LIQUID AND GASEOUS BIOFUELS-NICHE OR MAINSTREAM?

1 Background

Historically, fuel transitions have occurred over periods of several decades and have been associated with major industrial and economic developments in the world. The concept of Biofuels is not new, since Wood and Hay, from ancient times have been the mainstay of agrarian economies.

The advent of the industrial era in eighteenth century Europe provided the necessary impetus for the emergence of Coal and its domination through the nineteenth century [1]. The twentieth century witnessed petroleum fuels overtake Coal as the preferred fuel, but still the world is dependent on fossil fuels.

Towards the end of the previous century, it was recognized that global warming due to greenhouse gases is the primary factor for Climate change. The Kyoto protocol of 1997, followed recently by the Glasgow declaration at COP26 in 2021, crystallized  international consensus on the goal of achieving net Zero emission of Carbon Dioxide by 2050. This means phasing out of Coal and minimizing reliance on petroleum fuels.

Biofuels, therefore, have once again become relevant. From the viewpoint of sustainability, and for mitigating the Carbon Dioxide footprint of industrial, transportation and domestic fuels, the global focus is on liquid and gaseous Biofuels.

However, Biofuels are different from the other low Carbon energy options that the world is pursuing, such as renewables and Hydrogen. This is because Biofuels straddle the twin domains of food and energy. The World’s population has reached eight billion, an eight-fold increase since the beginning of the industrial era two centuries ago. Utilizing agricultural land, Water and fertilizers for growing energy crops may impact food production that depends upon the same land and resources. Evolving Biofuel technologies may however mitigate some of these concerns.

Given the above background, this article explores the role that Biofuels can play in the emerging mix of sustainable, low Carbon fuels. Technology maturity and production costs are key factors influencing widespread acceptance and adoption. Biofuels must compete with other energy sources, while navigating changing market and regulatory environments.

This article summarizes the manufacturing technologies and trends for Biofuels that are commercially important today and provides an overview of the current global Biofuels markets. The current trade flows, potential for growth and the challenges in mainstreaming are discussed.

2 What are Biofuels?

Biofuels are fuels that are produced directly or indirectly from biomass. In the evolving terminology of the energy industry, Biofuels are Organic non-fossil fuels of biological origin [2]. Broadening the definition of Biofuels allows low cost and abundant organic wastes such as biological sludge, wastewaters, agro-processing residues, organic Municipal Waste, food wastes and animal wastes among others, to be considered as potential Biofuel sources.

Biofuels are considered to be Carbon-neutral. This is because plants and trees absorb Carbon Dioxide from the atmosphere during their growth phase. The absorbed Carbon Dioxide is converted by complex photosynthesis processes into multiple Carbonaceous compounds, including primary metabolites such as Carbohydrates, Lipids, Proteins, Fatty acids, Amino acids and several secondary metabolites. When biomass is combusted, an equivalent amount of Carbon Dioxide is returned to the atmosphere.

Figure 1 is a simplified illustration of the Photosynthesis process [3].

Apart from Carbon neutrality, an advantage of Biofuels is that they are largely compatible with existing vehicles, combustion systems, pipelines, and storage infrastructure. Liquid Biofuels can be designed for blending with petroleum-based Gasoline or Diesel or even as full drop-in replacements.

2.1 First and Second-Generation Biofuels

The Biofuel technology landscape presents a mixed picture of established and evolving technologies. The focus of Biofuel technology at the current time, is on first-generation and second-generation biofuels. They are also termed conventional and advanced Biofuels respectively. The first-generation or conventional Biofuels are those that utilize food crops to obtain Sugar, Starch, and vegetable oils as their raw material. They are not considered a sustainable energy alternative in the long term, as they can induce food insecurity by competing with food outputs.

Second generation or advanced Biofuels are produced from non-food, cellulosic biomass, such as woody and straw residues from agriculture and forestry, fast-rotation plants, non-food crops (preferably grown on non-arable land), agricultural residue, organic fractions of municipal solid waste, digestion of biological sludge. The manufacturing processes for advanced biofuels are more challenging and expensive, but do not directly impact food security.

