The risks of using biomass for power

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Nov 18, 2005
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It sounded good to someone. Convert the coal-fired plant to biomass. The only problem is there isn't that resource in the country so England is importing it and taking down a ton of forest to supply these plants. They are burning 10 million tons of wood pellets annually. How is this sustainable or even sensible?
 
Its not. The fuel contracts for New England sales I have seen generally require an audit trail to establish that the fuel is a forest residual or pulled out of the trash stream.
 
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That answers a lot of questions, I had heard that Pinnacle had been bought, but didn't realize it was by Drax to produce pellets for their powerplant.

The areas that these pellet plants operate in are some of the areas hit hardest by the pine beetle, and if they are exclusively logging these trees then maybe this makes sense. Keep in mind these forests were the ones responsible for the massive BC forest fires of 2018, if some selective logging can remove the dry fuel in these forests maybe it's a good thing.

Eventually though this isn't sustainable, as high value timber will be taken for fuel, and Drax will need to find another source for it's pellets.

I think with lumber prices what they are, the writing will be on the wall for mass industrial pellet consumption. Timber sold for lumber will always command higher prices than timber sold for pellets, and North America is running out of land to log while lumber demand increases. Pellet production will get squeezed out. The unfortunate thing is households that heat with pellets will compete with government subsidized operations like Drax for fuel. IMO it makes more sense to burn that fuel in an 80% efficient pellet stove, than a 35% efficient powerplant half a world away.
 
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Its not. The fuel contracts for New England sales I have seen generally require an audit trail to establish that the fuel is a forest residual or pulled out of the trash stream.
How large are those contracts?

This is about Canadian sales to the UK, but the arboreal forests there benefit all.
 
NC has been stripping clean, healthy, sometimes virgin long leaf pine forests for pellet manufacturing. Those pellets almost all end up in European converted coal plants. Enviva is the worst offender. The paper I linked below cites 50+ acres a day are being cleared in order to export wood pellts.


 
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The plants I am familiar with were built around business model from30 years ago where the plant size was dictated on the availability of forest residuals from forestry operations. The usual approach was size the output based on getting 90% of the fuel within a 50 mile radius. Forest residuals would be generally defined as crowns of trees and logs not suitable for any other commercial sale. The other source was pre-commercial thinning operations. Pre-commercial thinning is generally used at least twice in forest management plan to improve the quality of the forest. Essentially its pruning the density of the trees growing in a stand to concentrate growth to fewer larger desirable species of trees. This costs the owner money out of pocket decades before they get the benefits so getting some revenue from the thinning's helps them decide to do this work and the result is improved forest stands in the future. In most cases its expanded to include both pre and post consumer untreated wood, and in the case of a plant I was involved with old railroad ties. The key with all these fuels are they are low cost, No owner in my area would voluntarily grow trees to turn into fuel. Chips eat up a lot of volume so the cost of diesel is significant, Once outside the 50 miles radius, the cost of the diesel starts to make moving the fuel un-economical. Generally the plants are selling into renewable markets and each market usually has rules on the fuel supply used to supply that power.

About 12 years I went to Power Gen which was a huge conference of power producers and suppliers. There were numerous seminars by industry experts. I was on the biomass/renewable track and one of the clusters of sessions was meeting the demand from Europe for pellets to supply power plants. There was lof of discussion about short rotation trees planted in plantations and at the time various big firms were staking out territory in the US to produce them. The Canadians as the west coast beetle kill problem and the still lingering collapse of the pulp industry along the Saint Lawrence watershed. The short rotation tree folks regarded the trees as just another form crop as they were in a 7 year rotation (from planting to harvest) and were racing to breed trees that cut that down. The big leap was to get a cold resistant Eucalyptus variety for the southeast. There were heavily genetically modified selective bred varieties that could go down to 5 year rotation but they could not grow much north of the florida border. Drax was even being discussed then.. There was also a huge pyrolysis plant to make "bio coal" pellets proposed for Millinocket Maine to supply the European market and the developer claimed the europe marker was unlimited. Generally the US biomass plants reapply their ash to local soils usually to farmers and the rotation is quite high so the soil is not depleted. This is not the case for short rotation plantations. Many of the soil nutrients go into the pellets and shipped offshore depleting the tree farm.
 
Sounds like a good plan for desertification if we're not careful.
 
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I did some quick calculations once to determine how much space you would need to sustainably power the US with wood. I came up with an area a little bigger than Alaska, CA and Texas. This was very basic using some forestry numbers etc.

Perhaps someone can enlighten me, why pellets instead of just wood? Seems to be a lot of unnecessary energy expense.
 
There are several reasons

Coal is non uniform when it comes into the plant, before it goes into the boiler its ground into smaller somewhat uniform chunkslike crushed rock. Boilers designs vary but the old standby is a grate type boiler. The grate can be vary large for a large boiler, bigger than the footprint of a house. The fuel has to be distributed across the grate in a fairly uniform thickness. Heated primary combustion air is used to throw the fuel onto the grate from chutes on the sides across the grate. By varying the air flow the pellets get carried different distances on cyclic rotation. Using pellets instead of cord wood means that the plant can skip the grinding step and go right into the distribution chutes.

Industrial pellets are equivalent to sausage, everything but the squeal goes in it;). Many of the Southeast pellets producers use fast rotation trees that are closer to big uniform weeds than trees. Its closer to conventional farming than tree farming. They just snip the trunks off and grind it before sending it to the pellet plant.

Pellets are easier to handle, they can move the pellets with bulk loading and unloading equipment.

Wood moved internationally needs to be sterilized to keep out invasive pests. A pellet mil inherently kills any invasives through the drying stage.
 
