Purpose: To date, very few studies have attempted to quantify the environmental impacts of a wave energy converter, and almost all of these focus solely on the potential climate change impacts and embodied energy. This paper presents a full life cycle assessment (LCA) of the first-generation Pelamis wave energy converter, aiming to contribute to the body of published studies and examine any potential trade-offs or co-benefits across a broad range of environmental impacts. Methods: The process-based attributional LCA was carried out on the full cradle-to-grave life cycle of the Pelamis P1 wave energy converter, including the device, its moorings and sub-sea connecting cable up to the point of connection with the grid. The case study was for a typical wave farm located off the north-west coast of Scotland. Foreground data was mostly sourced from the manufacturer. Background inventory data was mostly sourced from the ecoinvent database (v3.3), and the ReCiPe and CED impact assessment methods were applied. Results and discussion: The Pelamis was found to have significantly lower environmental impacts than conventional fossil generation in 6 impact categories, but performed worse than most other types of generation in 8 of the remaining 13 categories studied. The greatest impacts were from steel manufacture and sea vessel operations. The device performs quite well in the two most frequently assessed impacts for renewable energy converters: climate change and cumulative energy demand. The carbon payback period is estimated to be around 24 months (depending on the emissions intensity of the displaced generation mix), and the energy return on investment is 7.5. The contrast between this and the poor performance in other impact categories demonstrates the limitations of focussing only on carbon and energy. Conclusions: The Pelamis was found to generally have relatively high environmental impacts across many impact categories when compared to other types of power generation; however, these are mostly attributable to the current reliance on fossil fuels in the global economy and the early development stage of the technology. Opportunities to reduce this also lie in reducing requirements for steel in the device structure, and decreasing the requirements for sea vessel operations during installation, maintenance and decommissioning.

Waste-to-biomethane generation can supply 47% of India's electricity, 91% of transportation fuels, or all cooking fuels, while removing between 284 and 524 million tonnes of carbon dioxide-equivalent of greenhouse gases.

The continued drive to reduce Greenhouse Gas (GHG) emissions in order to mitigate climate\ud change has led to an increase in demand for low-carbon energy sources, and the development\ud of new technologies to harness the available energy in the wind, waves and tides. Many controversies\ud surround these technologies, however, particularly with regards to their economic cost,\ud environmental impacts and the implications of the variability of their output for security of the\ud electricity supply. In order to make informed policy decisions on future developments of the\ud electricity system, it is necessary to address these controversies and confirm the environmental,\ud economic and social sustainability of these new renewable generators.\ud This thesis specifically examines two key issues: whether new variable-output renewable energy\ud generators actually deliver a net reduction in greenhouse gas emissions over their lifetimes,\ud and whether they produce a viable energy return on energy investment. Although renewable\ud energy sources are themselves ‘carbon free’, GHG emissions (and energy consumption) occur\ud during the construction, maintenance and decommissioning of the generator infrastructure\ud required to convert this energy into electricity. Furthermore, the variability of the output power\ud from such generators has implications for the operation of the grid - there may be a requirement\ud for additional reserve capacity and the increased part-loading of conventional plant is likely to\ud reduce its operating efficiency. Carbon and energy paybacks are measures of the time required\ud for a new renewable installation to offset these life cycle impacts. The work presented in this\ud thesis examines both the life cycle impacts and the GHG emissions displacement of variable\ud renewable generation, using Great Britain as a case study, in order to provide a basis for\ud significantly more robust and reliable estimates of carbon and energy paybacks.\ud The extensive literature survey concentrates on two key areas: current calculation methodologies\ud and estimates for life cycle carbon and energy consumption of power generators; and\ud the marginal emissions displacement of variable renewable generation. A detailed life cycle\ud assessment of the Pelamis wave energy converter is presented, which sets the embodied carbon\ud and energy in the context of the wider environmental impacts and includes an examination\ud of the effect of different assumptions on the analysis results. In order to investigate the true\ud emissions displacement of renewable generation, a historical analysis of real data from the\ud National Grid was carried out, identifying the marginal displacement factor of wind power and\ud taking into account the effect of the efficiency penalties of conventional plant. The findings\ud of the analyses presented in this thesis are combined with information from the literature to\ud examine the actual carbon and energy payback of existing renewable generation infrastructure\ud on the British grid, and to provide detailed recommendations for future carbon and energy\ud payback calculations

Wave energy has the potential to play an important role in the UK's electricity mix in the coming years and it is important to understand the interactions of wave energy converters with the environment before considering them viable alternatives for other technologies. The aim of this study was to identify the environmental impacts of the deployment of the Oyster wave energy converter to the EMEC test site at Orkney, UK over its lifetime across three general categories: resource use, human health and ecological consequences. A full life cycle assessment was performed on two different models of the Oyster wave energy converter: Oyster 1 and Oyster 800. It was found that the latter is a fitting upgrade for its predecessor as it has lower environmental impacts in all categories; however, the high infrastructural needs of the Oyster technology makes its environmental performance worse than most other wave energy converters. Key sustainability indicators for energy converters include carbon footprint and energy payback period, and these were found to be 79 and 57 gCO₂ eq/kWh and 45 and 42 months for the Oyster 1 and Oyster 800, respectively. Although these are significantly higher than most estimates for other types of renewable energy converter, the carbon impacts are still significantly lower than for conventional fossil-fuelled power generation.