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106
Evaluation of Opportunities for Converting Indigenous UK Wastes to Wastes and Energy
AEA/ED45551/Issue 1
Table 54 Risks and barriers for wood fuel production
Level of Risk Comment
Technical Low Many projects for both pellet and chip worldwide.
Social & Planning Medium Some current waste wood installations can be
unsightly and “bad neighbours” creating noise
dust and fire risks from large quantities of stored
waste wood.
Sawmill based installations are positive due to
reduced transport of residue, job creation and
low additional impact.
Financial Medium Requires revenue from sale of fuel but market
not well established.
Waste wood derived fuel is still classed as a
waste which may give problems with sale and
use and hence price.
Standards and agreed specifications are needed
to make the fuel product a traded commodity.
Attractiveness depends on the price of oil as well
as incentives.
These aspects should be resolved within the
next few years.
Regulatory Medium Waste wood derived fuel is still classed as a
waste which may give problems with sale and
use hence a reduced price.
The legal status needs to be clarified. Standards
would help to clarify definitions.
Market depends upon incentives for heat and
electricity these can change due to extraneous
factors.
These aspects should be resolved within the
next few years.
7.1.6 Thermochemical fuels
The purpose of thermochemical processes is to produce a fuel with an increased energy density and
physical and chemical properties that are both more consistent than the source material, and better
matched to the requirements of the conversion technology.
The fuels in this category are derived from lignocellulosic materials such as wood, crop residues, paper
and board. The two main categories are
Char, Oils and liquors from pyrolysis either as separate liquid and char products or slurry of the two.
Char is similar to coal in some respects being friable and having a relatively high calorific value,
unfortunately it contains less than half of the energy value of the source material. Pyrolysis liquids are a
mixture of complex carbohydrates and hydrocarbons that contain up to 70% of the energy of the source
material. The relative proportions of char and liquids depend upon the reaction conditions in the process.
Torrefied material. Torrefaction is the heat treatment of the material at temperatures between 200°C
and 300°C that results in the removal of all moisture and a subsequent degradation and shrinkage of the
polymeric structure of the material. The changes produced by this process give an end product that is
more energy dense, friable and less susceptible to take up moisture from its environment. These
changes make it easier to transport, store and to use, particularly when pelletised. Torrefaction has the
advantage of producing a consistent fuel that retains over 90% of the energy of the source material.