It may be noted that even as second-generation technologies are being gradually adopted, research has commenced on third-generation feedstocks such as microalgae.

In terms of commercial relevance at this point in time, only the following four liquid Biofuels are significant:

• Bioethanol
• Biodiesel
• Renewable Diesel
• Bio-jet Fuel

Among gaseous biofuels, Biogas is the only well-known Biofuel and there are thousands of biogas plants in operation all over the world.

Figure 2 Illustrates first, and second-generation feedstocks used to make the prominent liquid and gaseous Biofuels in the market.

3 Biofuels Manufacturing Processes

3.1 Bioethanol

Ethanol or Ethyl Alcohol can be manufactured from biomass by fermentation and thermochemical routes. It can also be made through the petrochemical route, by the hydration of Ethylene using Steam. The term ‘Bioethanol’ is used to describe only the biomass-based Ethanol.

First Generation Bioethanol is produced by fermentation of Glucose and Fructose obtained from sugary and starchy raw materials. These processes have been well established at an industrial scale for more than a century.

Second generation Bioethanol is made from lignocelluloses. There are fermentation and thermochemical routes, both of which are not commercially viable at this time. The fermentation route involves decomposition of Cellulose to Sugars by various means and then fermenting the Sugars. The thermochemical route produces Syngas by partial oxidation of wood followed by catalytic conversion of Syngas to Ethanol. Second generation Bioethanol technology may take a long time before it can be commercial deployed on a large scale and is not discussed further in this article. Globally Sugarcane is the dominant source of Sugar for Bioethanol while Corn is the  source of starchy feedstock.

Figure 3 illustrates the major feedstocks and routes for producing first generation Bioethanol. It can be seen that 57%of current world’s production of Bioethanol is from Corn (also called Maize). while 34% is from Sugar. It is also seen that all the Bioethanol in the market today is from food crops.

3.1.1 Bioethanol from Sugars

Sugar in sugarcane is present  as Sucrose, which has the molecular formula C₁₂H₂₂O₁₁. Sucrose is a Disaccharide and is made up of two mono-saccharides called Glucose and Fructose, both of which have the molecular formula C₆H₁₂O₆.

Fully mature Sugar cane stalks contain about 12-15% Sucrose on wet weight basis. At low pH or under the influence of enzymes such as Invertase, the Sucrose is hydrolysed into two monosaccharides,  Glucose and  Fructose, in equimolecular proportions.

Traditionally, Bioethanol is produced in distilleries situated adjacent to sugar plants as part of the same complex. Sugar juice is extracted by crushing sugarcane stalks in the sugar mill and clarifying the juice prior to sugar crystallization. Bioethanol can be made either from the sugar juice or from molasses, which is the mother liquor left behind after crystallization and separation of  sugar crystals. Cane molasses has 45 to 60 % Sucrose and 5 to 20 % Glucose plus Fructose. Some distilleries use only sugarcane juice, others only molasses, and many use an optimal mixture of both, as the nutrient availability in molasses is higher. The mineral composition of sugarcane substrates vary widely, depending on the molasses proportion used to formulate the media, sugar cane variety and maturity, soil, climate, and processing of cane juice.

Bioethanol is traditionally made from Sugar by a batch fermentation process known as the Melle-Boinot process [9]. Some distilleries use continuous fermentation technology. The  fermentation is performed by a species of yeast known as  Saccharomyces Cerevisiae (brewer’s yeast or baker’s yeast). The overall biochemical reaction and  stoichiometry can be represented as follows:

C₆H₁₂O₆ →  2 C₂H₅OH + 2 CO₂

The Carbon Dioxide evolved during fermentation can be bottled and sold. In both batch and continuous processes, after the end of fermentation, yeast cells are collected by centrifuging and re-used in the next fermentation cycle. Up to 90-95 % of the yeast cells are recycled, resulting in high cell densities inside the fermenter. This enables a residence time of about 6 to 10 hours for completing the fermentation to Ethanol. The fermented liquor leaving the centrifuge, contains  Ethanol at concentrations of  8 to 12 % (v/v) and is pumped to distillation columns for 95% pure Ethanol recovery. Further dehydration of Ethanol for example, by molecular sieves, is usually needed to meet automobile fuel blending specifications. Figure 4 shows the process scheme.

