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Debate Continues Over Carbon Neutrality of Biomass's picture

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  • May 2, 2018

Recently, Scott Pruitt announced that the Environmental Protection Agency will now consider the burning of biomass for energy to be carbon neutral. The agency memo points out that the use of biomass for energy can bolster domestic energy production, reduce wildfire risk, and help ensure that forests continue to remove carbon from the atmosphere.

The memo further states that “Managed forests improve air and water quality while creating valuable jobs and thousands of products that improve our daily lives.”

Despite the ruling, using biomass for energy remains a contentious issue. Scientists and various non-governmental organizations have raised concerns that forests clear-cut for fuel may not regrow as planned. Due to the amount of time required for trees to grow there is the possibility that economic or other factors may force landowners to abandon or change the planned regrowth. This means that the carbon dioxide released through energy generation might not ever be removed from the air again.

However, designating energy derived from the burning of biomass as carbon neutral is in line with the wishes of many in the industry. This ruling supports the sector’s calls for the deregulation of biomass carbon dioxide emissions, which would exempt the industry from some provisions in the Clean Air Act and could help make energy from biomass a competitive alternative to fossil fuels.

Such an idea is not new. In 2016, as part of a larger bipartisan energy bill, a group of Senators tried to pass a similar change which would have recognized wood burning as carbon neutral. Additionally, a provision in the federal spending bill introduced in March of this year encouraged officials to “reflect the carbon-neutrality of forest bioenergy and recognize biomass as a renewable energy source.” Similar rules are already in place in the European Union where biomass generation accounted for 64% of total renewable generation in 2015.

1. Is biomass as an energy fuel carbon neutral?

2. Even if it is not entirely carbon neutral, is biomass generation preferable to fossil fuels?

3. Is it likely that increased biomass generation will decrease demand for other renewables?

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Matt Chester's picture
Matt Chester on May 2, 2018

The discussion around these type of accounting practices is really fascinating. Really highlights how the politics/economics of carbon emissions are just as important at this stage as the actual results.

Willem Post's picture
Willem Post on May 2, 2018

Proponents of wood burning often claim it is “carbon neutral”, so it is ok. In addition, wood burning provides jobs for loggers, etc.
Proponents fail to add “over a period of at least 80 years”.

Assuming a tree is harvested after it is has sequestered CO2 for about 40 years. Burning that tree immediately releases that CO2.

That CO2 would take at least 40 years to be sequestered again due to new tree growth.

That process cycle, 1) sequestering for 40 years, 2) burning 3) sequestering again for 40 years is called “carbon-neutral”, however, the cycle lasts at least 80-years; an inconvenient truth not mentioned.

NOTE: Actually, the process cycle is about 85% “carbon-neutral”, because no process is 100% efficient. Various resources and a wood burning plant were used as part of the process, all of which required energy and emitted CO2; another inconvenient truth not mentioned.

Burning wood emits even more CO2 per million Btu than oil, coal or gas; another inconvenient truth not mentioned. That CO2 will become part of all CO2 in the atmosphere.

Vermont’s forests already are 100% busy, 24/7/365 sequestering only 50% of Vermont’s 8.3 million metric ton/y. The additional CO2 of wood burning would not be immediately sequestered, because there is no spare forest to do so.

Regrowing the wood that has been cut would take at least 40 years, so the CO2 of the first year of burning would take at least 40 years to be sequestered. The CO2 of the second year of burning would follow the same cycle, except shifted by a year on the timescale.

Each year, the CO2 addition of wood burning is quick, but the sequestering decrease is very slow. In NE it takes at least 40 years to regrow the wood, so eventually almost as many years of CO2 would accumulate, provided the forests maintain their sequestering ability.

By year 50 the wood burning plant would be closed, but its accumulated CO2 would take at least another 40 years to become zero. So the whole cycle becomes: 1) 40 years of tree growth and CO2 sequestering, 2) burning for 50 years, 3) 40 years until all CO2 is sequestered.

NOTE: It is BETTER to burn wood RELATIVE to burning fossil fuels over a period of about 80 years, because the forests will eventually absorb the wood burning CO2, but not all of the fossil and other manmade CO2. The proof of that is the CO2 buildup in the atmosphere, etc. See Chapter 6 of this study. See Exhibit 6-2a and 6.2b, and APPENDIX 1.…

The above describes the CO2 lifecycle of just one wood burning plant.

As a large number of wood burning plants have been operating all over the world over hundreds of years, there permanently is a quantity of wood burning CO2 in the atmosphere; the more wood burning, the greater the quantity.

