American Centre for Life Cycle Assessment LCA VIII 30 September - 2 October 2008, Seattle A Life Cycle Assessment of small to medium sized heat producing bio-energy systems Marcelle McManus* David Lewis * Corresponding Author M.McManus@bath.ac.uk DLewis@rac.ac.uk
Contents Drivers and context for bioenergy Bioenergy options Case studies Energy paybacks Comparisons with other small renewables
Drivers for Bio-energy Kyoto Renewable Energy Targets Fuel Security RTFO (in Europe) Easy to use with current infrastructure and technology
Bio-heat and bio-fuel Much research focused on the use and production of bio-fuel (in the UK road transport accounts for approximately 22% GHG emissions, and heat and power production 37%) Bio-heat is often used on a very small scale New builds sometimes want bio-heat but are concerned with emissions
Resources Conversion Technology Fuel Use Arable/Annual Crops Oil Seed Rape Cultivation, harvesting, transport etc Pressing/ Esterification Enzymatic Transesterification Bio-Diesel Wheat Maize Sugarbeet Hydrolysis/ Fermentation Ethanol (1 st and 2 nd Generation) Bio-Oil Vehicles Potatoes Pyrolysis FT- Diesel Herbaceous Perennials Miscanthus Gasification DME (dimethyl ether) Switchgrass Methanol Reed canary grass Woody Perennials Digestion Hydrogen Short Rotation Coppice Pine/Spruce Bio-Methane Residues & Wastes Forest Residues Co-firing Heat Straw Organic Municipal Waste Waste fats and oils Small scale burning Large scale burning Electricity
Resources Conversion Technology Fuel Use Arable/Annual Crops Oil Seed Rape Cultivation, harvesting, transport etc Pressing/ Esterification Enzymatic Transesterification Bio-Diesel Wheat Maize Sugarbeet Hydrolysis/ Fermentation Ethanol (1 st and 2 nd Generation) Bio-Oil Vehicles Potatoes Pyrolysis FT- Diesel Herbaceous Perennials Miscanthus Gasification DME (dimethyl ether) Switchgrass Methanol Reed canary grass Woody Perennials Digestion Hydrogen Short Rotation Coppice Pine/Spruce Bio-Methane Residues & Wastes Forest Residues Co-firing Heat Straw Organic Municipal Waste Waste fats and oils Small scale burning Large scale burning Electricity
Tree cuttings Remainder of wood sold to slough heat and power or sold for composting Chipping process (total wood produced?) and wood store Hire of chipper (percentage of production?) Production and Materials 300 tonnes required March May with an estimated 100 tonnes required for the rest of the year (weather dependant) Backup LPG and oil boilers (to be replaced with new oil fired boiler) Electricity used during use Boiler and insulated piping Ash disposal Data for the backup boiler not included in this study Boiler maintenance LPG Boiler (500,000kwh/yr / 70,000litres/yr LPG) Avoided heat and associated avoided impacts Heat produced and used in plant nursery (heat requirement 650,000kWh/yr) Oil boiler (150,000kWh/yr / 7000litres/yr oil)
Boundaries and concept Is it a waste study? Or is it an energy study? Differing boundaries would result in differing outcomes If CO2 emissions and uptake are considered at every stage (as suggested by Rabl et al) then boundary issues become significant Is the waste attributable to the park (how does one evaluate parkland?)
Normalised 400 600 kwh Boiler 7 6 5 4 3 2 1 Production 0 Carcinogens Resp. organics Resp. inorganics Climate change Radiation Ozone layer Ecotoxicity Acidification/ Eutrophication Land use Minerals Fossil fuels Low alloy steel Fireclay High alloy steel Synthetic rubber Stainless steel Transport Welding
Avoided Burdens Avoided burdens widely applied as an allocation method, and implicitly supported by ISO 14041 However, this doesn t necessarily make it right (Heijungs & Guinee, (2007)) How do we compare what is happening with what would have happened? Is it acceptable in biomass situations to compare the use of biomass with the use of the alternative?
