Co-firing is burning biomass alongside coal in the same power station boiler. The biomass replaces some coal and cuts the station's net carbon emissions.

How can a coal power station be converted to burn biomass?

Coal-fired units can be modified to burn wood pellets instead, with new fuel storage, handling and milling equipment. Drax in North Yorkshire converted several of its units in this way.

Why must woodchip moisture content be controlled?

Water in the fuel must be evaporated before the wood burns, which uses up part of its energy. Wet chips burn cooler and smokier and may rot or heat up in storage.

Compare the energy content of freshly cut and seasoned woodchip.

Freshly cut wood can be about half water and gives much less useful heat per tonne. Chips dried to around 25–30% moisture release considerably more energy and burn cleanly.

CCEA A-Level Environmental Technology 3930

Fossil Fuels

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Global Action on Energy Conservation and Climate Change

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Macrogeneration

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Microgeneration

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Energy From Wind

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Energy From Biomass

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Energy Storage

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Land Contamination and Remediation

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Energy Performance of Buildings

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Emerging Technologies

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Sustainable Urban and Rural Communities

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The Code for Sustainable Homes

Topic overview Purpose, levels and assessment of the Code Energy, carbon dioxide and water categories Materials, surface water run-off and waste categories Pollution, health and wellbeing, management and ecology categories Measuring the performance of an existing building Performance profiles, improvements and evaluation

Energy From Biomass

Combustion, woodchip and fuel quality

3 things to know
AS 1

Overview

Why combustion dominates, co-firing and coal-to-biomass conversion, woodchip moisture, species, particle size and bark, woodchip against pellets, energy contents, and fuel, boiler sizing and payback calculations.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Numbers

What proportion of the energy obtained from biomass comes from combustion?

Key term

Why does combustion dominate the use of biomass for energy?

Key term

What is co-firing?

Questions from this subtopic

Each one with the model answer underneath.

1
What proportion of the energy obtained from biomass comes from combustion?
Model answer
More than 90% of the energy obtained from biomass is released by burning it. Most biomass is burned directly in stoves, boilers and power stations.
2
Why does combustion dominate the use of biomass for energy?
Model answer
Combustion is a simple, well-proven technology that works with most dry biomass. Existing boilers and power stations can be adapted to burn it.
3
What is co-firing?
Model answer
Co-firing is burning biomass alongside coal in the same power station boiler. The biomass replaces some coal and cuts the station's net carbon emissions.
4
How can a coal power station be converted to burn biomass?
Model answer
Coal-fired units can be modified to burn wood pellets instead, with new fuel storage, handling and milling equipment. Drax in North Yorkshire converted several of its units in this way.
5
Why must woodchip moisture content be controlled?
Model answer
Water in the fuel must be evaporated before the wood burns, which uses up part of its energy. Wet chips burn cooler and smokier and may rot or heat up in storage.
6
Compare the energy content of freshly cut and seasoned woodchip.
Model answer
Freshly cut wood can be about half water and gives much less useful heat per tonne. Chips dried to around 25–30% moisture release considerably more energy and burn cleanly.

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Fossil Fuels

Global Action on Energy Conservation and Climate Change

Macrogeneration

Microgeneration

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