Copyright Mike Hillard
Having researched the global forest rather extensively, I am aware just how overharvested it is, so I never understood why huge wood burning power stations were being built. And the biggest surprise of all was that they were being built in the UK– after all we are only about 17% self sufficient in timber. Even without these power stations we import 83% of all the timber we use. So how come they are being built? The answer is the EU with its wisdom.
The EU decided some time ago that burning biomass is a good environmental thing to do and that it is a renewable energy source. [It is the same EU that decided biofuels were a great idea and that all our road diesel must soon contain 20% biodiesel – see a coming White Paper]. They therefore subsidise every kw.hr of power produced from a woodchip power station by about 8p (it receives 1½ ROCS for the technically minded), and the financial viability of such stations is totally dependent on this subsidy which can provide ? of its income. If you check how much you pay for your electricity it may well be about the same as the subsidy!
The EU bases its policy on the notion that burning biomass, and in this case wood chips, is sustainable – so we will now consider if that could be true. Incidentally, we are not talking small scale with these power stations as some are 350MW or about ?rd the size of a single nuclear reactor. They are huge.
There are 3 separate things to consider:
- The Energy Balance – that is how much energy is used to get the trees from the forest to the combustion chamber, compared with the amount of energy the wood contains? To be zero carbon this figure needs to be zero.
- The Carbon Balance – that is how much carbon is emitted compared with a gas fired power station? Again the figure needs to be zero.
- Does the world have the sustainable forest to support such an energy source?
A. The Energy Balance
Trees are felled somewhere in the world and at some stage converted into chips generally about 1” or 25mm in size. These are then partially dried and transported to a power station where they are burnt. The argument is that the carbon absorbed by the tree when growing = the carbon given off when being burnt. We will see if this is true across the entire process.
How much recoverable energy is there in wood?
There are various numbers flying around concerning the amount of wood these power stations must burn, so we will work through the figures scientifically, the calculations being in Box 1 below.
1 ton of wood at 35% moisture contains 2,959 kw.hrs and can produce 986 kw.hrs of electricity.
The Timber Journey
Only 17% of the UK’s timber requirement is supplied from the UK, so the notion that these power stations are going to use UK sourced timber is impossible. They cannot.
- All the stations being built have argued they are going to use sustainable imported timber, and the regions I know looking to be sourced from include:
- North America
- South America (Brazil featuring heavily)
- South Africa
- In the forests the trees have to be felled; stripped of branches, and then pulled to a roadside station by a very heavy duty diesel powered machine.
- From there in one or more transport movements the logs are probably taken to a Chipping plant logically close to or on the Port where enormously heavy duty machines chip them.
- The chips are then loaded into bulk carriers by heavy mechanical equipment as they need to be loaded as quickly as possible.
- The bulk carriers sail to the quay by the power Station.
- More heavy duty machinery unloads the bulk carrier as fast as possible.
- The chips would need to be dried (or they could be dried pre shipping).
- Given these power plants are handling around 2 to 3 million tons of chips a year, more extremely heavy duty machinery transports the chips to the firing chambers.
How much energy does this process burn?
I suggest those who argue that burning timber is a zero carbon activity should consider the above, and if they wish to maintain their position – please track the timber. So now we need to estimate just how much energy is used during the entire process outlined above:
The Sea journey: (Detailed calculations in Box 3 below)
This varies with the length of the journey, so we will use the figures for an average distance route from Port Elizabeth in South Africa to Immingham on the Humber where 4 such power stations are planned.
This consumes 192.1 kw.hrs/ ton of 35% timber.
But the ship is very unlikely to have unloaded a 50,000 ton bulk load in Port Elizabeth, and will be unable to load 50,000 tons from either Immingham or Swansea, so it has to travel in ballast at both ends from its previous load and to its next load. Here there is a problem as the world’s bulk movements are not balanced. Little bulk travels to South America or South Africa – or to Canada, PNG or even North America – so getting the ships to loading port fully loaded is close to impossible.
