Biomass End User Guide

8/8/2019 Biomass End User Guide

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Biomass heatingA practical guide or potential users

In-depth guide CTG012


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www.carbontrust.co.uk

ContentsPreface 01

Executive summary 02

Biomass as a low carbon energy source 02

The need or biomass heating 02

Biomass uels and heating systems 03

Implementing a successul biomass system 03

Part 1 Introduction 07

1.1 What is biomass? 08

1.2 Why is biomass a renewable and low carbon

source o uel? 08

1.3 Why use a biomass heating system? 09

Part 2 Technical manual 15

2.1 Biomass uels 16

2.2 Biomass heating systems 36

Part 3 Implementation guide 49

3.1 Initial assessment 52

3.2 Detailed easibility 53

3.3 Procurement and implementation 72

3.4 Operation and maintenance 80

Glossary 84

Appendix A Conversion factors 86

Appendix B Basic calculations 88

The Carbon Trust would like to acknowledge the support and input o the ollowing organisations and individuals

in the preparation o this guide:

Biomass Energy Centre, Black & Veatch Ltd., Buro Happold Ltd., Peter Coleman (AEAT Ltd.), Department o Energy

and Climate Change, Econergy Ltd., Forest Fuels Ltd., Forestry Commission, Andy Hall and Geo Hogan (Forestry

Commission), Anthony Haywood (Cwm Rhonda NHS Trust), Imperative Energy Ltd., Invest Northern Ireland,Richard Landen, Ali Nicol, Walter Poetsch (BSRIA), RegenSW, Gideon Richards (CWP Ltd.), Andrew Russell (Mercia

Energy), Scottish Government, South West o England Regional Development Agency, Daniel Sullivan (Optimum

Consulting), Welsh Assembly Government and Wood Energy Ltd.


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01Biomass heating: A practical guide or potential users

Recognising the potential impact o biomass heating

in this range or commercial and industrial applications,

the Carbon Trust launched the Biomass Heat Accelerator(BHA) in 2006. By working with existing biomass heating

projects across the UK, the BHA has identied that a lack

o customer knowledge and understanding o biomassheating technology is a signicant barrier to wider uptake.

This guide, prepared with the assistance o Black

& Veatch Ltd., is the rst major publication rom theBiomass Heat Accelerator and is intended to provide

practical guidance to businesses and public sector

organisations considering using biomass as an alternative

source o heating or space, hot water and/or processheat. The guide ocuses on existing, conventional

biomass combustion equipment that uses solid uels

such as wood chips, pelletised biomass uels and straw.However, much o the inormation in this guide will also

be o relevance to those involved with other types o

biomass projects (e.g. biomass CHP schemes).

The rst section o the guide introduces the concept

o biomass as a low carbon source o uel and the key

benets o its use. It also covers some o the high-level

policy and market aspects o biomass use in the EU andthe UK.

The second section provides a detailed technical

overview o the properties o biomass uels and typicalbiomass heating equipment.

The third section contains a process guide covering

details o the steps required to take a biomass system

rom initial concept to ull implementation. Althoughthis is not intended to be denitive, and individual

circumstances and projects will vary, the section is

intended to help potential site owners approach suchprojects in a logical, structured manner.

The inormation and processes laid out in this guide will

also help organisations adopt best practice approaches

and avoid common errors when installing biomassheating systems. The guide should help users to design,

procure, implement and operate successul, cost-eective

biomass heating solutions and achieve signicant

carbon savings.

Throughout this guide, the term site owner is used

to mean an individual or organisation considering

implementing a biomass heating system at a specicsite. However, the guide will also interest project

developers, energy managers, those acting on behal

o clients to help them speciy and procure biomass

heating systems or other interested stakeholders such

as government bodies.

Preface

1 http://www.carbontrust.co.uk/publications/publicationdetail?productid=CTC512

The Biomass Heat Accelerator

The Biomass Heat Accelerator is one o the

Carbon Trusts Technology Acceleration projectswhich aims to accelerate the uptake o this low

carbon source o energy.To achieve this, the Biomass Heat Accelerator isworking with a range o the UKs leading installers

and manuacturers o biomass heating equipment

to reduce the total cost o projects. The Biomass

Heat Accelerator is also working to reduce risksin the uel supply chain through quality assurance

and inormation provision.

More broadly the aim o the project is to increaseawareness and understanding o biomass heating

technology amongst the customer base as a lack

o this presently restricts wider market uptake.Visit: www.carbontrust.co.uk/biomass or more

inormation on the Biomass Heat Accelerator.

In 2005, the Carbon Trusts Biomass Sector Review1 highlighted the signifcant

potential o biomass heating in the UK. It showed that carbon savings o up to20 million tonnes o CO2 per year could be achieved using UK biomass resources

alone. It also identifed that using biomass or heating typically gives the most

cost-eective carbon savings o all uses o biomass and that this is particularly

the case or small-to-medium scale applications (100 kWth-3MWth).


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02 Executive summary

Biomass as a low carbon energy sourceBiomass is a orm o stored solar energy and is available

in a number o dierent orms. These include wood,straw, energy crops, sewage sludge, waste organic

materials and animal litter.

Although burning biomass releases carbon dioxide

to the atmosphere, this is oset by the carbon dioxideabsorbed in the original growth o the biomass, or

captured in the growth o new biomass to replace the

materials used. As a result, using biomass or heatingresults in very low net liecycle carbon emissions

relative to conventional sources o heating, such as gas,heating oil or electricity.

The need or biomass heating

Heat in all its orms presently accounts or nearly hal

o the UKs carbon emissions2. The UK has a legal

requirement to reduce carbon emissions by at least26% by 2020 and 80% by 2050 (against a 1990 baseline)

under the Climate Change Act3. Meeting these targets

will require a major shit away rom ossil uel heating

systems to lower carbon orms o heating.

In June 2008, the Governments Renewable EnergyStrategy consultation proposed that under one possible

scenario 14% o the UKs heating may need to comerom renewable sources by 2020 or the UK to meet its

share o the EU 2020 target or total renewable energy.

Given that less than 1% o UK heat demand is currentlymet by renewable sources, this implies a dramatic and

rapid transormation in the way heat is provided over the

next decade. To help deliver this step change in renewable

heat the Government took powers in the 2008 EnergyAct to establish a Renewable Heat Incentive (RHI) to

give nancial support to those generating renewable

heat. An overview o the RHI appears on page 66.O all possible renewable heating solutions, biomass

has the potential to deliver some o the most signicant

and cost-eective carbon savings, particularly orcommercial and industrial applications. In addition to

carbon savings, biomass heating also oers signicant

benets or users, including operational uel cost

savings and reduced uel price volatility. It can alsostimulate local economic activity by creating uel

supply chains and make use o resources that would

otherwise be treated as waste and sent to landll.

Executive summary

2 http://renewableconsultation.berr.gov.uk/consultation/chapter-4/executive-summary/3 http://www.dera.gov.uk/environment/climatechange/uk/legislation/index.htm


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Biomass uels and heating systemsBiomass heating is a mature, proven technology and

has been used successully or many years in countriessuch as Austria, Finland and Denmark. The two key

elements o a biomass heating solution are the uels

and the heating system.

The most commonly used sources o biomass heatinguels are virgin wood, certain energy crops, industrial

wood residues and certain agricultural residues. Biomass

uels are typically delivered as woodchips or woodpellets, but can also be in other orms such as logs or

straw bales. Fuel is normally provided by one or morededicated suppliers, but on-site materials can also beused in some situations, such as on arms.

The key characteristics o a biomass uel include its

moisture content which aects its energy content (the

caloric value), and the particle size/grade. Factors whichaect uel costs include the type o uel and its associated

market availability, the quality o the uel, the orm the

uel is delivered in and the proximity o the uel sourceto the point o use.

The heating system itsel consists o biomass boiler

plant, ancillary equipment (such as control systemsfues and pipe work), and inrastructure to receive andstore uel and transer it to the main boiler unit. Fuel

can be stored in various ways, such as dedicated storage

acilities (either above or below ground), integratedacilities within existing buildings, or in removable

storage containers.

Biomass plant can vary rom small, manually edsystems with ew controls, to ully automatic systems

with advanced controls and remote monitoring. The

types o plant available range rom moving grate, plane

grate, stoker burner and batch-red systems with thechoice o system dependent upon uel grade and type

and the degree o automation required, with costs

varying accordingly.

Biomass heating equipment is best suited to operating

relatively continuously. This means that a heat store

and/or back-up plant are useul means o smoothing

demand. Biomass systems are also typically physicallylarger than equivalent ossil-uel systems.

Implementing a successul biomasssystem

The Carbon Trusts experience o working with existing

biomass heating installations has shown that there iscurrently a wide variation between common practice

and best practice.