The same is true for the world’s forest fires. As there are a large number of forest fires all over the world on a permanent basis, there permanently is a quantity of wood burning CO2 in the atmosphere; the more forest fires, the greater the quantity. See Global Carbon Budget 1959-2016 in URL.

NOTE: Forest fires do not use various resources and a wood burning plant hence they are much closer to 100% “carbon-neutral”.

Rick Engebretson's picture
Rick Engebretson on May 2, 2018

Glad “biomass energy” is viewed favorably. One question to add at the top, “What else are you going to do with this growing fuel?”

As regards the experts’ concerns, a tree will most often get pushed over by other trees in a crowded fast growing forest. Stripping the land of forest with big machines is like stripping the ocean of fish with big boats; you run out of fish before you pay for the boat.

So it’s all about how you do it and what you do with the biomass trees or grass. Since nobody burns unrefined oil in their car, it’s not hard to think some chemistry is needed.

Willem Post's picture
Willem Post on May 2, 2018

Thé US southeast is being stripped of trees that are chipped for use in Germany and the UK.
Removing wood from the forests depletes soils, unless clear-cut forests are replanted and then fertilized every year.

Engineer- Poet's picture
Engineer- Poet on May 3, 2018

Willem, I’m not sure your analysis applies to anything other than clear-cuts.  In particular, biomass removed as part of thinning stands does not particularly diminish the CO2 uptake of the zone and in fact allows the remaining trees to grow faster.  Carbon returned to the atmosphere by burning thinned trees is probably removed within years rather than decades.

We’d do better by seeing that carbon taken up in annual growth cycles is kept from returning to the atmosphere, but short cycles are not as bad as you make them out to be.  Our real problem is that NPP isn’t enough to keep pace with fossil emissions.

Engineer- Poet's picture
Engineer- Poet on May 3, 2018

“What else are you going to do with this growing fuel?”

Good question.  It’s been asked before in Vermont and Maine, where the demise of paper plants has led to a multi-million ton/year surplus of growth over consumption.  Foresters are looking for things to do with e.g. thinned trees and finding their traditional markets shrunken or gone.

The US could probably do something about this by prohibiting the export of fuel wood, forcing it to be processed into other products here.  For instance, a ton of bone-dry wood at 45% carbon has about 16-17 GJ of energy, but if it was processed into 1.2 tons of methanol (37.5% carbon by mass) the same amount of carbon would yield ~20 GJ LHV and a whopping 22.7 GJ HHV; that’s a boost of about 40%.  Liquids also travel more easily than pellets do, and MeOH in particular can be burned far more efficiently in both power plants and other things.

If we’re going to truly make a difference we have to stop taking the easy way out, both for ourselves and others.

Helmut Frik's picture
Helmut Frik on May 3, 2018

I do not know any imports of pellets from the US in Germany. Germany is producing a lot of wood in itself, and so do the estern neighbouring countries. ” The market for pellets in Germany, Austria and lesser extent France and Italy is more isolated and depends mostly on the production in this region itself.”

Bas Gresnigt's picture
Bas Gresnigt on May 3, 2018

Climate change is about long term changes.
So when you burn each year 1.2% of the trees the whole process is low carbon like nuclear.*)

When the state obliges that for each tree at least two new trees have to be planted (one in the same area, one elsewhere in areas with little trees) than the process may end being beneficial for the climate.
*) As it’s roughly as expensive as nuclear, it emits far more CO²/KWh than wind, solar & storage (though much less than fossil).

Rick Engebretson's picture
Rick Engebretson on May 3, 2018

EP, that’s the insight I was looking for. Clearly cellulose is an uniquely strong, lightweight, high volume solid material. So plants like it, but cars (etc.) certainly don’t. You and I have discussed this before, so allow me to encourage more thinking.

When we say “strong chemical bonds” we are actually saying low energy state. The symmetry of cellulose “hydrogen bonds” require profound energy input to break. I have suggested solar photons since lightweight hydrogen vibration is fast. So direct “solar storage” in chemical energy is at least plausible using cellulose gasification.

But many LEDs are now extremely efficient emitters in the same optical wavelength. I don’t see why wind or nuclear storage could not perform photo-chemistry. Electro-chemistry is proving very difficult.

Making value added product from raw resources is everywhere. However, I fear we are in an era when loud music drowns out real music, big tractor/fertilizer/irrigation agriculture marginalizes real farmers, and (as Willem said) big diesel powered forestry forever pulverizes posterity.

Fire photons certainly work. My guess is the Germans and Finlanders will keep science alive. Best of luck.

Bob Meinetz's picture
Bob Meinetz on May 3, 2018

Helmut, though the UK and Belgium are buying big into U.S. wood pellet exports, Germany has indeed avoided that fate by putting Beethoven’s beloved Black Forest through the grinder in its mad rush to shut down carbon-free nuclear plants.

