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This is how you make a biomass wood pellet

6 October 2016

Sustainable bioenergy
Compressed wood pellets

Wood has been used as fuel for tens of thousands of years, but this wood – a compressed wood pellet – is different. It’s the size of a child’s crayon and weighs next to nothing, but when combined with many more it is a smart solution to generating cleaner electricity compared to coal.

Wood pellets like these are being used at Drax Power Station to generate electricity and power cities. Not only are they renewable and sustainable, but because they are compressed, dried and made from incredibly fine wood fibres, they’re also a very efficient fuel for power stations.

This is how a compressed wood pellet is made at the Drax Biomass Amite BioEnergy Pellet Plant in Mississippi.

The wood arrives to the yard

Wood arrives at the plant via truck and is sent to one of four places: the wood storage yard, the wood circle (where wood is primed for processing), the piles of sawdust and woodchip, or straight into processing.

Bark is removed and kept for fuel

Logs are fed into a debarker machine, which beats the logs together inside a large drum to remove the bark. The bark is put aside and used to fuel the woodchip dryer, used later in the process.

Thinned wood stems become small chips

The logs – low-value fibre from sustainably managed working forests – need to be cut down into even smaller pieces so they can then be shredded into the fine material needed for creating pellets. Inside the wood chipper multiple blades spin and cut the logs into chips roughly 10mm long and 3mm thick. The resulting chips are fed into the woodchip pile, ready for screening.

Chips are screened for quality and waste is removed

Chipped down wood can include waste elements like sand, remaining bark or stones that can affect pellet production. The chips are passed through a screener that removes the waste, leaving only ideal sized wood chips.

The biggest hairdryer you’ve ever seen

The wood chips need to have a moisture level of between 11.5% and 12% before they go into the pelleting process. Anything other than this and the quality of the resulting pellets could be compromised. The chips enter a large drum, which is blasted with hot air generated in a heater powered by bark collected from the debarker. The chips are moved through the drum by a large fan, ready for the hammer mill.

Wood pellet Hammer Mill

Small woodchips become even smaller woodchips

Inside the hammer mill there’s a spinning shaft mounted with a series of hammers. The wood chips are fed into the top of the drum and the spinning hammers chip and shred them down into a fine powdery substance that is used to create the pellets.

Putting the chips under pressure – a lot of pressure

The shredded woodchip powder is fed into the pellet mill. Inside, a rotating arm presses the powdered wood fibre through a grate featuring a number of small holes. The intense pressure heats up the wood fibre and helps it bind together as it passes through the holes in a metal ring dye, forming the compressed wood pellets.

Resting and cooling down

Fresh pellets from the mill are damp and hot, and need to rest and cool before transporting off site. They’re moved to large storage silos kept at low temperatures so the pellets can cool and harden, ready for shipping.

One of the biggest domes you’ve ever seen

This is the final stage before shipping. Specially designed and constructed storage domes are used to store the wood pellets after they are transported to the Mississippi River, Louisiana and before they make their way across the Atlantic to the UK.

The 4 most common myths about renewables

Power generation

Renewables make up more of the world’s energy mix than ever before. And yet, misconceptions about these new or alternative technologies – such as biomass, solar and wind – are common.

Some of these concerns are – for the time being – partly justified, some completely subjective, and some are demonstrably wrong. Here’s a closer look at the most pervasive myths and what truth there is behind them.

Renewables are unpredictable

An oft-repeated misconception is that renewables aren’t a full-time solution to our power needs. It’s true that solar isn’t generated at night and wind turbines don’t operate in still weather, but the canon of renewables is bigger than its two most well-known technologies.

Tidal power still depends on environmental factors, but tides are much more predictable than wind or sunlight. For countries lucky enough to have ready access, geothermal power – which uses heat from the earth’s core to power generators – is even more reliable.

Biomass solutions, such as compressed wood pellets, are a fuel-based power source, meaning they are flexible so can be used to generate electricity on demand and operate as a base-load power option, much like coal or gas. At Drax Power Station renewable electricity is generated on demand using compressed wood pellets and delivered to the National Grid 24-hours-a-day.

Now, thanks to advances in weather forecasting, the National Grid can plan ahead to balance the system with other renewable and low carbon technologies when the sun isn’t shining and the wind isn’t blowing. Just a few years ago the primary fall back was relying on coal power stations to pick up any slack.

It might not be possible to power the world entirely with one renewable source, but the right mix of technologies could provide an answer to the question of how to ensure a stable and secure low carbon energy supply.

Heavenly Scene Stormy Skies

Renewables are expensive

There is some truth in this, but it’s important to note that these costs are falling. Many of the high costs associated with renewables have been down to a lack of infrastructure investment.

A number of the components required in construction of structures like wind turbines and solar panels are expensive. And, as many renewable facilities need to be located in different areas to existing traditional facilities, extensive power grid extension is often needed. But these are problems that once set up, should bring down the costs of renewables such as solar and wind.

Setting up biomass-powered facilities is considerably cheaper. Compressed wood pellets can be used in upgraded coal power stations, so there’s no need for expensive new connections to the high-voltage electricity transmission system.

There are even ways renewables could bring about cheaper power for consumers. Research commissioned by Drax and published by NERA Economic Consulting and Imperial College London found that, if the same government support offered to some renewable technologies (i.e. wind and solar) were open to all (such as biomass), consumers could see potential savings of £2 billion on their energy bills.

Renewables are ugly

While this isn’t necessarily an opinion shared by everyone, it is one that is often cited. Onshore wind farms often draw the most ire, but they aren’t alone. Large investments are being made in offshore wind farms, which are both more discrete and better positioned to take advantage of stronger offshore currents.