In order to successully design and deliver a highperorming, cost-eective biomass heating solution it is

essential that site owners ollow a structured approach

to system implementation.

The key phases o this approach are as ollows:

Initial assessment

In this phase the aim is to understand quickly whetherbiomass is likely to be an appropriate, alternative

heating solution or the site beore embarking

on a detailed easibility study and engaging with

potential suppliers. This phase typically involvesa basic assessment o site suitability, a basic

economic appraisal and a review o other potential,

non-nancial benets.

Detailed easibility

In this phase the aim is to acquire all the necessary

inormation on which to make a rm decision on

whether to proceed with a project. This includes: adetailed assessment o site heat demands, required

system characteristics, detailed capital and operating

costs, logistics, uel availability, uel storage, andany required permits/consents.

Procurement and implementation

The ultimate aim o this phase is to successully

install, commission and hand over a ully operational

biomass heating system. This involves speciying,

tendering or and implementing a biomass heatingsystem and associated uel contracting.

Operation and maintenance

This is an ongoing phase which involves uel quality

monitoring, system perormance monitoring androutine, planned maintenance.


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04 Executive summary

Structure o the guide

Part 1 Introduction

An introduction to biomass and biomass heating;the rationale underpinning biomass use; anintroduction to uel supply operations and biomassheating technology.

Part 2 Technical manualCovers detailed aspects o the uel used in biomassheating and delivery/storage methods. Describesthe basic components o a biomass heating systemincluding outline design and sizing strategies/integration options.

Part 3 Implementation guide

A summary guide to conducting a detailed easibilitystudy or a biomass system, implementing a project

and planning operation and maintenance.

Page 07

Page 15

Page 49

About this guide

This guide has been prepared with input rom some othe UKs leading experts in biomass technologies, and

brings together a host o issues that potential users willwant to consider. It covers a wide range o topics rom

choice o uels to contracting structures. Inevitably it

cannot be more than an introduction to the considerationsapplicable to each dierent subject, or exhaustive in

its treatment.

The Carbon Trust recommends, and this guide assumes,that prospective users will take advice on their specic

needs and circumstances rom proessionals in the eld,

including not only technical consultants and installers,

but legal, planning and other specialists as required.

The guide is designed to assist readers in navigatingthrough what can appear to be a complex technology

and engaging eectively with expert advisers to ensure

successul implementation.

This guide does not purport to give detailed Health &

Saety inormation, and accordingly should be read in

conjunction with specic installation advice.


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Stages in a biomass heating project implementation

Initialassessment

Assess basiceconomics

Assess basic sitesuitability

Detailedeasibility

Determine site heatdemand(s) and demand

prole

Assess necessarypermits and consents

required

Assess spatialconstraints which wouldinfuence system design

Determine plant size

and boiler plant designoptions

Perorm ull economicappraisal

Determine uelavailability, type,

sourcing, price andquantities required

Procurement andimplementation

Establish preerred

contract type

Detailed systemdesign

Apply or externalnancial assistance

i available

Installation/construction works

Commissioningand training

Issue tenders orproject

Prepare systemspecication

Review tender returnsand select preerred

bidder

Speciy and procureuel

Apply or/acquire anynecessary permits and

consents required

Operation andmaintenance

Standard operationalmaintenance regime

Annual maintenance

Ongoing perormancemonitoring

Decision tocarry out detailed

assessment

Initial decisionto investigate

biomass heating

Decision topurchase biomassheating equipment

Handover


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This section o the guide introduces the concept o biomass as an alternative

uel or heating. It describes the carbon cycle and the sustainability o biomass

as a uel. It also gives a basic introduction to the technology, the state o

the current market in the UK and the EU, and general aspects o using this

source o renewable, low carbon energy.

Part 1 Introduction


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08 Introduction

1.1 What is biomass?

Biomass is organic matter o contemporary biologicalorigin (i.e. that was living recently) such as wood, straw,

energy crops, sewage sludge, waste organic materials,and animal litter. It can be viewed as a orm o stored

solar energy which is captured by the organic matter

as it grows. This energy is released by combustion(burning) or ermentation and distillation (to produce

liquid transport uels). Biomass materials used as uel

sources can provide heat, electrical and motive power.

Biomass already makes an important contribution tothe UKs renewable energy supply, representing 82%4

on a primary input basis in 2006 (1.9% o total primary

energy consumption). Biomass has considerableuntapped resource potential and, in uture, could play

a signicant role in helping the UK to meet a range o

existing renewable energy and greenhouse gas (GHG)reduction targets.

Combusting biomass uels (such as wood, straw or

energy crops to produce heat or hot water and to raise

steam or space or process heating applications) iscurrently recognised5,6 as being one o the most cost-

eective ways o using biomass or energy conversion

purposes, in terms o the cost per tonne o carbon

emissions avoided.In the context o small heating systems, the term

biomass normally reers to wood-based uels such aswoodchips or wood pellets, but it can also include other

materials such as straw bales and more conventional

wood logs.

1.2 Why is biomass a renewable and

low carbon source o uel?The sun is the primary source o energy contained

within all biomass uels its energy is captured andstored via the process o photosynthesis. This energy

can be released and used (e.g. by combustion). When

this occurs, CO2 and other by-products o combustion

are also released. However, the CO2 released is largelyoset by that which was absorbed in the original growth

o the biomass, or which will be captured in the growth

o new biomass to replace the biomass being used(as illustrated in Figure 1).

Consequently biomass is considered to be a low

carbon technology i the material is derived romsustainable sources.

In contrast, when ossil uels are combusted, they release

CO2 that was captured by photosynthesis millions oyears ago, and it is the release o this ossil CO2, as

opposed to contemporary biogenic CO2, that is the

major contributor to global climate change.

Although the CO2 resulting rom the combustion obiomass can be recaptured by the new growth o

sustainable biomass, some net emissions still result

rom the cultivation, harvesting, processing andtransportation o the uel, and the manuacture and

operation o the necessary equipment (e.g. the biomass

plant). These processes consume ossil uels and thus

lead to some CO2 emissions.

Figure 1 A typical biomass carbon cycle

Atmospheric carbon dioxide, water and sunlight

Carbon releasedback into the atmosphere Converted into new plant material

through photosynthesis

Harvested and burnt

4 BERR (July 2007) UK Energy in Brie(includes all biomass sources). http://www.berr.gov.uk/whatwedo/energy/statistics/publications/in-brie/page17222.html5 The Carbon Trust (October 2005) Biomass Sector Reviewor the Carbon Trust. www.carbontrust.co.uk/biomass6 Dera (May 2007) UK Biomass Strategy. http://www.dera.gov.uk/environment/climatechange/uk/energy/renewableuel/pd/ukbiomassstrategy-0507.pd


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Although there are some net CO2 emissions rom using

biomass, the considerable body o publicly available

research indicates that using solid biomass or heatingtypically gives reductions in carbon emissions o around

90% relative to using ossil uel heating systems, when

these net emissions have been taken in to consideration.

Table 1 shows the typical ranges o carbon emissionsper unit o power which are achieved or biomass when

used or heating and electricity conversion, relative to

conventional uels. These gures include raw materialsupply, production, transport, energy generation and

eventual disposal.

However, some emissions comparisons between

biomass and conventional uels, oten understate the

carbon-saving benets that biomass technologies oerrelative to ossil uels. Unlike the gures in Table 1, they

oten ail to account or the embodied and operational

carbon emissions associated with the upstreamactivities o exploration, extraction, transportation and

processing o ossil uels, whereas these are explicitly

accounted or in any liecycle assessment. When the

ull upstream emissions associated with ossil uels

are also taken into account, the net carbon emissionso most biomass heating scenarios are even lower.

1.3 Why use biomass heating systems?

Using biomass is one o the only cost eective andpractical ways to provide space heating, hot water

and process heating/steam rom a low carbon source.Also, using biomass sources or heating provides more

cost-eective carbon savings than or other uses (e.g.

or electricity or transport uels). It typically oers thehighest carbon savings per unit mass o biomass, and

the highest carbon savings that can be obtained by

using a unit o land to grow biomass8.

While organisations may choose to implement a biomassheating system or a number o dierent reasons, the

major drivers are as ollows:

1) Signicant carbon savings. Biomass heating systemscan play a major role in reducing an organisations carbon

ootprint. Many organisations now have commitments

or requirements to reduce their overall emissions andimprove their environmental perormance implementing

a biomass heating system could help to do this.

