Displacing coal with wood for power generation will worsen climate change, say researchers

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New research has challenged the view that wood bioenergy is carbon neutral, and shows that wood pellets burned in European and UK power plants actually emit more carbon dioxide (CO2) per kilowatt hour than that generated by coal.
This is because wood is both less efficient at the point of combustion and has larger processing and supply chain emissions than coal. Their research shows that using wood instead of coal in power generation increases the amount of CO2 in the atmosphere, worsening climate change until—and only if—the harvested forests regrow.
Wood is increasingly being used to replace coal as a source of electricity generation in many regions such as the European Union (EU) , where policymakers have declared it “carbon neutral.” However, researchers at MIT, Climate Interactive, and UMass Lowell reveal that displacing coal with wood for power generation can make climate change worse for many decades or more.
In the new study, “Does replacing coal with wood lower CO2 emissions? Dynamic lifecycle analysis of wood bioenergy”, the researchers examine the climate impact of replacing coal power generation in the EU and UK with wood pellets sourced from forests in the Southern United States. The research is published today in Environmental Research Letters. (The paper can be accessed online at )
US forests are a main source for EU wood pellet imports, which have been rising as demand has grown. These forests grow back slowly, so it takes a long time to repay the initial “carbon debt” incurred by burning wood instead of coal. For forests in the central and eastern US, which supply much of the wood used in UK power plants, the payback time for this carbon debt ranges from 44 to 104 years, depending on forest type—and assuming the land remains forest. If the land is developed, or converted to agricultural use, then the carbon debt is never repaid and grows over time as the harvested land emits additional carbon from soils.
Lead researcher Prof. John Sterman sums up the findings this way: “It’s like an investment in which you give your bank $1,000 today. They promise to pay you back, but only over 80 years, and only if they don’t go out of business first or decide there’s something else they’d rather spend your money on. You’re better off if you keep your money. In the same way, it’s better to keep the trees on the land and keep all that carbon out of the atmosphere.”
The researchers also explored an increasingly common scenario in which hardwood forests harvested for bioenergy are replaced with faster-growing loblolly pine plantations. Surprisingly, replanting with fast-growing pine plantations worsens the CO2 impact of wood because managed plantations do not sequester as much carbon as natural forests.
They also found that continued growth in wood use, as many predict, will worsen climate change throughout the rest of this century, or longer.  This is because the first impact of substituting wood for coal in power generation is an increase in CO2 emissions.  Even if the forests eventually regrow, notes Prof. Sterman, each year the new carbon debt from increased harvest and combustion outweighs the regrowth, just as borrowing more on a credit card each month than one is able to pay back will steadily increase what he or she owes. For countries using wood bioenergy as a component of their climate policies this could take them backwards. Indeed, bioenergy from wood made up 44% of the EU’s renewable energy production in 2015.
“We’re seeing many of the countries, states, and even institutions leading on climate embracing bioenergy from wood because they think it is ‘carbon neutral.’ Our analysis shows that these good intentions may be leading to outcomes that are bad for the climate: net carbon emissions that are worse than coal for many decades and, potentially, for the rest of this century or more,” says co-author Juliette Prof. Rooney-Varga.
Porf. Sterman says, “A molecule of CO2 emitted today has the same impact on the climate whether it comes from coal or biomass. Declaring that biofuels are carbon neutral, as the EU, UK and others have done, erroneously assumes forest regrowth happens quickly and fully offsets the emissions from biofuel production and combustion. One way to address the challenges raised in this study would be to count emissions where they occur, for example, at a power plant, and monitor and count carbon removed from the atmosphere by regrowth on the harvested land.”
Critically, the analysis does not support continued coal use as it is the most carbon intensive fuel and a major contributor to climate change. The researchers stress energy efficiency, solar, wind and storage as the cheapest, safest, and quickest ways to cut greenhouse gas emissions while providing the goods and services people need.


  • Peter Todd

    It seems very negative and short term focused to ignore the fact that wood is a renewable resource. I accept the fact that you can put a short term view that wood produces more CO2 than coal or gas but that is somewhat irrelevant in the long term if the resource is renewable. Some countries don’t have as much wind and sun as Australia but have lots of forests. They do regrow. Wood used as a Bio Fuel would be a sensible option in that situation as long as health effects are managed. We have to solve the climate problem, so we should not be try to rule out practical viable solutions.

