Application of microwaves on the production of liquid biofuels

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.

The project could have significant impacts for biofuel producers and across the wider biobased industry, as well as society and the public sector. The major short-term contribution will be to improve the scientific understanding of the microwave-assisted biomass-to-liquids (MWBtL) process. The underpinning aim is to confirm the microwave technology as a route for process intensification, allowing simpler equipment and shorter processing time compared to current technologies. The project will deliver evidence of the feasibility of the application of microwave heating to biofuel production in the lab-scale environment. This will increase confidence in the public and private sectors to further invest in the validation and demonstration of the technology in a relevant environment.
The project offers an opportunity to develop new processing capabilities for the production of biofuels. Biofuel producers will benefit from the development of the MWBtL technology through the availability of a new and cost-effective biomass-to-liquid (BtL) route that will allow them to enlarge their product portfolio and offer lower prices. The confirmation of MWBtL as a feasible technology will increase the use of microwaves as the platform technology in other conversion processes within the biobased sector. Microwaves also have potential in processes such as biomass drying, energy from waste, feedstock pretreatment prior anaerobic digestion and bioethanol synthesis, transesterification for biodiesel production, or biochar production. The successful implementation of the MWBtL process has the potential to impact on the development of energy storage systems for intermittent renewable energy, and benefit the growth of the clean technologies sector. Since the electricity required for the generation of microwaves can be produced from renewable energy such as wind and solar power, the MWBtL and renewable sources could be combined through a chemical energy transmission system. In this system any excess electricity produced during peak periods could be used to generate the microwave radiation required for the MWBtL process, and stored as chemical energy in the resulting biofuel, which could be then combusted to recover the energy during valley periods or used elsewhere. The manufacturers of microwave systems for industrial applications of microwave energy will benefit through the expansion of the knowledge, which will enable them to improve the design of microwave devices when applied to liquid-solid reaction systems.
End-users of fuels in the road transport, aviation and shipping will benefit from the project through the availability of environmentally friendly biofuels. They could access more affordable fuels as the enlargement of the BtL technological portfolio favours the penetration of biofuels into the UK transport sector and increases competitiveness among producers. The public sector could take advantage through aiding the deployment of MWBtL biofuels that contribute to meeting the targets on reducing greenhouse gas emissions, increasing use of renewable energy, and increasing energy efficiency. The public sector will also benefit through the contribution of the project to the realisation of the bioeconomy strategy, which has become integral part of the UK's political agenda because it contributes to priorities such as economic growth, job creation, climate change, innovation, and sustainability. The research could increase the national wealth by positioning the UK industrial sector as leader on the application of microwaves to industrial processing. The processing breakthroughs and new knowledge on the microwave technology are applicable beyond biobased and renewable energy processes. Sectors such as oil and gas, mineral and polymer processing, pharmaceutical and fine chemicals synthesis, or food processing, to name some examples, can benefit of the consolidation of microwaves as alternative heating source to conventional electric and gas heaters.