2) Operational cost savings. The costs o biomass uels

are typically lower than the ossil uel being displacedand biomass heating systems can thereore provide

attractive operational cost savings. The scale o savings

depends on the price o the ossil uel being replaced and

the cost o the biomass uel used. On a unit cost-basis,biomass uels can be cheaper than many ossil uels

commonly used or heating. Cheaper uel translates into

lower running costs, and hence annual savings whichover time help pay back the higher capital outlay on the

biomass system (compared to ossil uel systems). When

replacing electric, LPG or heating oil systems, the paybackon capital can be very rapid (in some cases


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10 Introduction

4) Wider sustainable development benets. Fuels used

typically with biomass heating systems tend to have

diverse and localised uel supply chains. Using biomassuels or heating can have positive side-benets along

this supply chain such as improving the biodiversity

o existing woodlands9 and providing opportunities orrural employment and economic diversication.

5) Resources diverted rom landll. Using certain

biomass resources as uels can divert them rom

becoming wastes and being sent to landll. Currentlyc.10 million tonnes o waste woods are produced each

year10, the majority o which goes to landll. Some

organisations produce co-products such as wood o-cuts,

sawdust and tree-surgery residues (arboriculturalarisings) that can be used as a biomass uel. Disposing

o such wastes normally has a considerable associated

cost and using wastes as uels can thereore also bringsignicant nancial benets11.

6) Reduced exposure to climate-change related

legislation. Biomass uels do not register as part o anorganisations overall carbon emissions (or ossil uel

consumption), thus reducing exposure to the Carbon

Reduction Commitment (CRC) and the EU EmissionsTrading Scheme (EU ETS), i the organisation is subject to

these schemes. A biomass heating system can also help

organisations to meet their Climate Change Agreements(CCAs) by reducing emissions o greenhouse gases andconsumption o ossil uels.

7) Improved energy perormance ratings or buildings.

Using biomass heating equipment in new orreurbished building stock could help to improve its

overall environmental/energy perormance. As such,

it could help achieve higher ratings in such schemes asBREEAM (Building Research Establishment Environmental

Assessment Method) and the Code or Sustainable

Homes. Installing a biomass heating system in a new or

reurbished building could also help it to achieve lowercarbon emissions as represented in an EPC (Energy

Perormance Certicate) and DEC (Display Energy

Certicate). Biomass systems can also assist compliancewith Part L o the building regulations and Merton

Rule12 requirements.

In summary, within the context o changing energyprices and the need to reduce carbon ootprints while

also diversiying sources o energy, biomass heating

oers a number o advantages which merit its urtherinvestigation by interested organisations.

9 Forestry Commission (2007) A Wooduel Strategy or England. http://www.orestry.gov.uk/england-wooduel10 Dera (2008) Waste Wood as a Biomass Fuel. http://www.dera.gov.uk/environment/waste/11 Using biomass resources that are (or could be seen to be) wastes can be aected by waste legislation and potential users should read section 3.2.5

in detail beore pursuing this route.12 The Merton Rule is a planning policy, pioneered by the London Borough o Merton, which requires the use o renewable energy on-site to reduce

annual carbon dioxide (CO2) emissions in the built environment and is now in use by many local authorities around the UK.

Case study:

Bell Bros Nurseries Ltd

Bell Brothers Nurseries Ltd is one o the UKs market

leaders in growing bedding plants and supplies

to all parts o the market including DIY stores,

supermarkets, wholesalers and local councils. Theenterprise has over 50,000m2 o modern, automated

glasshouses which require year-round heating to

maintain optimum growing conditions. Historicallythe main heating uel had been heating oil. Rises

in the price o this uel and the associated increase

in running costs led to the need to investigate other

alternatives. The nurserys management beganresearching the viability o biomass as an alternative

heating solution to reduce heating costs in 2004 /5.

Ater a detailed easibility study, a decision wastaken to install a 2MWth biomass boiler in October

2007 which is expected to deliver approximately

60-70% o the annual heating requirement to33,000m2 o glasshouses. The boiler is o a moving

(reciprocating) grate design and is expected to

consume c.2000-2500 tonnes o wood-chip (or

equivalent) per annum. The moving grate design waschosen to enable the system to burn a wide variety o

dierent types o potential biomass uels (including

lower quality woodchips, miscanthus grass,agricultural residues, and uels with high moisture

contents up to 55-60%). This gives Bell Brothers

Nurseries considerable uel fexibility and could

allow them to take advantage o very low cost uels.

The project received a capital grant which amounted

to 17.5% o the total capex. Depending on ossil uel

prices, the project is expected to achieve payback in4 years.


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Biomass heating technology overview

A biomass heating system is any heating system that

primarily uses biomass as a uel (some systems canalso dual-re with a ossil uel to meet peak demands,

or or back-up).

Biomass heating systems can be used or space heatingo buildings, hot water production, steam production,

or any combination o these. They can be used at

almost any scale, rom domestic (c.10kWth) throughto light commercial (c.50kWth to several MWth), to

industrial or district heating systems (up to hundreds

o MWth

). While this guide ocuses on the scale range o

100kWth 3MWth, most biomass heating systems havestrong similarities above and below this size range.

The key elements o a whole biomass heating

solution are:

Fuel delivery rom a uel supplier.

Fuel reception, storage, and extraction rom storageto the boiler unit.

A specialised biomass boiler unit.

Ancillary equipment: fue (chimney), ash extractionmechanism, heat storage, connecting pipework,

expansion tank, re dousing system, controls systemsand possibly an integrated ossil uel system.

From an operational perspective, one o the most

notable dierences between a biomass heating

system and a conventional ossil uel heating system isthat the biomass boiler is best suited to being operated

relatively continuously (between c.30% and 100% o

its rated output). This means that a heat store, and/or

a ossil uel system to manage peak demands, is otenspecied in addition to the biomass boiler. Also, a

biomass heating plant will be considerably larger in

volume than an equivalently rated ossil-uel plant due,in part, to the inherent combustion characteristics o

solid, organic materials.

Biomass uel is typically woodchips or wood pellets,

but it can also be other biomass material such aslogs and straw bales. I t is normally delivered rom a

dedicated uel supplier, but it can be on-site material

(e.g. on arms and estates), or delivered rom a uel

supplier in a less processed orm (e.g. logs, slabwood,roundwood etc.).

Fuel must be physically delivered into a uel storage

system (a small shed-type building or purpose-builtspecialist store) and then must be transerred into the

combustion grate o the main boiler via a mechanical

handling system (e.g. screw auger/ram stoker).

The biomass boiler is the heart o the biomass heating

system, and there are many dierent types and models.

These are usually classied by the type o biomass

they are suitable or use with (e.g. dry woodchip,wet woodchip, pellet, log, bale, etc.); by the type o

combustion grate; and also by their rated thermal

output. They vary rom manually ed, generally small,boilers with ew controls, through to ully automatically

ed boilers with automatic ignition and ull remote

monitoring and control systems. The choice o boiler

type is determined, in the rst instance, by the uelthat is intended to be used, and then the level o

automation required; this is a trade-o between

convenience and cost.

The ancillary equipment (such as the fue/chimney)

and ash handling is mostly determined by the type

and size o the boiler, whilst the need or thermal

stores (e.g. hot water cylinders) and ossil uelstand-by is determined by the site heat load and

reaction times required.


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12 Introduction

The biomass market

When considering the installation o a biomass boiler

or CHP system, it is helpul to appreciate the currentposition o the biomass market. This section provides

some statistics on the contributions o biomass to

global energy supplies and observations about thecurrent state o the UK biomass energy supply industry.

Contributions o biomass to energy supplies

Worldwide in 2006, o the 12.7% o primary energythat was supplied by renewables, almost 75% (9.5% o

total) came rom solid biomass13 (around 1,100 Mtoe14).

This is due to the widespread use o solid biomass or

domestic purposes in developing countries. However,while contributing more than any other orm o

renewable energy, solid biomass is also growing

more slowly than other orms. For example, whilewind energy grew at an average rate o 24.5%/year

between 1990 and 2006, solid biomass increased

at only 1.5%/year. This is perhaps due to developednations giving solid biomass relatively little priority

as a commercial energy technology, and growth

in developing countries increasing only due to

population growth.Looking at Europe, the extent to which heat is derived

rom biomass sources varies signicantly between

countries. Figure 3 shows that at most (Sweden), heatrom biomass sources provide approximately 38%

(~60 TWh/year) o the countrys overall heat demand.

For comparison, the UK currently uses about 0.7 Mtoe o

biomass to supply heat15, this is equivalent to less than

0.6%16 (~4 TWh/year) o the UKs overall heat demand.

There is signicant potential or a greater proportion o

the UKs heat to be derived rom biomass. For example,it is estimated that a contribution o 6% (a more

than tenold increase) is achievable i just industrial,

commercial and residential heat customers thatare located o the gas grid switched to biomass17.

Moreover, there is a strong requirement to move to

biomass and other low carbon heating uels to mitigate

climate change. Currently around hal (49%) o the UKstotal primary energy demand is in the orm o heat and

meeting this demand with ossil uels causes about

hal (47%) o the countrys total carbon emissions.

