Review of Biomass Calculations in Achieving Net Zero Emissions Scenario.

Guest post by Don Healy

February 4, 2021

From page 200 of the Princeton University Net Zero America Report we have the following quote”

“Biomass plays an especially important role because i) it removes CO2 from the atmosphere as it grows and so combustion of hydrocarbon fuels made with biomass carbon results in no net CO2 emissions to the atmosphere, ii) it can be converted into H2 while capturing and permanently sequestering its carbon, resulting in a net negative-emissions fuel, and iii) it can similarly be used to make negative-emissions electricity.”

This supposition seems to be prevalent in many studies to achieve net zero carbon emissions and the idea of using biomass to meet climate objectives has now become acceptable to the EU and adopted in a rather massive fashion.  As I recall, biomass was not considered originally to be a non-carbon renewable resource, but in recent years has been adopted with a vengeance. As more scientists scrutinize this assumption and examine the facts of the matter, it would appear that this assumption is very highly questionable. Over the last few years there have been numerous reports that the EU has been able to rely strictly on renewables for various periods of time, however, it appears that perhaps the tabulators of these statistics have been gaming the system.

The inclusion of biomass as a renewable energy source took place in 2009 when the EU committed itself to 20 percent renewable energy by 2020.  Several countries, including the UK started subsidizing the biomass industry and by 2014 it made up 40% of the renewable budget, and is currently about 60%, obviously a much greater share than sources like wind and solar that we normally consider as renewables.  Much of this biomass feed stock comes from the United States, Canada and Eastern Europe where trees have been pulped, pressed into pellets, heat-dried in kilns and shipped Europe where they are used as fuel in retired coal fired power plants.  The same trend is occurring in the U.S., but not yet to the same scale.

The UK has been especially aggressive in adopting biofuels and purchases about 75% of the wood pellets produced in the U.S. for use in power plants there. Below is a graph of the sources of renewable energy in the UK.

UK_Energy_in_Brief_2020.pdf

As we can see from the graph above, those sources that were previously considered renewable energy sources, namely hydro, wind and solar, made up just over 25% of the renewables in 2019, with biomass (next to the last line in the table above) making up approximately 35% , or more than 1.4 times the amount of all other renewable energy sources, and this from a sector that much of which was not even considered renewable prior to 2009.

Increase in renewable energy sources over time showing dominate role of biomass.

The theory is that biomass is both renewable and carbon neutral.  An examination of the processes involved reveals that this proposition is not supportable with facts. Consider the following:

  1. Wood pellets have a relatively low energy density compare to the coal or natural gas they are replacing. 
  2. Emissions of CO2  per BTU of energy produced from wood pellets is at best slightly less than, and in some cases higher than coal, and double that of natural gas.
  3. The toxicity of the airborne waste from wood burning is considerable.  Not as bad as from coal, but certainly more hazardous than natural gas.
  4. Including the cost of harvesting the wood, processing and drying the pellets, and then shipping them thousands of miles further increases the carbon footprint of wood pellets.
  5. Simply leaving the trees to grow, if one is applying sound forestry practices would maintain a massive carbon sink.
  6. Wood burning also releases emissions such as nitrogen dioxide, which is 300 times more potent than CO2, and many other pollutants, many of which are carcinogenic.
  7. It is true that the harvested areas can be reforested and once again the reforested areas can begin to sequester carbon, but to provide the fuel necessary to meet our energy needs we will start by creating a monstrous carbon sequestration deficit such that it would be many decades, and possibly hundreds to years to reach breakeven, if ever. 

The claim made by many of the producers and commercial users of wood pellets is that for the most part, just the waste portions and non-commercial vegetative matter is used to make the pellets, however investigators have found that this is simply not the case.  For economic reason, whole trees are more commonly utilized, and in the U.S. much of the supply comes from the southern eastern U.S. where trees can reach commercial size in 30 to 40 years when harvested for lumber.

It would appear that a majority of the logs are of merchantable size and could be milled into lumber, obviously not meeting the waste material quality standard claimed. Numerous other operations in both the U.S. and Europe show the same quality issue.  It should be pointed out that if lumber is produced from the harvested tree, a majority of the carbon will be sequestered for an extended period of time, perhaps hundreds of years.  When converted to wood pellets and burned the carbon content, on average about 40% of the mass, is immediately dumped back into the atmosphere as CO2.  The proponents claim that the clear-cut areas are immediately replanted, but a review of the growth process of basically all living things including trees follows a sigmoidal curve.

The trees being cut for wood pellets are just reaching the log, or exponential phase on the graph above.  They are just entering the stage where they become most efficient at packing on mass, 40% of which is carbon absorbed from the atmosphere.  The new trees that would be planted in their place will face many years of a much lower growth rate.  If these trees are not being utilized for lumber, this is the very worst time to harvest them from the standpoint of carbon sequestration.

