Pre-treatment and Conversion

The Pre-treatment and Conversion Topic Group comprises three strands:

Pre-treatment, led by Jason Hallett
Catalysis, led by Chris Hardacre
Pyrolysis, led by Tony Bridgwater

The topic group leads are supported by Katie Chong.

Pre-treatment

The limiting factor in many biomass valorisation processes is the efficiency and cost of the primary fractionation process which separates the cellulose, hemicellulose and lignin in biomass without compromising the inherent value of these individual biopolymers. The most important aspects of a biomass fractionation (pre-treatment) strategy are cost and flexibility. The feedstock flexibility in particular controls the ability of the process to handle variations in feed composition and source, and translation of the technology across systems.

We have focused on developing simple, cost- and energy-efficient fractionation technologies based on very low-cost ionic liquids (liquid organic salts) to extract lignin and hemicellulose, leaving a pure cellulose pulp for further valorisation. The lignin fraction can also be recovered for further processing. This enables the production of fuels, chemicals and materials from all three streams at low cost (comparable with food-grade sugar from sugar beet or sugar cane) and with a low-carbon footprint, essential for low-carbon fuels and chemicals.

The key step was design of an ionic liquid that was cost-comparable to bulk organic solvents, and integrating it into a process that uses low-energy inputs. In Supergen Bioenergy, we are demonstrating this technology on metal-contaminated biomass feedstocks, where the solvent extracts the metals along with the lignin.

A key challenge in utilising biomass is its upgrading to value added chemicals and fuels. In addition, the production of sustainable sources of hydrogen to deoxygenate biomass is critical if bio resources are to be employed effectively. These conversion technologies need to be able to be performed on a wide range of biomass sources as well as needing to be flexible in location and size.

The project aims to utilise solar energy for the deoxygenation of biomass/bio-oil to create fuels and value added chemicals.

Deliverables will include:

An optimised process including the use of thermal activation in batch and continuous flow
In-situ and ex-situ spectroscopic techniques to understand the process.

Fast pyrolysis is a relatively recent technology that converts biomass and solid waste into high yields of liquid (known as bio-oil) for use as fuels, and which can be upgraded to chemicals and biofuels. The key requirements are:

• Small biomass size to permit very high heating rates
• Carefully controlled temperature to optimise liquid yield
• Rapid removal of char to avoid vapour cracking and loss of yield
• Very short hot vapour residence times to avoid vapour cracking

The planned work will:

Explore how ash in biomass affects the yield and quality of the bio-oil and whether this can be controlled by blending
Explore how biomass pretreatment affects the yield and quality of the bio-oil especially where lignin is a major component of the feed material
Explore how chemicals such as levoglucosan can be maximised by controlling the feedstock and its characteristics and deduce a technoeconomic analysis of alternative processes.

Experimentation will mostly be mostly performed on a 1 kg/h continuous fluidised bed fast pyrolysis system as shown below. This will produce sufficient quantities of products for a meaningful assessment of product quality and deliver samples to other partners.