Determining Carbon Footprint of a Waste Wood Burning Power Plant

Transcription

1 Determining Carbon Footprint of a Waste Wood Burning Power Plant Arto Huuskonen Metso Corporation / MW Power Renewable Energy World Europe 2012

2 Determining Carbon Footprint of a Waste Wood Burning Power Plant 1. Backgrounds 2. Methods and scope 3. Results 4. Conclusions and recommendations

3 Determining Carbon Footprint of a Waste Wood Burning Power Plant Backgrounds Biomass is often marketed as a CO2 neutral fuel based on its relatively short carbon cycle CO2 sequestration s = 1 CO2 bound in biomass n = 1 3

4 Determining Carbon Footprint of a Waste Wood Burning Power Plant Backgrounds Biomass is often marketed as a CO2 neutral fuel based on its relatively short carbon cycle The biomass carbon cycle is however often incomplete - All biomass is not replaced by new plants - Fossil fuels are used during the acquisition and processing of biomass - Fossil fuels are used during the processing of residues from power plants CO2 CO2 sequestration s s = 11 CO2 from carbon stock changes c = n - s CO2 from fossil fuel use fp 0 CO2 from fossil fuel use fa 0 CO2 bound in biomass n = 1 Biomass is not necessarily CO2 neutral 4

5 Determining Carbon Footprint of a Waste Wood Burning Power Plant Backgrounds You can t manage what you don t measure: Managing and reducing the GHG emissions requires that their sources are known - You can manage only at the level of your measurement When determining the carbon footprint of biomass, one has to take into account the possible CO2 sequestration - The GHG emissions cannot be measured. Instead, the emissions have to be calculated based on some carbon footprint method Several methods are suggested for determining the GHG emissions of biomass based energy production - Depending on the boundary settings, the different methods can result in completely different results - No consensus exists on which is the preferable method: the European Commission for example has suggested a different method than what is used in a number of life cycle assessments (LCA) 5

6 Determining Carbon Footprint of a Waste Wood Burning Power Plant 1. Backgrounds 2. Methods and scope 3. Results 4. Conclusions and recommendations

7 Determining Carbon Footprint of a Waste Wood Burning Power Plant Methods For this study a method is used, which follows the basic guidelines of the carbon footprint method proposed by the European Commission (DIR 2009/28/EC) Some modifications are made to the EC s method for it to better suit the purpose of this study: - No emission savings have been considered - Secondary feedstock have been treated similarily as primary feedstock - Emissions from the disposal of incineration residues have been included in the calculations GHG emissions are commonly reported relative to the fuel use (kg CO2-eq/MWh fuel). This approach is however limited because it fails to take into account the benefits of combined heat and power (CHP) In this study the GHG emissions are also studied relative to the amount of energy produced (emission allocated to the produced energy based on exergetic content) 7

8 Determining Carbon Footprint of a Waste Wood Burning Power Plant Scope MW Powers Biopower 5 was chosen to be studied in detail. The calculations were done so, that they can be applied also for other types of biomass power plants The studied power plant is a modular biomass power plant with output of ca. 10MW heat and 5MW electricity. A plant integrated with a sawmill was taken as the starting point for the assessment 8

9 Determining Carbon Footprint of a Waste Wood Burning Power Plant Scope The calculations were set to cover all parts of the value chain apart from the construction of infrastructure Emissions from acquisition of fuel and supporting materials Emissions from related transportations Emissions from combustion Emissions from disposal of residues Production of auxiliary power Acquisition of biomass biomass Sawmill: Processing of biomass Emissions from harvesting Emissions from related transportations Emissions from carbon stock changes Emissions from production and use of energy Emissions from related transportations Inventory data mainly from literature power biomass Biopower 5 CEX: Combustion of biomass power thermal energy Case specific data ashes Disposal of ashes Emissions from processing of waste Emissions from decomposition Emissions from related transportations Inventory data mainly from literature At least 90% of the GHG emissions are covered 9

