What are the advantages of biomass fuels and are they worth investing in?
Biomass fuels have been around since Prometheus stole fire from the gods – or to put it more factually, since early man learnt how to ignite wood and dry grass to warm the cold night air and cook meat. These early ways of cooking over open flames are still with us and in parts of the world cooking using wood or animal dung for fuel is still common.
Biomass for fuel is becoming a credible modern fuel source. What is it? And what are the advantages of biomass for modern users? This article takes a broad overview of some of the useful forms of biomass available to homeowners and institutions.
Modern biomass boilers will usually accept wood chip, wooden logs or pelleted wood. Each of these has its advantages and disadvantages.
Biomass fuel is a blanket word for all the types of grown materials - living or dead - that can be burnt and used for heating or cooking. It includes wood, straw, dried grasses and husks and animal dung. In many parts of Asia and Africa people still rely on dried cow dung for domestic cooking. While this might seem, superficially, to be a sustainable use of resources, the resulting smoke accounts for a good deal of ill health.
There is also a number of industrial waste products that can be used as biomass fuels. For example, nut and seed shells discarded during processing can make a useful fuel. Plants that are being used to supply biofuel include switchgrass and coppiced willow.
Another example of biomass fuel is Miscanthus, also known as Elephant grass. It is a tall grass originating in China and Japan. A hybrid is used. Miscanthus needs very little nutrient to grow and only needs a little water.
It compares very favourably with corn or wood as a source of ethanol, producing a lot more output per acre. Another advantage that this kind of biofuel has is that as it is not a food source there is less effect upon food prices from its usage as biofuel.
There are other types of biomass fuel in common usage based on foods such as corn and sugar. These crops have a primary purpose of supplying food. Use of such crops as biomass for fuel compromises food security as the decreased availability of the crop for food pushes up prices for consumers. These types of biomass fuel are often converted to bioethanol to add to gasoline for running cars and trucks. They are sometimes referred to as "first generation biofuels".
In this article I am looking at the advantages of biomass fuels for domestic heating - not for transportation, or in power plants.
One of the advantages of biomass fuels is that they can offer a cleaner heat source than some traditional fuels. But the combustion unit used is critical.
Anyone who has stood around an open bonfire will know that wood burning is not exactly pollution free or clean. In fact there is a type of pollution called “black carbon” which does a lot of damage in terms of climate change. It is thought to be second or third in importance after carbon dioxide. It is a bi-product of coal burning and biomass burning. One effect is that it casts a pall of dark pollution over some areas of the earth and leads to more absorption of the energy as the sun’s rays strike the earth.
Modern biomass burners are a lot more efficient than open fires and the gases and particulates of partially burnt material are far fewer. Biomass fuel used in modern biomass burners is around 90% efficient in energy converted to heat and the effects on the climate change emissions compare very favourably with those of other fuel sources.
Biomass heaters are available for homes and larger buildings such as schools and hospitals.
Biomass has another advantage in that it can promote sustainable industries around the growing and harvesting of trees.
Many countries have lost large swathes of natural woodland in the rush for development. Here in Britain we lost a lot of our forests during the late Neolithic and Iron Age and again in Tudor times when wood is was in demand for boat-building and housing. Similar forces were at work in continental Europe. By the mid 19th Century global deforestation was already rampant. The industrial revolution accelerated the demand for resources and land worldwide.
Now, in Britain we have a country that is only 13% forested. Most of the losses occurred generations ago. We cannot return to an Arcadian past where most of the country is wooded. But we can increase forestation sensitively and use some of the timber produced in a sustainable way to create both fuel and wood products. A side benefit is that more jobs would be generated.
This economic effect of growing more trees does not necessarily occur where biomass fuels are used. In Africa, for example, there is concern that deforestation is resulting from the use of wood for fire. This is adding to greenhouse gas production rather than cutting it. The traditional use of wood for cooking also causes health problems, especially for women and children as inefficient indoor fires belch smoke into the living space.
Charcoal is a popular fuel for urban residents in parts of Africa; the same reservations apply. While the burn maybe cleaner than for wood, there are the same pressure on dwindling forests.
Biomass heating has limited scope for development here in Britain because we live in a heavily populated and industrialised country. There is a limit to how many woods we can plant simply for provision of fuel. One of the reasons that the industrial revolution took place as it did was that wood was simply not efficient enough as a power source for the new machinery being developed in the eighteenth and nineteenth centuries. It would be folly to suppose that we can all return to the power sources of that era.
Another limit on the use of wood as a biomass fuel is that wood is far less dense than, say coal. The amount of heat produced is far less for a similar volume. Wood also needs to be dried before efficient burning can take place. Also, many types of wood are unsuitable for burning.
Please see my page on wood burning for more on this.
For most people, the best biomass fuels to use for domestic heating will depend heavily upon what is available locally.
Here in Suffolk, woodland is a good source of biofuel and the choice is between logs, wood chips and pelleted wood. The benefits are that local traditional woodland is supported and extended and this is particularly good for biodiversity.
New sources of biomass fuels are now being trialled locally. Willow coppiced and cropped in rotation has some benefits. It provides more heat per acre than wood. However, visually it is much more like a plantation.
In selecting a biomass fuel for use at home it makes sense to see what is easily available locally and to select a fuel which will continue to be available in the long term. The best biomass fuels are sustainable, cheap and easy to source.
In some areas, waste products from manufacturing or agriculture may be available as biomass fuel. If these materials are suitable for burning in modern heating appliances then this may be a relatively sustainable source of heating.
Biomass fuels work well in the context of a wider economy that provides them as a side benefit. Growing wood or other materials for burning is usually far less sustainable. If you grow a wood simply to clear fell and burn the trees you are harming the local environment.
One of the often mentioned advantages of biomass fuels from wood is that it is carbon neutral; this is only partly true. The tree sequesters CO2 during its life and the CO2 is returned to the atmosphere when it dies. But it may take many years for the CO2 produced by burning a tree to be re-absorbed as replacement trees take years to grow. In the short-term, more CO2 is being released. The carbon neutral argument carries some weight if the number of trees being planted for felling is higher than the number being felled.
Logging damages habitat profoundly - even if sensitively done. See this fascinating article from the NY Times Sunday Review. Logging activities were shown by sound recordings to be impacting on birds and other wildlife, even when the amount of timber removed was just a small percentage of the available wood.
A better way of producing biomass fuels is where harvesting fuel can be a small part of a managed woodland where other economic benefits are also being found. In Agroforesty schemes, for example, a permaculture approach is used. Trees are interplanted with crops to enhance wind protection and to fix nitrogen in the soil. A small amount of dead wood is harvested for fuel by the farmer.
What does all this mean for us?
Most urbanites will not have access to a meaningful supply of biomass as a fuel source. If you live in a town near wooded countryside you might be able to source wood or pelleted wood, sustainably grown and harvested.
People who live in the countryside may well be able to source enough wood or woodchip to run a domestic system. It really depends who you are and where you are.
So if you are thinking about getting a biomass heating system, do your research as to how available - and sustainable - your chosen biomass source is. You will also need to carefully consider whether the type of heater you buy is just for supplementary heating or whether you want to invest in a system that will deliver all your heating and hot water requirements for your home.
For more on this please see the page on woodburners.