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This was recent here and probably a large( if not the largest) reason to export pellets.

 
Peakbagger referenced something above that I was considering when reading this thread. One of the reasons forest fires are a benefit is they keep the the nutrients for the forest in that forest. I know we are all on here because we burn wood in our homes, and yes, every tree we pull does take some nutrients with it, but at the individual home scale, its minuscule. Even with lumber logging, at least a lot of tops are left (at least they are in hardwood forests here in Ohio). If it becomes economically beneficial to take everything from a patch of forest, they will be just like our fields in the midwest... depleted of the nutrients they need to grow our food in the net 50-60 years. Climate change is increasing desertification fast enough without more help.
 
Coal is non uniform when it comes into the plant,

I can understand if you are trying to retrofit a plant, the transportation issue and pests are also good point But let's suppose you are building one these from the ground up and you will be using regionally sourced wood, why design it to burn pellets? The only thing that crosses my mind as to why you would want to do that is the moisture content of the wood.

The only thing I'm saying is seems like an awful lot of energy expense to turn wood into pellets when you have industrial scale boiler where logs are the equivalent of giant pellets to begin with.
 
I can understand if you are trying to retrofit a plant, the transportation issue and pests are also good point But let's suppose you are building one these from the ground up and you will be using regionally sourced wood, why design it to burn pellets? The only thing that crosses my mind as to why you would want to do that is the moisture content of the wood.

The only thing I'm saying is seems like an awful lot of energy expense to turn wood into pellets when you have industrial scale boiler where logs are the equivalent of giant pellets to begin with.

I can't speak for all plants, but the ones in our area burn anything from sawdust to large scrap wood. These are the residues left over from log processing, a lot of it is bark, which isn't used in wood pellets. Waste wood power plants have grinders or other equipment to reduce the size of any large pieces before entering the boiler.

I'm not aware of any wood pellet fuelled facilities in western Canada, these pellets are more valuable when sold overseas.
 
Yes the moisture issue also factors in for shipment. Why ship water across the ocean when it provides no benefit to the buyer?. I think I mentioned the 50 mile radius guideline for designing regional biomass plants?. The reason for that is if someone is shipping water (wet chips) the cost of diesel fuel to truck the useful fuel (dry wood) starts to approximate the BTU content of the wood. The Drax plant in England and the RWE plants in Germany are strictly political constructs. The rules in Europe and England say dont burn fossil so they buy the cheapest biomass they can find and that is North America. Europe has sustainable forestry and England long ago chopped down many of their forests and converted them to fields so they cant supply the volume they need. If real worldwide carbon accounting was in place the entire program will fall down.
 
Yes the moisture issue also factors in for shipment. Why ship water across the ocean when it provides no benefit to the buyer?. I think I mentioned the 50 mile radius guideline for designing regional biomass plants?. The reason for that is if someone is shipping water (wet chips) the cost of diesel fuel to truck the useful fuel (dry wood) starts to approximate the BTU content of the wood. The Drax plant in England and the RWE plants in Germany are strictly political constructs. The rules in Europe and England say dont burn fossil so they buy the cheapest biomass they can find and that is North America. Europe has sustainable forestry and England long ago chopped down many of their forests and converted them to fields so they cant supply the volume they need. If real worldwide carbon accounting was in place the entire program will fall down.
We might be seeing the accurate carbon accounting very soon.
 
Has to happen soon. Otherwise we are just shuffling the deck chairs on the Titanic.
 
Might be the real major step in the right direction to prevent real issues. Carbon regulation is realist, easy to implement and economically beneficial.
 
We're starting to see the downsides of pellet production, we're running out of harvestable timber and the pellet plants are buying up/allocated timber that would normally go to pulp mills. Combine that with sawmills closing due to lumber prices and some pulp mills are closing down due to lack of chips for feedstock.

 
Great post, this is just more evidence of my previous post about Enviva destroying NC habitats. More people need to know about the export economy for wood pellets
Similar to oil. People are distracted from the knowledge of or forget about how much of our oil capacity is exported.
 
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Folks keep using that broad brush to make all biomass power evil, its not. Biomass exported for power does seem to be a con, local biomass power supplied by local forest products residuals does make sense and is arguably renewable. The trick is it currently takes some quantity of fossil fuels to chip the waste wood and truck it to a biomass power plant. At some point the BTU content of fossil fuel used to make and transport the chips exceeds the BTU content of the chips. When I did local biomass power plants the economic radius for chips was about 50 miles, so the plants needed to be small (usually 20 to 30 MW). During the last big biomass boom at the tail end of the Obama administration, there were numerous 50 to 75 MW plants in the eastern US built which implies that the economic radius had increased. I know the local 75 MW biomass plant that used to be the pulp mill I worked at gets chips from farther away. There is a local mountain pass that rarely ever had chip trucks supplying our pulp mill due to fuel cost that is routinely being used to feed the biomass boiler. Given recent high power costs I expect its a much large radius but transatlantic is pushing it.

The BTU cost to make the chips out of the waste wood is somewhat fixed but transportation is definitely a variable. Hard to imaging trucking wet chips hundreds of miles to a pellet plant and then shipping around the world balances out. The big "but" is that reportedly DRAX and other European boilers does not factor in the embodied energy in getting the chips to the plant in England or the EU, thus the pellets are treated as a carbon free drop in for coal. Without worldwide accepted standards someone is always going to have their thumb on scale.
 
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The big "but" is that reportedly DRAX and other European boilers does not factor in the embodied energy in getting the chips to the plant in England or the EU
^^^^^ this. The global energy landscape will look very different in 24-36 months. I wouldn’t want to be making my livelihood on biofuels then.
 
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