With the introduction o new targets across the EU or

the total primary energy to be supplied by renewables,

as agreed by EU Heads o State in 2008, the questiono how much heat biomass sources could provide

over the next decade is highly topical. Considering the

proposed UK target o 15% total primary energy, the

recent BERR Renewable Energy Strategy consultation18suggests that 14% o the UKs total heat demand may

need to be derived rom renewables by 2020, with

a little under hal o this (c.6.4%) coming rom solid

biomass. This is roughly equivalent to 39.8 TWh/a(3.4 Mtoe).

State o UK biomass industry

The UK biomass heat industry is currently small,

refecting the relatively small amount o heat and

electricity derived rom biomass. The majority obiomass boilers are manuactured and imported rom

other European countries, with UK companies tending

to ocus on biomass system installation, operation

and maintenance. Approximately 35 rms are activein the installation o commercial scale systems o

greater than 100 kWth capacity, with services rangingrom supplying and commissioning boilers to completeturnkey installations, including design and installation

o district heat networks.

13 Source: International Energy Agency (2006 data).14 Million tonnes o oil equivalent.15 Source: BERR energy statistics. The gure is or 2007 and includes several orms o biomass in addition to solid biomass.16 0.6% is an estimate o the total heat provided rom renewable sources.17 Source: Oce o Climate Change.18 Source: Renewable Energy Strategy Consultation. http://renewableconsultation.berr.gov.uk/


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19 EurObservER Barometer project(2007) www.erec.org/projects/ongoing-projects/eurobserver (note that the gures used in this chart exclude the useo biomass in domestic applications, thus the countries which eature most signicantly in this gure are those having developed the use o districtheating networks).

20 Van Steen, H (2007) European Commission Renewable Energy Policywww.greenpowerconerences.com/renewablesmarkets/documents21 Estimated rom UK Energy in Brie 2008 BERR.

The biomass market (continued)

Considering biomass uel supplies, at least 70%21 o the

UKs biomass by total primary energy is estimated tooriginate rom the UK, while the remainder is imported.

There are estimated to be over 200 UK companies and

organisations directly involved in the supply o biomassuels. Current suppliers o solid biomass uels range

rom small companies or individuals who may also

operate other businesses in addition to uel supply,

through to large scale, orestry contractors supplyinglarge quantities in bulk. Recently, a number o biomass

uel supply cooperatives/brokers have emerged who

provide a single contracting party but draw upon uelsourced rom a number o suppliers.

Figure 2Gross solid biomass heat production rom thermal and CHP plant in EU countries, 200519

2.5

2

1

1.5

0.5

0

Sweden

France

Finland

Denmark

Austria

Germany

Belgium

CzechRepublic

Poland

Slovakia

Netherlands

Hungary

Slovenia

Heat(MTOE)

Country

CHP plants

Thermal heat plant only

Figure 3Shares o biomass in the national heating markets o EU countries, 200620

40

30

20

10

0

Sweden

Finland

Lithuania

Latvia

Estonia

Portugal

Austria

Slovenia

Denmark

France

Greece

Spain

Italy

Poland

Germany

Hungary

Ireland

Czech

Republic

Belgium

Slovakia

UK

Ne

therlands

Lux

embourg

Cyprus

Malta

Biomassshare(%)

Country


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Part 2 Technical manual

This part o the guide is a reerence manual containing key background

inormation on the main elements o a biomass heating solution:

uel (characteristics, sourcing, reception, storage), and plant (design,

eatures, operation).


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16 Technical manual

2.1 Biomass uels

This is an introduction to the range o types, physicalcharacteristics, standards, and the delivery/storage

methods o biomass uels suitable or heating systems.

2.1.1 Sources o uels

There is a wide range o original sources o biomass uels

which can be broadly dened in terms o wet and dry

sources. Under these two broad headings, the sourcescan be grouped into ve categories:

1. Virgin wood

Dry includes roundwood,

harvesting residues (brash), bark,sawdust, crowns, and residues o

tree surgery.

2. Energy crops

Dry includes woody energy crops(short rotation orestry, willow,

eucalyptus, poplar), grassy energy

crops (miscanthus and hemp); sugarcrops (sugar beet); starch crops

(wheat, barley, maize/corn); oil crops(rape, linseed, sunfower); and even

hydroponics (lake weed, kelp, algae).

3. Agricultural residues

Wet includes pig and cattle slurry,sheep manure, grass silage.

Dry includes poultry litter, wheat

or barley straw, corn stover.

4. Food residues

Wet includes wastes rom various

processes in the distillery, dairy,

meat, sh, oils, ruit and vegetables

sectors.

5. Industrial residues

Wet includes sewage sludge.

Dry includes residues rom

sawmills, construction, urnituremanuacturing, chipboard

industries, pallets.

Not all these sources, are suitable or use in the types

o biomass heating plant considered in this guide.

This guide concerns itsel with dry biomass uels only.

The typical sources o uel or such biomass plant are:virgin wood, woody and grassy energy crops, certain

agricultural residues, products such as wheat or barleystraw and in some circumstances pressed oil cakes22

and certain industrial wood residues.

Virgin wood

Virgin wood is untreated and ree o chemicals and

nishes. It comes rom a variety o sources; orestry is the

primary source, with other sources being arboriculturalarisings (tree surgery waste) and co-products rom wood

processing acilities (such as sawmills, urniture actories).

Typically, high quality logs and stemwood enter the

wood processing industry, leaving less valuable timberavailable or processing into wooduel. This generally

includes branches, bark and brash23. The provenance

o the virgin wood is o critical importance as this canaect both plant perormance and any environmental

permits that may be required (see section 3.2.5) .

22 Some existing users o heating-oil red plants have investigated using biodiesel in place o heating oil in conventional plant. However, it should benoted that using biodiesel in this manner may not oer signicant cost benets over heating oil and will have the associated sustainability/carbonsaving uncertainties that using biodiesel as a vehicle uel has.

23 It should be noted that high levels o dirt (rom stumps) can cause perormance issues with boilers and wood rom seaside and roadside areas cancontain high levels o salts which can also aect plant perormance/service lie.

Courtesy o Econergy

Courtesy o B&V


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18 Technical manual

Fuel supply and sustainability

Like conventional heating systems, biomass systems

are reliant on physically produced and traded uelsupplies. The availability and costs o these supplies

vary over time, subject to the demand or uels or

energy production but also due to wider market actors,(or example, the case to grow dedicated energy

crops depends on conditions in the arming industry).

Yet it is possible to estimate the total quantity o

biomass available or heating systems in the UK,as outlined below.

The production o organic material or energy purposes

(heat, electricity and transport) can have environmentaland socio-economic impacts, some o which are

negative. Over the past year, media attention has been

drawn to these impacts and cases made or improved

sustainability standards and changes in Governmentpolicy27. Fortunately, the types o biomass uel used or

UK heating systems are unlikely to raise sustainability

concerns, as this box explains.

UK uel supplies

It is currently estimated that 3.11 MToe (36.2 TWh) o

biomass is being used annually to generate electricity,and 0.45 MToe (5.2 TWh) to produce heat28. Studies

o UK biomass resources suggest this usage is about

hal the total quantity o biomass currently available.The 2005 Biomass Task Force29 estimated this as 4.8-5.7

Mtoe (55.8-66.3 TWh), and 5.6-6.7 Mtoe (65.1-77.9 TWh)

was suggested by a more recent study30.

Current resources represent only a raction o what

could be available in uture. In a scenario in which

quantities o biomass rom orestry and waste

resources stay the same as today, but increasing

amounts o energy crops are produced, 8.3 Mtoe(96.5 TWh) has been orecast or 202031. This is

equivalent to almost one hundred and orty thousand400 kWth boilers (operating at a 20% capacity actor).

This suggests that or the oreseeable uture, sucient

UK biomass uel resources could exist to supply a largenumber o new biomass heating systems thereore

in theory, any new installation should not have diculty

in securing supplies.

From the perspective o site owners, biomass uels

can be purchased rom an increasingly wide rangeo suppliers. However, since biomass heating is still

currently an early-stage market, extensive uel supply

chains have yet to be ully developed. As consequences

o this:

Fuels tend to vary in their specications and quality,and obtaining biomass o a required or desired

standard can sometimes be challenging. Forurther details, see the box on uel standards and

specications on page 23.

Sourcing uels may be dicult in certain areaso the UK. However, new networks o suppliers arebeginning to take shape with support rom bodies

such as regional development agencies. A list o

such supplier networks is available on the Carbon

Trust website (www.carbontrust.co.uk/biomass).

