Wood fuel for thought
Posted: 24 August 2007 08:36 AM   [ Ignore ]
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http://www.theecologist.org/archive_detail.asp?open=y&content_id=1041#5064 

Wood fuel for thought
Today’s energy policies are concerned overwhelmingly with generating electricity. But 84 per cent of the energy we use at home is to heat our rooms and hot water. What if that energy could come from a source which is not only renewable, but is cheap, readily available, and even improves the environment it is extracted from? Adam Nicolson reports on the growing potential for wood fuel in Kent…
Date:23/08/2007       Author:Adam Nicolson
       

If you go out in the woods today you’re sure of a big surprise. Almost unnoticed, the total weight of the trees in the south-east is expanding by an estimated million tons a year – opening up the possibility of an environmentally sound solution to our energy needs.  Not only are the existing tree getting bigger, the number of trees is increasing and hedges are getting thicker.  As a result, a good percentage of the carbon dioxide being pumped out by our cars and our oil-fired central heating systems is being absorbed by the trees.

The growth of our woods provides huge benefits, including more cover for animals, a massive stimulus for invertebrate and bird life and a more extensive carbon sink. However, it is also a sign of failure and neglects.  Woods are no longer being maintained. In particular, the coppice woods of the south of England, which used to provide hop poles, fencing, hurdles and even the wood that was pulped to make paper, are being neglected.

There are thought to be more than 40.000 acres of coppice woodland in the south-east and a large proportion of those acres has been abandoned. The flowers that used to thrive around the coppice stools, when the wood was being cut regularly, are now finding themselves shaded out by a solid leaf canopy.

But, intriguingly, the world is beginning to turn back to what the trees can give us. As the price of oil and gas fluctuate wildly, the idea that wood might become one of the fuels of the future is enjoying a renaissance. And almost uniquely, as a fuel, its harvesting an create and enhance beautiful landscapes rather than destroy them.

‘This is the dream fuel,’ says Sara Kassam, sustainable development co-ordinator for the transformation underway around Ashford. ‘It is good for the woods, the atmosphere and local employment, as the wood has to be managed. And it is good for your pocket, because the fuel is going to be cheaper than gas or oil in the future, and for fuel security.’

The technology may not be viable at the level of the individual house, but larger-scale institutions are suitable candidates. Ashford has commissioned a study of seven of these, including an office block, a public swimming pool, a leisure centre, a hospital and a housing estate. Each of the seven would require, on average, about 1,000 tons of wood a year. Local woodland owners and contractors would be paid £50 a ton and, if all seven schemes came off, more than 5,500 tons of carbon dioxide would be saved each year by the simple mechanism of the new trees re-absorbing the carbon that the burning wood released.

It is a closed loop. Except for the impact of chipping the logs and trucking the chips to the boilers – this vast amount of energy use would be almost carbon neutral.

Like mushrooms, the new wood-burning boilers are popping all over. However, the boiler cost two or three times as much to install as a gas or oil equivalent and the woodchips have to be stored undercover for at least a year before they can be burned if their moisture content is to drop below the necessary 30 percent. But the payback comes soon enough.

Nick Sanford, who runs the elegant 17th-century Godinton House near Ashford for a private trust, has commissioned a woodchip boiler to heat 3,000 sq ft of offices in converted farm buildings on the estate. He will burn chestnut chips from Godinton’s own coppice. ‘I look at it this way: a ton of woodchips cost £45-£50. You get the same amount of heat from them as from 400 litre of heating oil. And that costs £165.”

Sandford expects to gather 75 tons of usable wood per acre of coppice once every 12 years. That shrinks to 60 tons when the wood is dry and his boiler will use 20 tons a year. In other words, to heat his offices he must have a wood of four acres and coppice a third of an acre each year on a 12-year rotation. The result: a beautifully manage wood, no pollution, money saved and fewer oil tankers. If the 40,000 acres of southern English coppice were put to this kind of use, there would be 30 million sq ft of English offices, schools, libraries, museums, houses and galleries that could be heated and watered in a way that was making wood beautiful. And what could be more admirable than that?

