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TSEC Biosys TSEC Biosys 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 1 TSEC Biosys TSEC Biosys Sustainability issues: a focus on Biodiversity, water use and life-cycle GHG balances 2 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 TSEC Biosys TSEC Biosys Aim TSEC Biosys TSEC Biosys 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 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 TSEC Biosys TSEC Biosys 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 TSEC Biosys TSEC Biosys Key findings: Plants (example) TSEC Biosys TSEC Biosys 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 Key findings: Predation (example) • Predation rates highest in arable land > willow SRC > set-aside for both small mammals and ground invertebrates Predation pressure TSEC Biosys TSEC Biosys Main Conclusions - Biodiversity TSEC Biosys TSEC Biosys • In agricultural landscapes, willow SRC increased farmscale 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. Water TSEC Biosys TSEC Biosys 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. Water New data collected from field measurements for Miscanthus and model developed Miscanthus compared with other bioenergy crops, arable crops, grassland and woodland TSEC Biosys TSEC Biosys Water • TSEC Biosys TSEC Biosys 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. Main Conclusions - Water TSEC Biosys TSEC Biosys 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. Life Cycle GHG balances TSEC Biosys TSEC Biosys 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 Pre-harvest GHG balances - role of soil in the GHG balance TSEC Biosys TSEC Biosys • 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 Pre-harvest GHGs • TSEC Biosys TSEC Biosys Previous literature based analysis (St Clair et al 2008) of pre-harvest GHG balance (management and soil balance) generated 4 ‘rules’ :1. 2. 3. 4. 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 TSEC Biosys Yield map C inputs Climate maps TSEC Biosys Soil variable maps RothC GHG balance Map 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 TSEC Biosys TSEC Biosys Pre-harvest GHGs: Summary TSEC Biosys TSEC Biosys • Revised analysis in TSEC-BIOSYS enhances these ‘4 rules’ for UK 1. Don’t replace woodland with any bioenergy crop - emission of up to 4 CO2eqt/ha/year 2. Don’t replace grasslands with OSR or winter wheat - net emissions ~ 1 CO2eqt/ha/year 3. SRC and Miscanthus on arable and grassland saves up to ~4-5 CO2eqt/ha/year 4. OSR and winter wheat on arable land is neutral Key sensitivites Crop 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 TSEC LCA GHG balances TSEC Biosys TS E C TSEC Biosys (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) Bios ys TSEC LCA Model (whole life-cycle) TSEC Biosys TS E C TSEC Biosys Bios ys • 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 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 TS E C Bios ys Forest residue extraction Bios ys (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 TSEC Biosys TS E C TSEC Biosys 11 Tree Species 4-6 Yield Class Ranges 28 UK Regions Volume-dependent transport emissions TSEC Biosys TS E C TSEC Biosys Bios ys - a new UK dataset from TSEC-BIOSYS Based on biomass bulk densities + vehicle volume capacities 0.3 0.25 0.2 0.15 0.1 0.05 Road Pellets Electric Diesel 5.5 7.5 18 26 32 40 0 44 KG CO2 eq./t-km 0.35 Rail Chips Bales Marine Land-use change and Carbon sequestration - integration TSEC-BIOSYS Theme 2 and Theme 3 TS E C Bios ys 6 4 2 0 -2 -4 GHG benefit Replace arable soil Replace Grassland incl. prev. LU management with oilseed rape with winter wheat with SRC poplar with Miscanthus with oilseed rape with winter wheat with SRC poplar with Miscanthus with oilseed rape with winter wheat with SRC poplar -6 with Miscanthus Annual net emissions, t CE ha -1 GHG cost Replace Forest/Semi-natural incl. fossil fuel displaced Waste Wood and Arboricultural Arisings Waste TS E C Bios ys -No value to anyone anywhere -Would have been disposed Landfill Kg CO2 eq/tonne Landfilled (100 Year Time Frame) 2500 -Collection SOURCE 2000 -Reference system? 1500 DEFRA WRATE 1000 500 Damen & Faaij,2003 0 -500 0% 20% -2000 IPCC 60%default 80% Mann & Spath,2001 -1000 -1500 40% Gardner et al., 2002 SINK Degradation Rate of Landfilled Wood (% ) Carbon Sequestered Electriciy Credits Methane Emissions Overall Greenhouse Gas Balance 100% Net sink or source? Highly sensitive to degradation rate Main Conclusions: GHG balances TSEC Biosys TS E C TSEC Biosys • 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 Bios ys …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 TS E C Bios ys Emission Savings TS E C Bios ys E.g. SRC chips % Savings CO2 eq. savings? Compared to? Biomass Required Per Year Co-firing (10%) 9% 3,191,301 Coal 3,726,898 Dedicated Electricity 92% 165,048 Grid electricity 300,000 CHP (Electricity) 94% 33,181 Grid electricity 54,000 CHP (Heat) 97% 59,519 Natural Gas 54,000 Heat alone 94% 331 Natural Gas 500 Overall Emissions TS E C Bios ys 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 1000 900 Emissions (Kg Co2 eq./MWhe or t) 800 700 600 500 400 Heat is ‘best’ use for biomass - High conversion efficiency -Lower overall emissions per MWh 300 Per MWh 200 100 0 Heat (alone) Heat (CHP) Heat Heat (Natural Gas) Electricity (CHP) Electricity (Dedicated) Electricity (Co-firing biomass) Electricity (Co-firing coal + biomass) Electricity Electricity (Natural Gas) Electricity (Grid) Electricity (Coal Fired) Summary: GHG balances TSEC Biosys TS E C TSEC Biosys • 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 Bios ys TS E C Bios ys Report available August 09 Overall Summary TSEC Biosys TS E C TSEC Biosys Bios ys • 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 Acknowledgements TSERC-BIOSYS Researchers:Carly Whittaker, Jon Hillier, Rebecca Rowe, Philip Sinclair, Sophie Jablonski TSEC Biosys TS E C TSEC Biosys Bios ys Thank you TSEC Biosys TSEC Biosys TSEC Biosys TSEC Biosys www.tsec-biosys.ac.uk 35