Quality control
The domestic RHI sets out minimum fuel quality standards, without which
householders are unable to claim their RHI payments, explains Robert Burke,
HETAS
H
ETAS has been working with
Gemserv and Woodsure to
launch a biomass suppliers list,
so that householders will be able
to fi nd a local supplier and meet
the RHI criteria.
For domestic users, automatic pellet
and chip fi red stoves and boilers and modern
batch fed appliances mean it’s now possible
to provide lower output heating for the smaller
home. Using a biomass stove or boiler offers
an ideal way for developers to meet their
target carbon emissions, and the domestic
RHI makes biomass extremely attractive
and cost effective especially in rural areas
compared to other fuels like oil.
To ensure safe and effi cient operation of
wood and biomass appliances, it’s essential
that a good quality fuel is used. Moisture
content has the biggest effect on heat output
as any water in the fuel has to evaporate away
before the wood or biomass will burn, using
up energy and reducing the amount of useful
heat as opposed to steam up the chimney.
To help end users identify good quality,
sustainable fuel, HETAS certifi es the
Woodsure accreditation scheme for woodfuel.
The scheme has four categories covering
logs, chips, briquettes and pellets. HETAS has
also been approved as the UK certifi cation
body for ENplus by the European Pellet
Council (EPC). ENplus is the only Europe wide
assurance scheme for pellets which meet the
new European standard (EN14961-2) for solid
biofuels. As the dedicated certifi cation body
for the UK solid biomass industry HETAS is
able to certify both producers and traders
under the ENplus scheme.
ENplus certifi cation sets out minimum
standards for ash content, ash melting
temperature, wood pellet size, dust, moisture
content and heat output. Pellets with low ash
content will burn more effi ciently, whereas
high ash levels could point to impurities in
the pellets such as bark. A low ash melting
temperature below 1200°C could lead to
clinker, potentially damaging the appliance.
Having a consistent pellet size is
important; domestic appliances usually take
6mm pellets whereas commercial boilers take
8mm pellets. Each individual appliance will
have been installed and commissioned for a
specifi c pellet diameter, and if the wrong size
is used it will affect combustion conditions
meaning the boiler becomes less effi cient.
Wood pellet dust will also affect the appliance
by blocking the feed system, and to comply
with ENplus wood pellets should contain less
than 1 percent dust. ENplus certifi ed pellets
should have a moisture content of 10 percent
or less and should emit 4800 kW/h of heat
per tonne of fuel burnt. Both requirements
are important for the safe and effi cient
combustion of pellet burning appliances.
The scheme also covers distribution as
pellets need to be handled correctly in transit,
otherwise they can start to break down
causing a high percentage of dust in the boiler
hopper feed which can clog up the a biomass
boiler. All of these issues are addressed by the
certifi cation process.
For boiler and chimney manufacturers,
fuel quality is also of paramount importance.
Burning biomass with high moisture content
will reduce effi ciency combustion and in some
cases affect the fi gures that manufacturers
claim. Installers will get frequent call backs
to equipment that isn’t working properly, or
is expensive to run. The end result is general
dissatisfaction with the boiler or heating
system – simply because the end user was not
using guaranteed quality fuel.
A full list of approved fuel suppliers is
available on the HETAS website at
www.hetas.co.uk.
To ensure safe and effi cient operation of wood and
biomass appliances, it’s essential that a good quality
fuel is used
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