3.1.2 Bioethanol from Corn (Maize)

The Corn grain contains about 70-72% Starch, formed by photosynthesis. Starch is a carbohydrate polymer made by the linking of Glucose units into long chains. The intermolecular Glucose bonds must be broken to release Glucose for fermentation to Bioethanol.

Distilleries using Corn Starch  can buy Corn Starch powder or start from the Corn kernel and extract Starch for use in the Bioethanol plant. Integrating a distillery with an existing Corn kernel  processing facility is the most viable option, as there will be multiple product streams generated from the Corn refining process.

Corn starch can be extracted from the Corn kernels by wet or dry milling processes. Wet milling involves softening the Corn kernels by steeping in Water treated with Sulphur-Dioxide. This is followed by  grinding and centrifuging to separate Starch granules from the rest of the kernel. In dry milling, the Corn kernels are ground using hammer mills to expose the Starch granules. For the purpose of making Bioethanol, the hammer mill is a cheaper option and is briefly described in the following paragraphs. The dry milling process scheme is illustrated in Figure 5 .

The process is as follows [10]:

The first step is milling to grind the Corn kernels, to expose Starch that is within the kernels. Dry milling as shown the Figure 10, is done is Hammer mills to produce a fine powder called meal. The next step is termed mashing, in which Water is mixed with the meal to form a mash. Alpha-Amylase enzyme is added here to begins the breakdown of starch. The mashed slurry is then subjected to steam cooking, either by passing through a steam jet cooker or in a cooking tube a temperature of about 125 -140 degrees Centigrade. The cooked Starch is then cooled and further liquefied by adding Alpha-Amylase again. At this point, the Carbohydrate polymer chains are all significantly smaller than the original Starch polymer and are called Dextrins.

The fermentation  process starts with the Dextrins being broken down to fermentable sugars in a reaction known as Saccharification. This is achieved by adding another enzyme called Gluco-Amylase. At the same time yeast and nutrients are added so that the Glucose formed by breakdown of Dextrins is  simultaneously fermented to Ethanol. The technology is termed Simultaneous Saccharification and  fermentation (SSF).

A typical Corn-to-Ethanol facility has three or more fermenters operating batchwise in staggered cycles of 48-72 hours until the mash is fully fermented. The fermenter operates anaerobically. Commercial yeast strains for Ethanol production can effect fermentation at 32-35 °C (90-95 °F). At higher temperatures metabolic activity rapidly declines. Yeast prefers an acid pH, and the optimum pH is 5.0-5.2. Released CO₂ is removed from the system through the scrubber. After completion of fermentation, the fermented  liquid is separated from the rest of the biosolids  centrifuges and sent to distillation columns for recovery of Bioethanol. The  biosolids are processed into various by-products and CO₂ is usually bottled and sold.

3.2 Biodiesel

Biodiesel is a Diesel fuel alternative, produced from biomass with high oil content, such as soybeans, rapeseed/canola, oil palm as well as waste oils such as used cooking oil. First generation Biodiesel is made by a simple trans-esterification (i.e., ester exchange) process  in which the oil in these feedstocks is reacted with Methanol in the presence of a catalyst to form a Methyl Ester with similar properties to conventional diesel fuel.  Hence Biodiesel is also referred to as Fatty Acid Methyl Ester (FAME) Biodiesel, to distinguish it from other renewable Diesel alternatives such as Fatty Acid Ethyl ester (FAEE) or Hydrogenated Vegetable Oil (HVO).

