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Power Station Fuel
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4089 Posts
10 Replies
whjohnson
569 Posts

Never mind wood pellets. My next tool purchase will be a chainsaw to go with the log burner I shall also be purchasing. If Boris thinks I am going to pay £2K pa to heat my home and fill his mate Cameron's windmill subsidized pockets he has another thing coming.

Grumpy
130 Posts

Fortuitously we have just moved to a place with an acre of unmanaged woodlands and a few hundred yards of similarly unmanaged Cornish banks so we will have enough timber to last our lifetime. We've just taken delivery of a small (270kg) masonry stove and if it's as successful as anticipated it will be followed by it's big brother.

The guy felling our scarier trees said he used to work for an outfit that had an enormous chipper that could swallow a two foot dia tree. When I asked why you would chip good timber like that he said “for biomass”

So now we have a huge machine with an equally huge carbon footprint burning gallons of fossil fuel to chip perfectly good timber to transport it God knows how far to burn in a power station that produces more CO2.

Is it just me?

 

Chris Pearson
3186 Posts

And where does all this biomass come from? USA, I think.

Like Grumpy, we have plenty of firewood. Some came from a tree which we felled on a surveyor's advice because it was too close to the house. Most of the rest came from trees which were being felled in the immediate neighbourhood. I suppose that the biggest problem in suburbia is having somewhere to store it.

broadgage
974 Posts

I heat largely with wood, obtained locally. Either from sustainably managed woods, or more often from trees that had to be taken down in any case for safety reasons.

I presume that a petrol chainsaw is used to cut the trees, and a diesel truck is used to deliver them, so not entirely green, but better than gas, electricity, oil, or coal.

I see no harm in the modest use of locally produced fire wood, but am opposed to importing it from afar.

whjohnson
569 Posts

Don't worry, Boris won't be having us undermine Carrie's green credentials by permitting us to burn wood and logs, he'll be along to ban the sale of log and wood burning stoves shortly. This will be followed by a green tax on trees, with those big landowners like Cameron's father in law getting even more tax-funded subsidies to grow more. Meanwhile, the subsidies for windmills are being diverted towards making gas more expensive.

Smoke-free zones coming to a town near you soon.

dcbwhaley
100 Posts

whjohnson: 
 

Don't worry, Boris  he'll be along to ban the sale of log and wood burning stoves shortly. 

The sooner the better.  Whilst the short cycle CO2 emissions are trivial the PM2.5 particulate emission is enormous:  750 times worse that an HGV diesel engine

 

Denis McMahon
349 Posts

Thanks for your entertaining comments, everyone, but I'd like to take a more serious look at this.

So Drax Power Station is the country's biggest emitter of carbon dioxide, at 15·6 Mt/year.

I am prepared to believe this as a statistic in isolation; it seems quite plausible. We need, of course, to take a wider view.

It seems that the Drax operation is justified because it fits the definition of "renewable sources". The trees cut down to provide its fuel can be replaced. Whereas if we mine the soil for coal, oil, etc., once these fuels are gone they are gone.

This seems a sound enough argument for continuity of fuel supply well into the future. Is it a sound argument for curtailing the CO2 in the atmosphere?

Ember makes a good point. To fuel Drax, we are cutting down trees, thereby removing absorbers of CO2. It may take around 50 years for the replacement trees to reach maturity and absorb CO2 at the same rate as those sacrificed.

Putting it another way, if Drax had have kept on burning coal, those trees would not have needed to be cut down and would be continuing to act as CO2 absorbers. But we need to consider the CO2 emmission of coal burning as compared with biomass burning.

People sometimes refer to carbon offset trading or similar terms, which can sound like an accounting trick and leave us sceptical. It will take us up to 50 years to cancel the effects of burning biomass today. Yet we are aiming to be carbon neutral in less than 30 years. Does this work out? Let us see.

The Drax Group website at www.drax.com has many pages. I have been sifting through to find out more. According to a recent press release, it has slashed its CO2 emissions since 2012. A graph illustrates this, an impressive downward slide of 90%. Are these net figures, after taking account of carbon trading? No, they are absolute emission figures, I find, after delving through other pages.  Elsewhere the figures are reinforced by quoting the CO2 emissions from various fuels. Coal is 937 t/GWh. Biomass is 120 t/GWh. On another page I find that the figure quoted for biomass is a full-cycle figure; i.e. it takes into account the energy used to reduce the timber to biomass and tranport it to Drax.