    • Terry J Wall

      Well said..

    • Daniel

      I wonder if technology re purposed from coal carbon capture and storage could be used to capture emissions from these plants. That would make them a potential method to reduce CO2.

      • Peter Todd

        Same Issue for the current coal power station capture and storage. Just too difficult and expensive. As long as you grow wood as fast as you burn it, there is no negative effect on the climate as a long term CO2 emissions issue. Short term there is an issue as we are still burning so much fossil fuels. The morality issue is the first world, who is burning most of the fossil fuels, telling the second and the third world that they should not be burning wood as a source of energy.

    • André Balsa

      The essential difference between wood and coal in terms of carbon emissions is that coal is *fossil* carbon, whereas wood is exactly as you point out, renewable, in other words, it’s just cycling between the atmosphere and trees.

      We have to zero emissions from fossil fuels – coal, oil and natgas. Emissions from wood burning don’t really matter.

    • Mike Shackleton

      The issue is you need energy to cut down, chip, transport the wood pellets. If the pellets are recovering wood waste such as sawdust that’s a good start but putting it into ships and sending it from the US to the EU adds to the embodied energy of the fuel. It’s worse than shipping coal because coal is a lot more calorific than wood pellets.

  • Terry J Wall

    By planting over grazed properties, who’s carbon bank has regularly been robbed by ignorant land owners, with contour planted superior species, spaced to survive, then selectively harvested as individual trees reach a stage of static growth, humanity gains:
    Jobs,fibre, humidity, increased rainfall..
    By now you will see where this is leading….a tiny light at the far end of the pipe of survival.
    Everything and I mean everything else will be proven to be totally inadequate..

    • mick

      yep i think that was a major point replanting with garbage(soft woods and short cycle crops,also low efficient burning value/method could not the latter be addressed with longer flame path at a different angle than 90 degree vertical similar to modern household wood heaters?

  • Farmer Dave

    The results of the research reported on here make sense, and confirm the unease I have had about substituting wood pellets for coal. Fortunately, here in Australia we have such excellent solar and wind resources that I am unaware of anyone proposing to burn wood specifically for power generation. Indeed, my understanding is that such a proposal would be uneconomic. I think there are two circumstances in which the use of biomass to generate electricity make sense. The first is on site cogeneration, in which a site which needs both electricity and steam and which has a biomass waste stream available to it burns that waste to generate electricity and steam. This is a reasonably common arrangement at sugar mills where bagasse waste is burned for cogeneration. The second is a suggestion made by BZE in their very first stationary energy plan, which relied heavily on solar thermal with storage plants to provide dispatchable electricity. They suggested that some of the plants could have backup boilers fired by wood pellets – which can be stored for long periods – for the relatively rare periods of simultaneous cloudy weather at their planned widely dispersed plants.

    It is very important to distinguish between the very large scale use of wood pellets to replace coal for electricity generation, and the much smaller scale use of wood pellets made from wood waste burned in small boilers to provide renewable heat. Saw milling is a very inefficient business; recoveries of less than 40% are usual, and so a substantial amount of wood waste can be available to make the pellets. This use of wood pellets made from waste to provide renewable heat is particularly valuable if it displaces gas or LPG.

  • John Saint-Smith

    It seems to me that the critical balancing factor is to harvest and burn less carbon as wood than is sequestered in your replanted forests every year, giving a net negative emissions output. It isn’t an ideal option, but its better than coal, oil or gas.

    But he best thing by far to do with wood is to use laminated slabs in long-lived multi-story commercial, industrial and residential buildings, replacing millions of tonnes of concrete and steel both of which consume vast quantities of fossil fuel in their production,

    • Ren Stimpy

      Biomass is mostly wood waste that has drawn carbon down from the atmosphere in a recent carbon cycle, so instead of being left to rot it is used as fuel,it is a very tiny variance to the emission outcome. Compare it to digging up great big megaton (in fact gigaton) globs of ancient carbon to burn them i.e. filthy coal and oil that had been safely sequestered out of our atmosphere for millions of years but our current crop of ‘geniuses’ dug up to burn for fuel. We could use some brainpower to pursue better cleaner solutions to energy demand, but first we have to divorce ourselves from the established selfish rorters.

