With the impetus of creating a circular economy, where none of the inputs or products exit the supply chain and thus lead to waste, biofuels are gaining traction. Biofuels have been in existence from the early days of human evolution; for example, wood and animal fats being used as energy sources for heating and cooking.
Biofuels are sources of energy derived from biomass, which can be of plant or animal origin. Currently, since they are found in abundance, providing high energy value at a cheap price, conventional energy sources like coal and petroleum are being used extensively. While fossil fuels are derived from biomass, they are formed by the decomposition of organic matter buried for millions of years.
With the depletion of fossil fuel reserves, along with their negative impact on the climate, biofuels are a perfect compliment, as they are a reliable renewable energy source that can assist in mitigating climate change. Biofuels have been around for a long time but have been overlooked for fossil fuels, which are readily available at cost-effective prices. Biofuels were in focus in the 1970s due to the energy crisis, but the interest was lost when fossil fuel supplies resumed.
The different types of biofuels:
Biofuels are categorized into three types: first, second, and third generation. These characterizations are based on the source and process technology.
First-generation biofuels are made from fermentation and esterification of sugar and lipids, respectively. What makes first-generation biofuels different from other generations is that the biomass source is a food source as well, and hence there has always been a “food versus fuel” argument against these biofuels.
Second-generation (2G) biofuels are derived from non-food biomass such as organic waste, food waste, wood, and other crop residues. The process of producing second-generation biofuels starts with pretreatment, using either mechanical/physical, thermochemical, or biochemical reactions. This step breaks down the lignin and cellulose components of the plant material and is followed by hydrolysis, which unlocks the sugars in the fibers of the plant. After pretreatment, the unlocked sugars are processed to produce ethanol.
This process is similar to the first-generation ethanol process. Gasification of the biomass produces syngas comprising of hydrocarbons, carbon monoxide, and hydrogen. The syngas is then separated to produce hydrogen, which is used as fuel, while the hydrocarbons can be used as an additive.
Biofuels derived from algal biomass constitute third-generation (3G) biofuels, and these include but are not limited to ethanol, biodiesel, and biogas. Production of algal biomass depends upon the capture of carbon dioxide using photosynthesis and water, after which the biomass can be extracted for biofuel.
Can 2G biofuels serve as a potential alternative energy source?
Second-generation biofuels are ideal for generating value out of cellulosic biomass like crop residues such as stalks, leaves, stems, bagasse, and empty palm fruit bunches. These are ideally burned at the origination site or incinerated as boiler feed to generate energy. Second-generation bioconversion of biomass is a promising technology that transforms lignocellulosic biomass into fuel and high-value chemicals, thus offering an alternative source of energy along with inputs for the chemical industry. Following pretreatment, the process generates multiple raw material fractions, such as cellulose, lignin, protein, fibers, and lipids. Among these fractions, lignin and cellulose are of the greatest interest.
Lignin can be used to produce biochemicals. Sulphonates, guaiacol, catechol, ferulate, and vanillin are a few of the high-value biochemicals derived from lignin, while cellulose is processed to produce biochemicals like polyols (xylitol, erythritol), acids (lactic, succinic, levulinic), and ethanol, to name a few.
As of 2016, roughly 67 plants producing 2G biofuels were operational globally, including commercial, demonstration, and pilot plants. Few of these have stopped operations since then. These plants are located across the globe, with the most found in the United States, followed by Europe, Asia, and Africa, in that order.
Lately, China, India, Indonesia, and Malaysia have shown interest in the technology, driven by government initiatives. For example, in 2018, the biofuels policy of the government of India earmarked a viability gap fund of USD 735 million for 5 years, along with financial incentives, tax incentives, and higher purchase prices to encourage the setting up of 2G plants, which is expected to result in the commission of at least four commercial 2G plants in the next couple of years. In November 2019, Indian Oil Corporation Ltd. received clearance to set up a 100-kiloliter-per-day 2G ethanol plant with an investment in excess of USD 100 million.
Key players in the 2G biofuel arena:
Notable players in the 2G biofuels segment operating commercial plants in the United States include Dupont, ADM, Cargill, Summit Natural Energy, Calgren Renewable Fuels, Quad County Corn Processors, American Process, and Pacific Ethanol. In Europe, Total and Beta Renewables are each operating one plant. In Asia, Tianguan and Longlive (China), India Glycols, and Izumi Japan have commercial 2G plants. BTG, Valmet, Axens, and Praj Industries are leaders in this technology, while Novozymes is key in providing enzyme technology. In the biorefinery landscape, Borregaard is a key player in lignin derivatives, while NatureWorks and Corbion produce lactic acid derivatives.
2G is promising, but…
Unfortunately, despite being promising, 2G bioconversion hasn’t been able to unlock its true potential. Challenges include achieving scalable conversion technology, biomass aggregation, capital issues, and value chain integration. The technology, though available, has yet to achieve scalable yields and efficiencies. The nature of the raw materials also adds to the challenges in terms of quality, handling, and processing. The aggregation and logistics involved with biomass add to these limitations on 2G technology.
Additionally, the technology is not lucrative for venture capital funds who, though willing to take the risk, view 2G as too capital intensive, while investors like pension funds find the technology to be uncertain.
Lastly, the most critical limiting factor is the gap in the value chain. Stakeholders within the value chain are experiencing fragmented capabilities like sourcing biomass, technology, and distribution of the products. To meet these challenges, second-generation biofuel projects can be structured by collaboration among key stakeholders, bringing together feedstock suppliers, investors, technology partners, distribution networks, and government agencies.
Are 3G biofuels more sustainable?
Algal biofuels, which combine the production of high-value industrial chemicals with the use of cheaper inputs like wastewater or seawater, make third-generation generation biofuels highly sustainable. The potential of algal biomass is unmatched compared to any other biomass source. Algal biomass can produce ten times more biofuel compared to other biomass sources. Biodiesel, butanol, ethanol, gasoline, methane, vegetable oil, and jet fuels are the fuels derived from algal biomass.
One of the benefits of algal biofuel is that the oil produced can be refined to produce biodiesel or fractionated to produce components of gasoline. The other benefit is that the algae species can be genetically modified to produce species that can produce higher volumes and a greater range of products. According to the US Department of Energy, the production of algal biomass would utilize 0.42% of US land to meet the energy demands of the country. This reflects on the efficiency of algal biomass.
Third-generation biofuels have a flip side, though, since producing algal biomass requires huge volumes of water, nitrogen, and phosphorous. The amount of greenhouse gas produced from these inputs will be in excess of that saved by using algal biofuels. Exxon Mobil in 2013, after an investment in excess of USD 600 million, concluded that algal biofuels won’t be economically viable for another 25 years. Despite this single limiting factor, third-generation biofuels are being extensively researched.
Second-generation biofuel technology will be a significant enabler to reduce dependency on fossil fuels for energy and industrial processes. Typical biorefinery inputs would consist of polymers, food ingredients like polyols, antioxidants, and fibers, and/or ethanol. Third-generation technology also has a huge potential to supplement our energy needs, and it can become economically successful by limiting inputs and increasing efficiencies and product range.
To achieve the objective of a circular economy, biorefineries need to achieve the optimal scale and product mix to make them economically viable businesses. Second- and third-generation bioconversion have the capability to complement fossil fuel resources and make significant contributions to achieve a circular economy and a healthy planet for future generations.
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