Biomass Thresholds for Electricity, CHP and Heat Generation

1. Biomass Thresholds for Electricity, CHP and Heat Generation Nigel Mortimer, Charlotte Hatto, Garry Jenkins and Onesmus Mwabonje North Energy Associates Limited nigel.mortimer@northenergy.co.uk

2. Outline • The Questions • The Basis for Calculations • The Answers • The Headlines NORTH ENERGY ASSOCIATES LTD

3. The Questions: Fundamentals - I • What is the “best” use of wood fuel in Scotland: • domestic heat production (15 kWt to 320 kWt)? • commercial and industrial heat production (50 kWt to 20 MWt)? • combined heat and power generation (CHP; 1.8 MWt to 125 MWt, and 0.4 MWe to 50 MWe)? • power only generation ( 5 MWe to 350 MWe)? • Wood fuels: • forest wood fuels; roundwood and residues (bark and branchwood) • waste wood; “clean” and “unclean” NORTH ENERGY ASSOCIATES LTD

4. The Questions: Fundamentals - II • Focus exclusively on greenhouse gas (GHG) emissions: • carbon dioxide (CO2) • methane (CH4) • nitrous oxide (N2O) • Effects of “technology” and “scale”: • technology thermal efficiency • scale transport distance NORTH ENERGY ASSOCIATES LTD

5. The Basis for Calculations - I • Attributional Life Cycle Assessment (LCA): • European Commission’s Renewable Energy Directive (extended to biomass energy) • allocation excludes “wastes and residues” • plant, machinery and equipment manufacture and maintenance excluded • Net carbon stock changes in forest excluded: • affects each individual forest wood fuel equally • comparison between different uses of same wood fuel (not between different wood fuels) • avoids comparison of negative values NORTH ENERGY ASSOCIATES LTD

6. The Basis for Calculations - II • MS Excel workbook with 21 biomass chains: NORTH ENERGY ASSOCIATES LTD

7. The Answers: Q1 -Basics • “Do wood-fired heat and CHP plants have lower total GHG emissions than those of power only plants that use the same source of wood fuel?” • Comparing 1 MWh of heat with 1 MWh of electricity • Variations in: • thermal efficiencies (range of current values) • heat-to-power ratios for CHP plants (range of current values) • round trip transport distances (possible values by road in Scotland: • within forest = 16 km • to processing = 66 km • to end users = 80 km to 600 km NORTH ENERGY ASSOCIATES LTD

8. The Answers: Q1 – Comparison with Fossil Fuels for Domestic Heating NORTH ENERGY ASSOCIATES LTD

9. The Answers: Q1 – Comparison with Fossil Fuels for Commercial and Industrial Heating NORTH ENERGY ASSOCIATES LTD

10. The Answers: Q1 – Comparison with Fossil Fuels for Power Only Generation NORTH ENERGY ASSOCIATES LTD

11. The Answers: Q1 – Example of Wood Fuel Comparison – Forest Residues NORTH ENERGY ASSOCIATES LTD

12. The Answers: Q2 -Basics • “What is the maximum distance for delivering wood fuel to heat and CHP plants at which their total GHG emissions equal those of power only plants using the same source of wood fuel?” • Still comparing 1 MWh of heat with 1 MWh of electricity • Average values for thermal efficiencies and heat-to-power ratios (for CHP plants) • Comparative radii of supply: • “local” = 50 km • “regional” = 200 km • “national” = 500 km NORTH ENERGY ASSOCIATES LTD

13. The Answers: Q2 -Idealised Modelling - Power Only Generation (most favourable case) NORTH ENERGY ASSOCIATES LTD

14. The Answers: Q2 -Idealised Modelling – Heating and CHP Generation (typical case) NORTH ENERGY ASSOCIATES LTD

15. The Answers: Q2 – Method NORTH ENERGY ASSOCIATES LTD

16. The Answers: Q2 – Results for Forest Wood Fuels NORTH ENERGY ASSOCIATES LTD

17. The Answers: Q2 – Results for Waste Wood Fuels NORTH ENERGY ASSOCIATES LTD

18. The Answers: Q3 - Basics • “What Proportional Price Differential is required to ensure that the total GHG emissions of heat and CHP plants do not exceed those of a power only plant using the same source of wood fuel?” • Comparison of heat with electricity: • weighting of “value” of electricity to “value” of heat • Emissions Trading Scheme: • weighting = 2.0 • Proportional price differential = price of electricity/price of heat NORTH ENERGY ASSOCIATES LTD

19. The Answers: Q3 - Method NORTH ENERGY ASSOCIATES LTD

20. The Answers: Q3 – Results for National Delivery of Forest Wood Fuels NORTH ENERGY ASSOCIATES LTD

21. The Answers: Q3 – Results for National Delivery of Waste Wood Fuels NORTH ENERGY ASSOCIATES LTD

22. The Answers: Q3 – Approach in Extended Renewable Energy Directive NORTH ENERGY ASSOCIATES LTD

23. The Answers: Q4 - Basics • “Is there a GHG emissions threshold to the scale of CHP plants?” • Complex considerations: • thermal efficiency • heat-to-power ratio • weighting of value of electricity to value of heat • scale and relationship to transport distance • Simple results not possible NORTH ENERGY ASSOCIATES LTD

24. The Answers: Q4 - Outcomes • Importance of “good quality” CHP for new wood-fired plants: • minimum “power efficiency” > 20% • “Quality Index” ≥ 105 • as scale increases, higher overall thermal efficiency required • Realistic constraints on CHP scale: • heat demand • district heating? NORTH ENERGY ASSOCIATES LTD

25. The Headlines - I • On a 1 MWh heat to 1 MWh electricity basis, heat and CHP plants have lower total GHG emissions than power only plant • For electricity generation, some overlap for larger scale CHP with low overall thermal efficiencies with smaller scale power only plants with high thermal efficiencies • National supply feasible with lower total GHG emissions for roundwood pellets for domestic heating, roundwood and unclean waste wood chips for commercial and industrial heating, and roundwood and clean and unclean waste wood chips for CHP NORTH ENERGY ASSOCIATES LTD

26. Thank you for your attentionNigel MortimerE-mail:nigel.mortimer@northenergy.co.ukTel: 0114 201 2604