Sustainability

When considering biomass and issues o sustainability,

it is important to understand that:

The types o solid biomass likely to be used or UKheating systems (e.g. wood chips or pellets) arebased on eedstocks di erent to those used or thecurrent generation o liquid biouels (e.g. palm oil)

or transport.

This distinction is highly signicant to the carboncases or such types o biomass and other aspects

o their sustainability, with solid biomass oeringmany advantages over current transport biouels.

For example, whereas growing palm oil in a developing

country may involve land degradation or large-scaledeorestation (both o which could increase carbon

emissions), using compressed sawdust or residue

materials such as orestry brash in the UK to make

wood chips and pellets requires no such compromises.Such materials (residues, sawdust, brash) are:

Unlikely to have been grown on prime agriculturalland, so are not in competition with ood crops.

Likely to have been harvested as part o a sustainableland management process. For instance, the majority

o UK orestry activities are subject to Forestry

Commission sustainable management regulation.

27 UK Government perspectives are given in the House o Commons Environmental Audit Committee report Are Biouels Sustainable(2008),and the Department or Transport report Review o the Indirect Eects o Biouels.

28 Dera UK Biomass Strategy (2007).


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2.1.2 Types o uel

The majority o raw biomass materials (eedstocks)

require some orm o processing beore they becomebiomass uels. Processes can range rom simple cutting

and drying to more involved processes like pelletising.

The method o processing which a biomass eedstockundergoes is important because it will determine its

eventual application and useulness as a uel and will

also determine the type o biomass heating plant that

can be used or a project.

29 Dera (2005) Biomass Task Force Report to Government.30 Dera (2007) UK Biomass Strategy(2007).31 Dera (2007) UK Biomass Strategy(2007).32 For details o other relevant standards, see the box on page 23.

Fuel ormat Utilisation

Logs Most commonly used in small-scale systems (


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20 Technical manual

Characteristics

Biomass uels have a range o characteristics which

aect their perormance and also the type o biomass

heating equipment they can be used in. Some o themost important actors are listed below and a table

presenting the most common uels and their associated

characteristics is given at the end o this section.

Caloric Value (CV)

This is a very important characteristic; i t indicates the

heating potential o a uel and is a measure o its energycontent. It is dened as the amount o heat released

rom a specic unit o uel by its complete combustion.

Biomass uel CVs are conventionally expressed as MJ/kg.The caloric value o a uel is expressed either as Gross

Caloric Value (GCV also sometimes known as Higher

Heating Value (HHV)), or Net Caloric Value (NCV also

sometimes known as Lower Heating Value (LHV)).

Net Caloric Value (NCV) is the quantity o heat giveno by the complete combustion o a unit o uel when

the water vapour produced remains as a vapour andthe heat o vaporisation is not recovered. This can be

calculated by subtracting the heat o vaporisation o

the water produced rom the GCV. The NCV is more

widely used in the UK than the GCV.

Gross Caloric Value (GCV) is the quantity o heatliberated by the complete combustion o a unit o uel

when the water vapour produced is condensed, andthe heat o vaporisation is recovered. The water is

condensed by bringing the products o combustion

(fue gases) below 100C (as in a condensing plant).This generally does not apply or biomass as the fue

gases cannot be cooled below c.130C, and hence the

water vapour cannot be condensed.

Note that (or wood) the GCV is usually 6-7% higher

than the NCV.

The key determinant o biomass materials caloric value

is the inherent moisture content (MC). The MC o materialcan vary greatly rom c.5-8% or wood pellets, c.35% or

conditioned uel and up to 65% or reshly elled timber.

The greater the MC the less energy is contained withinthe uel.

Moisture content (MC)

This is expressed as a percentage, measured eitheron a wet or dry basis. Wood suppliers (or example)

typically use the wet-basis method because it givesa clearer indication o the water content in timber.

The wet basis calculation expresses the moisture content

as a percentage o the mass o the material including

any moisture. In the ormula below oven dry mass isdened as the mass o biomass which has had all themoisture driven out:

Wet basis

MC = Fresh mass Oven dry mass x 100 (%)Fresh mass

The dry basis calculation expresses the moisture

content as a percentage o the oven dry mass:

Dry basis

MC =Fresh mass Oven dry mass

x 100 (%)

Oven dry mass

A higher MC implies a lower caloric value as each unit

mass o uel contains less oven dry biomass which is

the part o the uel that actually undergoes combustionto release heat. The eect is more noticeable or most

biomass heating systems where the water vapour in

the combustion products cannot be condensed. This is

because the moisture in the uel also has to be vaporisedbeore combustion can occur and this requires energy

input that cannot be recovered later.

The majority o the biomass industry uses wet basiswhen discussing biomass uels.

Figure 4 shows the caloric value o wood (measured in

MJ/kg) as a unction o its moisture content (MC). Clearly,dry wood has greater energy content than wet wood, and

this is refected in the typical market price or wooduels.

The ormula or calculating the eect o uel moisture

content on net caloric value is outlined in Appendix B.

Figure 4The eect o moisture content (MC) on

caloric value (NCV)

20

0

5

10

15

0 25 50 75Netcalorificvalueoffuel(M

J/kg)

Moisture content (%)


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Bulk density

This is a measure o the mass o many particles o the

material divided by the volume they occupy; the volumeincludes the space between particles. The higher the bulkdensity, the more mass o uel exists in a given volume.

For example wood pellets (c.660kg/m3) have a higher

bulk density than wood chips (c.250kg/m3). Bulk density,unlike density, is not intrinsic to a material; or example,

the same piece o wood could have dierent bulk

densities i processed into logs, pellets or woodchips.

Moisture content also aects bulk density as each particlehas a greater mass but does not occupy more space.

This is an important point because uels with higher

moisture contents will have greater masses and,thereore, have lower bulk densities. With higher moisture

content comes lower energy density, and thereore the

volume o uel required or a given amount o heat will

be larger.

Energy density

Energy density is derived rom the bulk density o a uel

and is a measure o the energy contained within a unito uel. Energy density is conventionally expressed inMJ/m3.

It can be derived by multiplying caloric value (MJ/kg)

by bulk density (kg/m3).

Energy density is an important variable that will help

users understand volumetric uel consumption rates,

the size o uel storage required, the number o deliveries

required and the total annual quantity o uel required.

Table 3Typical bulk, caloric and energy densities o dierent biomass and ossil uels

Energy density = CV x Bulk density

(MJ/m3) (MJ/kg) (kg/m3)

Source: Gastec at CRE Ltd. and Annex A, Digest o UK Energy Statistics 2007

Fuel

Net

CV1

MJ/kg

CV

kWh/

kg

Bulk density

kg/m3

Energy density

by volume

MJ/m3

Energy density

by volume

kWh/m3

Lower Upper Lower Upper Lower Upper

Woodchips @ 30% 12.5 3.5 200 250 2,500 3,125 694 868

Log wood (stacked

air dried: 20%MC)

14.6 4.1 350 500 5,110 7,300 1,419 2,028

Wood solid oven dried 18.6 5.2 400 600 7,440 11,160 2,067 3,100

Wood pellets 17 4.7 600 700 10,200 11,900 2,833 3,306

Miscanthus(bale 25%MC)

12.1 3.4 140 180 1,694 2,178 471 605

House coal 29 8.1 850 24,650 6,847

Anthracite 32.1 8.9 1,100 35,310 9,808

Oil 41.5 11.5 865 35,898 9,972

Natural gas - - - 36 10.13

LPG 46.9 13.0 500 23,472 6,520


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22 Technical manual

Particle size/dimensions

Biomass heating systems require physical handling

mechanisms or transerring uel rom where it is storedto where it is combusted (in the plant). Fuel particlesthat are too large can jam certain uel eed systems

(e.g. augers) and, thereore, particle size is an important

characteristic o a biomass uel. All biomass uels cancome in a wide variety o shapes and sizes. Aside rom

moisture content, the particle size is the other key issue

to consider when matching system design with the uel

available (see box on page 23 or urther details on uelspecications and classes).

Certain uel eed systems can handle uels with a broader

range o particle sizes (e.g. walking foors and ramstokers). Others (e.g. those designed to use pellet uels)

can only tolerate a more narrow range o particle sizes.

Mechanical durability

I the system being specied can only use pellet uels,

then the mechanical durability (how well the pellets stay

together during handling) is a key consideration andshould be specied. One issue that can occur with pellet

uels is disintegration (during the handling process).

Good quality pellets should have a mechanical durability

o at least 97.5%, meaning less than 2.5% o the pelletswill be broken down ater delivery. Many pellet uels need

some orm o additive to act as a binding agent, which

should be known and specied by the manuacturer.

Very small particles in the uel (such as sawdust) may

represent a certain proportion o the total weight o

a sample o biomass uel. Excessive amounts o such

material may cause problems such as compaction inaugers and smothering o the re bed.

