Bio-based activated carbon for water purification

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 is activated carbon or activated charcoal which is typically produced from conventional charcoal. Activated carbon plays a major role in water purification

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 activated carbon can  significantly reduce the net greenhouse emissions from these.

Further, use of low value biomass as a raw material significantly reduces the cost involved in activated carbon based purification processes. Sale of biomass also creates a revenue model for farmers.

How does this work?

First the biomass undergoes a pyrolysis process at 500°C–600°C in the nitrogen atmosphere. Then the char is treated at 800°C–1000°C through a physical or chemical activation process in the steam atmosphere to enhance the char surface area.

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

The challenge lies in commercializing the pyrolysis technology due to technical challenges associated with heat transfer in fast pyrolysis and related costs. Innovations in these areas could enhance adoption of the technology at scale.