FRIDAY, FEB 3, 2023: NOTE TO FILE

Module 4-10

Biomass Heating

The word biomass means wood and/or other biological materials that can be burned to generate heat. The reason biomass heating is carbon neutral is that the trees and/or plants have sequestered the same amount of CO2 during their growth as emitted when burned. Wood is the main source for biomass heating and is generally used in two forms, namely:

1. Logs or wood chips, with the trees grown in a continuous cropping and sustainable way. Typically, a fast-growing tree is chosen and harvested in a process called SRC or Short Rotation Cropping. This means harvesting after around eight years of growth. The area required is then eight times the area of trees to be harvested each year. In Northern Europe the area of forest required for sustainable wood production is ~0.7 hectares per house. If willows are the crop of choice, the trees are smaller and harvesting happens every three years. Usually the wood is chipped and dried after cropping. 

2. Wood pellets, made from wood and other waste agricultural products, such as the remains of rapeseed after pressing for oil. The advantage of wood pellets is that they are drier than wood chips and have a higher energy output per tonne. They are also easier and less bulky than chips. For example, pellets can be blown into storage hoppers from trucks and act like oil for stoking.

Wood chip boiler and wood chips feeding to boiler / Comparison Of Wood Chip And Wood Pellet Installations

Wood chips need to have a moisture content of 25% or less for efficient burning. Wood chip boilers require more operations than the same size of pellet installation, because of the large bulk and handling of the irregularly shaped chips. Boilers and chip storage is more expensive as a capital cost than for the same heating capacity of a wood pellet installation. In Northern Europe, the current bulk price of chips is ~€80/tonne and the current bulk price of pellets is ~€165/tonne.

Many installations now are multi-fuel biomass boilers, i.e. the boiler can handle chips and/or pellets or pellets and/or logs. The storage of chips, pellets and logs is, of course, different. All boilers are automatic in operation and flame control. They all have to be de-ashed regularly.

Typically, large installations of over 250 kW tend to use chips. Smaller installations will use pellets, which are easier to handle and less bulky to store. A good choice for a house or small cluster of houses is a boiler that can handle pellets and logs.

Why Consider Wood Fuel?

• A renewable fuel and CO2 neutral;

• Heat is one third of UK energy equation;

• Security of supply and perhaps local;

• Price stability;

• A mature and highly efficient technology suitable from 5kW to 50MW;

• Space heating and process steam.

RET Screen Software

The RETScreen Clean Energy Project Analysis Software is a unique decision support tool developed with the contribution of numerous experts from government, industry, and academia. The software, provided free-of-charge, can be used worldwide to evaluate the energy production and savings, costs, emission reductions, financial viability and risk for various types of Renewable-energy and Energy-efficient Technologies (RETs). The software (available in multiple languages) also includes product, project, hydrology and climate databases, a detailed online user manual, and a case study based college/university-level training course, including an engineering e-textbook.

 

Wood stoves and wood boiler systems are also available with automatic refuelling systems, remote control, mobile activation, and highly efficient programmes to optimize combustion and increase efficiencies. Among the advantages of these systems are:

• Fully automatic feed

• Automatic ignition

• Capacity control

• Remote system control and monitoring

• Typical efficiency 90% +

• Very low ash remains – c.0.5-1.5%

 

Module 4, lesson 11

 

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