Life Cycle Assessment of Torrefaction

25/03/2014
Life Cycle Assessment of Torrefaction
‘Using Life Cycle Assessment to assess integrating
Torrefaction into Bioenergy Systems’
Ref: ECN
Paul Adams
Sustainable Energy Research Team, University of Bath
Email: [email protected]
Phone: +44 (0) 7815 152 594
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
Overview of Presentation
Supergen
Bioenergy
Hub
Introduction
to LCA
Goal &
Scope of
LCA
System
Boundary
Life Cycle
Inventory
(data)
Modelling
the System
Future Work
Unanswered
Questions
Gaps in
Knowledge
Potential
Results
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
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25/03/2014
Supergen Bioenergy Hub
Further
information:
Develop a whole system overview of the
impacts of incorporating torrefaction into
bioenergy systems, evaluating the extent to
which these benefits can counteract energy
requirements, environmental impacts, and
economics
www.supergenbioenergy.net
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
Work Package 1.7 – Aims & Objectives
• “Whole system” approach to
evaluating Torrefaction
• Started off broad – now more
narrow
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
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What is ‘Life Cycle Assessment’ ?
“a technique for assessing the environmental aspects and
potential impacts associated with a product, system or service”
ISO 14040 – International Standard Organisation
Feedstock
Transport
Storage
Energy and
raw material
requirements
Drying
Torrefaction
Cooling
Emissions to
Air, Water &
Soil
Grinding
 Assessing energy & resource
requirements + emissions & wastes
implications for each life cycle stage
Densification
Transport
End Use
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
Goal & Scope – what is the Question?
• Goal & Scope is crucial as different questions result in different answers
• Effectively the Qs we are asking are:
• ‘What are the energy and GHG balances for a proposed torrefaction
system and how does this compare to conventional wood pellets?
• How do other environmental burdens compare, e.g. resource/water use
and emissions to air/water/soil’
• Functional unit is therefore defined as 1MJ of torrefied pellet
• ISO 14040 & ISO 14044
• Goal  Intended application, reasons for carrying out the study, intended
audience
• Scope  the product system to be studied; the functional unit; the system
boundary; categories used; data requirements; assumptions; limitations,
etc.
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
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System Boundary
Ref: Shirley, 2014
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
System Boundary
•
System Boundary is where we define what we include and what
we exclude (outside of boundary or scope).
•
This involves some judgement and is likely to be refined as the LCA
develops.
•
All items which have a material impact on results should be
included.
•
Use existing studies to decide on the system description and if
items can be left outside of the boundary.
•
Don’t leave out items because no data! If in doubt include in the
LCA, or clearly justify exclusion.
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
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Life Cycle Inventory
• Overall objective is to quantify the following:
• energy inputs, raw material inputs, ancillary inputs, other physical inputs,
• products, co-products and waste,
• emissions to air, discharges to water and soil, and
• other environmental aspects.
• Primary data is preferred for accuracy of LCA study – work with developers
• However it is not always possible – especially with new or emerging technologies, which
are still not widely used or commercially available
• Therefore a combination of the following is needed:
• Experimental data (e.g. work carried out by Leeds and industrial partners)
• Literature (e.g. variety of useful studies available – quality is difficult to verify)
• Databases (e.g. secondary data such as energy supply, ancillary services, equipment, etc.)
• Not perfect!!
• Use sensitivity analysis to assess implications of different data / assumptions
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
Modelling the System
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
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Modelling the System
Torrefied
Pellet Plant
Unit Process 3
Scale of plant
Pellet Plant
Throughput (a.r. tonnes per year)
Material loss (%)
Plant output (dry tonnes per year)
Operating factor
Maintenance
Useful Economic Life (UEL)
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
Modelling the System
Torrefied
Pellet Plant
Unit Process 3
Torrefied Pellets (TP)
TP transport
to end-user
Unit Process 4
Pellet Plant
Pellets
Pellet
transport to
end-user
Truck
Train
Ship
Distance
Capacity
Lifetime
Speed
Fuel consumption
Loading/unloading
Unit Process 5
Steel
industry
Gasification
Co-firing
Standalone
combustion
Other?
