News and Trends

After, semi-industrial experiments starting December 2016, researchers from Egypt's National Research Centre have recently produced a biofuel suitable for airplanes.

The centre was tasked by the Egyptian Ministry of Civil Aviation to find a local biofuel that can fuel aircrafts. This decision was done to support the implementation of the International Air Transport Association plan, which aims to cut carbon dioxide emissions caused by aviation companies in half by 2050.

The researchers made biodiesel from the seeds of jatropha, whose seeds contain 20-25% oil. This oil can be extracted using organic solvents such as hexane. However, since the properties of jatropha oil differ from traditional engine oils, such as viscosity, density and degree of combustion, it needs to undergo a number of chemical processes to be adapted for use in running engines.

Currently, the fuel is suitable for car engines. However, to be suitable for jet engines, the fuel should be able to resist freezing until at least minus 45°C.

The Dubai-based Neutral Fuels has just become the first company to produce commercial biofuel from dairy waste.

The new fuel has the same quality as the company's vegetable oil-derived biofuel, which has fuelled McDonald's UAE's logistics fleet for the past four years. Karl W Feilder, chairman and CEO at Neutral Fuels, said the project was inspired by Dubai's "Zero Waste by 2030" target.

UAE is the second largest producer of dairy products in the Gulf region after Saudi Arabia and is expected to grow further through 2021. With UAE's annual fresh milk production of 167,000 tonnes, every 1% of waste that is processed into biofuel will result in 1.67 million litres of biofuel, which then can reduce the carbon footprint by 4,460 tonnes of carbon and equivalents. Adding the waste from making butter, cream and ghee, the volume of biofuel from the dairy industry could more than double.

Neutral Fuels is one of Dubai's most successful recycling companies, and its biorefinery is an example of a waste-to-energy plant. It also has ongoing research into new production techniques and feedstocks.

The Indian government is set to make a biofuel policy framework that will help increase farmers' income, cut down crude oil imports and encourage global automobile companies to launch their flexible fuel vehicles in the country.

The move is part of Prime Minister Narendra Modi's plan to increase farm production by 2022. The move will also facilitate setting up close to 1,500 industrial units for ethanol production in villages, creating more job opportunities. The government projects that the alternate fuel industry could be worth 1 trillion rupees.

The government wants to have more alternative fuels on the country's energy mix to moderate petroleum product consumption. India is currently the third largest energy consumer in the world after the US and China. Prime Minister Modi, in 2015, previously set a target of reducing import dependence on hydrocarbons by 10% by 2022.

The oil ministry is set to prepare two policies: one on the production of ethanol from various agriculture sources and another on the production of methanol from coal. Once implemented, the move could bring down crude oil import bill by Rs1 trillion.

Research and Development

Lignocellulosic biomass is an abundant and inexpensive resource for biofuel production. However, pretreatment is important to allow efficient enzymatic hydrolysis of cellulose. Wet oxidation of biomass, which uses hot acetone, water, and oxygen, was found to be a potential pretreatment method for plant biomass. The resulting cellulose-rich fraction will have the potential to be used for cost-competing production of bioethanol. The team of Constantinos Katsimpouras of the National Technical University of Athens aimed to test the feasibility of this pretreatment method in beech wood.

The team pretreated beech wood residual biomass using acetone/water oxidation process for the production of cellulosic ethanol. The effect of pressure, reaction time, temperature, and acetone-to-water ratio on the final composition of the pretreated samples were then evaluated. The team also determined the optimal pretreatment conditions for maximum bioethanol production. 

The optimization of the pretreatment allowed efficient utilization of beech wood residual biomass for the production of cellulosic ethanol. The process also obtained lignin, which can be upgraded towards high-added-value chemicals.

Brown rot fungi has the ability to selectively degrade cellulose in wood while leaving the lignin intact. They generate highly reactive oxygen species that alter the chemical structure of wood and work with enzymes that break down cellulose chains. However, reactive oxygen species could also damage the fungal enzymes and the wood structure, so researchers have hypothesized that the fungi spatially segregate the oxidant generation process from the enzymes using chemical barriers.

