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T SEC-BIOSYS: A whole systems approach to bioenergy demand and supply www.tsec-biosys.ac.uk Richard Murphy Imperial Col

T SEC-BIOSYS: A whole systems approach to bioenergy demand and supply www.tsec-biosys.ac.uk Richard Murphy Imperial College London. Biomass role in the UK energy futures The Royal Society, London: 28 th & 29 th July 2009. Sustainability issues: a focus on

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T SEC-BIOSYS: A whole systems approach to bioenergy demand and supply www.tsec-biosys.ac.uk Richard Murphy Imperial Col

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  1. TSEC-BIOSYS: A whole systems approach to bioenergy demand and supply www.tsec-biosys.ac.uk Richard Murphy Imperial College London Biomass role in the UK energy futures The Royal Society, London: 28th & 29th July 2009

  2. Sustainability issues: a focus on Biodiversity, water use and life-cycle GHG balances

  3. Biomass and sustainability The overall ‘sustainability’ of biomass use in the UK is affected by numerous issues e.g. • Direct and indirect land use • Greenhouse gas balances • Water use in agriculture and forestry • Biodiversity protection and management • Transport impacts • Rural economy and livelihoods • Waste management

  4. Aim TSEC BIOSYS has focussed on analysing and quantifying 3 key attributes of the environmental sustainability of biomass energy systems for the UK • Influence of perennial biomass crop production on biodiversity indicators (SRC willow,) • Water consumption of perennial biomass crops (Miscanthus) • Life-cycle greenhouse gas balances for a range of UK and imported biomass sources – both pre-harvest and whole life-cycle analyses

  5. Biodiversity Work conducted in Theme 2 by Rebecca Rowe, Univ. Southampton Limitation of previous Willow SRC biodiversity studies: • Small or non-commercial sites – little on commercial • Few direct comparison between SRC and arable land and none for set-aside land. • Limited number of species (birds, pest species) • Few studies on ecosystem processes

  6. Biodiversity • Three field investigations on willow SRC, Arable and set-aside land:- • 2006: Comparison of flying invertebrate and ground flora diversity and abundance between • 2007: Comparison of ecosystem process of herbivory, decomposition and predation • 2008: Detailed investigation of predation pressure

  7. Key findings: Plants (example)Species Richness & Abundance • Species richness • Similar in all headlands • In the cultivated area set-aside land > willow SRC > arable land • Ground flora biomass • Similar in set-aside and willow SRC, reduced in arable land

  8. Key findings: Predation (example) • Predation rates highest in arable land > willow SRC > set-aside for both small mammals and ground invertebrates Predation pressure

  9. Main Conclusions - Biodiversity • In agricultural landscapes, willow SRC increased farm-scale biodiversity. • Willow SRC provides a more stable, less intensive environment for plants, invertebrate and small mammals which are uncommon in arable land. • Willow SRC provides a breeding site for several small mammal species • The effect of willow SRC on ecosystem process are significant and complex.

  10. Water Work conducted in Theme 2 by John Finch, CEH Main focus: What are the potential impacts of energy crops on water resources? • Water quality is not a significant unknown: • Biomass crops have lower inputs so are positive; • Concerns about sediment mobilisation are unlikely to be realised; • Biofuel crops = status quo; • A major concern is water resources: • High yield = high water use.

  11. Water New data collected from field measurements for Miscanthus and model developed Miscanthus compared with other bioenergy crops, arable crops, grassland and woodland

  12. Water • The annual harvests leave a period of a couple of months, in the spring, when the substrate is exposed – so evaporation occurs; • Leaf fall into January so there is storage for interception losses; • The deep roots provide soil water to support transpiration in summer; • Miscanthus seems less sensitive to soil water stress than the other vegetation types.

  13. Main Conclusions - Water For the soil and climatology of the site: • The annual water use of Miscanthus is comparable to that of permanent woodland; • The annual water use of SRC willow is comparable to that of winter wheat; • Both are higher than permanent grassland But • More field validation needs to be done; • The model can then be run in a spatially distributed form for various crop distributions.

  14. Life Cycle GHG balances Work led in Theme 2 by Jon Hillier and Pete Smith and in Theme 3 by Carly Whittaker, Nigel Mortimer and Richard Murphy. Main focus: To what extent can energy from biomass contribute to meeting the UK’s greenhouse gas targets? A TSEC-BIOSYS Life Cycle Assessment (LCA) model was developed:- • Utilises current, UK-specific case studies • Encompasses relevant UK biomass supply chains (including some imported biomass) • Scope for future scenarios and varying scales of energy production

  15. Pre-harvest GHG balances - role of soil in the GHG balance • The soil C pool is the balance of accumulated inputs and emissions • C inputs depend mainly on plants growing on the soil • C emissions depend mainly on the size of the C pool • Under constant land use tends to an equilibrium where C inputs balance emissions • Average equilibrium soil C:- • SRC ~110 t/ha • Miscanthus ~100 t/ha • Winter wheat ~45 t/ha • OSR, ~55 t/ha

