The UK government is exploring the potential viability of a different pathway to a diesel-biofuel blend by issuing a tender to encourage refineries or other companies to investigate the use of hydrogenation.
Hydrogenation is a process in which biomass is mixed with conventional diesel through heating in the refinery process in such a way as to create a product chemically very similar to petroleum diesel, but somewhat more environmentally friendly.
This Government is committed to encouraging the development of greener fuels. Thanks to the duty incentives we have introduced over the last few years, the use of biofuels in the UK has grown from almost nothing to nearly 9 million litres of fuel a month.
...We intend to lead the rest of Europe in [hydrogenation] by encouraging, in partnership with refiners, the development of this process.
Hydrogenation could provide greener road fuel on a larger scale for motorists in the UK. This invitation to bid for Government support will help us to test the potential of a biomass-based fuel.—John Healey, Financial Secretary to the Treasury
The invitation to tender invites applicants to bid for Government support in the form of duty concessions to run such pilot schemes. The Government intends to use data collected from any such project to help inform its future policy on support for hydrogenation.
The UK does not intend to replace the current duty incentive for biodiesel with the incentive for the hydrogenation process. Conventional biofuels manufacturers will be able to continue to produce bioethanol or biodiesel and take advantage of the 20p per liter duty incentive for these fuels.
The UK government appears to view the hydrogenation process as an alternative route that would involve giving refiners a reduction for each liter of diesel produced using this process.
In one hydrogenation approach, discovered in the 1980s and later developed by the CANMET Energy Technology Centre (CETC), Natural Resources Canada, the biomass-derived additive functions as a cetane enhancer.
CANMET’s process converts vegetable oils, waste greases, animal tallow and other feedstocks containing triglycerides and fatty acids into a high-cetane, low-sulfur diesel fuel blending stock called SuperCetane. The process (schematic at right, Click to enlarge) employs a conventional commercial refinery hydrotreating catalyst and hydrogen.
The product generated by CETC’s process is a hydrocarbon liquid, which can be distilled into 3 fractions: naphtha, middle distillate and waxy residues. The middle distillate, which makes up most of the product, is the SuperCetane.
It has a cetane number (a measure of ignition quality) of around 100—comparable to commercial cetane additives. The specific gravity of SuperCetane is similar to regular diesel while its viscosity is similar to biodiesel. It is 97% biodegradable as compared to 45% for regular diesel.
The cetane number increases linearly with the concentration of SuperCetane, unlike commercial additives, whose impacts are limited above a certain concentration. Further, when SuperCetane is blended with commercial additives, the cetane value of the final blend is improved synergistically.
Fuel economy savings are an added benefit of SuperCetane—in a six-month test program using a fleet of Canada Post delivery vans operating in Vancouver, Canada, fuel economy savings of 8% were achieved.
Among the commercial applications for SuperCetane under investigation are:
As an additive to B20 bio-diesel to reduce NOx emissions.
As an additive to low-grade middle distillates such as those derived from oil sands.
As a source of renewable n-paraffins for refinery and petrochemical applications.
As a waste disposal option for the rendering industry.
The UK government is wondering whether or not hydrogenation, owing to economies of scale and integration with the existing petroleum refining infrastructure, might provide a cheaper way of introducing biofuel into the market. The stated intention is not to replace the conventional method of biodiesel manufacture in the UK but to augment it and work alongside it.
There is much unknown about hydrogenation processes: mass & energy yields; economics; sustainability (LCAs); blending ratios; and specifications. A fundamental question that should be answered during this process is whether or not hydrogenation represents the best fuel use of available biomass.