When I worked on bringing fresh water from Canada (where there is lots of it) to where it is needed in the Middle East, it became clear that the most cost effective way of doing it was to sail the ships back in ballast. This would mean they would have to return empty. Clearly some ships (certainly on the longer journeys) would load to elsewhere, but to put it into perspective – one of these modest power stations will consume over 2 million tons of timber a year. This will require our carriers to make a delivery every week to each such power station. The notion Swansea or even the UK can export 2m tons to South Africa on a regular basis is between extremely unlikely and impossible, so there is a considerable addition to the above energy figure. It cannot be more than double, so adding 50% is a reasonable estimate.
This adds a further 96.1 kw.hrs/ton of timber, but this figure could be doubled for a ballasted return.
The collection from the forest:
There is one thing that is certain – the forest is not beside the dock! It is also clear that the distance will vary hugely, but the forests are in large countries generally covering very large land areas. In Brazil the distance from the port could be a lot more than 600 miles, whereas in South Africa it could be around 300. But yet again, the vehicles carrying huge logs are purpose made and will have to return empty, so these distances really have to be doubled as apart from anything else, the forest interiors do not have a need for huge volumes of goods. It is one way traffic.
Road vehicles carrying 25 tons of timber will be doing not more than about 7 mpg. This assumes the vehicle is very well maintained, but having travelled the developing world extensively you are often grateful the vehicle has a windscreen! So this is a very generous figure, giving 86 gallons for the shorter and 172 gallons for the longer journey.
The collection transport therefore adds between 273and 546 kw.hrs per 35% ton.
Drying the timber:
Here I am obliged to the Kielder Forest Company in the UK who have done some extensive work on calculating the most effective drying process, and the result is that 110 gallons of diesel is used to bring 25 tons of sawn timber down to the 35% moisture level.
The drying process therefore adds 408kw.hrs per 35% ton.
So just the three elements of the sea journey; the transport from forest to port, and the drying have already consumed between 970 kw.hrs & 1338 kw.hrs of the 2959 kw.hrs in the wood, but there are a number of energy consuming activities still unaccounted for, some of which I will try to calculate in due course.
So more than between 35% and 45% of the energy in the wood has already been used.
But this leaves the following to estimate:
- The felling and extraction of the trees to the road vehicle extraction point.
- Any intermediate handling – i.e. at assembly points.
- The handling and loading of the timber/chips onto the ships.
- The offloading of the ships.
- The chipping operation where whole trees are fed into rotational chippers.
- The energy used at the power station for the entire process.
- Anything else I have missed.
Clearly most of the energy embodied in the wood will be used bringing the wood from where it grew to where it is burnt. Doesn’t seem to make any sense does it?
- B. The Carbon Balance
If we compare the energy accounted for so far, it is all diesel but diesel emits 38% more carbon than gas for the same amount of energy. The amount of carbon already accounted for is therefore between 48% and 62% of what would have come from a gas powered station for the same output. And there is still all the carbon from the operations we have not yet analysed.
So far from being a zero carbon fuel, it probably emits about as much as a gas burning power station supplying the same amount of electricity (and it could be more), but this is before we account for the carbon emitted from the soils after the lumber extraction! Let’s try to get this into perspective, though every soil will emit different amounts of carbon when torn up and laid bare.
Taking South America, on average (State of the World Forests – UNFAO) each hectare holds 106 cubic metres of standing timber. As the biggest trees are not wanted for wood chipping, this is a reasonable figure to use, but that 106 m³ is not more than 65 tons of timber at 35% moisture. So each ton of wood chips is responsible for 1.5% of the emissions from a hectare. But how much comes from each hectare?
The amount of carbon released every year from peaty soils cleared for Palm Oil palms – is about 200 tons/hectare, and the 2003 Global Canopy Programme Report estimates 2 billion tons of carbon is released annually from the 50M acres cleared every year. This is 40 tons/acre or 99 tons/hectare. So cleared forest emits about 100 tons of carbon/acre.
Now it will be argued that the forest isn’t cleared but replanted which raises two issues:
- Taking this additional timber from one forest that may be replanted simply means the local demand will be taken from another that isn’t. It is the way it is. So the impact of forest clearance will result in deforestation somewhere. This means the 99 tons per hectare is the figure to be used.