• Assume both ‘Pellet’ and ‘Torrefied pellet’ use the same feedstock
• Therefore the important part for comparative LCA is what happens
between biomass reception and either end product (gate-to-gate) or end
use (gate-to-grave)
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
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Modelling the System
Ref: Shirley, 2014
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
Difficulties with Modelling
• A wide range of data sources is required which reduces
the accuracy of the LCI
• Difficult to find consistent data through the whole
system, e.g. different feedstocks, operating parameters
• Difficult to validate data from literature especially if
assumptions and data not transparent
• No commercial plants operating, or difficult to obtain
data (confidential)
• The theoretical system doesn’t exist, i.e. we are
modelling a proposed system
• Need LCA to support develop of technologies, i.e.
positive results may encourage policy support (LCA is
now widely used in UK bioenergy industry)
 Chicken & egg situation?
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
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Potential Results
Supply Chain
GHG Emissions1
(gCO2e/MJe)
Unit Process Contribution2 (%)
1
2
3
4
5
Forest Residues
16 - 23
19
5
16
59
1
Short Rotation Forestry
24 - 46
38
4
14
43
1
Default values calculated for standard wood pellets using the Biomass Carbon Calculator (no LUC)
1 – Range of results depends on assumptions of biomass drying (low = biomass used, high = electrical drying)
2 – % contribution results displayed are for biomass drying
• Energy use & GHG emissions associated with feedstock supply are marginal assuming forest
residues (North America) are used, but drying (if non-biomass) and transport important
• Short Rotation Forestry – cultivation, drying (if non-biomass) and transport important
• Using default values shows pellet production is between 5-15% of total GHG emissions
 Potential for GHG savings where transporting long distances or complex logistics
 But need more data on energy/GHG from torrefaction process to draw firm conclusions
• Results for torrefaction will depend on mass-energy balance results, type/location of
feedstock, type of drying, and how the supply chain is configured.
• Too early to make firm conclusions
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
Gaps in Knowledge
• Type and amount of energy consumed in the torrefaction process (gate-to-gate)
• How much utility fuel is needed? Can torr-gas realistically fuel the torrefaction stage
and provide some additional heat for drying?
• Realistic mass-energy balances for commonly used feedstock (i.e. does lab data
correlate to large scale?)
• Water used in the system for cooling and other processes
• Local emissions such as leaching from stored torrefied material?
• Effect of torrefaction on grinding (energy savings?)
• End-use properties?
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
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Data Requests
• LCA is a data hungry methodology
• Better information leads to improved decision-making
• Policy-makers rarely mention torrefaction, but if we can produce robust study with
interesting results we have the opportunity to influence Governmental support
• Without LCA results unlikely torrefaction will become realistic commercially in UK
• Therefore if you can help with any aspects of the LCA please do
Ref: http://www.thebookpeople.co.uk
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
Conclusions
• Energy & GHG LCA should be simple if we can obtain realistic data on torrefaction
process (gate-to-gate)
• Other emissions are more difficult to quantify due to limited knowledge / publications
• With ‘Sustainability Criteria’ torrefaction industry will need to demonstrate GHG
savings. With lots of imported biomass transport benefits could be crucial.
• At present torrefaction not even recognised in most Government documents and in
particular there is no option in the Biomass Carbon Calculator!
• Therefore a pressing need to provide robust results for LCA to support development
of torrefaction in the UK and elsewhere.
Ref: University of Leeds
Ref: ECN
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
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Conclusions
• Let’s be like Buster and keep
searching until we find the eggs!
• Eventually if you keep looking you
will start to find the answers.
Ref: http://www.thebookpeople.co.uk
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
Thank You for your attention
Ref: ECN
Dr Paul Adams
Sustainable Energy Research Team, University of Bath
Email: [email protected]
Phone: +44 (0) 7815 152 594
LCA of Torrefaction – Leeds Workshop
1st & 2nd April 2014.
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