For most of its active life, though, the diesel engine has run on oil-based fuel. Renewed talks of running diesel engines on alternative fuels have slowly been changing this over the last two decades, yet those types of diesels run on non-oil-based fuel constitute a very small percentage of all diesel engines out there. Some city bus services, as well as farms, run their vehicles on pure biodiesel, having fully renounced the conventional stuff, but for the most part, this is only a droplet in the bigger scheme of things.
Yet this means it is feasible (at least in theory, because in practice I’m sure Big Oil would have something to say about this) to shift diesels from running on the conventional stuff to cleaner and more renewable sources. And, even though they aren’t really mainstream alternatives, there are plenty of options that could get the job done.
Biodiesel
Biodiesel is a generic term referring to diesel fuel made from natural sources that don’t include any oil-based components. These can be both vegetable oils or even animal fats processed to be used as fuel. Probably the most common crop it’s made from is rapeseed, but palm oil is also used and, well, pretty much any oil-rich crop.
It can be mixed with regular diesel fuel, or it can be used on its own. However, it’s not perfect because it doesn’t store as well as normal diesel fuel (it’s not really usable after eight months), it doesn’t yield quite as much power from engines and it can have higher viscosity too - the latter may make it difficult for the fuel to circulate in lower temperatures, although this can be fixed through the use of thinners and additives.
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Used vegetable oil
Recycled cooking oil essentially falls under the biodiesel category. However, it differs because in not needing its own production process, it’s even greener than the purpose-made variety. So it not only requires less energy to make, but its green credentials are further improved because it would otherwise just be a waste product - this is a great way to burn it and also find a genuine use for it at the same time.
You can’t just empty your deep frier into the tank of your diesel vehicle, though. The oil first has to be filtered to remove impurities and, just like regular biodiesel, it needs to be mixed with additional chemicals for engines to run well on it. In fact, if an engine is run exclusively on repurposed cooking oil, it will also need a fuel heater placed somewhere along its fuel lines. Otherwise, the system might get clogged up when temperatures drop due to the fuel’s increased viscosity.
Blue Crude-based fuel
Blue Crude is a product patented by a German company called Sunfire. It is made using clean energy, air tan water and it bears the promise that it can completely replace oil in the petrochemical industry. Automaker Audi also managed to create a very similar oil replacement a few years prior (which it called E-Diesel), but now it’s partnered with Sunfire after confirming the qualities of its new fuel.
The process to obtain it is very simple - water is subjected to electrolysis to separate it into its constituting elements. Then the resulting hydrogen is mixed with carbon dioxide extracted from surrounding air before being subjected to the Fischer-Tropsch process that converts the mix into a liquid.
The resulting product is called Blue Crude and it can then be converted into E-Diesel whose properties include a high cetane number, as well as no sulfur or aromatic compounds - this translates to a fuel that provides engines with a lot of power and once burnt emits fewer harmful chemicals in the process.
Dimethyl Ether (DME)
DME, the shortened form of Dimethyl Ether, is a gas you might find as one of the ingredients in hairspray, but its uses go far beyond that. It has been proven to be a viable fuel for compression ignition engines which can run on it with minimal modifications. Moreover, it actually improves a diesel engine’s emissions rating by practically eliminating the dreaded particulate emissions - actual engine performance isn’t affected either, so it sounds like a viable solution.
Australia is heavily reliant on diesel fuel and it’s here where efforts are being made to begin production of DME for use in commercial transport vehicles. The technology is already available, it’s just that producing DME is currently about three times more expensive than the production process for conventional diesel.
The New Holland T6 Methane Power is the world’s first 100% methane powered production tractor and is key to CO2 reduction without compromising performance. The T6 Methane Power tractor is the final piece of the jigsaw to complete the virtuous cycle of the Energy Independent FarmSM concept. Farmers can make use of agricultural or animal waste (as well as specifically-grown energy crops), to generate biomethane, which powers the tractor, which, in turn, helps to grow those very crops. Alternatively, refilling can be performed directly from the gas grid network or at specific biomethane stations New Holland can provide an eco-friendly solution to all your business needs.
Biomethane can be produced from a mixture of specifically-grown energy crops and waste plant or food material, the latter in both liquid and solid forms. This material is either harvested from the fields or gathered at the farm from sources such as food factories, supermarkets and restaurants and canteens, and fed into a biodigester, where it is broken down by bacteria in a process known as anaerobic digestion (AD).
As the biomass and waste breaks down, biogas is released in a two-stage fermentation process lasting around 60 days. This is eventually refined to produce fuel-grade biomethane, a product which can then be used to power the concept tractor.
Other worthy mentions
The fuels above are currently the most promising, but they are certainly not the only other fuels a diesel could be run on. Butanol from biomass is also mentioned in studies on the matter, although it difficult to use it on its own and it needs to be combined with conventional diesel in variable proportions in order to work.
Ethanol can also be used to power diesel engines, although, just like Butanol, it needs to be mixed with another fuel to burn (and especially lubricate) properly - it can’t make up more than 15 percent of the fuel mixture, though.
Fuel made from algae is also on the list of promising alternatives. Apparently, some species of microalgae are excellent at producing oil (up to 60 percent of their entire weight). The rest of the process is pretty much the same as that for making regular biodiesel.
