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Friday, 16 March 2012

Biomass – Energetic Goo or Environmental Mess?

Biomass – What Is It?

The answer to that is complex. If we are talking about solar or hydro in an energy context the meaning will be clear. Sun or water are the resource and the result is power. While biomass can easily be described as raw material of plant, animal or human origin, this covers a wide range of individual substances and sources. The leafs you gather in your garden and throw on the compost heap fall under it, but so do energy crops and sewage sludge, basically anything organic that can be burnt directly or converted into something that is a fuel.

Conversion Processes - Biomass to Biofuel

It is an energy source that has been in use for hundreds of thousands of years since humans first managed to control fire. What was once simply the only way to provide warmth and cook a meal, is now heralded as a major staple of low-carbon energy for the future. In many ways that is perfectly true. But there are issues that need to be addressed or at least entered into the equation if we don’t want something beneficial to leave behind the nasty stench of questionable environmental value. Below is a list of raw materials that are most common in this category (adapted from the website of Environmental Protection UK).

·      Virgin Wood

  • Dry – includes roundwood, harvesting residues (brash), bark, sawdust, crowns, needles and residues of tree surgery

·      Energy crops

  • Dry – includes woody energy crops (short rotation forestry, willow, eucalyptus, poplar), grassy energy crops (miscanthus and hemp), sugar crops (sugar beet), starch crops (wheat, barley, maize/corn), oil crops (rape, linseed, sunflower), and even hydroponics (lake weed, kelp, algae)

·      Agricultural residues

  • Wet – includes pig and cattle slurry, sheep manure, grass silage
  • Dry – poultry litter, wheat or barley straw, corn stover

·      Food residues

  • Wet – includes wastes from various processes in the distillery, dairy, meat, fish, oils, fruit and vegetables sectors

·      Industrial residues

  • Wet – includes sewage sludge
  • Dry – includes residues from sawmills, construction, furniture manufacturing, chipboard industries, pallets.

Serious Concerns                               

Brown Haze

It sounds really excellent. Fossil fuels release carbon dioxide (CO2) that is not recycled plus other undesirable elements. What was once locked into oil and gas is released and that’s about it. In contrast biomass captures and amasses carbon during growth, whether that is a human being or a tree (although the tree wins with about 49% of its chemical make-up against 18%). So there should be no net disadvantage when the material is used as fuel. What was stored is emitted and then will be turned into new growth of new life. Unfortunately, there is more to it.

Apart from CO2 also released are nitrous oxides, ozone, sulphur oxides and particulates. In case of sludge and industrial residue it could be toxins as well. It is generally accepted that wood, especially, burns cleaner than coal or oil but more polluting than gas. Only, particulate matter in smoke is of great concern, as it leads to respiratory and heart disease or even death. In a long-term study researchers from Sweden, the Maldives and India investigated the nature of the so-called ‘Brown Haze’, a thick cloud of smog that hovers over large parts of East Asia during winter months. To their surprise it turned out that this pea soup of airborne waste products was created far more by burning biomass than by combustion of fossil fuels.

The Fight for Land

And the worrying is not just over what is in the atmosphere. The food-versus-fuel debate rages about the land grab in favour of biomass crops such as oil palms, miscanthus and Jatropha. One of the best known members of the club, sugar cane, is allegedly eating into rainforests. It doesn’t help that efforts are under way to improve the potential of these plants with the help of genetic engineering. That alone is enough for many people who claim an environmental sensitivity for themselves to reject the expansion on a large scale of this sector.

As this often plays out in Africa, South America or Asia, it might come as a surprise that Scotland and Wales have been thrown into the mix. Friends of the Earth, an environmental campaign group, is hurling its fury at plans to build massive biomass power stations there. They are planned to run mainly on wood (pellets and waste), but these regions, or in fact Britain in its entirety, would not be able to supply the massive amounts needed to keep the turbines spinning. The energy released by burning the feed stock is not turned into heating but electricity. The campaigners claim that this is criminally inefficient. A statement supported by the need to import most if not all of the timber, which would add tons of carbon emissions on the way. Funnily enough, in America where a lot of the timber in all its forms for European power stations comes from, voices are becoming increasingly audible that complain from the other side of table. There the uneasiness is based on the question why such a resource is being shipped half around the world when their own country needs clean energy just as much.

It’s Not All Doom And Gloom

As I said before, these issues need to be addressed or the claim of zero-carbon status of biomass rings hollow. Despite that, this energy resource has an important role to play. Research has shown that plant material can be a way to capture and store carbon. Burning will release a certain amount, and it takes years for a new tree, for example, to grow and collect what was once contained in its predecessor. However, going up in flames meant a heap of ash was left behind that consisted up to 45% of calcium carbonate that was not returned to the atmosphere.

Also, biomass is not just wood. Many waste products can be turned into something useful instead of clogging up landfill sites. Apart from energy, the process often produces a valuable fertiliser particularly during anaerobic digestion. Exhaust gases can be cleaned and toxic by-products removed. Thousands of open fires in developing countries cannot simply be chucked into the same bucket as a modern power station with the finger pointing at deadly air pollution. Already, co-firing (adding materials such as straw) with coal is reducing fossil emissions in power stations. Better, more effective forest management and inclusion of a higher number of privately owned woodland do not automatically turn everything into barren deserts. Most importantly, a low-carbon future will need many different routes to the same goal. Biomass is an essential part of it.

Applicability at Home

For the private end-user the method that makes the most sense is the biomass boiler. Due to availability and technical issues (cleaning exhaust gases, storing feed stock, etc.) wood will be the most common fuel. There is, of course, the good old stove. Current models offer good efficiency and will release 60% – 70% of the energy into the room (in contrast to fire places where that same proportion disappears up the chimney). Some can actually be connected to the central heating system but most will be used as stand-alone units in individual rooms.

As a full replacement for oil or gas you can install a biomass boiler for both heating and hot water. They come as batch fuelled (open the door and put a few logs in) or continuously fuelled (a feeding system supplies pellets/shavings as needed). A fully automated installation for a three-bedroom house will set you back between £11,000 - £15,000 ($17,000 - $23,500). With governments keen to promote these types of microgeneration, grant schemes like the Renewable Heat Incentive (RHI) help to make such an expense more palatable well. However, farmers might find anaerobic digesters more appropriate, particularly if they have livestock that provides the necessary raw material for free. Like other biomass solutions they have the advantage that they work by night and without wind. The chief fuel made by the bacteria in the digester is methane, which can be used in a generator for electricity or in a combined-heat-and-power unit. In Britain the power is subsidised by the Feed-in-Tariff scheme, whereas the heat might attract payment from the RHI. The digestate can be used as a fertiliser on the farm or sold.

In any case, whether on a large scale or for a private home biomass is a source of low-carbon energy that must not be pushed aside and buried under short-sighted generalisations. It isn’t perfect just as everything else isn’t. But properly handled it is a precious element of our push towards a sustainable future.


Our most basic common link is that we all inhabit this planet. We all breathe the same air. We all cherish our children's future. And we are all mortal.
John F. Kennedy

Until next week




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