Application of microwaves on the production of liquid biofuels

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The Climate Change Act 2008 set the challenging goal of reducing the UK greenhouse gas emissions (GHG) by 80% by 2050. The road transport, aviation, and shipping emit approximately 33% of UK greenhouse emissions, and the sector consumes around 38% of the total final energy consumption. The UK Government has acknowledged the key role of the use of biofuels, fuels made from renewable sources such as biomass and waste, in order to decarbonise transportation and ensure energy security.Fast pyrolysis is consolidating as route for conversion of non-edible biomass into liquids (bio-oil) that can be used as biofuel precursors. The bio-oil presents a much higher content in oxygen than the crude oil (10-40 wt.% of oxygen in the former compared to < 1 wt.% of O in the latter). And because of this oxygen content, it is not compatible with the petroleum-derived fuels and infrastructure (pipelines, processing units, engines...) currently used. Therefore, the bio-oil requires upgrading stages to remove the oxygen before being applicable in the existing systems. The addition of the upgrading stages makes the biomass-to-liquid process more complex and incurs in higher capital and operating costs. Technological breakthroughs are now required for clean and affordable biofuels to become available. This project sets out a new approach: using microwaves to heat simpler and more efficient processes for the production of biofuels from biomass. Microwaves applied to chemical reactions have shown similar advantages to those that anybody can observe when heating a glass of milk in the household microwave or on the stove. The microwave oven is faster and cleaner. In addition, for the particular application of microwave pyrolysis of biomass, bio-oil with lower oxygen content has been produced. But there is not systematic study which shows the advantages of using microwave pyrolysis. So in this project we aim to understand how changes in temperature or reaction time have an influence on the amount of the produced bio-oil and its composition (oxygen content). We are also testing the hypothesis that microwaves can aid the catalytic upgrading process to enhance the quantity and quality of the produced biofuel compared to conventional upgrading. There is virtually no work done on the microwave upgrading of bio-oil. But good results are expected based on the results from microwave pyrolysis and some studies on microwave upgrading of petroleum fractions; those have shown that better oil is produced compared to conventional processes. The hypothesis will be tested through a programme of laboratory experiments. If microwaves can be demonstrated to produce an upgraded bio-oil with lower oxygen content at similar (or better) operating conditions than conventional processes then it is a more efficient process and, when scaling it up, will potentially be more economic and sustainable.Developing the microwave-assisted biomass-to-liquid process as an economic and sustainable route for biofuel production will benefit the penetration and cost of biofuels into the UK transport sector. Microwaves can have an impact in the development of clean technologies as it can be coupled with other renewable energy technologies. Microwaves are generated from electricity. GHG emissions can be avoided when using microwaves if the electricity required for their generation is produced from renewable energy sources such as wind and solar power. Moreover, the applicability of microwave heating is huge and extendable beyond the biomass conversion; it can be used in multiple sectors, from pharmaceutical processes to production of plastics. Overall, the knowledge gathered during this project will impact the development of microwaves applied to industrial processes and will help the UK industrial sector to position itself as world leaders in the use of this technology in the mid- and long-term.