Biomass boilers (54) typically burn wood-derived fuel to produce heat for a central heating system, similarly to a gas boiler. Since their output cannot be easily regulated, they usually require the incorporation of a water heat storage tank.
Although traditional wood-stoves (55) are considered aesthetically pleasing, they are very inefficient (0-20%) and polluting due to low temperature partial combustion. Furthermore, substantial amount of heat is dissipated due to the large volume of warm air going out through the chimney. However, modern wood-stoves (55) can be very efficient (60-80%) and clean during their operation, as only a small amount of air is released in the environment. [EST, 2010]
Economical & Environmental Issues
In economical terms, wood-fuelled heating can have a payback of around 3-5 years for Europe, mainly as a result of low fuel costs [EST, 2010]. Biomass is generally considered carbon neutral, although a lot of debate is going on whether this is true or not. During their operation, biomass boilers emit the amount of CO2 that it absorbed during its lifetime (carbon sink). Therefore, the only net emissions to be taken into account are those from processing and transportation of the fuel. It is quoted, as a rule of thumb, that for a transportation distance of around 40km it breaks-even in terms of CO2. Even shipping woodchips from the other side of the world could cost no more than 120kg of CO2 per ton. Thus, a biomass heating system has a clear advantage in CO2 savings in comparison to gas, oil or electric heating. [Harrison, 2008]
Another ambiguous issue is whether land should be used for energy or food purposes, as there is increasing turbulence globally due to the increase of food prices. Implementation of biomass energy systems is considered to be opportune only at a limited scale (a small percentage of all the houses in a location) [EST, 2010]. For the case of Ameland, wood resources are relatively scarce on the island and furthermore they can be used as a construction material. Most forests on the island are planted in the North and are used mainly as wind breakers. [Jansen, 2009]
Technical and Technology Issues
A major drawback of biomass technologies is that they require a lot of dry space for storing the biomass fuel. As an indication, a typical family home needs almost 30m3 of storage space for a year’s fuel.Three different types of wood-fuel are currently used for biomass boilers. Wood-pellets are high energy-consistent (high calorific value), easier to handle and store but also more expensive (2.5£/kWh, UK price) and difficult to find them locally. As for wood-chips, they are more inconsistent in calorific and moisture content. They are less expensive (1-1.5£/kWh, UK price) but frequent maintenance of the boiler is required, and therefore they are preferred for installations of larger scale. Lastly, logs are energy-consistent but necessitate manual handling and daily fuelling of the boiler [Harrison, 2008].
In the Netherlands, domestic heating by biomass fuel is rather uncommon, mainly due to the lack of specific support schemes, the well-established natural gas infrastructure and the limited storage availability in houses, as typical Dutch dwellings do not have a cellar or other convenient spaces to store biomass fuel. [Junginger, 2009]
For the moment, other biomass technologies, such as biomass digesters, are only effective on a larger scale and therefore are not included in Renova as an option. Renewable natural gas, defined as gas derived from biomass, can be upgraded to a quality similar to natural gas and thus be distributed to customers via the existing gas infrastructure. According to the Energy research Centre of the Netherlands (ECN), renewable natural gas is cheaper than alternatives where biomass is used in a combined heat and power plant or local combustion plant. Energy unit costs can be reduced through 'favourable scale and operating hours', and the capital costs of the end-consumer can be diminished by distribution through the existing gas infrastructure [van der Drift et al., 2005]. The potential for biomass-fueled micro-CHP is elaborated in the sub-step on micro-CHP technologies.
When evaluating the potential of a biomass technology, the local availability and use of biomass is the first thing to be investigated. Such systems are recommended only at a limited scale depending on the biomass capacity of the local environment. Furthermore and instead of wood which is the most typical fuel, other biomass types can be considered for providing the heat supply of houses in the North Sea Region. Domestic organic waste from the kitchen and the toilet could be treated in a “Cradle to Cradle” way instead of “Cradle to Grave”, so that they generate useful energy. Furthermore, if biomass boilers are widely adopted, there might be a good opportunity for local production of pellets or chips made of available types of biomass. For Ameland, this could be compressed straw or Elephant grass. To end with, such technologies could be very opportune only if the specific house and location satisfy the requirements discussed.