Germans who aren’t shy of sacrificing tradition at the altar of renewables are investigating the potential for burning cuckoo clocks, which turn out to be a highly-combustible source of green energy. One challenge for German Bio-Cuckoos has been finding an economical way to remove the clocks’ birdcall mechanisms, to avoid the mournfully-reminiscent cry they make when the clocks are burned.

Engineer- Poet's picture
Engineer- Poet on May 3, 2018

I have looked at your pages and not found any direct references to data supporting your claim.  (Generally, the best way to do cites is to either hyperlink the text directly to the source, or reference a footnote with the hyperlink.)

One of the issues is the efficiency of conversion.  Perhaps today’s old coal-fired plant converted to wood-firing is roughly 25% efficient.  It is not a direct-carbon fuel cell plant converting biomass to biochar (50% efficiency to char, other byproducts not included) and making electricity directly from the char (up to 80% efficiency).  If the off-gas from the biochar production is clean enough to feed e.g. a SOFC, the system could have an overall efficiency of perhaps 70% (plus high-temperature off-heat).

True, nobody’s doing this today.  That’s probably because the programs are aimed at greenwashing, not actually solving problems.

Bas Gresnigt's picture
Bas Gresnigt on May 3, 2018

Didn’t see any degraded wood in Germany in the past 30years.
They follow the usual policy of replacement with new trees,

Engineer- Poet's picture
Engineer- Poet on May 3, 2018

Sorry, I screwed up and missed a factor of 1.2.  That should be 23.9 GJ/ton biomass LHV and 27.2 GJ/ton biomass HHV.

Incidentally, relatively low-grade waste heat is sufficient to crack MeOH to CO and H2.  1.2 tons of 2:1 v/v H2/CO mixture has a LHV of 28.89 GJ and HHV of about 32 GJ.  This would be significant if e.g. gas-turbine waste heat was employed to crack methanol before combustion, effectively recycling exhaust heat back to the combustion chamber.  Recapturing sensible exhaust heat as hot fuel gas would improve this further.

Engineer- Poet's picture
Engineer- Poet on May 3, 2018

I’ve looked at the chemistry.  Photons are not required; phonons have been doing the job for over a century.

The symmetry of cellulose “hydrogen bonds” require profound energy input to break. I have suggested solar photons since lightweight hydrogen vibration is fast. So direct “solar storage” in chemical energy is at least plausible using cellulose gasification.

Heat is sufficient to do the trick.  Apply enough heat and perhaps some water, and your lignocellulose winds up as mostly diatomic gases with some methane and CO2 mixed in (plus residual water).

If we’re exporting biomass-derived fuels, we should be sending them out in the most efficiently-usable form possible.  If wood pellets only yield ~4 GJ(e)/ton at the destination, while the same biomass made into methanol could yield almost 14.4 GJ(e) in CCGT plants and over 27 GJ(th) in condensing furnaces, we should be insisting that our customers up their game.  Methanol also burns cleaner than even propane (hi, Willem!).

Helmut Frik's picture
Helmut Frik on May 4, 2018

Bob, come here and look at the forests before publishing such nonsense. There is still more wood growing here than being harvested, what is used is waste wood which is cut when taking care of the forest, and which was left to rot previously. Cuting down whole forrests is more US traadition, here in germany most often single trees are harvested within the forrest, cutting all trees is rare.
It is worth to be discussed wether some of the wood would be better left to rot, or if the emissions of burning wood are bad enough to stop it, or if there is too much fuel needed in harvesting the wood. Or if the wood could be put to a better use than burning it in a oven.

Bas Gresnigt's picture
Bas Gresnigt on May 4, 2018

Seems to me that rotten trees may also emit CO2???

Sean OM's picture
Sean OM on May 13, 2018

What hasn’t been mentioned is a tree has like half of it’s Mass as roots which aren’t harvested. The forest being harvested for pulp paper is different then you grow for lumber. Most research for tree biomass is usually popular or Birch and harvested in 3 to 5 year cycles since both types of trees can be coppiced. Bamboo is also used.

The main opposition to biomass was really the fly ash. However it is used in the UK for generation and district heating areas that were serviced by coal. .

Because they never harvested the pulp for paper the woods are over grown and contribute to forest fires.

The pellets they ship to the UK are higher density then just wood and more uniform for easier burning. They are also larger in diameter then what we were as pellets in the US.

Allipower labs and thrive off grid both make small scale gasifiers that integrate into the grid.

Rex Berglund's picture
Rex Berglund on May 14, 2018

ARPA-E is running 18 programs to enhance farming of seaweed to take advantage of the vast ocean potential.

