UK scientists to tackle challenges of converting rice straw into biofuels

In recent years, biofuels and biobased chemicals have been blended with petrol to create a more sustainable alternative.

The Aston University researchers are to examine issues that currently hinder the conversion of rice straw into an alternative fuel.

Currently the production of biofuels mainly relies on sugar crops such as sugarcane and sugar beet, which raises major concern about the competition between growing crops for food or fuel.

However, plant dry matter such as rice straw is seen as a better alternative to current crops because it doesn’t affect food security. Rice straw is often treated as an agricultural waste by-product and is removed by burning in the field.

The vicious cycle of straw burning​

According to the International Rice Research Institute, open-field straw burning has increased dramatically over the last decade. Globally, roughly 800 to 1,000 million tons per year of rice straw is produced, with about 600 to 800 million tonnes per year produced in Asia. This continues to rapidly increase due to shorter turnaround time required for intensified rice cropping, it says.

Open-field crop burning is hazardous to the environment and human health alike. It releases dangerous pollutants into the environment and can deplete soil nutrients like nitrogen and organic matter. Several countries, including India, have taken steps to stop the burning process.

The new research is being led by Dr Alfred Fernandez-Castane, senior lecturer in biochemical engineering and principal investigator at the Energy and Bioproducts Research Institute (EBRI) at Aston University, alongside a Marie Curie fellow, Dr Longinus Igbojionu.

Their two-year project, an integrated approach to ethanol production from rice straw via microwave-assisted deep eutectic solvent pretreatment and sequential cultivation using Candida tropicalis and Saccharomyces cerevisiae, will explore cleaner and cost effective methods to extract rice straw’s energy-containing molecules.

 “The problems envisaged with the conversion of rice straw to ethanol can be categorised into four main challenges and resolving each challenge will lead to a major advance on the current state of the art,” Dr Alfred Fernandez-Castane said.

“The first is to develop pre-treatment conditions which will break down complex polymers thereby allowing the removal of lignin.

“The next is to investigate novel biomass pre-treatment technologies combining green solvents and microwaves and how different methods affect morphology, structure and crystallinity of biomass. The next is to develop novel biotrasnformations using the yeasts Candida tropicalis and Saccharomyces cerevisiae to convert sugars into ethanol efficiently.

“These three challenges will lead to the fourth scientific challenge which is to make the process sustainable and scalable, such as recycling the wastewater created and even the possibility of using the by-product of yeast for animal feeds.”

The team believes that the research will help contribute to combating global warming and decreasing avoidable deaths by protecting global food security, minimising CO2 emissions by reducing the burning of straw and decreasing the farmland needed for growing energy crops.

The research will end in November 2025.