3.2 1 Biodiesel by FAME process [11]

The FAME process starts with purification of the feedstock since trans-esterification is extremely sensitive to impurities. The fat molecules in vegetable oils and animal fats are mainly Triglycerides, that react with Methanol in presence of acid or base catalyst. While refined vegetable oils do not require purification, waste oil and  animal fats have many impurities including free fatty acids (FFA), phospholipids, phosphatides, carotenes, tocopherols, Sulphur compounds, Water, solid particles, Sodium Chloride that must be removed. Various pre-treatment operations are used, such as acid degumming  to remove phosphatides and alkali metals, pressure filtration to eliminate solids and heating under vacuum to strip fatty acids and Water.

Purified feedstock can then be reacted with Methanol. Most commercial processes perform trans-esterification using homogeneous Alkali catalysts in batch reactors. Alkaline metal hydroxides (e.g., NaOH, KOH) are the most often used commercially.

The reaction temperature is maintained at about 50 to 70 degrees Centigrade to ensure that the reaction medium is not very viscous. The transesterification between Methanol and Triglycerides involves three reversible steps in sequence. First Triglycerides are converted to Diglycerides, then to Monoglycerides, and finally to  Esters and Glycerol.

The reaction goes to completion in a few hours and the Biodiesel (Methyl Ester) is separated from Glycerol and Methanol by settling. The lighter phase is Biodiesel, which floats on top while the bottom is a mixture of Glycerol and excess Methanol.

The Biodiesel is subjected to post-treatment by Water washing to remove catalyst residues and sodium soaps from the Methyl Esters. Acidulated water using Phosphoric acid is added to the raw Methyl Esters to break catalyst residues and Sodium soaps.

The bottom layer is sent for distillation to recover Methanol and Glycerol. The separated Glycerol has a market in the  pharmaceutical, cosmetic and food sectors.

Figure 6 is a schematic of the FAME process.

3.2.2 Renewable Diesel

Renewable Diesel, also referred to as hydrotreated vegetable oil (HVO) or hydro-processed Esters and Fatty acids (HEFA), is another Diesel fuel alternative. HVO Diesel is fully compatible with petroleum Diesel and can also be upgraded to Biojet Fuel. It is superior to FAME Diesel in performance and most importantly unlike FAME products, the quality does not vary with the feedstock. HVOs are straight chain paraffinic hydrocarbons that are free of aromatics, Oxygen and Sulphur and have high Cetane numbers.

HVO Diesel can be produced through catalytic hydrogenation of vegetable oils under pressure. The pre-treatment is in principle the same as for the FAME process, however it is not necessary to remove Free Fatty Acids. They can be produced in stand-alone facilities especially using green Hydrogen produced by electrolysis. It also an economic option to install the HVO unit within Crude oil refineries having conventional SMR Hydrogen plants equipped with Carbon capture and Sequestration facilities. The HVO process is briefly described below.

• The first stage of hydrogenation, termed hydrotreatment, takes place at 30 – 50 barg pressure and at temperatures between 300 °C and 450 °C, in the presence of a catalyst. Triglycerides in the vegetable oil are converted to straight chain paraffinic compounds by the saturation of double bonds followed by a cleavage to Fatty Acids and the hydrogenation of Glycerol to Propane and Water. Finally, the Fatty Acids undergo a combination of hydrogenation or decarboxylation reactions yielding paraffins.
• Next the paraffins have to be isomerised and cracked to get the required combination of straight chain, branched chain, and cyclic paraffinic hydrocarbons. Catalytic isomerization is performed at 300 – 400 °C, the severity of which is dictated by the desired fuel products. The change in the molecular structure of the hydrocarbons allows matching the properties to the market specifications of the fuel.
• Finally, HVO Diesel, Biojet fuel, Gasoline and Naphtha fractions are separated by distillation.

Figure 7 is a simplified sketch of the HVO process.

