Including Impacts of Particulate Emissions on Marine Ecosystems in Life Cycle Assessment: The Case of Offshore Oil and Gas Production Karin Veltman,y* Mark AJ Huijbregts,z Henrik Rye,§ and Edgar G. Hertwichy yIndustrial Ecology Programme, Norwegian University of Science and Technology (NTNU) Høgskoleringen 5, NO-7491, Trondheim, Norway zDepartment of Environmental Science, Radboud University Nijmegen, Nijmegen, the Netherlands §Marine Environmental Technology, SINTEF Materials and Chemistry, Trondheim, Norway (Submitted 19 January 2011; Returned for Revision 31 March 2011; Accepted 7 June 2011) ABSTRACT Life cycle assessment is increasingly used to assess the environmental performance of fossil energy systems. Two of the dominant emissions of offshore oil and gas production to the marine environment are the discharge of produced water and drilling waste. Although environmental impacts of produced water are predominantly due to chemical stressors, a major concern regarding drilling waste discharge is the potential physical impact due to particles. At present, impact indicators for particulate emissions are not yet available in life cycle assessment. Here, we develop characterization factors for 2 distinct impacts of particulate emissions: an increased turbidity zone in the water column and physical burial of benthic communities. The characterization factor for turbidity is developed analogous to characterization factors for toxic impacts, and ranges from 1.4 PAF (potentially affected fraction) m 3 /d/kg p (kilogram particulate) for drilling mud particles discharged from the rig. The characterization factor for burial describes the volume of sediment that is impacted by particle deposition on the seafloor and equals 2.0  10 1 PAF m 3 /d/kg p for cutting particles. This characterization factor is quantified on the basis of initial deposition layer characteristics, such as height and surface area, the initial benthic response, and the recovery rate. We assessed the relevance of including particulate emissions in an impact assessment of offshore oil and gas production. Accordingly, the total impact on the water column and on the sediment was quantified based on emission data of produced water and drilling waste for all oil and gas fields on the Norwegian continental shelf in 2008. Our results show that cutting particles contribute substantially to the total impact of offshore oil and gas production on marine sediments, with a relative contribution of 55% and 31% on the regional and global scale, respectively. In contrast, the contribution of particulate emissions to the total impact on the marine water column is of minor importance. We conclude that particles are an important stressor in marine ecosystems, particularly for marine sediment, and particulate emissions should therefore be included in a (life cycle) impact assessment of offshore oil and gas production. Integr Environ Assess Manag 2011;7:678–686. ß 2011 SETAC Keywords: LCA Characterization factors Offshore oil and gas production Particulate emissions Marine ecosystems INTRODUCTION Fossil fuel is predicted to dominate energy consumption up to 2035 (EIA 2010). To make up for reduced production from maturing fields, oil and gas exploration activities on the Norwegian continental shelf have increased dramatically in the last 2 years (OLF 2009). Strict emissions controls have resulted in a substantial emission reduction of hazardous chemicals in the period 1997 to 2007 (SFT 2008). However, during oil and gas exploration and production, large quantities of particles are emitted to sea, which can also adversely affect marine ecosystems (Patin 1999; Smit et al. 2008). Commonly used impact assessment methods, such as life cycle assessment (LCA), do not yet include impacts from particulate emissions on aquatic ecosystems. Because LCA is increasingly used to assess the environmental performance of fossil energy systems, the incorporation of physical impacts due to particulate emissions to water can be of importance. Two of the dominant emissions of offshore oil and gas exploration and production to the marine environment are the discharge of produced water and drilling waste (Neff 2008; OLF 2009). Although environmental impacts of produced water are predominantly due to chemical stressors, such as polycyclic aromatic hydrocarbons (PAHs) and metals, a major concern regarding drilling waste is the potential physical impact due to particles (Patin 1999; Neff 2005; Smit et al. 2008). Drilling waste consists broadly of 2 components: drill cuttings and drilling mud. Drill cuttings are particles of crushed rock carved out of the well during drilling. Drilling mud is a specially formulated mixture consisting of a high- density mineral, such as barite or ilmenite, and various additives suspended in water or an organic fluid phase (Patin 1999; Neff 2005). It is an essential element in modern drilling technology, serving various functions, such as transportation of drill cuttings to the surface, cooling and supporting the drill pipe and bit, balancing subsurface and formation pressures, and preventing a blowout (Neff 2008). Drilling mud is usually reprocessed and recycled during drilling. However, when the mud characteristics are altered, it may be discharged to the environment, reinjected into a well, or transported onshore for reprocessing or disposal (as hazardous waste). The mode of disposal, and consequential environmental impacts, depend Integrated Environmental Assessment and Management — Volume 7, Number 4—pp. 678–686 678 ß 2011 SETAC * To whom correspondence may be addressed: karin.veltman@ntnu.no Published online 6 July 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/ieam.246 Life Cycle & Sustainability