Hydrothermal Upgrading of Biomass/Lignin
Lead Research Organisation:
Imperial College London
Department Name: Chemical Engineering
Abstract
Greenhouse gas (GHG) emissions are directly related to expected climate changes in the future. Preliminary estimates for the year 2016 indicate these emissions decreased 0.6% in the European Union, which is 24% below 1990 levels. This value falls within the 20% reduction target (compared to 1990 levels) demanded by the European Union Renewable Energy Directive for 2020 but is still far from the 40% target for 2030. It is also required that by this year at least 27% of the consumed energy comes from renewable sources. CO2 represented 81% of the total greenhouse gas emissions in the EU during 2016, with 29% originated in the power generation industry and 25% in road transportation. While carbon capture could be effective in reducing emissions in power generation and manufacturing industries, it is not feasible for road transportation. Therefore, it is an urgent matter to find drop-in replacement transport fuels, which minimise environmental impact and are economically viable, particularly whilst technologies and large scale infrastructure are being finalised for vehicles, powered by batteries or H2 generated using renewable energy.
The production of biofuel from biomass, which acts as both a renewable source and a carbon sink, is an attractive alternative to conventional liquid fuels. However, EU directives also require sustainability from biofuel production. On one hand, it means the demonstration of actual emissions savings (less than 70% of GHG emissions compared to fossil fuels). On the other, it means ensuring that biofuel production does not replace crops previously destined to the food market. This is translated in a 7% limit to biofuels used in transportation derived from crops grown in agricultural land. It is therefore imperative to move the biofuel production from food-based crops (1st generation) to other non-food sources such as micro-algae, organic waste and lignocellulosic materials (2nd generation).
The upgrading of lignocellulosic material has been the subject of many studies over several decades. It includes processes such as fermentation, fast pyrolysis and hydrothermal upgrading via carbonization, liquefaction or gasification. The hydrothermal liquefaction (HTL) process is based on the chemical transformation of biomass in aqueous medium, typically close to the critical point of water (usual conditions: 200-350 bar and 270-350 oC). Bio-oil is produced and after further refinement, it can be used as transportation fuel. Compared with the available processes, using hot pressurised water presents several advantages such as: higher quality biocrude (lower oxygen content and increased HHV); higher energy efficiency (feed drying is not required); larger variety of products (diesel and/or gasoline) based on conditions manipulation; dissolution of pollutants in aqueous phase and elimination of pathogens. These advantages suggest that this process is a viable option not only for lignocellulosic material, but also micro-algae and organic wastes (e.g. plastics, municipal waste, sewage sludge).
The overall objectives of this PhD research project will be 1) to investigate experimentally the hydrothermal upgrading of lignocellulosic biomass, to make transport fuels, and 2) to develop a techno-economic and life cycle assessment to determine the viability of this process.
The production of biofuel from biomass, which acts as both a renewable source and a carbon sink, is an attractive alternative to conventional liquid fuels. However, EU directives also require sustainability from biofuel production. On one hand, it means the demonstration of actual emissions savings (less than 70% of GHG emissions compared to fossil fuels). On the other, it means ensuring that biofuel production does not replace crops previously destined to the food market. This is translated in a 7% limit to biofuels used in transportation derived from crops grown in agricultural land. It is therefore imperative to move the biofuel production from food-based crops (1st generation) to other non-food sources such as micro-algae, organic waste and lignocellulosic materials (2nd generation).
The upgrading of lignocellulosic material has been the subject of many studies over several decades. It includes processes such as fermentation, fast pyrolysis and hydrothermal upgrading via carbonization, liquefaction or gasification. The hydrothermal liquefaction (HTL) process is based on the chemical transformation of biomass in aqueous medium, typically close to the critical point of water (usual conditions: 200-350 bar and 270-350 oC). Bio-oil is produced and after further refinement, it can be used as transportation fuel. Compared with the available processes, using hot pressurised water presents several advantages such as: higher quality biocrude (lower oxygen content and increased HHV); higher energy efficiency (feed drying is not required); larger variety of products (diesel and/or gasoline) based on conditions manipulation; dissolution of pollutants in aqueous phase and elimination of pathogens. These advantages suggest that this process is a viable option not only for lignocellulosic material, but also micro-algae and organic wastes (e.g. plastics, municipal waste, sewage sludge).
The overall objectives of this PhD research project will be 1) to investigate experimentally the hydrothermal upgrading of lignocellulosic biomass, to make transport fuels, and 2) to develop a techno-economic and life cycle assessment to determine the viability of this process.
Organisations
People |
ORCID iD |
| Christopher Tighe (Primary Supervisor) | |
| Artur Andrade (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509486/1 | 01/10/2016 | 31/03/2022 | |||
| 2194409 | Studentship | EP/N509486/1 | 01/11/2018 | 31/07/2022 | Artur Andrade |
| EP/R513052/1 | 01/10/2018 | 30/09/2023 | |||
| 2194409 | Studentship | EP/R513052/1 | 01/11/2018 | 31/07/2022 | Artur Andrade |
| EP/T51780X/1 | 01/10/2020 | 30/09/2025 | |||
| 2194409 | Studentship | EP/T51780X/1 | 01/11/2018 | 31/07/2022 | Artur Andrade |
| Description | This research has demonstrated that a compound containing ether bonds (dibenzyl ether) can be hydrolysed through contact with supercritical water in a confined jet configuration. o This type of chemical bound represents a significant part of lignin, which may be liquified individually or as part of biomass. o Therefore, this is a stepping stone in showing how the supercritical hydrothermal process can be effectively utilised for the liquefaction of lignocellulosic biomass, and ultimately in the production of sustainable liquid fuels and chemicals • The existing experimental apparatus was expanded to accommodate: o Off-line analysis of liquid products through phase separation and quantitative methods). o Variable reactant conversion (interchangeable reactor sections). o Non-isothermal behaviour (real-time temperature measurement in different sections of the reactor). o Feed degassing. Furthermore, through quantitative analysis and accurate modelling of the continuous process, key parameters were estimated. These are of importance for an eventual scale-up from bench-scale and techno-economic analysis and were estimated based on a mathematical model that accounts for: o Reactor geometry. o Fluid properties based on the Statistical Associating Fluid Theory (SAFT) equation of state. o A variety of different forms of rate equations relating to proposed reaction mechanisms and possible rate limiting steps. o Mass transfer limitations and heat losses. A computational fluid dynamics model is currently being developed to describe the fluids mixture at the jet's outlet. Finally, in collaboration with a visiting Chinese Scholarship Council student from Tianjin University in China, the developed HTL process was tested in with glucose and glycine, which are other liquids that can be used as models for components of biomass. |
| Exploitation Route | • Direct use of estimated parameters in the design of scaled-up reactors, and techno-economic analysis of processes including dibenzyl ether hydrolysis. • Further research the application of the hydrothermal liquefaction process to different feeds. Considering increasingly more complex organics, from small molecules to large biopolymers with known composition, to actual lignocellulosic biomass. • Characterise the bio-crude produced and evaluate the need for downstream upgrading, typically by hydrodeoxygenation. • Inclusion of this process in a wider bio-refinery process that goes from feed collection/processing to deployment of refined biofuel. • Evaluation of the process techno-economic feasibility. |
| Sectors | Chemicals,Environment,Manufacturing, including Industrial Biotechology,Transport |