Tag: forests

The biomass carbon story

There is an important difference between carbon dioxide (CO2) emitted from coal (and other fossil fuels) and CO2 emitted from renewable sources. Both do emit CO2 when burnt, but in climate change terms the impact of that CO2 is very different.

To understand this difference, it helps to think small and scale up. It helps to think of your own back garden.

One tree, every year for 30 years

Imagine you are lucky enough to have a garden with space for 30 trees. Three decades ago you decided to plant one tree per year, every year. In this example, each tree grows to maturity over thirty years so today you find yourself with a thriving copse with 30 trees at different stages of growth, ranging from one year to 30 years old.

At 30 years of age, the oldest has now reached maturity and you cut it down – in the spring, of course, before the sap rises – and leave the logs to dry over the summer. You plant a new seedling in its place. Through the summer and autumn the 29 established trees and the new seedling you planted continue to grow, absorbing carbon from the atmosphere to do so.

Winter comes and when it turns cold and dark you burn the seasoned wood to keep warm. Burning it will indeed emit carbon to the atmosphere. However, by end of the winter, the other 29 trees, plus the sapling you planted, will be at exactly the same stage of growth as the previous spring; contain the same amount of wood and hence the same amount of carbon.

As long as you fell and replant one tree every year on a 30-year cycle the atmosphere will see no extra CO2 and you’ll have used the energy captured by their growth to warm your home. Harvesting only what is grown is the essence of sustainable forest management.

If you didn’t have your seasoned, self-supplied wood to burn you might have been forced to burn coal or use more gas to heat your home. Over the course of the same winter these fuels would have emitted carbon to the atmosphere which endlessly accumulates – causing climate change.

Not only does your tree husbandry provide you with an endlessly renewable supply of fuel but you also might enjoy other benefits such as the shelter your trees provide and the diversity of wildlife they attract.

Mushroom - Brown cap boletus in autumn

No added carbon

This is a simplified example, but the principles hold true whether your forest contains 30 trees or 300 million – the important point is that with these renewable carbon emissions, provided you take out less wood than is growing and you at least replace the trees you take out, you do not add new carbon to the atmosphere. That is not true with fossil fuels.

It is true that you could have chosen not to have trees. You could instead build a wind turbine or install solar panels on your land. That would be a perfectly reasonable choice but you’ll still need to use the coal at night when the sun doesn’t shine or when the wind isn’t blowing. Worst of all you don’t get all the other benefits of a thriving forest – its seasonal beauty and the habitat that’s maintained for wildlife.

Of course, the wood Drax needs doesn’t grow in our ‘garden’. We bring it many miles from areas where there are large sustainably managed forests and we carefully account for the carbon emissions in the harvesting, processing and transporting the fuel to Drax. That’s why we ‘only’ achieve more than 80% carbon savings compared to coal.

5 things you never knew about forests

Background. Fir tree branch with dew drops on a blurred background of sunlight

Forests and the products we derive from them are one of the most ubiquitous aspects of human civilisation. Despite the rapid pace of modern life, that isn’t changing.

Forest still covers 30% of the world’s land and in the UK more than an estimated 55 million m3 of wood was used in 2015 – either directly through furniture, books or hygiene paper, or indirectly, in infrastructure like fences, railways or through biomass electricity generation.

Behind all this lies the forest and the industry surrounding it. But how much do you really know about forests?

In some regions forests are increasing

Mention forestry, and there are plenty of people who make the jump to the activities of unscrupulous developers and deforestation. But while forest land is declining worldwide (in fact, we’ve lost 129 million hectares since 1990), the good news is the rate of decline is dropping sharply, down 50% across the same period.

A lot of this is thanks to growing environmental awareness, responsible forestry management and reforestation around the world. 10,000 hectares of new woodland was created in the UK in 2014 and in the USA, where a third of all land is forested, forestland has been consistently increasing over the last 25 years. There’s been an increase of roughly 7.6 million hectares between 1990 and 2015.

Vigorously growing forests absorb CO2 faster

It’s well known that trees are “the lungs of the earth”, but not all trees or ages are equally effective at absorbing the greenhouse gas CO2. A growing, younger forest is a better sink for carbon dioxide than a forest that is mature and stable. This has implications for the way these resources are used – notably when it comes to the sourcing of material for compressed wood pellets.

Whereas coal releases carbon that has been trapped underground for millions of years, wood releases carbon captured within its lifetime, making it a very low carbon fuel once manufacturing and transportation are factored in. The technique is to harvest trees when they have stopped growing at a fast rate, use the wood for forest products such as timber, pulpwood or compressed wood pellets for energy and replant the area with new, high growth potential trees. The result is a forest with a steady stream of CO2-hungry young trees and a steady stream of renewable raw material.

Forests can stop floods

 A study led by the Universities of Birmingham and Southampton and funded by the Environment Agency, found that forests in Europe play an important role in mitigating the effects of heavy rain.

Thanks to the buffering abilities of the forest canopy and the enormous water absorption capacity of woods and forests, they can slow the flow of a sudden downpour of rain overfilling nearby streams or rivers. This water will eventually be released but slowing its movement mitigates flash flooding.

Different parts of the forest have different uses

The primary commercial product from forests is not a hard one to guess: wood. But there’s more to it than that. For construction timber, the lower, thicker parts of a tree’s trunk are used. Smaller parts of the trunk are used as pulpwood which can be used to make paper, panels or for energy. Residues from the wood processing industry such as sawdust can also be used for compressed wood pellets.

With the rise of the internet, smartphones and e-readers the paper market has been shrinking. Manufacture of high-density wood pellets helps replace demand for wood once used by the paper market, as pellets can be made using low-grade wood, thinnings and residues not used in construction or furniture.

Trees talk to each other

Until recently it was thought that trees perform most of their biological functions in isolation from each other. But biologists have learned in recent years that in fact they communicate and help each other.

Under the forest floor, trees’ roots are linked by bright white and yellow fungal threads, called mycelium. In a forest, these threads act as a kind of network, linking trees to one another.

These links enable trees to share nutrients, carbon and water. Some species of tree also increase nitrogen uptake in the soil and help to improve the conditions in which other species grow. In fact, research by the University of British Columbia, indicates that certain large, older trees that rise above the forest act as ‘mother trees’ which actively help to ‘manage’ the resources for the other trees in the forest.

Based on their findings, it seems trees not only talk to each other, but help each other grow too.