity with drain fat ?


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