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Posted: 24 August 2007 01:20 PM   [ Ignore ]   [ # 1 ]
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The logic escapes me as to how burning wood at a rate 4 times faster than it can be regrown, thus dumping 4 times more carbon into the atmosphere than growing trees can absorb, can be considered not polluting. Seems to me those 60 net tons of wood Sandford will burn in 3 years that took 12 years to grow, would nomally be released into the atmosphere at a very slow rate over time, if the fuel trees were simply left to decay over time.

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Posted: 25 August 2007 03:35 AM   [ Ignore ]   [ # 2 ]
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Actually, it wouldn’t consume more wood that can be regrown.
The 20 tons are produced by a third of an acre, harvested on a 12 year rotation, and the idea is that the growth of the new wood will absorb the carbon emissions of the burned wood.
All best,
Cristiana

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Posted: 25 August 2007 07:43 AM   [ Ignore ]   [ # 3 ]
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I will have to think about this more to be convinced, but as of now I cannot see how small seedling trees through the growing cycle until mature for harvest can offset the mature trees being cut for fuel even on a rotation basis.  The amount of CO2 absorption is also highly dependent on nutrients and water available to feed the trees.

One thing I do know for sure, when people in my neighborhood are burning wood in their fireplaces on those cold still winter nights, and there is a dense haze of smoke in the air that makes my eyes burn, I consider that pollution.

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Posted: 29 August 2007 12:28 PM   [ Ignore ]   [ # 4 ]
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Hi Texbird,

Good questions all ... some thoughts follow, hope they help.

I cannot see how small seedling trees through the growing cycle until mature for harvest can offset the mature trees being cut for fuel even on a rotation basis. 

Coppicing is about cutting wood but not killing the trees - think of it as a really harsh pruning job, the trunk and root system remain intact and you just remove a buch of the top (aka ‘above ground biomass’).  Because of this, the tree is able to grow much more rapidly than a seedling ever could, thereby fixing carbon at a much greater rate.

By the way, in Texas, there is a well established ‘pest’ tree called Chinese Tallow (Sapium sebiferum) which is a great candidate for both coppicing wood production and oil (read: biodiesel) production.  It is a pest, no question, but that particular cat is already well out of that particular bag, so maybe time to make some lemonaide from the lemons in hand ... if you will.

The amount of CO2 absorption is also highly dependent on nutrients and water available to feed the trees.

This is quite true, but not particularly of concern here as the productivity of the trees has already been established.  In fact, the nice thing about such non-food crops is that they can potentially ‘consume’ waste streams such as grey water and treated sewage, such that those nutrients are going into something useful rather than into our rivers and oceans (where they often do a great deal of harm).

when people in my neighborhood are burning wood in their fireplaces on those cold still winter nights, and there is a dense haze of smoke in the air that makes my eyes burn, I consider that pollution.

You’re absolutely right here, there’s carbon and then there’s smoke, they’re quite different, but both are produced by burning wood.  And since the smoke produced by home fireplaces and wood burning boilers is produced exactly where we live, this is clearly a serious consideration when it comes to biomass burning as a source of energy.  That said, we shouldn’t throw the baby out with the bathwater just yet, as there are many other options.  The most obvious option is to use a wood burning stove or boiler which is designed to burn completely with various controls and catalytic converters.  These are expensive, but they apparently work quite well.  Also pellet stoves which burn processed wood products are very clean and low maintenance.  But ultimately,  if you live in a place where there are inversions in the winter, any wood burning is going to contribute to local pollution levels in your neighborhood and wider community.

Lots of folks are working on processes which will turn that cellulose and other energy rich components of wood and other biomass into alcohol.  That can be done in the lab, but it’s not yet cost effective yet at a large scale.  Keep tabs on companies like Novozymes and Iogen ... they’re working hard at that process and once they get it unlocked, all sorts of agricultural and forestry ‘waste’ is suddenly going to disappear and become quite sought after. 

The other option is a process called by a variety of non-catchy names like thermal depolymerization - basically it’s a way of converting any carbon source - sugars, cellulose, lipids, sewage, car tires, etc. into something more useful like oil, such that it can be used in existing technology.  This sound too good to be true, but there are several groups working on this and several demonstration plants up and running ... check out http://www.changingworldtech.com/ for more details.  Y’all can’t do this at home, but at the community scale, this kind of biomass to energy conversion process could be quite useful in the future.

