I found this press release from MTU / Rolls-Royce that says they've been trialling the use of hydrotreated vegetable oil to fuel their engines (that are used in some trains on the British railway network), that it reduces CO2 emissions by up to 90% along with other emissions reductions, and that existing engines will require easy or no conversion.
Rolls-Royce releases <em>mtu</em> rail engines for sustainable fuels
www.rolls-royce.com
The applicable engines are:
- Series 1600s (used in 800s, 802s, 805s and 810s, and also as the "emergency"/depot engine in 801s)
- Series 1800s (used in 195s, 196s, 197s, 172s and HybridFLEX)
- Series 4000s (used in the MTU re-engined 43 / HST power cars)
The ~90% figure is only true if a certain provision in the "2009" carbon accountancy rules is used namely waste feedstocks are regarded as Zero Carbon (due to being waste and the carbon already accounted for elsewhere) in an effort to incentivise waste re-use. So the carbon saving is waste feedstock (100%) - reprocessing and distribution carbon costs (~10%) = ~90%. There will also be slight changes in fuel consumption but this is complex due to difference in fuel densities and energy content.
In reality the quantity of CO2 coming out of the exhaust is similar to diesel.
This carbon accountancy rule is incompatible with "net zero" accountancy requirements as CO2 is still CO2 irrespective of origin, hence this may not be a long term solution.
A reasonable level of Hydrotreatment is also done on diesel to clean it up and help it combust better (e.g. remove Sulphur (reducing SO2) and PAH (reducing PM and indirectly NOx)) and increased levels of hydrotreatment on diesel (e.g. as Sweden mandates for polluted areas) reduces air quality pollutants.
Non hydrotreated diesel is also incompatible with modern emission reduction technologies (e.g. SCR with Ad-blue to reduce NOx)
The big problems with Hydrotreatments for diesel or HVO is that they typically use methane as a hydrogen source, the source of which was often cheap Russian gas.
Most of the HVO in Europe is processed in Finland / Netherlands and utilised what was cheap Russian gas.
There are also been some issues with diesel hydrotreatment, availability and pricing in that before February about 9% of UK Diesel came from Russia having been hydrotreated there. (The tankers returned in the other direction with Jet A-1 produced in GB refineries to Russia).
Most other European countries were /are much more reliant on diesel hydrotreated in Russia or using cheap Russian natural gas than the UK.
I've had a discussion about MTU 4000 engines from a marine use perspective with a friend who works in the industry, regarding an MTU 4000 hydrogen gas turbine becoming available next year.
Hydrogen HSTs anyone?
A 4000 running on hydrogen is still a conventional internal combustion engine and in reality a modification for their existing CNG /LNG 4000 but with modification to turbos, fuel and injection systems (and no DPF).
