New low-cost method to turn plant waste into biofuels

Scientists have developed a novel method that could make it much cheaper to produce biofuels such as ethanol from plant waste, and help reduce the dependence on fossil fuels.

The approach features an ammonia-salt based solvent that rapidly turns plant fibres into sugars needed to make ethanol.

It works well at close to room temperature, unlike conventional processes, according to the study published in the journal Green Chemistry.

"Our pretreatment system can slash -- by up to 50-fold -- the use of enzymes to turn solvent-treated cellulose (plant fibre) into glucose (a sugar) used to make bioproducts like ethanol," said lead author Shishir P. S. Chundawat, an assistant professor at Rutgers University-New Brunswick in the US.

"Similar processes could greatly reduce the cost of producing biofuels from waste biomass like corn stalks and leaves," said Chundawat.

The solvent can also extract more than 80 per cent of the lignin in plant waste.

Lignin, which binds to and fortifies plant fibres, could be used to help upgrade valuable aromatic chemicals in the future, according to Chundawat.

Corn stalks, leaves and other residue -- called corn stover -- and switchgrass, for example, have tightly packed cellulose microfibrils, which are tiny strands thinner than fibres.

Microfibrils are difficult to break down using enzymes or microbes, making it hard to turn many plant-based materials in biomass into biofuels or biochemicals, researchers said.

Biomass includes microbial, plant or animal-derived materials used for renewable energy production and industrial processes.

Speeding up the conversion of cellulose into sugars like glucose with enzymes requires suitable solvents or heat- and chemical-based pre-treatments.

In the last 150 years, several solvents that can break down cellulose fibres have been explored, the researchers said.

However, most solvents remain costly or require extreme ranges of operating pressures or temperatures to be effective, they said.

The ammonia-salt based solvent system quickens the conversion of cellulose into sugars using enzymes, according to the researchers.

It can greatly reduce the cost of biofuels production because enzymes can account for about 15 to 20 per cent of the cost of making biofuels like ethanol from biomass, the noted.