3.3 Biojet Fuel

Conventional Jet fuel is a Crude Oil distillate corresponding to the Kerosene fraction, that is further processed to meet the specifications for use as Aviation Turbine Fuel.  Biojet Fuel is the term used for Biomass derived Jet fuel. Renewable feedstock-derived jet fuels can contribute significantly to reduction of the Carbon footprint of the aviation industry. Many process technologies that convert biomass-based materials into jet fuel substitutes are available. Some are available at commercial or pre-commercial scale, and others are still in the research and development stage. Potential feedstocks for producing Biojet fuel include oil-based feedstocks, lignocellulosic feedstocks, and gas-based feedstocks, such as biogas and syngas. There are four primary routes for production of Biojet fuel, depending on the feedstock[13]:

• Alcohol-to-Jet (ATJ):

ATJ fuel, also called alcohol oligomerization, is fuel converted from alcohols such as Methanol, Ethanol, Butanol, and higher alcohols. There are many pathways to make alcohols from biomass. A typical three-step ATJ process that converts Alcohols to jet fuel includes alcohol dehydration, oligomerization, and hydrogenation. Figure 8 shows the overall process diagram for Ethanol, Isobutanol, and n-Butanol conversion to Biojet fuels.

• Oil-to-Jet (OTJ):

Oil based feedstocks such as vegetable oils, waste oils, algal oils, and pyrolysis oils can be converted to Biojet fuels by three different technologies:

• • Hydro-processed renewable jet (HRJ), also known as hydro-processed Esters and Fatty acids (HEFA).
  • Catalytic hydro-thermolysis (CH) also termed hydrothermal liquefaction.
  • Pyrolysis (also known as hydrotreated depolymerized cellulosic jet (HDCJ).

When processing vegetable oils, the fatty acid profile is an important issue. The hydrogenation step is important to saturate all the unsaturated fatty acid molecules. Hence, a greater Hydrogen supply is needed if more unsaturated Fatty Acids are present in the oil. HRJ and CH utilise oil and fats containing Triglycerides. The Pyrolysis process uses Pyrolysis oil obtained during cellulosic pyrolysis (heating in absence of air).

Only the HRJ conversion technology is at a relatively high maturity level and is commercially available. The principles of the technology are identical to that discussed under renewable diesel manufacturing process (HVO). The process can be tweaked to get the required distribution of different hydrocarbon fractions. Figure 9 is a block diagram of the process illustrating the chemistry involved.

• Gas to Jet (GTJ):

The GTJ Biofuel pathway can utilise biogas, convert it to Syngas and synthesize liquid biofuels by catalytic gas to liquid (GTL) processes. Syngas from biomass can also be used. This pathway is well known in the fossil fuel industry as it uses the Fischer-Tropsch synthesis scheme. GTL processes have  been used at mega-scale in Qatar, South Africa  for several decades to convert natural gas as well as syngas gas from coal  into liquid fuel. Given small scale at which biogas or biomass gasification is typically performed, GTJ plants do not make economic sense at this time.

• Sugar to Jet (STJ):

There are many pathways to convert Sugar to jet fuel. The most prevalent  is a thermos- chemical process that involves catalytic conversion of Sugar to hydrocarbons. In this process, biomass feedstock is first converted into solubilized sugars. This conversion process is typically done via biomass pre-treatment and enzymatic hydrolysis of lignocellulosic biomass feedstocks to create C5 and C6 sugars. The hydrolysate is then  purified and reacted with Hydrogen to yield polyhydric alcohols via hydrogenation or short-chain oxygenates via hydrogenolysis. The resulting hydrotreated product is sent directly to the Aqueous Phase Reforming Reactor where at High temperature and pressure it produces a mixture of saturated and unsaturated hydrocarbons, Carbon dioxide and Hydrogen. Further hydrotreating similar to GTJ process followed by Distillation yields Biojet fuel.

