
RFNBO
Renewable fuel of non-biological origin
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Renewable fuels of non-biological origin (RFNBO), term introduced by the EU Renewable Energy Directive 2018/2001 (RED II), are a category of fuels produced from hydrogen derived from renewable energy (except biomass sources) in the form of heat or electricity, and CO2 deriving from fossil sources such as flue gases or from direct air capture (DAC) techs, or N2 captured from air [EC, 2022].
H2 with CO2 or N2
Since CO2 and N2 are not energy carriers, all energy transferred into such carbon- or nitrogen-based fuels derive from hydrogen. Fuels that may be produced by combining H2 and CO2 or N2 are hydrocarbons, alcohols, and ammonia. Together w/ advanced (or 2nd gen) biofuels, RFNBO consist in a ready alternative to fossil liquids fuels for the market being fully drop-in.
Within the category of RFNBO, in addition to i) pure hydrogen, derived from water and renewable energy (except biomass sources) in the form of heat or electricity, there are ii) e-fuels (H2 plus CO2 or CO) iii) solar-derived fuels (when H2 uses the sunlight as energy source to split hydrogen from water), iv) other fuels derived from renewable heat, and v) fuels from microbes thru synthetic biology, cyanobacteria or chemical catalysis.
Indeed, RFNBO may designate renewable hydrogen itself but also its derivatives, i.e., advanced fuels based on renewable hydrogen. One of the main techs to produce RFNBO is electrolysis powered by renewable electricity to produce H2 [TE, 2023].
Food security
Since food security, according to Food and Agriculture Organization (FAO), of United Nations, has multiple dimensions, such as availability, accessibility, stability and utilization, the production of the renewable fuels of non-biological origin contributes to enhanced economic conditions of rural communities, new job opportunities, increasing overall food availability, food accessibility &affordability [FAO, 2020].
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Certification
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Renewable hydrogen deriving from renewable electricity needs harmonized, coherent, and consistent certification schemes which deliver guarantee of origin (GoO) that can be recognized and used at a global level. Such certification schemes could allow us to use a single methodology to calculate the greenhouse gas (GHG) emissions and life cycle assessment (LCA) of hydrogen [EC, 2022].
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Viability
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The production of RFNBO will depend on the availability of surplus renewable electricity and its price. The availability of economical CO2 (concentrated in flue gases or from industrial process or from DAC) or N2, as well as the green hydrogen supply, are crucial to reduce the production costs. RFNBO conversion pathways are at early TRLs, and still need tech improvements, demonstration, de-risking, and commercial validation in the future.
Automotive industry promote e-fuels as an alternative solution to the phasing out of the internal combustion engine for cars & trucks. But there are opposing views due to its poor efficiency & high-cost for drivers and manufacturers. Anyway, the first incentives are targeting aviation & maritime transport sectors [TE, 2023].