      • John Saint-Smith

        As the article points out:=
        “Surprisingly, replanting with fast-growing pine plantations worsens the CO2 impact of wood because managed plantations do not sequester as much carbon as natural forests.”

        Your ‘recent carbon cycle’ might be as long as 600 years in the case of mature trees. Accelerated combustion specifically of wood waste can raise atmospheric CO2 over several decades – long enough to cause global warming.

        In fact, in those countries that are using it, Germany and increasingly India, ‘biomass’ is mostly agricultural by-products like sugar cane bagasse, vegetable trimmings, straw, food waste, human and animal manures and other rapidly cycled sources of carbon. We should stick to those sources, and leave the trees for building and other services.

        • Ren Stimpy

          No. One single carbon cycle sequesters carbon from the atmosphere into trees and other carbon sinks within one year. The recent carbon cycles are simply incomparable to the carbon cycles which happened a million years ago under different conditions. So billions of humans digging up giga-tonnes of coal and oil to burn from otherwise deeply buried places – thereby releasing ancient CO2 into our current atmosphere – is overwhelming nature’s capability of dealing with variance.

          • John Saint-Smith

            What is ‘one single carbon cycle in one year?’ Call me stupid but I have no idea what you are referring to. The tree that absorbs the CO2 takes 600 years to complete its cycle.

            I was able to understand the difference between coal and recently recycled wood before you told me about it the first time. Please try to understand that what the article is actually discussing the difference between wood and other forms of biofuel, which, do cycle within one year.

            Once again, from the article:
            “New research has challenged the view that wood bioenergy is carbon neutral, and shows that wood pellets burned in European and UK power plants actually emit more carbon dioxide (CO2) per kilowatt hour than that generated by coal.”

            What I have been trying to distinguish is the fact that wood has a relatively slow sequestration cycle. When you burn a lot of wood that takes hundreds of years to grow, you are making lots more CO2 per kwh than you would be if you were using coal. In the short term that will raise the CO2 in the atmosphere more than burning coal, not lower it. Its subtle, but real, and we can’t afford to accelerate CO2 accumulation in the short term.

            As I have said, by all means use short cycle biowaste for energy generation, keep the wood carbon sequestered as long-term wood products, burning it all this year will mean it will be many years before other trees are able to re-absorb that CO2.

            Now, please don’t tell me about coal again.

          • Ren Stimpy

            “wood has a relatively slow sequestration cycle”

            What? Relative to the multi-million year sequestration cycle of coal and oil? Relative your arse!

          • John Saint-Smith

            No, you are the one who keeps banging on about coal. That’s enough on this pointless debate. Just read the article again and leave the comments section to the grown-ups.

          • Ren Stimpy

            The climate change issue is all about coal and oil. Everything is related to coal and oil and the need to stop using those as fuels.

            The world is not going to stop using wood for building. Waste products from building with wood can either be let to rot in the ground generating methane, or they can be turned into pellets and used as fuel. Comparisons of lifecycle emissions aside, if used as fuel for power generation wood pellets act to reduce the demand for coal, making coal less profitable, accelerating coal’s demise.

            Biomass plants will probably undergo their own demise soon enough as energy storage options become extremely cheap with renewables in a few decades time. Meanwhile they are helping to disrupt the coal market.

            The “one year carbon cycle” is relevant to plantation forests because the trees that are harvested each year are immediately replanted. It would be very rare to find a 600 year old tree in a mass produced wood product or building.

        • Farmer Dave

          So, John, given the inefficiency of saw milling, what would you do with the waste? If it goes to landfill it will generate some methane as it decays, which is worse for the climate than carbon dioxide.

    • Mike Shackleton

      Cross laminated timber is one of the more exciting construction developments in recent times. The Forte building in Melbourne Docklands was the tallest timber residential building in the world at the time of completion. All the panels were manageable by two people and they screwed the panels together using brass wood screws. A lot more flexible than reinforced concrete – services are installed by cutting holes through the panels with a hole saw!

  • There’s more than a hint of misguided lobbyists in the statement “The researchers stress energy efficiency, solar, wind and storage as the cheapest, safest, and quickest ways to cut greenhouse gas emissions while providing the goods and services people need.”
    Writing off the entire bioenergy and waste-to-energy industry on the back of some research on wood pellets is quite a stretch.

