1 year ago

Climate Action 2010-2011


SPECIAL FEATURE | Drax the environment in which the biomass is cultivated and harvested; the forest management techniques used; any resulting changes in land use; and the period of time over which the GHG implications are examined. Establishing a lifecycle emissions standard for biomass is a transparent way of demonstrating the true carbon savings of electricity generated from biomass. At Drax we call this a ‘Field to Furnace’ assessment. Specifically, we require that 100 per cent of our biomass fuel passes a rigorous analysis of its lifecycle CO 2 emissions across the supply chain, from harvesting and cultivation through combustion. Further, we also stipulate that all of the biomass fuel we purchase delivers a CO 2 reduction of at least 70 per cent over the Drax coal-fired plant, currently the most efficient such plant in the UK. The European Union and UK government are both targeting a similar reduced CO 2 standard of 285kg CO 2 /MWh (carbon dioxide per megawatt-hour), for biomass generation, compared to the European fossil plant average of 713kg CO 2 /MWh. Our ‘Field to Furnace’ assessment also underpins the importance of selecting markets, suppliers and fuels that best fit the scale and technology of a particular project. There are three areas where the lifecycle CO 2 emissions analysis of biomass takes place: 1. The field (planting, cultivation and harvesting) At Drax we seek to source as much of our biomass material as we can locally. However, the limited land mass and large demand for renewable energy in the UK requires us to take a global approach to sustainable fuel sourcing. We also believe it is important to maintain diversity in our biomass fuel portfolio and not overburden any one market for all our fuel needs. While the production and diversity of biomass fuels available for energy production is enormous, many of these fuels are wastes or by-products of other existing industries. For example, forestry lands are managed primarily for lumber production and agricultural lands are primarily managed for higher value food crops. The secondary products from these operations – such as tree tops and branches, bark, and thinnings from forestry and byproducts such as straw, seed husks, and bagasse from agriculture – are usefull biomass fuels. Utilisation of these materials for power generation ensures an effective use of their intrinsic carbon. Residual materials that are wastes or by-products of other primary industries, offer additional greenhouse gas (GHG) reduction benefits in that the lifecycle GHG assessment generally demonstrates little or no additional emissions for their planting, cultivation and harvesting. 2. The supply chain: processing and transportation The most efficient and convenient means of bulk transportation, storage and handling of biomass involves removing excess moisture and compressing the material into a dense pellet as near to the point of origin as possible. The additional costs and CO 2 emissions associated with this pellet-making process are taken into account in the overall lifecycle emissions assessments but are typically offset by reduced transportation/handling costs and decreased GHG emissions, which in turn can provide an overall benefit in terms of the lifecycle emissions. It is also common to find pellet processing facilities that utilise a portion of the biomass fuel to run some of the more energy intensive processing equipment. When sourced sustainably, electricity generated from biomass can achieve significant carbon savings over the least carbon intensive fossil fuel plant. When transporting large volumes of material the distance travelled is far less important than the mode of transportation. As illustrated in Figure 1, bulk marine transportation is the least carbon intensive mode of transportation available. This is because of the substantial volume of material that can be transported Figure 1. Shipping costs: cash and carbon. Carbon emission factors taken from the UK’s Department for Environment, Food and Rural Affairs’ (Defra) 2008 annexes to the guidelines for Defra’s GHG Conversion Factors. Cost factors are based on freight calculators and pricing quotes from freight companies. | 20 |

SPECIAL FEATURE | Drax Figure 2: Greenhouse gas comparison of imported versus domestic biomass. Figure 3: Fuel life cycle emissions (in kg CO 2 /MWh). References: (1) UK Department of Energy and Climate Change (ROO 2011) July 2010. (2 & 3) Friends of the Earth (Cymru) June 2004. (4) European Commission. SEC (2010) 65, SEC (2010) 66. (5) Environmental Agency. by each ocean-going vessel. For example, the electricity produced by Drax using biomass pellets that have been transported 17,000 km from Western Canada to the UK would generate a total carbon footprint of 191kg CO 2 / MWh. A similar assessment conducted for the electricity produced by the same volume of biomass, but this time transported by truck a distance of 335 km from Scotland to the Drax power station in North England, (returning empty), would generate a total carbon footprint of 184kg CO 2 /MWh. The breakdown of these two examples is shown in Figure 2. Despite the transportation distance being over 25 times greater from Western Canada than from Scotland, the lifecycle GHG emissions from the delivered biomass are similar. Such analysis underpins the investment Drax is making in specially designed rail wagons to increase volume stowage and further reduce the environmental impact of domestic logistics. 3. The furnace (fuel handling and combustion) The final stage of converting biomass material into electrical energy involves transferring the fuel from storage to the boiler, combusting the biomass to generate steam which drives the turbines and then disposing of the ash. The relatively small amount of GHGs emitted in this stage are from milling the biomass pellets into finer particles and the small amount of GHGs emitted from the stack during the combustion. It is at this final stage that the benefits of predictable around-the-clock generation can be realised. Biomass generation is one of the few large-scale renewable technologies that can effectively substitute non-renewable generation (from gas, coal and provide important baseload support to other intermittent and seasonal forms of renewable generation (wind, solar, wave and small hydro). When using methodologies for assessing the lifecycle impacts of biomass, it is appropriate to set the resulting data in the context of emissions from other demanddriven generating technologies. As illustrated in Figure 3, these values are 440-695 and around 1,000kg CO 2 /MWh of electricity produced, for gas- and coalbased generation respectively. In this example, it is clear that even when assessing lifecycle emissions associated with importing biomass from the Pacific Ocean to the UK, the use of that biomass still offers undeniable benefits as an alternative to existing fossil fuel generation technologies. Sustainability throughout the supply chain Regardless of whether biomass fuel is foreign or domestic, the fact remains that when sourced sustainably, electricity generated from biomass can achieve significant carbon savings over the least carbon intensive fossil fuel plant. The many benefits of biomass are also an ideal fit for markets such as the UK where security of supply, firm capacity and renewable energy are all key objectives. Biomass is a diverse, well-proven and plentiful fuel source but it is not without its challenges. We cannot take its carbon benefits for granted. There is also more to biomass sustainability than simply measuring the GHGs of fuel across a supply chain. At Drax additional emphasis is placed on implementing a wide-ranging set of environmental, social and ethical principles and work proactively with our suppliers to ensure best practices are followed. The effort to combat climate change is a global challenge and one that requires transparency and care in how energy companies source and process their biomass material – from ‘Field to Furnace’. Drax is a power generation business responsible for meeting some 7 per cent of the electricity demand in the UK. Drax is actively pursuing a strategy of carbon abatement through efficiency improvements in the use of sustainable biomass as a substitute for fossil fuels and has recently commissioned the world’s largest biomass co-firing facility in North England. Drax Power Ltd. Drax Power Station Selby, North Yorkshire YO8 8PH, UK Tel: 01757 618381 Website: | 21 |