3.4 Biogas

The existence of a flammable gas produced by biological decomposition of vegetable matter has been known to mankind for centuries. The composition and formation mechanisms were worked out in the nineteenth century. Biogas is produced in many different environments, including in landfills, sewage sludge and during anaerobic degradation of organic material. Biogas is comprised of methane (about 45-75% by volume), Carbon Dioxide (25-55%), and other compounds including hydrogen sulphide, Water, and other trace gas compounds.

Biogas production technology developed extensively through the twentieth century. There  are thousands of anaerobic digesters of various sizes and shapes operating throughout  the world. Anaerobic digester can be cylindrical, egg-shaped, or rectangular tanks, with fixed, floating or  membrane roofs among others. They are used to produce biogas from animal manure, municipal solid waste, liquid and solid organic industrial wastes and domestic wastes. The basic concept that drives the design of any anaerobic digester is to provide airtight, oxygen free containment systems in which various types of microbial consortia including methane producing bacteria can flourish by feeding on biodegradable substrates. Substrates can be liquid, solid or mixtures of solids and liquids. Depending on the feed characteristics and digestion environment anaerobic digesters can be dry type or wet type. In wet type the entire sequence of feed to digestion and withdrawal of digestate happens in slurry form. The organic bio-solids are first made into slurries by mixing with water to retain 5 to 20% dry solids and then fed into the digester.

Feasible biogas purification technologies exist for large-scale sewage and biowaste digesters, and the technologies for upgrading biogas, compressing, storing, and dispensing Biomethane are well developed [16].

Operation of biogas digesters requires experience since it is a delicate biological process. One of the issues facing the sector has been the high failure rate cause by improper operations. The other issues are huge land requirements for large scale facilities and feedstock sourcing and logistics related to collection and transport.

From a global energy perspective, Biogas is not currently considered as a major contributor to the mainstream Biofuels mix.  Given the technological maturity and ability to provide localised solutions it is more of a niche biofuel.

4 Biofuels Market Overview   

The state of play in the global Biofuels markets is evolving very rapidly. Liquid biofuels today are entirely focused on the transportation sector, due to ease of adoption, and sufficient experience in implementation and regulation. Globalization of supply chains has made progress in this sector.

With regard to industrial applications, liquid Biofuels have not been popular in the industrial sector. This may be because of issues of scale, availability, cost, and Biofuels policies which are oriented towards the transportation sector.

Gaseous Biofuels such as Biogas from anaerobic fermentation and Water Gas from biomass gasification have found many users in certain sectors of industry, for steam and power generation.

Despite all the debate and activity around sustainable fuels, the world is utterly dependent on fossil fuel at this time as seen from the recent fuel crisis sparked off by the Ukraine conflict.

4.1 Liquid Biofuels

This section discusses current and evolving market trends for the following four liquid fuels which are produced, consumed, and traded in significant volumes.

• Bioethanol
• Biodiesel
• Renewable Diesel
• Bio-jet Fuel

As pointed out earlier, they are all directed at the transportation sector. In 2019, just prior to the Covid pandemic, global transportation Biofuel production was 169 billion litres annually. The IEA estimated that in the year 2021, Biofuels met 3.6% of global transport energy demand, mainly for road transport. In terms of fossil fuel avoidance, the use of Biofuels in road transport avoids about 4.4% of global transport energy demand. The contribution of Biofuels to road transport is expected to rise to 15% in 2030 [4].

Note that Biodiesel and Renewable Diesel are categorized separately, since they are manufactured using very different technologies, though they compete for the same feedstocks.

Figure 8 shows the global growth projections during 2021 to 2026, for the above liquid Biofuels. The main case is based on current policies, whereas accelerated and NZE scenarios include implementation of pledges made at COP26 and increased policy support [5].

The Biofuels market is expected to register a CAGR of more than 7% during the forecast period of 2022-2027 [6]. As can be seen from Figure 9, North America dominates the Biofuel market.  The market is still driven by governmental mandate and policy-based incentives rather than commercial viability. The role played by ESG requirements as well as societal pressures to force this transition is also important.