Normalised Data for the use of the Nursery for one year 12 10 8 6 4 2 0-2 -4 Carcinogens Resp. organics Resp. inorganics Climate change Radiation Ozone layer Ecotoxicity Acidification/ Eutrophication Land use Minerals avoided annual energy boiler production insulated piping annual emissions annual woodchips
Normalised Data for the Fossil Fuel Impacts associated with the use of the nursery for one year 10 0-10 -20-30 -40-50 -60-70 avoided annual energy boiler production insulated piping annual emissions annual w oodchips Fossil fuels
Normalised Data for the impacts associated with 15 years of use 200 0-200 -400-600 -800-1000 Carcinogens Resp. organics Resp. inorganics Climate change Radiation Ozone layer Ecotoxicity Acidification/ Eutrophication Land use Minerals Fossil fuels avoided energy boiler production insulated piping emissions woodchips
Normalised Data Comparing Differing loading for the 400 600 kwh boiler 7 6 5 4 3 2 1-1 0-2 -3 Carcinogens Resp. organics Resp. inorganics Climate change Radiation Ozone layer Ecotoxicity Acidification/ Eutrophication Land use avoided annual energy boiler production insulated piping low load annual emissions mid load annual emissions full load annual emissions annual w oodchips Minerals
Emissions at lower loads Lower loads on this boiler produce fewer emissions If concerned by emissions (although does still meet legislation at higher emission levels) might possibly use larger boiler than required? What would the impact be?
Normalised Smaller Boiler Production 2.5 2 1.5 1 0.5 0 Carcinogens Resp. organics Resp. inorganics Climate change Radiation Ozone layer Ecotoxicity Acidification/ Eutrophication Land use Minerals Fossil fuels Low alloy steel Fireclay High alloy steel Synthetic rubber Stainless steel Transport Welding
Characterised Data for the Use of smaller the boiler over a year in a recreation site 100% 80% 60% 40% 20% 0% -20% -40% -60% -80% -100% Carcinogens Resp. organics Resp. inorganics Climate change Radiation Ozone layer Ecotoxicity Acidification/ Eutrophication Land use Minerals Fossil fuels annual avoided energy use boiler production annual woodchips
Normalised Data for the Use of the boiler over a year 2 1.5 1 0.5 0-0.5-1 Carcinogens Resp. organics Resp. inorganics Climate change Radiation Ozone layer Ecotoxicity Acidification/ Eutrophication Land use Minerals annual avoided energy use boiler production annual woodchips
Comparison of the two Boilers 10 0-10 -20-30 -40-50 -60-70 Carcinogens Resp. organics Resp. inorganics Climate change Radiation avoided annual energy for larger boiler w oodchips for larger boiler smaller boiler production Ozone layer Ecotoxicity Acidification/ Eutrophication Land use Minerals Fossil fuels larger boiler production avoided annual energy use for smaller system w oodchips for smaller system
Carcinogens Resp. organics Resp. inorganics Climate change Radiation Ozone layer Ecotoxicity Acidification/ Eutrophication Land use Minerals Comparison of the two Boilers (2) 4 3 2 1 0-1 -2-3 avoided annual energy for larger boiler w oodchips for larger boiler smaller boiler production larger boiler production avoided annual energy use for smaller system w oodchips for smaller system
Carcinogens Resp. organics Resp. inorganics Climate change Radiation Ozone layer Ecotoxicity Acidification/ Eutrophication Land use Minerals Normalised comparison of differing transport distances over a 15 year lifetime 120 100 80 60 40 20-20 0-40 avoided total energy boiler production total emissions total woodchips annual woodchips- transport x2 annual woodchips - transport x10
Energy Payback Small boiler approximately four months Large boiler approximately six months Comparison solar thermal (small household size) between two and three years
Concluding Remarks Using waste wood the embodied energy of both systems is paid back very quickly when comparing the systems with the alternative heating system Increasing the transportation distance in this case did not have a significant impact Emissions during the life time is the most significant negative impact, but the boilers still do comply with clean air legislation Emission data is not consistent with different loadings