Original source

This characteristic is important as it has a bearing on

whether or not the uel is classed as a waste, and thuswhether a project will need specic permits. The original

source and knowledge o the supplier may also indicatethat certain physical and chemical contaminants may

be present in the uel. For example, stones, gravel and

dirt (which can aect plant perormance through theormation o clinker in the combustion chamber, and

through jamming augers) can become caught up in

uel i it has been sourced rom tree surgery materials

originally. Also, material rom tree surgery can sometimesincorporate leaves and other green material (which are

not suitable or combustion in most biomass heating

systems). I it is known and accepted that the uel may

contain residual materials such as solvents, chemical

treatments and the others listed above, then the plant

must be specically designed to deal with these.

The source should be clearly identied when procuringuel to guide environmental consent practice and

plant specication.

Ash content

Although the amount o ash produced is partly dependent

on the type and perormance o the biomass plant it is

being used in, it is also an inherent uel property which isspecied as a uel characteristic. For example, a woodchip

or pellet uel would be expected to have an ash content

o around 1% by weight (1-3% by volume) o the uelconsumed, whilst miscanthus (a type o energy crop)and straw will be higher.

Chemical content

It is natural or biomass to contain low levels o mineral

salts and other trace non biomass material, taken up

rom the soil or air during growth. The presence o these

salts and other elements in virgin biomass uels doesnot normally cause any signicant issues, but it does

partly determine the level o gaseous/particulate

emissions, ash, and slagging (also known as clinkering).I, or instance, an annual crop is being used (e.g. straw)

then more care is required, as these can have higher

levels o alkaline metal salts.

For more detail on the specic properties o a wide rangeo biomass eedstocks used or uels, the Phyllis database

(www.ecn.nl/phyllis) contains inormation on a wide

range o dierent chemical and physical characteristics.

Note that uel characteristics such as the original

source, ash content, chemical content and, to

an extent, moisture content will have an eecton the level and composition o certain emissions

to the air rom the biomass heating plant that they

are ultimately used in. This should be borne inmind when choosing uel i local air quality is to

be a key consideration as part o the necessary

planning/consenting/permitting process required

or the project in question (see section 3.2.5 orurther detail).


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Fuel standards and specications

Successul operation o a biomass heating system

is strongly dependent on the use o properlyspecied uel.

To aid the matching o heating systems with uel

supplies, uel standards have been introduced inseveral European countries. One o the best known sets

o standards are the norm standards rom Austria,

which speciy size, moisture content and various other

important properties o solid biomass uels33. These

standards are being used by some UK uel suppliers

in the absence o equivalent UK standards.

The CEN (European Committee or Standardisation)is developing a common methodology or speciying

the key characteristics (those mentioned above plus

original source, caloric value, chemical composition,physical properties etc.) o all orms o solid biomass

sold within the EU, and also methods or testing these

properties. The CEN specications will eventually be

transposed into member states standards systems(e.g. those o the British Standards Institute).

At the time o writing, the specications are available

only in drat orm, yet they are suciently welldeveloped to be suitable or reerence in uel supply

contracts, and the nal versions are likely to be very

similar. They can currently be downloaded ree o

charge rom the Biomass Energy Centre website34.

Regardless o which set o standards are reerred to,

it is important that the site owner works closely with

both the uel supplier and system installer to ensurethat the uel purchased is suitable or the system,

that the uel supplier undertakes to deliver a consistent

quality o uel and that the uel can be stored andhandled at the site in the correct manner. Drat

uel supply contracts to acilitate such cooperation

can be downloaded rom the Carbon Trust website(www.carbontrust.co.uk/biomass).

33 http://www.sew.co.uk/links/SEWF_Chip_Spec.pd34 http://www.biomassenergycentre.org.uk/pls/portal/BIOAPPS.BSI_REGISTRATION_FRM.show


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24 Technical manual

2.1.3 Fuel delivery, storage, extraction and eed

This section deals with the delivery and storage o

biomass uel or heating systems as well as how it can

be extracted rom the store into the combustion unit.

A well-designed system or delivering, storing and

transerring solid biomass uel is essential to ensure

a smooth-running biomass heating system.

The solution must be t or purpose and suitable or

the lie o the installation (typically up to 20 years).

Specic site circumstances may mean that a degree o

compromise to the ideal solution is necessary. However,time spent planning and consulting with parties involved

in the design, installation and operation (plant installer,

uel supplier, engineering contractors, architects etc.) atan early stage will help to ensure that common problems

are avoided.

A good uel delivery, storage and extraction solutionwill typically:

3Allow delivery by standard vehicles thus allowing uel

supply rom a range o dierent parties.

3 Enable speedy and simple discharge o uel without

the need or large amounts o attendance by sta.

3 Prevent the ingress o water but also allow moisture

vapour to escape rom stored uel.3Allow sae dust venting and management where

required.

3Meet necessary building regulations and health andsaety requirements.

3Keep costs to a minimum35.

Fuel delivery

There are a number o dierent uel delivery and

reception options available. Ultimately, the nature o the

system adopted will be dependent upon:

The proposed uel or the application (wood pellet,chip, logs, bales etc.).

The area available and any other physical accessconstraints at the site.

The area required or the delivery vehicle to accessthe uel store.

The proposed delivery vehicles available romprospective uel suppliers.

The typical methods and vehicles used in supplyingbiomass uel or heating systems are outlined in Table 4

opposite. The major advantages and disadvantages oeach option are shown in Table 5 (overlea).

35 In most biomass heating projects, the uel delivery, storage, and extraction solution will be a major component o the overall cost. Careul design andalso, where possible, designing to minimal requirements can help to control this cost.


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Table 4Type o uel delivery method/vehicle and typical payloads

Images courtesy o: Wood Energy, Econergy, BSRIA, Highland Wood Energy, B&V

Delivery method Example Typical uel type Typical payload Availability

Flexible hose rom

a blower tanker

Most commonly

pellet but also chip

Pellet: c.15-20m3

(10-14 tonnes)

Chip: c.10-20m3(4.5-6 tonnes)

Pellet common

delivery vehicle.

Chip specialistdelivery vehicle,

not common.

Bulk bag deliveries Pellet or chip 1-2m3/bag Common in

some areas (e.g.Scotland).

Tipper trailer Pellet or chip Chip: c.20-30m3

(6-9 tonnes)

Pellet: c.20-30m3(14-21 tonnes)

Tipper trucks

widely available

and commondelivery method,

particularly or chip.

Scissor lit tippingtrailer

Pellet or chip Chip: 20m3-30m3(6-9 tonnes)

Specialist deliveryvehicle required.

Blower trough and

tipper truck

Chip c.20m3 (6 tonnes) Tipper trucks

widely availablebut blower troughs

are specically

purchased orsite uelling.

Hook lit bin/Ro-Ro

bins

Chip 30m3-35m3

(9-12 tonnes)

Specialist delivery

vehicle required.

Front loader Chip and bales c.1m3 (0.3 tonnes) Commonmachinery or arm/

estate application.

Walking foor

trailer

Chip 60m3 (18 tonnes) Specialist delivery

vehicle required suited to large

scale deliveries.


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26 Technical manual

Delivery system Benets Drawbacks

Flexible hose rom

a blower tanker High volume discharge possible

(up to 15-20m3 max payload).

Pellets may be deliveredthrough a hose over a length o

c.30m, thus beneting sites with

restricted access.

Metering o delivery is possible.

Specialist vehicles are required (though theseare relatively common amongst pellet suppliers).

Time taken or discharge will be approximately30-45 minutes or a ull discharge o 20m3.

Longer blower runs may result in high levels onoise during discharge.

I uel store is not designed or this method odelivery, wood pellets can become damaged and

disintegrate upon delivery causing excess dust.

Bulk bagdeliveries

Low-cost solution. Fuel type fexibility (suitable or

wood chip or pellets).

Suitable or smaller uelconsumption volumes.

Lorries with built-in cranes aregenerally widely available.

Low delivery volumes (1-2m3 per bag) andthereore deliveries may require multiple bags,

especially i using wood chip.

Fuel may be exposed to moisture i not coveredduring delivery.

More expensive due to the small load dischargeper delivery.

Tipper trailer High speed o delivery.

Tipping trailers/lorries aregenerally widely available,

thereore oering the potentialor uel supplier fexibility/

switching.

High volumes and dischargerates possible, which can

reduce cost.

Requires good vehicle access and clearance toallow tipper bed to be raised.

Requires large storage area to allow ull trailer

discharge (e.g. 20-30m3

). Requires underground/semi-underground store

or vehicle ramp to allow uel delivery.

Partial discharges are dicult to achieve.

Space may be required on-site or vehicle to turn.

Delivery by tipping may cause uel in the storeto be unevenly distributed (manual raking maybe necessary to rectiy this).