    • I totally agree. where practical, we need to turn waste into something useful, which is the case for wood waste, agricultural waste and waste to energy. What is missing in the article is that this does happen but primarily for economic reasons and that usually requires the conversion process to take place relatively close to the waste arising. The only reason coal fired power stations are also burning wood is because of miss guided government incentives.

  • Climatemonster

    I think this is a useful study, but it makes the assumption that a forest is cut down purely for biofuel, whereas the wood pellets for Drax in the UK are I gather made from by products of commercial timber harvesting. Saw this point made on Twitter recently here:

  • Bob Fearn

    Good article but fails to mention that trees don’t store carbon. This basic fact is ignored by all the biomass gangs.
    When a tree dies, as they all do, the stored carbon is released, one way or the other. Even if a tree is turned into lumber for a building that carbon is released when the building is destroyed in 100 or 500 years. If a forest is left in its natural state, which is rare now, the stored carbon is released when the tree dies. Net carbon storage in the long term, zero.

    • RobS

      You might want to run your little thought experiment on, after the tree dies it begins to decompose and turn into organic matter which is reabsorbed by the generation of undergrowth and trees that come after it, forests are constantly turning over at the individual plant level but as a whole a forest in it’s natural state stores vast amounts of carbon indefinitely.

      • Bob Fearn

        I wasn’t talking about “organic matter” and never implied that trees do not help with the creation of organic matter. I also never said that forests do not store a vast amount of carbon simply that the carbon in a tree is released when it dies and that all trees die. Therefore when a forest is established it no longer stores carbon.
        Still havig trouble with this “little thought experiment”.

        • RobS

          That’s just not correct, an established forest stores million of tonnes of carbon and as individual trees die the carbon released by them is immediately cycled into the growth of new vegetation.

    • Peter Todd

      The one way to store carbon from Biomass long term is to turn it into charcoal and bury it underground.

  • CO2 is CO2 whether it comes out of combusted coal or natural gas or bio fuel and our Sidel Carbon Capture Utilization System will take the CO2 out and transform it into useful – saleable products.

    • RobS

      Carbon capture and utilisation is vaporware and nothing short of a grant skimming scam and industry boondoggle, just like hydrogen, that’s always dangled as being ten years away, close enough to try and argue against deploying technologies that are ready now. When you have a plant ready to be start construction today which, including the CCS, can produce power for the 4c/kwh that the latest solar PPA’s are being bought for then let us know, until then run away.

    • André Balsa

      No. You are 100% wrong.
      CO2 from burning fossil fuels – coal, oil and natgas is entirely different from CO2 from wood burning.

      • AlanFSmith

        CO2 is Co2

        • André Balsa

          Actually, that’s not even true at the atomic level, since the CO2 from burning fossil fuels has a different carbon isotopes ratio than the CO2 cycling between the atmosphere and plants and animals and the oceans.
          But the main difference of course is that – as already mentioned – the CO2 from the burning of fossil fuels is the main greenhouse gas causing climate change.
          Only fossil fuel industry paid trolls refuse to understand this fundamental difference.

          • AlanFSmith

            Andre BalsaThe only difference is the presence of trace amounts of C14 in wood smoke compared to fossil C12 This makes no difference CO2 is CO2. The only reason that fossil fuel emissions exceed those from burning wood is that wood is just at the growing stage. Burn fossil fuels and leave the forests to absorb CO2.

    • Pixilico

      Making calcium carbonate involves spraying the CO2 stream with calcium hydroxide solution which, in its turn, is made by mixing calcium oxide (quicklime) with water. And how do you get that calcium oxide from? From calcium carbonate. You roast it at upwards of 800 ºC in a kiln, so you burn a lot o fuel and thus emit a lot of CO2 in the process, too. All that hype in the video about solving the CO2 problem makes no sense.

      • We do sorbent regeneration with a zero carbon footprint biofuel, which is also a byproduct of our Sidel CCU process.
        sorbent is a blend of materials and not just Calcium Oxide, which is
        obtained during the zero carbon footprint regeneration process.

        The other elements used in our sorbent mix actually start trapping CO2 long before they are added to the mix.
        also convert all the CO2 liberated either from the sorbent regeneration
        or from the Coal Fired Power Plants exhaust into end products using our
        organic sorbent.
        We are able to
        substantiate all our claims by detailed calculations of validated mass
        balance, and energy/thermodynamic analysis.

