Crop waste to ethanol

Background & introduction

The world produces hundreds of millions of tons of agricultural by-products every year that are considered “waste” - plant stalks & roots, leaves, nut shells, fruit waste and more.

A large part of these supposed waste can actually be converted to valuable products.

One of the valuable products that can be derived from plant waste is ethanol, an alcohol that is used to make spirits, as an industrial solvent, and increasingly as a transport fuel in the form of a blend to gasoline.

What are the key sustainability benefits?

Unused agricultural waste gets converted to CO2 if burnt on the fields or into methane if left to rot. Both CO2 and methane are greenhouse gases and thus converting these to ethanol can  significantly reduce the net greenhouse emissions from these.

An equally important benefit is the economic benefit to the society in the form of higher incomes for the farmer community. What was earlier wasted and was considered a nuisance can today provide them with substantial increases in their overall incomes.

How does this work?

Most agricultural waste is in the form of what is called lignocellulosic material - that is, the cellulose is bound by lignin, a glue-like material.

In order to convert this into ethanol, the cellulose needs to be first separated from lignin (in a process called pre-treatment), the cellulose needs to then undergo hydrolysis for conversion to simple sugar and finally the sugar needs to be converted to ethanol through fermentation.

Where is innovation needed (which part of the process)?

Innovation is needed largely for the pre-treatment process.

Today, two approaches are used: Physical methods and chemical methods. Both methods have their own challenges, especially in terms of costs. Innovations are needed to optimize the pre-treatment processes and reduce costs.