However, a team of scientists at the University of Minnesota, the U.S. Forest Products Laboratory, University of Wisconsin, Madison, Gyeongsangnam-do Agricultural Research and Extension Services in South Korea, and Pacific Northwest National Laboratory found evidence that brown rot fungi separates the oxidants and enzymes in time rather than in space. The team discovered this two-step wood decomposition mechanism by growing brown rot fungi in one direction along thin wood specimens separating the stages of wood decay linearly across the substrate. The wood was then cut into sections and analyzed for patterns of gene expression.

Researchers found that during the initial part of brown rot colonization, there was evidence of lignocellulose oxidation by reactive oxygen species and an increase in expression of genes important for plant cell wall swelling. These activities would weaken the structural integrity of wood and make it easier for enzymes to access cellulose chains. Then, only at the latter parts of colonization did brown rot fungi begin to produce glycoside hydrolase enzymes that break down cellulose chains into their component sugars.

This unique fungal strategy could provide important new clues for improved conversion of woody plant materials into renewable cellulosic biofuels.

Hot water hydrolysis process is commercially applied for treating wood chips prior to pulping or wood pellet production, and produces hydrolysis liquor as a by-product. Since the hydrolysis liquor is dilute, the production of value-added materials from it would be challenging.

A team of researchers from Åbo Akademi University in Finland and Lakehead University in the US proposed acidification as a possible method to extract lignin compounds from the hot water hydrolysis liquor. The acidification of hydrolysis liquor allowed the extraction of lignin compounds from the liquor, leaving behind fermentation inhibitors, such as furfural and acetic acid. The team then used membrane dialysis to remove inorganic salts from lignin compounds. The purified lignin compounds were found to be thermally stable.

Based on their results, the team proposed a process for producing purified lignin and precipitates of volatile compounds from the hydrolysis liquor.

Energy Crops and Feedstocks for Biofuels Production

Monolignol-like molecules can be integrated into lignin along with conventional monolignol units, resulting in hydrolyzable lignin, an easily removable form suitable for biofuel production. Disinapoyl esters (DSEs) were found to be promising lignin modifying units in this system. Researchers from Purdue University manipulated the metabolic flux in Arabidopsis thaliana to increase the amounts of DSEs by overexpressing sinapoylglucose:sinapoylglucose sinapoyltransferase (SST), which produces two main DSEs, 1,2-disinapoylglucose, and 3,4-disinapoyl-fructopyranose.

The team were successful in overproducing DSEs by introducing an SST-overexpression construct into the sinapoylglucose accumulator1 (sng1-6) mutant (SST-OE sng1-6), which lacks enzymes that would compete for the SST substrate, sinapoyglucose. Introduction of cinnamyl alcohol dehydrogenase-c (cad-c) and cad-d mutations into the SST-OE sng1-6 line further increased DSEs. However, while the team successfully upregulated the accumulation of the DSEs, the team did not find any evidence of the integration of these DSEs into the cell wall.

These results suggest that although metabolic engineering is possible, a deeper understanding of sequestration and transport mechanisms will be necessary for successful lignin engineering using this approach.

Biofuels Processing

Hemicellulose has been mostly ignored in biofuel production as surface reactions are capable of releasing only a quarter of the soluble sugars for ethanol production. However, a research team at Indian Institute of Technology Kharagpur (IITK) has found that to quickly produce soluble sugars from hemicellulose for the bioethanol industry, one has to look at its pores.

The IITK team have found that pore-scale phenomena can be used to increase the yield of fermentable sugars and bioethanol from hemicellulose. Therefore, water hyacinth, a free-floating perennial that contains up to 50% hemicellulose, can be an attractive feedstock for biofuel production.

The average cellulose-hemicellulose ratio in plant cell walls is around 2:1, which suggests that biofuel productivity and cost-effectiveness could be boosted by more than half if the hemicellulose could be reasonably used. Simultaneous production of cellulosic and hemicellulosic fuels from the same biomass would greatly improve the combined net energy value for cellulosic ethanol.