Patel, C; (2013) Techno-economic performance analysis and environmental impact assessment of energy production from biomass at different scales. Doctoral thesis (PhD), UCL (University College London).

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Abstract

Burning fossil fuels contributes largely to the release of CO2 emissions, which CO2 accounted for 84% of the total UK greenhouse emissions in 2009. Energy production can affect climate change because it is currently produced using non- renewable fuels. As a result the UK Government has set a target of 15% renewable energy use by 2020. Renewable energy is the production of energy using fuels that are produced and sourced sustainably. Maximising renewable energy by using alternative fuels to produce our heat and electricity can help decrease our emissions and reach Government targets. The main objective of this work is to investigate the techno-economic assessment and life cycle assessment of energy from different types of biomass in the UK context. Energy use in the UK and climate change is discussed to present a case for sustainable energy. An extensive review of the thermal treatment options, as well as the different types of biomass available in the UK has been presented. Issues related to energy from biomass such as food vs.. fuel and land vs.. fuel are also discussed. In this thesis two second generation types of biomass are individually investigated - solid recovered fuel (SRF) and forestry waste wood chips (FWWC). A techno-economic assessment was performed on small to medium scale combustion plants using SRF (50 ktpa and 100 ktpa) or FWWC (50 ktpa, 80 ktpa and 160 ktpa). These are waste forms of biomass one of which is a mixed waste source (SRF) and the other a single waste source (FWWC), of which we have a great untapped resource in the UK. Discounted cash flow analysis, internal rate of return and levelised cost for the plants are calculated. The techno-economic assessment for the SRF plants were done previously by Yassin et al., (2008) and updated in this study using new cost data, such as landfill disposal costs and the new banded ROC’s scheme. The techno-economic performance of the FWWC was devised in the same way as for the SRF plant to ensure consistency. The results showed that the small and medium scale SRF plants were technically and economically viable, whilst only the largest scale FWWC plant was economically viable. A sensitivity analysis on the economic assessment was also performed, to investigate changes in levelised cost when seven different parameters were changed by 10% and 30%. As a result of these investigations a life cycle assessment (LCA) was performed on the large scale plants to investigate environmental aspects of sustainability. Hot-spot analysis was conducted for both plants and landfill reference systems were investigated for the SRF plant, whilst the FWWC plant investigated the emissions associated with leaving wood in the forest. In addition, the plants were compared against fossil fuel alternatives at the same production scale. The results of the LCA showed that both types of biomass are more environmentally friendly than fossil fuel alternatives. The SRF hot-spot analysis showed that the Fairport Process releases the most CO2. The FWWC hot-spot analysis showed harvesting released most CO2. The work was developed further by investigating a first generation liquid form of biomass rapeseed oil (RSO) for the production of energy using internal combustion engines. RSO is grown in increasing amounts in the UK for bio-diesel production but can also be used crude to produce energy. A techno-economic assessment of energy from RSO was conducted at small (27 ktpa) to medium (40 ktpa) scale plants, using the identical methodology as above. The results found only the medium scale plant to be economically viable. A sensitivity analysis on the economic assessment was also performed using the same percentage changes as above. An LCA was performed for the 40 ktpa RSO plant. A base case was investigated and compared to the plant. A hot-spot analysis was investigated, which showed the harvesting and cultivating units released the most CO2. The effects of growing rapeseed oil and how we use our land is investigated. The results showed the plant releases least emissions when the rapeseed is grown on rotation, using reduced tillage methodology.

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