And hydropower projects like dams and tidal barrages can in the long term create whole new habitats, ecosystems and leisure facilities in the form of artificial lakes and surrounding forests.

Nobody uses renewables

In 2015, 99% of Costa Rica’s electricity came from renewable sources, including hydro, geothermal, wind, biomass and solar. Closer to home, Sweden draws more than 50% of its electricity from renewable sources, including 22% from bioenergy – 90% of which comes from forestry.

In the UK, renewables use is steady and rising, accounting for 25% of all electricity generated domestically in 2015. In the first half of 2016, 20% of the UK’s renewable power was supplied by Drax. Contrast those figures against coal, which in the UK declined from supplying 30.8% of UK power needs in Q1 2015 to just 15.8% in Q1 2016, and our increasing use of renewables is even more evident.

Consumers have been buying 100% renewable electricity tariffs from companies such as Good Energy for more than a decade. Businesses are increasingly getting in on the act too. Two thirds of the power generated by Drax in the first half of 2016 was sold directly to companies via Drax Group’s business electricity supplier, Haven Power.

And with campaigns such as RE100 challenging the world’s biggest firms to commit to renewable-only power, household brands such as Ikea, M&S and Google are either already 100% renewable or only a few years away.

Misconceptions about renewables will remain as long as we’re still in the transition out of fossil fuel use. But the industry has made huge strides from where it was just 10 years ago.

Thanks to better, more affordable technology, an increasingly friendly corporate sector, and a greater awareness of environmental issues at large, these products and services will continue to improve, grow and increasingly becoming more mainstream.

5 things you never knew about forests

Sustainable bioenergy
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.

How does Europe use biomass?

Sustainable bioenergy
Family on summer Senja coast (Norway, polar day)

At the heart of Norse folklore is a figure called Yggdrasil that connects its nine worlds and gods. It’s an immensely important and holy icon, but it is not a god itself – it is an ash tree.

That the central figure of mythical Scandinavian cosmology should be something as humble as a tree is no surprise, Scandinavia is a heavily forested region. Sweden, the largest country in the area, is more than 68% forest. Wood is an inherent part of life there. For thousands of years it’s been used as a resource and a fuel, and today is no different.

Throughout much of Europe the same is true. But, while historically wood was used only for cooking, heating and light, today its use as a form of energy also includes generating electricity and heat when formed into compressed wood pellets.

Europe and wood pellets

Nearly 22 million tonnes (Mt) of wood pellets were used in the European Union in 2015, making the region the leading wood pellet consumer in the world. It is also the world’s leading producer, creating roughly half of the world’s global output – largely from European trees.

A report from the Standing Forestry Committee, set up to represent the forestry industries in EU countries, found that just 4% of the woody biomass used in the EU was imported.

Of the 22Mt used across Europe, 10.5Mt was used for heating, while 11.5Mt was used for industrial uses like fueling power plants. But in the UK, the level of wood used for fuel falls some way behind EU averages. Thanks in large part to Drax and its transition from coal to renewable wood pellet-powered electricity generation, that’s changing, but the UK still has a way to go to catch the continental average.

Where is the UK falling behind and how is wood being used to power the rest of the continent? Here, we look at some of the largest consumers and producers of biomass in Europe and how it’s being used.

Sweden

Sweden is the third highest consumer of wood as a source of energy in Europe, trailing only Finland and Latvia in its use. A key use of biomass in Sweden is powering district heating systems. In a district heating system, rather than each building or home having its own boiler, whole areas of cities are heated through a single central plant distributing heat to buildings. These plants can be powered by a variety of fuels, but many run on wood pellets or distribute the waste heat captured at power plants.

rax_europe_biomass_sweden

Germany

In 1713, an accountant and mining administrator, Hans Carl von Carlowitz, published what is considered the first ever book to look in depth at forestry management, effectively kickstarting the modern idea of sustainable forestry. In the 300 years that have passed, Germany has embraced the cultivation of wood and has made wood and biomass a fixed part of its energy makeup.

More recently, the Renewable Energy Heating Act and Market Incentive Programme was passed in 2009, which requires new building owners to provide a percentage of their heat from renewable sources, including wood-fired boilers. The aim is to increase the country’s share of renewable heat to 14% by 2020.

Europe, Biomass, Germany

Finland

Nearly three quarters of Finland is forestland, making it one of the most forested countries in the world, let alone Europe. As a result, wood plays a large part in Finnish culture. Stora Enso, one of the world’s leading paper and packaging manufacturers is Finnish and more than 20% of the country’s exports are from wood and wood products. Coupled with a strong focus generating much of its energy from renewables, energy derived from wood and products made from wood is high.

drax_europe_biomass_finland

United Kingdom

In 2013, less than 10% of all energy used in the UK was generated from wood and wood products. This places it some way behind countries like Germany and Sweden, in part owing to a lack of infrastructure for providing heating derived from wood and wood biomass.

This could change if the government continues to back technologies equally in initiatives like the Renewable Heat Incentive (RHI). Available to homeowners, landlords and commercial customers, RHI provides incentives for installing generators of renewable heat such as wood pellet boilers.

To reach climate goals, the then Department of Energy and Climate Change noted that both biomass-driven electricity generation and heating should continue to increase in the UK. And with the upgrade of Drax and Lynemouth power stations from coal to compressed wood pellets, there are positive signs the UK can catch up to the European biomass average. In doing so, renewable biomass electricity generation can also help increase wind and solar power generation in the UK, and help create a more sustainable energy future.

drax_europe_biomass_united_kingdom