The graphic shows in simplified form how alternative fuels can be divided into groups. GtL (gas to liquid) occupies a special position here, as it does not offer any CO2 reduction potential, but, like HVO, complies with the EN15940 standard for paraffinic diesel fuels. GtL was mainly used in the past to blend with fossil diesel in order to offer so-called premium diesel for sale. This blend was usually around 26% in order to continue to comply with the EN590 standard for diesel fuels. Although GtL has better local emission values, it is not considered further here due to its fossil origin. 
 
The most widely used fuel with CO2 reduction potential is currently HVO100 (hydrotreated vegetable oil). “Vegetable oil” in this context is not a product from cultivated crops, such as rapeseed oil. Rather, the raw material for HVO100 is primarily so-called UCOs (used cooking oils from the food industry), tall oils from the timber industry, and other bio-based waste materials.

According to the EN15940 standard, an admixture of up to 7% biodiesel is legally permissible, but pure fuel is the better and more widely used choice. 

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Here are some advantages of HVO100 compact:
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-   Reduction of CO2 emissions by up to 90% 
-   Significantly reduced tendency for DPF and EGR to become clogged, even in stop-and-go or short-distance operation
-   Reduced AdBlue consumption; approx. 1/4 to 1/3 depending on engine design
-   Significantly longer shelf life as no biodiesel admixture (HVO100 is a 100% pure fuel)
-   No need to switch between winter and summer diesel due to significantly lower CFPP and year-round usability

-   Manufacturer approvals from almost all known vehicle and engine manufacturers are available 
-   Virtually odorless and soot-free exhaust gases during operation; the fuel is also crystal clear and virtually odorless
 
A frequently asked question in connection with HVO100 is where the necessary raw materials will come from if it is scaled up across the board. In addition to the UCOs already mentioned, tall oils from the timber industry and other fatty waste of biological origin are already being considered.

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In the future, the use of cultivated plants such as Jatropha Curcas will certainly be the most viable option. However, this does not involve the use of agricultural land, but rather so-called degraded soils, such as steppe landscapes, etc., which are not suitable for plant cultivation but can be turned back into arable land through oil plant cultivation.
 

In the future, so-called PtLe (Power to Liquid) fuels from regions with favorable wind and solar power like the MENA region will certainly ensure global scaling. Several projects are in the pipeline, but there is currently a lack of legal certainty in the EU for their ramp-up. Nevertheless, they offer the possibility of using existing infrastructure and also binding approx. 2.6 kg CO2 / kg of fuel in liquid form. This means they are not only an easily storable energy source, but also a defossilization option. PtLe are the only synthetic fuels that can be referred to as eFuels. They can be produced in any type, i.e., as SAF (Sustainable Aviation Fuel), gasoline, and diesel. 

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BtL (biomass to liquid) is a term used to describe all bio-based fuels that are not produced from biomass through hydrogenation, such as HVO100. BtL fuels can be either gasoline or diesel fuels.

 

The most widely used BtL fuel is classic biodiesel FAME (fatty acid methyl ester), which is sold commercially as a pure fuel under the designation B100 in accordance with the EN14214 standard, or, much more commonly in the EU, blended with conventional fossil diesel fuel in accordance with the EN590 standard at a concentration of 7%. Blends of up to 7% are considered uncritical; any blends above this level usually require explicit manufacturer approval and/or technical modifications to avoid problems in modern diesel engines. Nevertheless, B10 diesel (10% blend) is in preparation. Currently, FAME and HVO100 are mainly produced from waste fats, including those from the food industry.

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BtL gasoline fuels are either offered as pure methanol (see Brazil, where methanol from sugar cane cultivation has been widely used since the 1980s) or used on the basis of methanol or ethanol as for the production of gasoline fuel in accordance with the current EN228 standard. The latter are referred to as EtG or MtG (ethanol/methanol to gasoline). The prerequisite for classification as ReFuel is that the raw material must be bio-based. Unlike alternative diesel fuels, EtG and MtG generally comply with the current gasoline fuel standard EN228, which makes approvals or technical modifications unnecessary.

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