  16. Pre-harvest GHGs • Previous literature based analysis (St Clair et al 2008) of pre-harvest GHG balance (management and soil balance) generated 4 ‘rules’ :- • Don’t replace woodland with any bioenergy crop • Don’t replace grasslands with OSR or winter wheat • SRC and Miscanthus on arable are OK • OSR and WW on arable land is neutral

  17. RothC C inputs Climate maps Yield map Soil variable maps GHG balance Map

  18. Pre-harvest GHGs GHG balance - including emissions from farming (machinery, fertiliser, crop protection) Predicted soil emissions/sequestration For 4 bioenergy crops. Annualised 20 Year average using RothC

  19. Pre-harvest GHGs: Summary • Revised analysis in TSEC-BIOSYS enhances these ‘4 rules’ for UK • Don’t replace woodland with any bioenergy crop - emission of up to 4 CO2eqt/ha/year • Don’t replace grasslands with OSR or winter wheat - net emissions ~ 1 CO2eqt/ha/year • SRC and Miscanthus on arable and grassland saves up to ~4-5 CO2eqt/ha/year • OSR and winter wheat on arable land is neutral • Key sensitivitesCrop yield, Fertiliser usage, and Soil C balance (previous land use) – geographic location • There is a strong need for soil C data under Miscanthus and SRC for a range of soil types and climates

  20. TSEC LCA GHG balances (whole life-cycle) AIMS • Review and integrate relevant studies on carbon balances of bioenergy supply chains • Life Cycle Analysis approach • Produce coherent model applicable to the UK bioenergy sector • Sector not yet fully developed…Examine biomass projects in operation now • Produce flexible model • Assess carbon abatement ‘wedges’ for the UK • Depends on supply and end-use. • Produce series of multipliers (e.g Kg CO2/MWh or /ODT)

  21. TSEC LCA Model (whole life-cycle) • Covers : • 15 biomass supply chains • Land-use reference system (set-aside, grassland, managed grassland) • 5 Waste/residue reference systems (incl. mulching, heat production, landfill, fertilizer addition) • 10 Transport options (7 Truck, 2 Train, Marine) • 4 Outputs (Electricity, Heat, CHP, or Co-fired electricity) Output: Energy requirement and GHG emissions for specific supply chain with detailed breakdown of where all emissions occur

  22. Case Studies: Supply Chains Consumers: • Co-firing – Drax • Dedicated electricity – Wilton 10 • District heating – Barnsley • CHP – Literature Suppliers: • Miscanthus –Bical • SRC–Renewable Energy Growers • Forest Residues – Forestry Commission

  23. Forest residue extraction (example) The yield of forest resides on a particular site depends on tree species and yield class. Yields estimated using Forestry Commission’s BSORT model through a series of mass flow partitions to give biomass yield at each harvesting event throughout the rotation of the forest 11 Tree Species 4-6 Yield Class Ranges 28 UK Regions

  24. Volume-dependent transport emissions- a new UK dataset from TSEC-BIOSYS Based on biomass bulk densities + vehicle volume capacities

  25. Land-use change and Carbon sequestration - integration TSEC-BIOSYS Theme 2 and Theme 3 GHG cost GHG benefit

  26. SOURCE SINK Waste Wood and Arboricultural Arisings Waste • No value to anyone anywhere • Would have been disposed • Collection • Reference system? Landfill DEFRA WRATE Damen & Faaij,2003 IPCC default Mann & Spath,2001 Net sink or source? Highly sensitive to degradation rate Gardner et al., 2002

  27. Main Conclusions: GHG balances • Variability • Overall ‘greenhouse gas footprint’ is determined by a several factors and LCA ‘decisions’ Uncertainty can be found in • LCA methodology and decisions • Allocation procedures between co-products • Land-use reference system • Substitution/Avoided emissions • Data and constraints • Effects of residue removal on sustainability • Landfill behaviour (waste wood) • N2O emissions from soil

  28. …Kg CO2 eq. ‘per ODT biomass’ • Can depend on many factors • Quantifiable things • Inputs • Yield • Moisture Content • Material losses • Methodology Decisions: • Landfill behaviour • Land use change • Reference system TSEC-Biosys LCA Model is flexible

  29. Emission Savings E.g. SRC chips

  30. Overall Emissions • Biomass- electricity can offer significant savings • -Best generated as part of a CHP system • Shares plant construction etc. with heat output • Co-fired electricity is low but still burns coal E.g. SRC chips • Heat is ‘best’ use for biomass • High conversion efficiency • Lower overall emissions per MWh Per MWh

  31. Summary: GHG balances • Significant savings in GHG emissions available from a wide variety of biomass energy options • Savings dependent on specifics of the pre-harvest systems and the supply chain, including what is displaced • Highly flexible models and tools available for optimisation and forward looking analyses

  32. Report available August 09

  33. Overall Summary • Perennial bioenergy crops (SRC willow example) can support biodiversity in the agricultural landscape • Water demands for bioenergy crops (Miscanthus example) are broadly similar to other agriculture & forest land uses • Significant savings in GHG emissions available from a wide variety of biomass energy options

  34. Acknowledgements TSERC-BIOSYS Researchers:- Carly Whittaker, Jon Hillier, Rebecca Rowe, Philip Sinclair, Sophie Jablonski

  35. Thank you www.tsec-biosys.ac.uk

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