There are 2 main methods of using biomass for energy production:
- Stoves and Boilers: the biomass material can be burned directly in a stove or larger boilers to provide heat for households or communities (via a district heating scheme).
- Anaerobic Digestion: for biomass that is not suitable for burning it can go through a biological process to make it suitable for burning, or to use in internal combustion engines or purified and upgraded to be used for conventional gas applications such as transport.
For the rest of this document we will largely focus on the burning of biomass materials in stoves and boilers. Primarily the simplest use of biomass to burn it in a stove or boiler on site, which can then be used to generate heat and hot water for buildings. However, the can also be used for:
District Heating:
Uses a centralised, large boiler to provide heat for a number of buildings. Boilers to burn biomass materials tend to be larger and more expensive than traditional fossil fuel boilers. However, as the boilers get larger the cost discrepancy tends to decrease significantly, thereby making biomass boilers more economically viable. This is especially the case as the scale of installation reaches several hundred kW.
A typical district heating installation consists of a highly insulated “heat main” of flow and return pipes distributing hot water (or steam) past all buildings which might be connected. A junction point allows easy connection to each building, from which hot water can be taken from the main to a heat exchanger (heat substation) within each building. The heating circuit within the building is thus isolated from the heat main. Temperature measurement of the flow and return lines, plus a flow meter (together forming a heat meter), allow the actual heat usage within each building, or even apartment, to be separately measured, and delivered heat billed for accordingly. Remote meter reading by modem, secure web interface or drive-by are all possible, as are remote diagnostics to ensure reliable operation.
Combined Heat and Power:
Also known as co-generation, is the simultaneous generation of heat and electricity. A biomass boiler can be used to generate the steam required for steam turbines which then generates electricity. However, this requires large amounts of heat and thus is only used for larger scale energy generation projects, whilst the excess heat needs to be used within a close vicinity of the power generation. For smaller scale CHP there are a number of new technologies being developed, but these are currently not seen as economically viable at current prices.
There is also a third source of biomass use called tri-generation. This is an extension of CHP where the heat is used to power an absorption refrigerator to provide cooling in the summer. However, again this technology is un-developed and un-economical at current costs.
Stoves and Boilers:
The simplest way of using Biomass is to burn it in stoves and boilers in domestic and small commercial buildings to generate space heating and to heat domestic hot water. Burning the biomass in an enclosed structure such as a stove and boiler also now comes under the Renewable Heat Incentive (RHI) and benefits from these payments. However, the open burning of biomass, such as on open fires, is not included under the RHI. Below, we will run through each technology:
Log Stoves:
This is basically a wood fire enclosed in a burner stove. The stoves come in all shapes and sizes and can be quite modern these days. They are a relatively cheap way to heat a single room.
Log Boilers:
These are the next step up from log boilers and are essentially large, industrial sized log stoves that are used for space heating over a larger area. Due to their size and the amount of fuel required to run them, they tend to be more for commercial installations.
Visit the Biomass and Log Burners Home Page
Other pages of interest in this section:
- What is Biomass?
- How does it work?
- How much energy does it produce?
- How much does it cost?
- Are there Grants and Funding available?
- What is the Payback Period?
- Future Technology
- Overall Assessment
