Biomass or Coal?

I grow trees, I also burn wood for heat and am very interested in renewable energy and global climate change.

I am very worried about the growth in the use of biomass as an energy source and trees in particular. Locally at Discovery Park they are building a Biomass energy plant, I wondered how valid this was as a means of generating renewable energy in the context of Global Climate Change plant .

Biomass power plant in Discovery Park in Sandwich to go ahead after £160 million investment

I have started with some very broad assumptions and propose to look further into the numbers to see if they are valid.

1Kg of wood is equivalent to 1.7Kg of CO2. So a tree that adds 1Kg to its mass, takes 1.7 Kg of CO2 out of the atmosphere. Equally, burning 1 Kg of wood generates 1.7Kg of CO2

The wood variously sourced from:  Virgin forest, that is where an area of existing forest that has grown naturally is cut down; Plantations where the trees have been planted specifically for commercial use; Waste Wood where the wood is regarded as unusable except for burning.

So, considering the three types of wood

Virgin Forest

These trees will be alive and growing and potentially some hundreds of years old. The mass of wood will take years, equal to the age of the tree to replace if a sapling replaces the cut wood. A living tree, in particular a large one, is also growing and taking CO2 from the atmosphere. (Follows is a guestimate) If a mature but growing tree adds say 5% to its mass each year, a 50 tonne tree will add 2.5 tonnes of wood per year. Burning that tree will add the 50 tonnes.

A sapling will grow faster, but even if it doubles in size year on year for say 5 years, that 1/2 Kg year old sapling will sequester another 1/2Kg the following year, maybe weigh 20 Kg after 10 years. As an example, think of how heavy your Christmas tree is.

Forestry Commission:Mitigation: Planting more trees

The Biomass plant at Discovery park proposes to use Virgin wood and save 100,000 Tonnes of CO2 per year. One has to assume that what they are actually saying is they are replacing 100,000 tonnes of CO2 generated from coal or gas (very old trees) with 100,000 tonnes generated from not so old trees. If the average age of the trees being burnt is say 100 years and these burnt trees are replaced by saplings to be burnt at a similar rate, ie when they are 100 years old, this plant will only reach a state of being carbon neutral in 100 years having added 10 million Tonnes of CO2 to the atmosphere.

New Scientist: The renewable energy scam making global warming worse


A lot of forestry commission land is planted with conifer in serried ranks, often on moorland which hasn’t seen trees for millennia, but that aside. A commercial planted forest or coppiced woodland that is maintained and cut and replanted has to be regarded as sustainable in the same way as a farmer’s field that is used to grow crops. Virgin forest that is cut and replaced with commercial trees becomes a plantation. The main problem is the mono species, the lack of variety. Of course this can be mitigated with careful management, with islands of mixed native trees that might be left standing when the bulk of the wood is taken.   Realistically that is down to the forestry manager.

An additional concern is that the majority of plantations were established to feed the paper industry. Even with the move towards electronic publishing, there is still a massive use of paper and card. Just think of the growth in the use of cardboard simply to deliver mail order goods that used to be collected personally.

Waste Wood

There appears to be two types of waste wood. What we would regard as waste wood, old pallets, waste from manufacturing plants that use wood as a raw material, cuttings from the forestry industry. Then there is the other type where a wood or forest might be cut for commercial wood, only the best trees are usable, all other trees are thus regarded as waste. So a virgin forest might be cleared, one or two trees per acre used for the stated purpose, the rest is waste.   So, a company claiming to use waste wood and thus assuming heightened environmental standing, might well be clear felling virgin forest.

Coal / Oil or Gas versus Wood Biomass – To save the planet

Its 2018 and Global Climate Change is regarded as a NOW problem. Not in 100 years or 50 years, but NOW.  We have to work to reduce emissions now.

So, put very simply, chopping down trees and burning for energy is no more sustainable than burning coal! In fact I would suggest it is the worst possible solution as it removes an effective carbon sink that, in its mature form is removing far more CO2 than 2 foot saplings ever will – within the time-scales that are relevant.

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