10 Determining Carbon Footprint of a Waste Wood Burning Power Plant 1. Backgrounds 2. Methods and scope 3. Results 4. Conclusions and recommendations

11 GHG emissions Determining Carbon Footprint of a Waste Wood Burning Power Plant Results: hot spots in the value chain GHG emissions of biomass use arise mainly from the consumption of fossil fuels - Fossil fuels are needed for the harvesting, transportation of wood, and internal transportations at sawmill and landfill 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Equal mass shares 100% bark 100% raw saw mill chips 100% saw mill cut-offs 100% tops and branches Handling of ashes Production of auxiliary power Transportation of biomass Emissions from carbon stock changes Processing of biomass Acquisition of biomass High energy conversion efficiency minimizes the fuel consumption Minimized consumption of fossil fuels relative to the produced energy Minimized GHG emissions relative to the produced energy 11

12 GHG emissions kg CO2-eq/MWh fuel Determining Carbon Footprint of a Waste Wood Burning Power Plant Results: effects of deforestation GHG emissions of biomass: effects of sustainable forest management Hard coal Natural gas Biopower 5, no deforestation Biopower 5, 10% deforestation Biopower 5, 50% deforestation Sustainable forest management ensures power production with low GHG emissions. High energy conversion efficiency minimizes the risk of adverse impacts related to raw material acquisition by minimizing the amount of required fuel 12

13 Determining Carbon Footprint of a Waste Wood Burning Power Plant Results: impacts of integration with industrial processes GHG emissions of biomass: benefits of integrated biomass supply 400 % 350 % 300 % 250 % 200 % 150 % 100 % 50 % 0 % Fully integrated power plant (reference case) Partially integrated power plant Fully separated power plant Integrating power plants with sources of forest residues etc. significantly reduces the GHG emissions 13

14 GHG emissions kg CO2-eq / 1MWh electricity + 2,22 MWh thermal energyl Determining Carbon Footprint of a Waste Wood Burning Power Plant Results: benefits of cogeneration of heat and electricity GHG emissions of biomass: benefits of cogeneration when compared to dedicated power and heat production Biopower 5, no deforestation Wind power + heavy fuel oil w. 50% solar thermal energy Wind power + heavy fuel oil Biomass is an optimal solution when both electricity and thermal energy are required: biomass can help achieve GHG emission reductions even if it replaces fossil fuels only in the production of thermal energy. 14

15 Determining Carbon Footprint of a Waste Wood Burning Power Plant 1. Backgrounds 2. Methods and scope 3. Results 4. Conclusions and recommendations

16 Determining Carbon Footprint of a Waste Wood Burning Power Plant Conclusions and lessons learned Biomass is not CO2 neutral, but its CO2 emissions are still small compared to those of fossil fuels Up to 98% GHG emission savings can be achieved by using biomass for energy production Biomass carbon footprint is dominated by emissions resulting from acquisition, processing and transportation of fuel The solutions for coping with sustainability issues of biomass in general provide also a way for managing GHG emissions - Sustainable forest management The GHG emissions are 98% smaller when no deforestation occurs compared to situation with 100% deforestation rate - High energy conversion efficiency Cogeneration can help achieve emission reductions of over 90% even when replacing fossil fuels only in the production of thermal energy Also integration with industrial processes and careful consideration of local needs can help reduce the GHG emissions 16

17 Determining Carbon Footprint of a Waste Wood Burning Power Plant Recommendations for decreasing the carbon footprint What can Metso and MW Power do to minimize the GHG emissions of biomass power plants? - Maximization of energy conversion efficiency - High fuel flexibility to enable versatile feedstock use - Provision of transparent information for customers and power plant operators What can power plant operators do to minimize GHG emissions? - Application of most suitable technology - Careful design of logistics and interactions between processes - Efficient supply chain management 17

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