All best wishes,

Jamie

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Posted: 21 June 2008 06:57 PM   [ Ignore ]   [ # 5 ]
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Posted: 23 June 2008 08:37 AM   [ Ignore ]   [ # 6 ]
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Dear Jonbyrd,

Adding water to a gas powered engine is not a new idea, and there seems to be a small potential increase in efficiency in some internal combustion engines by adding a carefully controlled amount of water to the fuel.  I haven’t followed the details of this closely because it strikes me as an idea with a kernel of truth in it, but one with little practical application.  Today’s car engines are incredibly sophisticated and efficient and we expect them to last for hundreds of thousands of miles.  My guess is that critical components in such engines will have serious issues with the added water/steam, and ultimately you’ll pay for slightly increased mileage with decreased longevity. 

If anyone knows the details of this, please share.  My guess is that when the gasses in the combustion chamber ignite, the water is immediately converted to steam, expanding greatly and causing the amount of energy delivered to the piston to be increased. 

I don’t think this concept can work in a diesel engine because the injection pumps which generate the phenomenally high pressure used in modern diesel engines (upwards of 25000 psi in CRD engines i’m told) will not tolerate water ... thus the sophisticated water separators upstream of the pumps.

In any case, usually it’s good to ask yourself about these kinds of ideas which are ‘too good to be true’ what would happen if they were true.  In this case, wouldn’t all these car manufacturers who are deeply interested in fuel economy - indeed they compete over each MPG they claim their product gets - be snapping up this technology and making their cars more efficient and therefore attractive to buyers?  You bet they would.

All best wishes,

Jamie

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Posted: 23 June 2008 01:59 PM   [ Ignore ]   [ # 7 ]
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Growing any slow crop and then using it to burn is mostly an outdated concept.  Much better to push for technology that will improve solar and wind and geothermal energy sources in my opinion. Even if you do not kill the tree you are just taking a resource that takes labor and fertilizer and machine harvesting and all that effort, and you are then destroying it to make energy.  Surely mankind’s brain can see that if you have to destroy something in order to live, it is going to have negative effects. When man invented fire, there were no cities with millions of people living in them. What about energy from lightening, energy from the oceans currents, energy from space?  Use what nature has given us, don’t exploit it and destroy it, then have to wait for more to arrive before doing the same to that! Wood burning is quaint, yes, but it produces a lot of waste that is toxic any way you want to rationalize the re absorption as a new tree grows, or the like.  The only viable future on this planet is going to have to be ways of living that do not produce toxins. Anything else is a stopgap measure and a continuation of the methods that got us where we are right now. cool smile

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Posted: 23 June 2008 02:18 PM   [ Ignore ]   [ # 8 ]
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Dear Yellowfronts,

I couldn’t agree with you more - we’re swimming in energy, and we can be incredibly creative with our technology, but we’re sort of stuck in a 19th Century rutt - burning all this coal and oil and nonsensical stuff like this.

There’s a really interesting illustration here which indicates the amount of solar radiation hitting the planet over the course of the year: http://www.ez2c.de/ml/solar_land_area/

What’s fascinating are those black dots.  Not that one would consolidate the location of such energy production sites, but this gives you a sense for how much of the planet’s surface we would need to use to meet all our energy needs ... for everyone everywhere. Amazing stuff.

I think if we’re clever about this, we can go one step better and tap into our waste streams to get even more bang for our buck ... that is, to use algae and other second and third generation biofuel producers to 1. capture and consume human waste streams like CO2 from powerplants and solid waste from cities, etc. and 2. use those to enhance solar power collected in closed systems on non-arable lands.  So, yes, we can convert solid waste to methane, capture and burn it to displace fossil fuels (as we do at many land fills and sewage treatment plants), but if we take that process a step further, we can take those nutrient rich waste streams, combine them with solar power, fix a lot more carbon, and displace far more fossil fuels in the process. 

All best wishes,

Jamie

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