UK Wood Burning Power Generation-Notice Where The Wood Comes From

rowerwet said:

When they transport the wood in sailing ships I'll give the whole scheme some credit, until then it is as ridiculous as corn ethanol​

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Trains and barges (to ship the pellets to port) usually get in the ballpark of 250-500 miles per ton of cargo per gallon. Ocean going bulk freighters typically average in the range of 500-1000 miles per ton of cargo per gallon of fuel burned.

Figuring 17 million BTU/ton for the cargo, 130,000 BTU/gallon for fuel oil, 500 miles on the rails at 250 ton-miles/gallon, and 5000 miles on the freighter at 500 ton-miles per gallon, it looks like transportation accounts for about 10% of the energy value of the wood.

However, since the UK imports the overwhelming majority of their coal (primarily from Russia, the US, and South America), a similar energy loss applies there, too. Since coal is more energy dense than wood, the transportation should account for roughly 6% of the energy value of the coal.

Harvesting/mining, and processing energy would also need accounting for to make the comparison more complete.

begreen said:

Ten years back the rallying cry was American energy independence. Now the new budget bill seems to proclaim, how quickly can we sell the stuff.

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My brother works at Drax (the plant burning the overwhelming majority of imported wood), and among other things approves the wood as being suitable to burn in the plant. As I understand it Drax would have to close in the near future if it hadn't been converted to wood firing thanks to the UK commitment to phase out coal plants ASAP - indeed only half of the power station has been converted and my understanding is that the options are to convert or close the rest over the next few years.

begreen said:

I'd rather they burn their own garbage (literally) as fuel for heat and power.

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Does that not pose other problems ...local polutants come to mind..not all garbage is as clean as wood

Fluidized bed combustors help clean up sulfur and nitrogen oxide emissions. I'm not aware that they do anything for mercury, lead, or other heavy metals, but municipal waste is probably no worse off than coal in that regards.

I didn't know about the Portland-area plant, even though I lived there for a decade - Very interesting. I was expecting them to burn quite a bit of natural gas to aid the incineration, but the EIA data lists almost no natural gas consumption:
http://www.eia.gov/electricity/data....A&columnchart=ELEC.PLANT.GEN.50630-ALL-ALL.A

That data also indicates they get an average of 7 million net BTU/ton of "biogenic" waste (food, paper, yard waste, etc, ~2/3 of the waste) and 12 million BTU/ton for "non-biogenic" waste (mostly plastics, ~1/3 of the waste). That's significantly less than wood at 17 million BTU/ton, but more than I was expecting, despite the fact that the county seems to have decent recycling participation, too (reportedly about half their total waste gets recycled), which would remove a lot of the drier potential fuel.

It doesn't produce a lot of electricity - probably less 2% of what the county needs, so burning waste won't close many coal plants. I'm sure it's a lot more expensive to operate than a coal or gas plant, too.

However, the elimination of the waste has a pretty high value that might be enough to offset their operating costs. Using $30/ton for haul-away and landfilling as an alternative, the avoided cost of disposal works out to about $0.06/kWh, and the avoided cost of fuel compared to natural gas is around $0.03/kWh. My rough estimate here suggests it could cost them four times as much to operate as a coal plant while still selling their electricity for the same price.

They also say they use magnets recover another 3,000 tons of scrap iron from the ash per year, which should have a recycling value of ~$1/4 million and knock another fraction of a penny off their effective cost of electricity. A fraction of a penny doesn't sound like much, but when you follow the energy industry, you learn quickly that very small numbers can add up to a lot of money.

Sweden has to import trash to feed their WtE and Norway imports from England.
http://www.nytimes.com/2013/04/30/w...shortage-of-garbage-it-turns-into-energy.html

as usual, politics trumps sanity here: http://www.huffingtonpost.com/shawn-lawrence-otto/why-burning-trash-is-envi_b_3393445.html

this one was built in large part due to high percentage of surrounding communities landfill areas reaching capacity and closing with no available /suitable sites to open a new one: http://www.covanta.com/en/facilities/facility-by-location/semass/about.aspx

iamlucky13 said:

Fluidized bed combustors help clean up sulfur and nitrogen oxide emissions. I'm not aware that they do anything for mercury, lead, or other heavy metals, but municipal waste is probably no worse off than coal in that regards.

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Modern waste incinerators can burn quite clean, its all what they put on the tailpipe. Sulfur is usually taken out with some sort of alkaline scrubbing, NOx with SCR, the nasties like mercury lead are usually taken out with powdered carbon absorption or Trona (sodium sesqicarbonate). These product absorb the nasties and then a particulate removal device like a wet electrostatic precipitator takes the contaminated particles out flue gas. All these controls are costly and consume horsepower which reduces the plant efficiency and raise the cost of the plant substantially. Many of the recent Chinese plants were built for speed of start up and not emissions, reportedly many have some air pollution control equipment that if operated would reduce pollution output but typically once built, the plants are not held to operating standards so the emission equipment is bypassed to get more output. The same pollution technologies were developed for coal. With the exception of CO2 a modern coal plant can burn quite clean. What dooms it is low plant efficiency and very high capital cost. The problem is that once built, a coal plant may be around for 50 years so there is very large old fleet of these units that aren't state of the art.

Most Waste to Energy power plants are built as "waste volume reduction units" with some power as a byproduct. They general only get built where the waste disposal alternatives are more costly or legislated against. Some of the plants are now mining their ash to remove metals and other recoverable materials further closing the loop.

Trash burners got a bad rep in the US back 40 years ago where the air regulators didn't realize the impact and didn't have regulations in place. The developer stepped in and built cheap and dirty plants and the communities that hosted them bore the brunt of the long term impact.