Has the validity of the assumptions that allow the consideration of biomass as a renewable energy source been questioned by others?  The answer is a resounding yes.  Scientist Bill Moomaw, now a professor emeritus at Tufts, is a co-author of the Nobel Peace Prize-winning Intergovernmental Panel on Climate Report, co-author of four additional IPCC reports, and an expert on carbon sinks argues that it is a tragically shortsighted view of both carbon accounting and our current climate predicament. (1)

In 2009, as Massachusetts began debating whether to treat biomass as carbon neutral, he dove into the science. By assessing carbon emissions from bioenergy, and the slow regrowth rates of a replacement forest, he concluded that biomass stood to be “a serious problem.” To Moomaw, the question of whether biomass was ultimately carbon neutral was less important than whenit balanced out. (1)

Along with Mary Booth, a colleague who brought the issue to his attention, Moomaw and the Conservation Law Foundation convinced state officials to limit subsidies for biomass under the state Renewable Portfolio Standard. Unfortunately, the state later allowed large subsidies for burning wood to heat buildings. (1)

The analysis was later confirmed by a colleague at MIT, John Sterman, who did the math, and confirmed that burning wood today would worsen climate change, “at least through the year 2100 — even if wood displaces coal, the most carbon-intensive fuel.” (1)

It’s for that reason that in January of last year, Moomaw joined a group of nearly 800 scientists from across the world in petitioning the EU Parliament to end its support for biomass. (1)

Ironically, it turns out that burning wood for fuel has very little if any advantage over burning coal, other than in using strictly waste wood for the endeavor, and much of the waste wood is so dispersed that in many cases simply leaving the small pieces and chipping the larger pieces to decompose and enrich the carbon content of the soil would be a more practical choice. 

While our nation’s forests, particularly on federal lands, are overstocked and in need of thinning in many areas, clear-cutting as is done to produce wood pellets is an unnecessary waste of wood fiber.  Partial cutting to thin stands, reduce fire hazard and maintain the vitality of our forest resource is the best way to increase the carbon sink potential of our forested lands. Additionally, the esthetics issues of clear-cuts has long been an issue of contention, and one that once the public becomes more aware of current practices regarding wood pellet production is sure to create a major backlash.

Some thoughts:

  1. The current practice of using trees as a renewable and carbon neutral option simple does not make sense in theory or practice.  If we want to reduce our carbon emissions and yet still have uninterruptible power supply, we could start immediately by converting any existing operating coal fired plants to natural gas, and do the same with any old coal fired plants converted to wood pellets.  This would reduce the carbon emissions immediately by 40 to 50%, and reduce pollution by an even greater amount.  If carbon capture and sequestration does become economically feasible in the future it could easily be added to the gas powered plants and as the amount CO2 produced would be lower, the infrastructure necessary to accomplish this would be substantially reduced.
  2. If we want a non-carbon producing power source that is also capable of producing hydrogen which could be used to efficiently provide portable energy for our transportation needs and further reduce our need for fossil fuels, we need to add nuclear power to the mix.  High temperature electrolysis is much more efficient than conventional electrolysis and much less polluting than the chemical means we currently use to produce hydrogen.  Hopefully in the future, fusion will replace fission.  In the meantime, the new technology nuclear power plant designs provide safe and efficient means of generating sufficient uninterruptible power to balance out the inconsistencies that are an inherent part of wind and solar sources.  Perhaps it is time for the developed nations of the world to create a new Manhattan Project to decide on and develop the very best and safest nuclear plant prototype(s) to provide consistency and cost saving to said development worldwide.  The trend over millennia has been for mankind to move towards those fuels that have the highest energy densities; wood to coal to oil to natural gas and more recently to nuclear fission and perhaps in the future to nuclear fusion.  The trend is obvious.  To paraphrase Winston Churchill’s comment about Americans and apply it to the energy sector, the powers that be will do the right thing after they have exhausted all other options.
  3. A short review of history will reveal the fact the much of Europe, China, the Holy lands and many other areas were severely deforested to meet mankind’s home heating and commercial energy needs in the past.  With the adoption of coal, some of the European areas have reforested, but China is just now going through a massive reforestation project to reverse the earlier damage.  We do not need to revisit the errors of our past when better, rational options are so close at hand.

Sources:

  1. https://www.vox.com/science-and-health/2019/3/4/18216045/renewable-energy-wood-pellets-biomass
  2. https://futuremetrics.info/wp-content/uploads/2013/07/CO2-from-Wood-and-Coal-Combustion.pdf

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February 13, 2021 at 08:19AM

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