Biomass Woody biomass
Biomass, also known as biofuels or bioenergy, is obtained from organic matter, either directly from plants or indirectly from industrial, commercial, domestic or agricultural products.
The use of biomass is generally classed as a ‘carbon-neutral’ process because the carbon dioxide released during the generation of energy is balanced by that absorbed by plants during their growth.
Energy can be derived from woody biomass sources (including forest products, waste wood and straw) using combustion systems, which can be used to heat anything from a domestic stove or hot water system to an entire community. Biomass can also be used on its own or by co-firing it with fossil fuels in power stations, reducing greenhouse gas emissions by replacing a component of the fossil fuel required. In industrial or agricultural use, boilers fuelled by woody biomass such as cardboard, wood and waste pellets or straw can help reduce waste removal costs. For small-scale domestic applications of biomass the fuel usually takes the form of wood pellets, wood chips or wood logs Wood Pellets
Thanks to the current burner technology pellet consumption is very low; pellets have an efficiency rating of 93%. Not only is wood an environment-friendly fuel, it is also available in sustainable quantities. Woodworking industries produce a huge amount of wood waste which can be taken untreated and pressed into pellets. Wood waste is in plentiful supply. This combined with the relatively short delivery distances between the producer and consumer has made wood one of the most cost-effective fuels in recent years.
Pellets are made of 100% natural wood. Shavings and sawdust are compressed under high pressure and pressed into small cylindrical rolls and held together by lignin, contained naturally in the wood. This results in a clean, convenient fuel with a high calorific value and very low ash content (0.2%). Every year, more wood is renewed than is consumed. All of these facts are what makes the most convenient of all wood fuels such an interesting alternative in terms of both ecology and economy. Today’s wood burning boilers and stoves can no longer be compared to traditional solid fuel or wood fuelled appliances of the past. The biomass heating systems are super efficient and can be compared to high efficiency oil condensing boilers. Wood Chip
Some boilers designed for wood chips can also burn pellets, however boilers designed specifically for pellets cannot generally use wood chips. A wide range of boiler systems are commercially available but all share the same basic features of a boiler, a storage facility and a feed mechanism. The choice of whether to install a pellet or woodchip boiler will largely depend on local circumstances, for example the size of the heat load or the availability of the different fuel types. For most projects either solution will offer advantages and disadvantages, some of which are outlined in the table below:
| || Wood chips systems || Wood pellets systems |
|Fuel availability ||Can be readily produced locally ||May require significant delivery distances |
|Fuel quality ||Variable – must ensure boiler matches local supply ||Very standardised |
|Fuel storage ||Bulky fuel ||Compact fuel |
|Capital costs ||High installation costs compared to fossil-fuel alternatives ||Generally cheaper than wood chip systems although higher than fossil-fuel alternatives |
|Running (fuel) costs ||Very competitive – comparable to mains gas ||Competitive – comparable to heating oil |
The ideal choice for users who want to cover more or less the whole of their heating consumption by using wood, and who want to protect the environment (nature). Firewood is a modern, environmentally friendly fuel (stored solar energy), which is C02-neutral since the CO2 which is formed during combustion is consumed/transformed when new trees grow up. Furthermore, heating with
firewood is economic, depending on how you purchase it, but heating with firewood is not just a matter of economy - it is a life style. The firewood must be prepared, sawn and chopped to the right dimensions.
Wood combustion can be divided into the following stages:
During heating in the first stage, the moisture content of the wood
evaporates, and the wood is dried out.
During the second stage after drying out, the temperature rises
further and various energy-rich, combustible gases are driven out
of the firewood. During mixture with a suitable quantity of pre-heated,
secondary air, the gases are burnt off under turbulence and a good
temperature in the flame tunnel. As the gas burns completely without being cooled, a completely optimal combustion of the volatile substances in the wood is achieved and these substances comprise 80% of the calorific value.
The third phase is the burning out phase, during which the remaining charcoal is burnt out. Hardwoods contain the highest calorific value per cubic metre and softwoods contain least. Amongst other things, this means that if you fill up the combustion chamber with coniferous wood this will burn out more quickly, and it will be necessary to fill up more often than with, for example, beech wood.
ReGen (ni) offer a full design service to analyse the requirements and recommend the most efficient and cost effective equipment and solutions for your application.