It is important to note that the Biofuels market is presently almost entirely served by first generation Biofuels. Till the end of the twentieth Century, Bioethanol, propelled by Brazil and the USA, was the only liquid Biofuel of note. These  two countries continue to be at the top in Bioethanol production and utilisation in transportation. However, in the past two decades, the share of Biodiesel and Renewable diesel in Global biofuel production has increased nearly 10-fold, from 3.3% in 2000 to nearly 32% in 2020. In the year 2020, Corn and sugarcane contributed  to 64% and 26% of global Bioethanol production, respectively, and vegetable oils were used for 77% of global Biodiesel production [8].

Europe is the pace-setter for the world in Biodiesel and renewable Diesel adoption, driven by the Renewable Energy Directive that has set a target of 32% of renewable energy in the EU’s energy consumption by 2030.

Figure 10 shows the major Biofuel producers, consumers, and the import /export patterns [8] .

From Figure 10 it is apparent that there is a stark difference between the trading patterns of Bioethanol and Biodiesel. The main Bioethanol producers USA and Brazil have adequate production capacity to meet their needs, hence imports/exports are insignificant. This is also the case with China, European Union, and the other smaller players. International trade in transportation Bioethanol is not significant at this time. The Biodiesel trade scenario is quite different. Europe and the USA have to import Biodiesel to meet  their requirements, while Asia is the world’s leading exporter of Biodiesel. This is a pointer to the underlying market dynamics, dictated by land and  feedstock availability and cost of production. The fertile tropical regions of Asia are well placed to grow Oil seeds at lower costs than in Europe and the USA. Thus, a developing economy like Indonesia has emerged as a major exporter of oilseeds for Biodiesel. It is precisely this kind of trend that has the world worried about food security as more players from the Asian and African regions jump onto the Biofuels bandwagon.

The market status of individual liquid Biofuels are discussed in more detail in the following sections.

4.1.1 Bioethanol Market Status

In 1876, Nicolaus Otto, who developed the four-stroke internal combustion engine, used Ethanol to power an early engine. Henry Ford demonstrated a model-T car that used on Ethanol as a fuel. In the 1970s, sparked by the Oil crisis, some countries, led by  Brazil, started to focus entirely on Bioethanol as a fuel for cars.

Ethanol is a high-Octane fuel which can be blended in various ratios into gasoline in existing spark-ignition engines. Apart from its Cetane number boosting capabilities, it is an Oxygenate that reduces the emission of Carbon Monoxide from vehicle exhausts.

The largest producers of Bioethanol were the United States (63%), Brazil (24%), and China (2.5%). Fuel ethanol production reached 115 billion litres globally in 2019.The United States of America produces Bioethanol from Corn, Brazil almost entirely uses Sugarcane feedstock, while China utilises Corn, Wheat, Rice, and Sorghum.

Figure 11 shows global Bioethanol production by country or region, from 2007 to 2020.

Ethanol is permitted to be blended into Gasoline in various volumetric proportions as indicated below:

• E10: This is a low-level blend composed of 10% Ethanol and 90% gasoline. It is the most popular blend most countries and can easily be used in conventional, gasoline-powered vehicles.
• E15: This blend comprises 10.5% to 15% Ethanol in gasoline. Unlike E10, not all engines are capable of utilising E15.
• E85: This rich Ethanol blend containing 85% Ethanol in gasoline is recognized as an alternative fuel. It used in flexible fuel vehicles(FFVs), which have an internal combustion engine designed to run on E85.