Scissor lit tipping

trailer High volume discharge possible.

Can deliver uel to above-grounduel stores (less costly than

subterranean/semi-subterranean

counterparts).

Limited potential to change uel supplier asrequires a more specialist delivery vehicle.

Partial discharges are dicult to achieve.

Delivery by scissor lit tipping may cause uelin the store to be unevenly distributed (manual

raking may be necessary to rectiy this).

Blower troughand tipper truck

Flexible delivery solutionin space-constrained sites

(particularly retrot sites wherestandard uel delivery methods

may not be possible).

Requires careul discharge o material into theblower trough.

Discharge rate limited to c.25m3/hour.

Noisy delivery method (may cause disturbancein built-up areas).

Maximum blower distance is c.2.5m romthe trough.

Table 5Pros and cons o dierent uel delivery methods


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Fuel storage

Fuel storage acilities normally account or a signicantproportion o the overall capital cost o biomass heating

projects and careul consideration needs to be given to

their design and unctionality.

The most appropriate type o uel store is usuallysite-specic, and the decision should be based on a

reconciliation o the ollowing actors:

The fexibility/availability o the delivery method romthe uel supplier(s).

Available space at the site and any site-specicphysical access constraints.

The location o the existing or proposed plant roomin relation to the uel store.

Appearance/aesthetic requirements. Fuel type to be used, which will aect uel store

volume.

Site topography and geology (i.e. ground conditionsi a subterranean store is being used).

Costs o dierent congurations.

Liaison between prospective suppliers and the project

design team is essential to deliver a cost-eective

solution or uel reception and storage.

Fuel stores can be categorised into our main types,

(with variations on each present in the UK).

1. Below-ground/partially below-ground

(subterranean) stores.

2. Above-ground stores.

3. Integrated stores within existing buildings.

4. Removable containerised storage.

Logs and bales are normally delivered using less automated processes such as a sel-loading lorry with a crane (larger sizes) or via net bags(smaller sizes). Fork-lit trucks also used to deliver bales and move them around sites.

Delivery system Benets Drawbacks

Hook lit bin/

Ro-Ro bins Minimal civil works required

(concrete pad only).

Oers an integrated uel storageand delivery solution (cassette-

style containers o uel replaced

as necessary by uel supplier).

High volume o uel in onedelivery (c. 35m3).

Requires specialist uel supplier or Energyservices company (ESCo.) operator.

Ties up capital in the containers or supplier.

Above ground solution may not be suitable orall sites and aesthetics.

Front loader Simple solution.

Widely available.

Can deliver uel to out-o-reachlocations (above ground stores).

Low delivery volumes.

Slow speed o delivery.

Walking foortrailer

High volume discharge possible.

Widely available. Requires signicant amounts o space or

delivery and turning.

Photocou

rtesyoAsgardBiomass

Biomass boiler unit with automatic ash removal bin and

uel eed auger


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28 Technical manual

Wood log uels may be stored outside; however, they

should be covered to ensure uel remains dry/conditioned.

Bales may be stored in a simple, covered but ventilatedenvironment (e.g. barn).

Key considerations in the design and construction o

uel stores are:

1. Preventing the ingress o water but also having

sucient ventilation to allow the escape o any

condensation given o by the uel residing there.

2. Having sucient strength to be able to tolerate

the outward pressure exerted by a ull load o uel(and any inward orces imposed by surrounding

earth i using a subterranean store).3. Having a simple method o inspecting the level

o uel (e.g. hatch, window, webcam).

4. Keeping the interior ree rom electrical sockets,

switches, and exposed electrical ttings.

5. Meeting the relevant building regulations where

they apply (approved document J Combustionappliances and uel storage systems36 provides

guidance).

6. Minimising uel auger distances rom the plant.

7. Ensuring saety during deliveries (e.g. including a

stop bar) i uel delivery method requires a vehicleto reverse up to the store (can avoid the need or

additional sta to oversee deliveries).

8. Having appropriate security measures in place (i

it is in a place that will be accessible to the public)to prevent illegal access.

9. Allowing or complete discharge rom the supply

vehicle particularly i tipping.

The dierent physical properties o the two main sourceso biomass uel or heating (pellets and chips) necessitate

specic considerations:

Pellets:

I blower delivery is used, the storage unit will needthe appropriate couplings to allow connection to the

pellet blower hose (e.g. a camlock), and the end othis will need to be within the reach o the blower-

truck driver. Also, in this situation a fexible rubber/plastic sheet hanging opposite the inlet pipe is

advisable to avoid pellet damage during delivery.

The storage unit will need an exit port to allow therelease o air when deliveries take place (which can

be tted with a lter to reduce excessive dust exiting

the storage silo).

The point o entry or pellets must be high upenough to enable even lling.

I there need to be bends in the delivery pipework,tapered bends may be preerable, as a 90 angle

could cause damage to pellets during delivery. The foors o the storage unit will need a slope o

at least 40 going towards the eed mechanism

(e.g. auger) to ensure pellets can fow into it.

Any delivery pipe on the storage unit may needto be made rom metal and should be earthed to

prevent static build-up on plastic piping.

36 http://www.planningportal.gov.uk/england/proessionals/en/4000000000503.html


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30 Technical manual

Fuel type Storage location

Below ground

Use or sites with an elevation dierence, where land is at a premium or aestheticconsiderations demand.

Above ground

Lower cost than below ground, with easier access or maintenance. Widest range

o uel store types.

Building integrated

Can be above or below ground. Stores can be simple and cost-eective, i minimal modicationsto existing internal structures are required.

Below ground

See considerations above or pellets. Need to consider that the uel supply vehicle has adequate

manoeuvring space.

Above ground

Same cost advantage as or pellets, but reduces uel delivery vehicle fexibility.

Building integrated

Can be above or below ground. I minimal modications to existing internal structures are

required, these can be simple and cost-e ective, but will be governed by uel supply vehicleand the method o discharge.

Table 6Storing pellets and chips

Woodchips

Woodpellets


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Type o uel store

Purpose-built pre-abricated bunker

Typically lled pneumatically rom blower tanker. Fuel extraction via straight auger orvacuum tube.

Constructed bunker

Possible orms are adapted grain silos, modied storage bunkers, existing cellars with wood

panelling and basic concrete/brick covered spaces. Fuel extraction requires tapered foor tounnel pellets to a central auger. Typical uel extraction via straight auger.

Bag silo

Flexible bag which sits in a support rame. Simple and cost-eective, avoiding need or civil/

construction works. But needs to be positioned in sheltered area or building, not exposed

to rain. Typically lled pneumatically rom blower tanker. Fuel extraction by straight auger

or vacuum tube.Integrated storage hopper

Most suitable or small systems where hopper is attached directly to plant. Usually lled

manually using pellet bags. Fuel extraction by auger direct to plant.

Purpose-built pre-abricated or bespoke storage hopper

Preabricated steel structure or re-enorced plastic hopper. Usually available rom plant

manuacturer/supplier. Typically lled pneumatically rom blower tanker. Fuel extraction

via gravity: tapered foor to central auger.

Storage container

A shipping container, or example. Filled via blower unit or bagged or removable system to

allow o-site relling. Depending on the route rom uel store to plant unit, extraction can bevia straight auger, vacuum tube or gravity ed (inclined foor with auger running along base).

Bespoke internal structure

Can be constructed rom wide variety o materials, e.g. brickwork or main structure withwood panelled interior, or concrete. Filled by tipper trailer, pneumatically rom blower tanker

or ront loader. Fuel extraction typically via straight auger.

Purpose built external structure

Shed-type or lean-to external constructions can be built rom wide variety o materials;

highly fexible.

Constructed bunker

Can be constructed rom wide variety o materials, e.g. blockwork or main structure with

wood panelled interior, or concrete. Typically lled by tipper trailer. Fuel extraction typically

via walking foor or circular sweep-arm agitator.

Bespoke construction

Can be constructed rom wide variety o materials: blockwork with cladding, brickwork with

cladding or steel structures (either purpose built or o-the-shel designs such as ISO container

above). Highly fexible options available.

Bespoke internal structure

Typically suitable or retrot site, with installation within existing building. Can be

constructed rom wide variety o materials, e.g. brickwork or main structure with woodpanelled interior, or concrete. Filled by tipper trailer, pneumatically rom blower tanker or

rom bags (automatically or manually lited). Fuel extraction typically via straight auger.

Images courtesy o: Black & Veatch Ltd., Glyn Edwards, Imperative Energy Ltd., Wood Energy Ltd., Marches Wood Energy


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32 Technical manual

FuelEx

tractionandFeed

FuelEx

tractionandFeedistheprocessoremovinguelromthestoreand

transerringittothecombustiong

rate

othem

aincombustionunit.Anumberomethodsarealreadyinuseinthe

UK,asshowninTable7.

