The push for drop-in biofuels
Biomass comprises all organic matter/waste which can become sources of energy. It can be burned directly to create heat for space heating or industrial processes, and to create steam for heating, industrial processes, and electricity gen .
Unlike other renewable energy sources (RES), biomass can be converted into liquid & gaseous fuels (both called biofuels) thru thermochemical & biological routes, used mainly for transportation (typically as additive for gasoline or diesel oil), but also for heating & electricity production. Types of biofuels include straight vegetable oil (SVO), biogas, biomethane, bioethanol, biodiesel (FAME), renewable NG (RNG), hydrotreated vegetable oil (HVO), and sustainable aviation fuel (SAF) .
Biofuels play an important role in decarbonizing transport by providing low-carbon solutions for existing techs, such as light-duty vehicles, in the near term, and heavy-duty trucks, ships, and aircrafts with few alternative solutions, in the long term .
1st-gen (1G) biofuels - bioethanol & biodiesel
The two most common types of biofuels in use today are i) bioethanol, alcohol made by fermentation, and ii) biodiesel, produced from new and used veg oils & animal fats via transesterification, both of which representing the 1st-gen (or conventional) biofuels, i.e., (bio) fuels produced from edible food crop resources . The cost of feedstock for 1G biofuels represents about 70% to 90% of total production cost (and is higher for biodiesel than ethanol), making production industry very sensitive to changes in feedstock price [IRENA, 2019].
Biofuels are adaptable to current engine designs, performing fine in most conditions. Different from solar & wind, and similar to hydroelectricity, biofuels can be stored, and unlike hydroelectricity, they are modular and not location-dependent, providing a high degree of decentralization.
On the other hand, monoculture associated w/ ecological damage, use of fertilizers, water use, shortage of food, and industrial pollution are the main drawbacks of 1st-gen biofuels . Moreover, the average life-cycle surface power densities for biomass, wind, hydro, and solar power production are estimated to 0.30 W/m2, 1 W/m2, 3 W/m2, and 5 W/m2, respectively (power in the form of heat for biomass and electricity for the others) .
- Main producers
The U.S. is the leading producer of fuel ethanol in the world, w/ 15.4 bn gallons (58.3 billion liters) in 2022 (55% of global production), followed by Brazil, with 7.28 bn gallons (27.6 billion liters) in the same year (together they produced 81% of the world's ethanol from sugarcane & corn) [STAT, 2023]. They were also the largest biodiesel producers in the world, totaling 6.9 billion liters (U.S.) and 6.2 billion liters (Brazil) respectively, in 2021 .
2nd-gen (2G) biofuels
2nd-gen (or "advanced") biofuels tech, by its hand, uses non-food-based biomass sources such as perennial energy crops & agricultural residues/waste. Due to the global food supply crisis, increasing dependence on non-food crops and exploring the potential of waste-based resources may be the right option . While the CAPEX of 2G biofuel refineries is higher than that of 1G refineries for similar output, the OPEX is lower: e.g., 2G feedstock for cellulosic ethanol production is estimated to constitute 35–50% of total production cost [IRENA, 2019].
- Hydrotreated Vegetable Oil (HVO)
Promising to revolutionize cargo transport, Hydrotreated Vegetable Oil (HVO), a 2nd-gen biofuel (for 2nd-gen HVO) and the most significant representative of green diesel (directly replacing diesel or blending it in any ratio), is a paraffinic renewable diesel fuel produced by hydrotreating (the addition of hydrogen to molecules) vegetable oils, including waste cooking oils, or animal fats.
Given its high calorific value & low emission level, HVO, which grows in the world at much higher rates than ethanol & biodiesel, can be added to mineral diesel at any level, a procedure not contemplated by the biodiesel  . Using HVO without blending any other fuels into it (HVO100 works well in all diesel ICE, w/o any special adaptation), GHG emissions can be reduced by up to 90% .
- 2nd-gen Ethanol (2GE)
2nd-gen ethanol (2GE), a.k.a. cellulosic ethanol, is a biofuel produced from waste discarded in the 1GE production process, i.e., sugarcane bagasse & straw (waste from beet, wheat, or corn can also be used). 2GE has the same molecular structure, chemical properties, and characteristics of conventional sugar cane or corn ethanol, w/ the advantage of making the process even more sustainable, increasing the production capacity by up to 50% over 1GE with the same planted area.
In Brazil, Raízen (RAIZ4), a joint venture btw Cosan & Shell, currently produces 3.2 bi liters of ethanol and has invested in E2G tech in a strategy to increase its production up to 1 bi liters by 2030/31 (thru 20 E2G plants) using the same planted area [USP, 2023] [PH, 2022]. By 2024 it plans to expand E2G production to around 280 mi liters, corresponding to the total capacity of the four plants already announced to the market: Costa Pinto, Barra Bonita, Univalem, and Bonfim, all in São Paulo state (thru an investment of BRL 1.2 bn over a period of 22 months per plant) [OE, 2023].
GranBio, another Brazilian biotech company, has been operating the "Bioflex" plant (using GP+ & AVAP+ proprietary tech) in São Miguel dos Campos (Alagoas state), since 2017: it is the 1st E2G plant in Southern Hemisphere. GranBio wants to disseminate its "energy cane" (richer in pulp and 2.5x more productive) for SAF (AtJ process) production in Brazil [BE, 2023].
AVAP+ is a group of techs capable of converting any type of biomass (including wood chips) into cellulosic sugars (glucose & xylose), lignin, cellulose pulp, and nanocellulose w/ registered patents in the U.S. (Thomaston R&D Center, ATL) [GB, 2023]. Greenpower+ (GP+) is another GranBio proprietary tech for producing cellulosic sugar, 2G ethanol, and other products.
Raízen & GranBio have increased their production with an eye on the foreign market, considered more attractive for selling cellulosic ethanol [NC, 2022].
3rd-gen biofuels (a.k.a. "algae fuel") refers to biofuel derived from algae, a promising oil feedstock due to high lipid accumulation, which are capable of much higher yields w/ lower resource inputs, not requiring land or freshwater, therefore not competing for primarily agricultural land & water resources .
Key takeaways & perspectives on biofuels
Most common feedstocks for HVO are oil waste products, whereas the most common feedstocks for B100 (100% Biodiesel) are plant oils. Potential disadvantages for both come down to unsustainable feedstocks [SENNDER, 2023].
Globally, the biofuel share in transport fuel consumption are expected to rise from 4.3% to 5.4% during 2022-2027. Biojet fuel to make up 1-2% of jet fuel globally by 2027 .
In developed countries, 2nd-gen biofuels account for about 50% of total biofuels in 2030, and more than two-thirds in 2050. China & India follow this development with a short delay. The shares of 2nd-gen biofuels in these two countries are set at 10% in 2020, and one-third in 2030 .