4.1.2 Biodiesel: FAME and HVO Market Status

Biodiesel /Renewable Diesel is a high-Cetane fuel, which can be fully blended with fossil diesel to run on compression ignition engines. From the time that Rudolf Diesel invented the diesel engine, it could run on a variety of fuels, including vegetable oil. In 1900, one of the new diesel engines featured at the Paris Exposition was powered by Peanut oil.  In a 1912 speech Diesel said, “the use of vegetable oils for engine fuels may seem insignificant today but such oils may become, in the course of time, as important as Petroleum and the Coal-tar products of the present time”. As early as the 1930s, there was interest in splitting the Fatty Acids from the Glycerin in vegetable oil in order to create a thinner product similar to Petroleum Diesel. In 1937, G. Chavanne was granted a Belgian patent for an Ethyl Ester of Palm oil for use as fuel (FAEE Biodiesel in current terminology) [14].

Since 1992, Biodiesel has been commercially manufactured across Europe, with Germany being the largest producer in Europe. Nowadays Biodiesel is the most important alternative fuel in the EU representing 82% of the total Biofuel production [11].

Figure 12 shows the current global production pattern of Biodiesel.

With production capacities shifting to Asia in recent times, due to feedstock and processing cost advantages, Biodiesel is globalizing its supply chains in a way reminiscent of the traditional energy industry. It is quite noteworthy that Indonesia has overtaken Germany and USA in Biodiesel production, since it is insufficient in many food crops such as wheat, rice which grow in the same agro-climatic conditions. This does raise some concerns on the sustainability aspects of the trading pattern.

Blends of Biodiesel and conventional hydrocarbon-based Diesel are most commonly distributed for use in the retail Diesel fuel marketplace. Much of the world uses a system known as the “B” factor to state the amount of Biodiesel in any fuel mix:

• 100% Biodiesel is referred to as B100
• 20% Biodiesel, 80% Petro-diesel is labeled B20
• 7% Biodiesel, 93% Petro-diesel is labeled B7
• 5% Biodiesel, 95% Petro-diesel is labeled B5
• 2% biodiesel, 98% Petro-diesel is labeled B2

4.1.3 Biojet Fuel Market Status

Adoption of Biojet Fuel is now integral to the aviation industry’s strategy to reduce operating costs and environmental impacts. The global market for Biojet fuels was valued at 166 million USD in the year 2020 and expected to grow at a CAGR of 17.9 % till 2030. The USA is currently the leader in the adoption of Biojet fuels [17]. The Oil to Biojet fuel manufacturing pathway is the predominant technology at this time and competes with Biodiesel for the same raw materials and resources. Also, even in the USA the Biojet fuel initiative is driven by strategic considerations to improve overall energy security in case of disruptions in global supply chains.  At this time Biojet Fuel is a niche fuel and lagging behind Biodiesel /Renewable Diesel in speed of adoption.

5 Challenges to Biofuels growth

• Biofuel as a sustainable energy concept has shown promise and some early gains in the market thanks to the mainstream adoption of Bioethanol and Biodiesel. Apart from their environmental benefits, they can boost agricultural employment by utilizing marginal lands, rebalance trade inequities by bringing developing regions into global supply chains and ensure energy security for the world after fossil fuels are phased out.
• The major hurdles preventing Biofuel from rapid growth are the cost of production and reliance on food crops. In the case of second-generation Biofuels, feedstock costs contribute a large portion to the overall biofuel production cost. Rising prices for food, surface transportation, and power generation increase the input costs. To reduce feedstock costs Biofuel producers are now looking at micro-algae, but this technology will take a long time to mature.
• It may be noted that while Biofuel may be “green”, the factories that produce Biofuels source power for the factories mainly from existing electricity grids which are powered by fossil fuels. Similarly preparing second generation Biofuel by cutting trees for their wood is also of dubious value. The Carbon accounting process needs to become standardized and transparent for the emerging Biofuel industry to realize its full potential.
• The biggest challenge perhaps is that the world is adopting Electric vehicles quite rapidly and that may be followed by Hydrogen powered vehicles. This may lead to a phase-out of internal combustion engines and make transportation Biofuels irrelevant.

6 References

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15. Major biodiesel producing countries 2021 | Statista
16. Biogas and Biomethane industry Showcase Report – Biogas and Biomethane Industry Biogas World Media Inc. October 2020
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