        • Pixilico

          I wonder what it might look like:

          CaCO3 + highly concentrated solar heat —–> CaO + CO2.

          CaO + H2O ——> Ca(OH)2

          Ca(OH)2 + CO2 (from burning C-fuels)——> CaCO3 + H2O

          And so that cycle can go on and on. Again, basic science hints it’s possible, although it’s not guaranteed to be validated by prevailing economic conditions. The other sorbents you mentioned seem to be amines, widely used in industrial gas treatment otherwise known as sweetening.

          • Thanks for understanding the theoretical validity of
            our process,but some more information without breaching our proprietary
            will help clarify the Sidel CCU technology better.

            When we say renewable based calcination it can be solar, one of the
            options we put in front of our clients, but there are others like the
            fuel used is a zero carbon footprint fuel. There are some other
            approaches which we wish to keep confidential at this point of time
            Our sorbent mixture is proprietary, and yes amines are a part of the
            mix, but they are not manufactured synthetically. Synthetic manufacture
            of amines used by other amine based capture processes have a huge carbon
            footprint because of the manufacturing process. Our amine
            come from an agricultural source, and while growing in the field, the
            plant is already absorbing CO2 out of the atmosphere. The CO2 absorbed
            in our Sidel CCU System transforms the CO2 into useful stuff like our
            end biofuel and biofertilizer products but with zero carbon footprints,
            and we have an energy balance which is the best in all categories of
            carbon capture technologies.
            3) We also can capture water from
            the exhaust stack gasses and the heat energy. Energy is also being
            released in our reactor by the sorbent and CO2 reaction, so we achieve
            an attractive energy balance in addition to our recovery from
            4) Our process will also in the future deal with ash recovery and the other non benign constituents.

          • Pixilico

            Thanks for your kind reply.

  • Cameron Pidgeon

    If only waste and thinnings form a sustainable timber industry or coppiced wood is used, processed with renewable energy, and the biofuel is used locally or transported by renewable energy fuelled transport, then biomass is fine. This is not an unrealistic scenario and could provide extra income to timber industry and agriculture. However the study was referring to monoculture timber plantations grown in the us, harvested, processed and transported to Europe with fossil fuels. Not only are any emission savings from coal not burned lost from all that fossil fuel use, but as will nearly all biomass, the energy budget is way out of balance. If you used a chainsaw to cut firewood on your farm the energy yield from the wood is probably less than that used by the chainsaw. If you want efficiency forget open fireplaces and get a super efficient wood burning boiler for hydronic heating. Processing wood into pellets or other biofuels into ethanol or biodiesel would be hard to do without going into energy deficit.

  • PaulC

    The debate here seems to be confused. There are three separate considerations… One is the supply chain which is a question of whether the production and transport of pellets is more energy hungry than coal. The second is whether there is actually land clearance which is generating the biomass. And the last is whether it is better to use wood or coal as your carbon-energy source.

    If we say the supply chain is not especially significant (don’t have figures – so an assumption), then land clearing is important and not just for wood pellets because trees represent short-cycle sequestration of carbon (say 100 years). This remains a key message: clearing releases carbon.

    Coal reserves represent long-cycle sequestration of carbon [coal, gas, limestone, etc. over geological timescales], so we can distinguish between free carbon CO2, short-, and long-cycle sequestered carbon. Is it better to release carbon which is short-cycle or long-cycle sequestered?

    Well, it doesn’t really matter the source of free carbon. Whatever free carbon we release needs to balance against the short-cycle and long-cycle sequestration globally. That is the very definition of sustainability and it is clear that rising CO2 says we’re releasing free carbon faster than the planet’s capacity across short- and long-cycles to sequester it.

    The bottom line though is that given all the other processes/industries which release greenhouse emissions, it is probably better to aim for zero free carbon for electricity since that is much easier than fixing all the other GG emitters. We need to reserve our emissions budget for the hard problems.

  • Gary Amstutz

    Read the American Lung Association’s “State of the Air” report for 2017 for and read the warnings about burning wood. Particle pollution is damaging to your lungs, your heart, causes infections, and will shorten your life by years. You don’t want to burn wood.