- Even if we limited our analysis to the immediate forest, a substantially cleared forest in a region with a hot climate – is going to result in substantial carbon emissions for at least 15 years. Yet again we should be using the 99 tons/hectare. But if that forest is in northern latitudes where it is cold and wet – then the carbon losses will be greatly less unless the ground is again peaty.
So basing the carbon losses on the 99 tons/hectare, the annular carbon losses per ton of wood will be 1.5% of 99 tons which is 1485 kg of carbon/year either for say 15 years or for maybe 50 or more. So let’s now consider the total carbon emissions from the one ton of wood chips that are finally delivered to a UK Power Station:
From a gas fired power station – the 2959 kw.hrs emits: 137 kgs.
The carbon accounted for above – middle figure 1154kw.hrs of diesel: 74 kgs
Items 1 to 7 above not yet analysed: ?
Deforestation carbon – taken over even just one year would be: 1,485 kgs
Total so far: 1,559 kgs
Even if the forest emitted no carbon at all, the carbon from burning wood chips is going to be about the same as burning gas – but if you add even a smidgeon of soil carbon then wood chips are a nightmare.
Everything above has been defined so alternative operations can be compared, but if it were argued that the timber can be felled closer to the port, then additional felling will necessarily be done in the more distant and difficult regions even if it is to satisfy the local market.
The reality is that even without the carbon emissions from the soils, burning wood chips in UK power stations is not just not remotely zero carbon, it is about equal to the carbon emitted if we produced the power from a gas fired station. And no matter where the forest is cut – some carbon is emitted so regardless of how small it is – wood chips have to emit more carbon than the fossil alternatives.
For the EU to argue this form of power is zero carbon is incredible. It never could be. But for the EU to skew the market by subsidising the firing of wood at a level that will persuade companies to build such stations is frankly dreadful, and must call into question the competence of those concerned.
C. Is the Timber Operation Sustainable?
A 350mw power station operating continuously would produce 3.066M mw.hrs of electricity a year.
Each ton of chips produces 986kw.hrs so this power station would need at least 3.1 million tons of timber each and every year.
Measurement of trees and yields and logs is surprisingly complex, but the average UK yield across all our forests is about 2.43 tons/hectare at 35% moisture. But the figure for Finland, Sweden and Finland averages only about 1.86 tons, so taking the UK figure is reasonable. Here are some land areas of the sustainable forest required to produce the following amounts of energy:
Scenario M Tons/yr Land Area – M H/A
The 350mw Port Talbot Power Station 3.1 1.27
Total UK electricity – 383 tw.hrs/yr 396 162
Global electricity – 19,352 tw.hrs/yr 20,009 8,185
And the land areas concerned
Total UK Forest 2.65
Total UK land area 24.475
Total Global Forest 3,454
Total Global land area 13,048
Taking the UK figures, our total forest covers just 2.65m h/a so the Port Talbot power station would use 48% of all our forest. Shocking. And if we generated all our power from wood chips [which the EU considers an environmental solution] we would need more than 60 times our total forest – or nearly 7 times the total land area of the UK.
Let’s look at it another way. Suppose we have 2,200MW of wood burning power stations which would only provide about 5% of our electricity. They would burn about 25m tons of timber, increasing our total consumption from about 40m tons to 65m tons; increasing our imports from 31m tons to 56m tons, and reducing our self sufficiency from 17% to just 13%. Sustainable? What do you think?
Taking the global figure which is at least interesting as it does put the sustainable question into perspective – the land area required is 2½ times the total global forest, and the amount of timber just over 5 times total current global production which is already unsustainable.
It therefore begs a question – How on earth did we get into this mess? As I have said before, and will undoubtedly say again, others can do what I have done so there is no excuse for the EU reaching such a bizarre conclusion. I have not done anything astonishing.
And another question – What happens now that Companies have invested in building such power stations as a direct result probably of EU policy and their subsidy? I would argue that it is their own fault as if I can do this analysis then so could they have done. Companies that give false information or do not do their homework should get their just desserts. And countries that run with this obviously wrong information must also suffer the consequences. Put simply and unequivocally – these power stations need to be closed down or not be completed. Buyers or Investors – beware.
And another question – What if they use FSC certified timber. It is no more sustainable than any other timber (see Box 4 below).
So is saving the rainforests compatible with having wood burning power stations?