Willem Post's picture
Willem Post on May 14, 2018

In New England 70% of logging is by clear cuts.
About 30% is by culling sick, malformed, trees, i.e., junk wood

Willem Post's picture
Willem Post on May 14, 2018

No process is ever 100% efficient. Biomass burning, mostly woodchips, entails about 1.25 times combustion CO2, on an A to Z basis, i.e., logging, chipping, transport, storing, processing, burning, cleaning flue gases, disposing wastes, plus all the embedded CO2 of the A to Z systems.
It takes about 80 to 100 years in temperate climates, such as southern New England, such as Connecticut and Massachusetts, to NATURALLY regrow the clear-cut areas in the forests; it would take longer in northern New England, such as Maine. Google it.
It takes about 20 to 30 years “between harvests” in a Georgia, USA, climate to ARTIFICIALLY regrow the trees, in clear-cut areas in the Georgia pine forests, i.e., planted/managed forests, with periodic fertilizing, culling and pruning. That mode of growing trees is a very small percentage of all tree growing.
Millions of metric tons of Georgia pine wood pellets are exported each year to the UK, etc., for co-firing in coal fired power plants, because Brussels has declared that is “CO2-free”.

Bob Meinetz's picture
Bob Meinetz on May 14, 2018

Helmut, I don’t need to come to Germany. It took me all of 1.5 minutes to find this article in Der Spiegel, which claims Germany’s forests are being “brutalized” by the German biomass cartel:

Martin Kaiser, a forest expert with Greenpeace, gets up on a thick stump and points in a circle. “Mighty, old beech trees used to stand all over here,” he says. Now the branches of the felled giants lie in large piles on the ground. Here and there, lone bare-branch survivors project into the sky.

Kaiser says this is “a climate-policy disaster” and estimates that this clear-cutting alone will release more than 1,000 metric tons of carbon dioxide into the atmosphere. Forests are important for lowering levels of greenhouse gases, as large quantities of carbon dioxide are trapped in wood — especially the wood of ancient beech trees like these. Less than two years ago, UNESCO added the “Ancient Beech Forests of Germany” to its list of World Natural Heritage Sites.

It wasn’t any private forest magnate who cleared these woods out. Rather, it was Hessen-Forst, a forestry company owned by the western German state of Hesse. For some years now, wood has enjoyed a reputation for being an excellent source of energy — one that is eco-friendly and presumably climate neutral. At the moment, more than half of the lumber felled in Germany makes into way into biomass power plants or wood-pellet heating systems. The result has been an increase in prices for wood and the related profit expectations. The prospect of making a quick buck, Kaiser says, “has led to a downright brutalization of the forestry business.”

Engineer- Poet's picture
Engineer- Poet on May 15, 2018

No process is ever 100% efficient.

You really missed my point.  80% is not 100%.  It’s also a very long way from 25%.

If burning biomass at 25% efficiency to meet “climate-neutral fuel” targets is acceptable under the metric, then the metric is broken.  Ditto if the overhead for processing is so high.  Why not e.g. set up a portable solar farm in the cleared area and use the electricity for converting the feedstock to pellets?  Perhaps use the hot air off the PV panels to dry the feedstock to a given moisture content?  The input energy does not need to be either fossil or biomass.

Then there’s value-added processing.  If you can convert 1 kg of dry biomass at 16 MJ energy content into 30+ MJ of liquid fuel, then burn that liquid fuel at well over 60% efficiency in a CCGT (perhaps 70+% considering the possibility of recycling exhaust heat to fuel energy and back to the combustion stage) things look very, very different compared to the 25% figure for wood pellets co-fired with coal.

Processing to ash-free forms means that all the mineral components of the biomass are separated from the fuel stream.  That allows them to be put back on the land.  Fertilizer might be helpful, but not required.

I’m thinking of this mostly as a way of dealing with non-merchantable parts of trees harvested for lumber, thinned trees and cleared brush, but it is potentially applicable far beyond that.

Helmut Frik's picture
Helmut Frik on May 15, 2018

Yes, and what do you want to say with this? It is not in contradiction with anything I did write before.
Without wood pellets the price for wood not useable for construction would have fallen threw the floor because the need for it in the paper production has strongly fallen over the last years, paper production is shrinking.

Bob Meinetz's picture
Bob Meinetz on May 15, 2018

It’s not in contradiction? Then I’ll assume you agree with Martin Kaiser when he claims German biomass is a “climate policy disaster,” that beechwood is not suitable for construction, and the destruction of UNESCO heritage sites is justified by the aims of the Energiewende. Is that correct?

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