COP21 guest blog – Robert White, PhD student

Rob White is a first year PhD student in the Bioenergy Centre for Doctoral Training, and his work is focusing on biodiesel.

Biodiesel is a renewable transport fuel which is mainly produced from plant oils or vegetable fats. Nearly all heavy duty industrial machinery and some civilian cars utilise diesel engines, resulting in a global dependence upon fossil diesel. Significant reductions in greenhouse gas (GHG) emissions are observed when biodiesel is used as a transport fuel when compared to the equivalent of fossil diesel. By utilising more sustainably produced biodiesel, the contribution to climate change from the transport sector can be reduced1.

A current issue with biodiesel is the by-product glycerol. Fats are reacted with methanol over a catalyst to produce biodiesel and glycerol. For every ton of biodiesel 10%wt of glycerol is produced. Since biodiesel production has increased from ~one million tons in 2007 to five million tons in 2015 and is set to rise there is an excess of glycerol. Consequently the price of crude and refined glycerol has fallen to the point where it is unprofitable and a waste product in the current market. This increases the price of biodiesel make it a non-competitor for higher GHG producing fossil diesel.robs diagram

Figure 1 –  Trans-esterification of triglycerides (fat) to produce biodiesel and crude glycerol where R1-R3 are long chain hydrocarbons 2.robs graph

Figure 2 – World biodiesel and glycerol production from 2007-2023, adapted using data from the OECD biofuels outlook 3,4

A proposed solution to this problem is using glycerol as a feedstock in a reforming method to generate syngas. Reforming methods break down carbon rich feedstocks into more useful gases such as hydrogen. Investigations on the use of steam reforming have been popular to generate hydrogen rich syngas because it is a method with a strong industrial background from coal, methane and heavy oil reforming.

On the other hand, my work is focussed on generating a methane rich syngas from steam reforming of glycerol. This method requires different catalysts and supports at lower temperatures to favour the methane producing thermodynamics. The proposed syngas can be burned in the refinery to lower operating costs. This area has received little attention as hydrogen has many industrial applications such as the Haber process to generate ammonia and the promise of hydrogen fuel cells and a hydrogen economy in the near future.

To generate a methane rich syngas a thorough understanding of the steam reforming, water gas shift and methanation reactions is required (1) – (5).

 

robs reactions

Utilising Le Chatelier’s principle, the endothermic and exothermic reactions and appropriate catalysts will be crucial in manipulating the equilibrium to give the desired methane rich syngas. My current focus is determining which catalysts to use for my project by literature review.

 

  1. Basha, S. A., Gopal, K. R. & Jebaraj, S. A review on biodiesel production, combustion, emissions and performance. Renew. Sustain. Energy Rev. 13, 1628–1634 (2009).
  2. Encinar, J., Gonzalez, J., Pardal, A. & Martinez, G. Transesterification of rapeseed oil with Methanol in the presence of Various co-solvents. Proc. Venice (2010). at <http://scholar.google.com/scholar?hl=en&btnG=Search&q=intitle:TRANSESTERIFICATION+OF+RAPESEED+OIL+WITH+METHANOL+IN+THE+PRESENCE+OF+VARIOUS+CO-SOLVENTS#0>
  3. Biofuel Systems Group Ltd. Biodiesel Standards. (2013). at <http://biofuelsystems.com/standards.html>
  4. OECD. OECD-FAO Agricultural Outlook 2014. (OECD Publishing, 2014). doi:10.1787/agr_outlook-2014-en
  5. Azizan, M. T. Steam Reforming of Oxygenated Hydrocarbons for Hydrogen Production. (Imperial College London, 2014). at <https://spiral.imperial.ac.uk/handle/10044/1/24675>