Table7

Fuelextractionsystems

Extractiontype

Picture

Commentary

Fueltype

Typicalscaleo

f

applicability

Batch

ed

Onlyappropriateorbatch-redplants.

Requirescontinuedmanualintervention(daily).

Logs

10kWth+

Baleso

straw

30kWth+

Auge

rs(screw

eed)

Theprimarymeansomovingwoodchipand

woodpelletmaterialromtheuelstoretothe

plantunit.

Blockagesattranserpointsbetweenaugerscan

ariseithemanuacturersuelspecicationisnot

adheredto.

Lengthoaugershouldbeminimisedtoreduce

riskoblockages.

Chip

30kWth+

Pellet

10kWth+

Gravityed

Theuseogravity-edsyste

msisonly

appropriateorpelletplants.

Woodpelletsareeitheraugu

redalongthelengtho

ataperedfoor,orunnelled

toacentralpointviaa

baggedstore,etc.Fromheregravitydropsittothe

plantunitorasecondaryau

ger/pneumaticeed.

Pellet

10kWth+

Pneumatic/

vacuumeed

Thesesystemsrequirecare

uldesign,

considerationobends,length,sizeovacuum

tubes,andblowingpressur

es.Thissystemis

usuallylimitedtoapplicatio

nssmallerthan

50kWthandisonlyapplicab

letopelletsystems.

Pellet

10kW-50kWth


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Imagescourtesyo:PeterTeisen/Farm2000Ltd.,EconergyLtd,BSRIALtd.,Black&VeatchLtd.,Imp

erativeEnergyLtd.

Extractiontype

Picture

Commentary

Fueltype

Typicalscaleo

f

applicability

Agita

torarms

withauger

Agitatorarmswithanaugerrunarethemost

cost-eectivemeansoueltranseratthe

mediumscale,andconsequ

entlytheyarethe

mostwidelyused.

Essentiallythespringarms

agitatetheuel,

makingsureiteedsintoacentralauger,which

inturneedstheplant.

Theyareinstalledatanang

leand,thereore,

therewillbesomedeadspaceundertheagitator

discandarms(unlessaals

efoorisinstalled).

Thisareawillneedtobeaccountedorwhen

assessingavailableuelsto

ragevolume.

Agitatorarmlengthsmayn

eedtobedesigned

toavoiddamagetowallsan

darms.

Chip

30kWth+

Pellet

30kWth+

Walkingfoor

Walkingfoorsshufetheu

elalongthelengtho

theuelstoretowardsanau

gerwhicheedsthe

plant.Theuelismovedor

wardviahydraulic

rams/nswhichsituponaconcretepad.

Walkingfoor-basedsystem

scanreceivebulk

deliveryandarethereoresu

itedtolargersystems.

Theconcretepadandthew

allsothestoreneed

tobesucientlystrongtowithstandtheorces

andpressuresexertedbyaullloadouel.

Chip

1MWth+

Pellet

Generallynotusedor

pellets,althoughtechnically

theyarecompatible.

Conv

eyor

Conveyor(belt,chainorhydraulicreciprocating)

ormechanicalgrabsystemsaregenerally

concentratedatthelargesc

aleowooduel

installations,wherethereis

asignicant

throughputomaterial,orw

heretheuelisoa

largeparticlesizethatpreventstheuseoaugers.

Chip

11MWth+

Pellet

Notapplicablet

opellets

atthisscale.

Grab

Chip

3MWth+

Pellet

Notapplicablet

opellets

atthisscale.


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34 Technical manual

Fuel cost actors that infuence uel cost

All eedstocks require some orm o intermediate

processing to convert them into a biomass uel suitable

or use in a heating system this can be as simple as

drying in the case o wood logs or more involved suchas pelletisation. The major actors which will have an

infuence on price are outlined in Table 8.

Detailed uel costs

For the majority o heating applications, in the scale

range under consideration in this guide (0.1-3 MWth),

uel is supplied in the orm o woodchips or woodpellets37. Table 9 provides an indication o the cost o

a variety o processed and unprocessed wooduels.

The cost o dierent orms o biomass uel is highlyvariable across the UK, and Table 9 provides guideline

gures only38.

Containerised solutions

Some suppliers oer containerised systems where

the plant(s), uel storage, handling and all associatedbalance o plant are contained within single,

preabricated units. Systems o this kind up to 450kW

in size have been installed in the UK (with largersystems possible using modular capacity). They

are, essentially plug and play options that oer

several advantages such as minimising disruption

to existing buildings, speed o installations andsimplicity. In the right circumstances, they can be

very cost-eective solutions. Image courtesy o Imperative Energy

Table 8Factors aecting wooduel price

Logistics Quality Market

Distance rom rawmaterial supply.

Delivery vehicle.

Frequency andvolume o delivery.

Discharge rates.

Form o delivereduel e.g. slabwood 50 MWth IPPC Part A1 (Large

Combustion PlantDirective applies)

Environment Agency

Residues or which WIDapplies treated wood

e.g. painted urniture

3 MWth WID applies (IPPC Part A1) Environment Agency

Table 21 Summary o environmental permissions or biomass heating equipment

(IPPC): Integrated Pollution Prevention and Control(LA-IPPC): Local Authority Integrated Pollution Prevention and ControlSource: AEA Energy and Environment

Initial

assessment

Detailed

easibility

Procurement and

implementation

Operation and

maintenance


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3.2.6 Perorm ull economic appraisal

As well as o ering lower carbon emissions, biomass

heating systems can have lower lietime (or net present

value) costs than ossil uel plants. This is due to thecosts o biomass uels being lower than those o several

ossil uels typically used or heating (e.g. heating oil,

LPG, electricity).

However, the capital costs o biomass systems tend to

be higher than or ossil uel boilers. Consequently, in

order to choose biomass systems on nancial grounds,

one needs to take a long-term view towards the overallinvestment, rather than a short-term view o just

upront costs.

This section introduces the main actors aecting costs,both capital and operational, and gives a worked example

or a 400 kWth biomass heating system.

Beore perorming an economic appraisal o theproposed system, it is useul to understand the dierent

components, structure and indicative levels o biomass

heating systems costs, both capital and operational.

The main reasons why biomass heating systems are

more expensive than equivalent ossil uel systems are:

1. Some o the basic principles o solid uel combustion

mean that the biomass plant unit needs to be largerthan typical ossil uel systems. Also, biomass plants

will generally contain more mechanical components

(such as ans, ash extraction equipment etc.).

2. As solid uel systems, biomass heating plants

need uel storage acilities (and extra space to

accommodate the larger plant unit itsel). Unless anexisting building can be used to perorm this unction,

uel and plant storage is usually a signicant part o

overall system cost.

3. Some orm o uel extraction/eed method will be

required (e.g. a screw auger), which adds to overallsystem cost.

4. At present in the UK, biomass systems are sold insmall numbers (compared to the market or ossil

uel equipment) and are oered by a relatively

small number o providers. Accordingly biomassheating equipment does not benet rom the

economies o scale that ossil uel equipment does.

5. The majority o systems installed in the UK are

imported rom continental Europe which can involve

additional importation costs. In addition, variations inthe Sterling-Euro exchange rate at the time o systemprocurement can have an eect on nal costs

(although this could be positive as well as negative).

Capital costs

Figure 17 provides a cost breakdown o the major

elements or a recent real-lie example o a (500 kW th)biomass heating system.

Individual site circumstances will mean that the actual

costs o projects may vary signicantly even or systems

o a similar installed capacity.

The reasons or such variations are largely connected

to the specic circumstances o the site and the owners

requirements or the project:

1. Some sites may be able to make use o existing

buildings or simple on-site structures to act as the

uel storage acilities and/or boiler housing acility.However, certain projects may require very complex

constructions/alterations to enable a biomass heating

system to be deployed.

2. Certain contract structures can have an impact ontotal costs or example i the site owner is able to

carry out any necessary civil, electrical and/or design

works in house this can reduce the overall capitalcost. However, complex contracting structures within

projects (multiple layers o contracting companies)

may increase costs as contingency unding is

actored in to take account o any uncertainties inthe contract.

3. Historically, some projects have been specied

above the minimum unctional levels necessary orcorrect operation. This is usually either or aesthetic

reasons or because the system is to orm part oan exemplar or demonstration scheme to promoterenewable energy.

4. In some cases sites require signicant building

alterations or integration works to enable

retrotting o a ull biomass heating solution.

Figure 18 (over) gives illustrative installed capital costs

o complete biomass heating systems across a number

o size ranges and shows a spread o costs within eachsize range.

Initial

assessment

Detailed

easibility

Procurement and

implementation

Operation and

maintenance

8/8/2019 Bioma

Documents

Biomass End User Guide