There are some mitigating points. Although the replacement trees may take 50 years to reach maturity, they will absorb increasing amounts of carbon dioxide as they grow. Also, some of the timber is felled anyway, for purposes of providing finished timber for bulding structures, furniture, etc. Much sawdust is produced in timber yards, and there is inevitably "waste" in the form of pieces of timber that are small or of irregular shape, therefore unsuitable for purposes other than reducing to biomass.

Drax has much to say about Carbon Capture Utilisation and Storage (CCUS). Together with other electricity organisations it was researching this in previous years but it seems the research stalled for reasons of economics. My reading of this is that the process of extracting carbon dioxide consumes a lot of power, which must be deducted from the power sent out by the station, thereby reducing its merit in terms of cost per unit sent out hence making it uneconomical to run except possibly at times of extreme peak demand. However, the much lower emissions from biomass fuel make research on CCUS worth a revisit. Good luck to Drax on this one. CCUS is still a speculative idea under development but if it could be made economically viable it could be the saviour of the Planet, particularly if the spin-off could be applied at small scale. We might even be able to keep our gas boilers! The thermodynamic efficiency of heat pumps makes them an attractive prospect, but I foresee many practical problems.

I see the Drax biomass operation as slightly imperfect solution to our current energy needs, bearing in mind that it will take time to provide all our energy needs from genuine CO2-zero sources. It is better than no solution at all and it will be a useful stopgap arrangement to take us over the next 30 years.

What do others think?

Denis McMahon: 
 

……..

So Drax Power Station is the country's biggest emitter of carbon dioxide, at 15·6 Mt/year…..It seems that the Drax operation is justified because it fits the definition of "renewable sources". The trees cut down to provide its fuel can be replaced. Whereas if we mine the soil for coal, oil, etc., once these fuels are gone they are gone.

This seems a sound enough argument for continuity of fuel supply well into the future. Is it a sound argument for curtailing the CO2 in the atmosphere?

Yes. Not only renewable, but biomass is (argued to be) carbon-neutral. I accept the argument, which is pretty simple, as follows.

The trees have recently grown, sequestered CO2, and by being burnt are releasing the CO2 they have recently sequestered. There is a carbon cycle, but it is on the order of 20-30 years, which is within the natural variability of most of (all?) the essential climate parameters. 

(There is of course also a carbon cycle with fossil fuels, but it is on the order of 300-350 million years, hence the problem.)

Other biomass fuels take the form of oil. Aviation has tried rape (Brassica napus) and of course there is also maize (Zea mays), sunflowers (Helianthus app.) and Sylphium. I think the jury is out on how well any of these might work as larger scale energy sources, say for a place such as Drax.

dcbwhaley has a point that burning wood can (I emphasise the conditional) contribute extensively to pollution, viz, particulates. Wood burning is allowed in Germany for heating residences (anywhere, whether dense or not). Two of my immediate neighbours do so, and sometimes in winter it stinks; the air is hard to breathe. BTW, pollution of this sort contributes to atmospheric cooling (negative radiative forcing). It also contributes more obviously to respiratory problems and poor public health (well known for 200 years).

The most efficient individual-building heaters in Germany run on wood pellets. A heating engineer I know has a free-standing family home which he claims costs him less than €100 per year to heat. And we have real winters (frequently -7°, often -10°, occasionally -15°, last February -18°). 

Properly designed wood burners, of course, get rid of all the polluting components, just putting out gases and water vapour. 

 It may take around 50 years for the replacement trees to reach maturity and absorb CO2 at the same rate as those sacrificed.

I'd wondered about that. I said 20-30 years above and I think that is right for forest harvesting in Germany, but I don't know for sure. I'll check.

 

Denis McMahon: 
  It may take around 50 years for the replacement trees to reach maturity and absorb CO2 at the same rate as those sacrificed.

[PBL] I'd wondered about that. I said 20-30 years above and I think that is right for forest harvesting in Germany, but I don't know for sure. I'll check.

Info I have found so far is that there are short-lived plantations for trees to be used as biomass for energy-generation. Mostly poplar and willow. The growing time to harvest is (can you believe this?) 3-10 years. So a lot less than my guess!

Denis McMahon
349 Posts

Thank you, Peter. The short cycle you describe puts things into perspective.

You could probably think of the Drax operation as a type of investment. The general definition of an investment is an initial outlay of money or some resource, from which you ultimately intend to profit. In this case, we could say that the forests initially sacrificed are the investment made to ultimately achieve carbon neutrality once the cycle has run full term. If this will take only ten years it is well worthwhile. 

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