Photocatalytic bioethanol Production

One of the greatest challenges in the 21st century is to meet the global energy demand. Dwindling supplies of fossil fuel, combined with detrimental release of green house gases (GHG) have lead to the quest for renewable sources of fuel/energy with EU targets of 10% energy from renewable by 2020. Wind, solar, tidal and biofuel from crops (sugar cane and corn) are rapidly being introduced as alternative energy supplies. However, use of food crops has been widely criticised due to escalating population, food prices and deforestation for cultivation of energy crops hence there is an urgent need to develop more sustainable alternatives that do not impact global food production. One approach is the exploitation of significant quantities of available fibrous waste, which consist largely of cellulose. This waste, generated by agriculture, forestry and industry (e.g. paper manufacturing) can be exploited for biofuel production. It has been estimated that in the UK alone, annual excess straw exceeds 5.7 million Tonnes. This abundant waste resource, coupled to the fact that they are geographically evenly distributed across the country, could offer localised, low energy solutions for production of biofuel.
As a carbohydrate cellulose consists of sugar molecules which can be fermented to provide ethanol but unlike starch the structure of cellulose prevents simple release of bound sugars. Previous attempts to harness cellulosic waste have used extreme treatment conditions to release the usable sugars. In existing pre-treatment procedures, enzymes, acid and alkali explosion, wet oxidation, steam explosion may be combined with high pressure and temperature. These procedures are expensive, energy demanding and generate hazardous waste.
In this project, we propose a cost effective, low environmental impact approach to produce bioethanol from cellulosic waste by photocatalysis combined with fermentation in a single reactor. Photocatalysis is a process which uses a catalyst to accelerate a photoreaction by generating free radicals, and is commonly exploited in a range of applications (waste water treatment, antifouling paints, self-cleaning glass). Photocatalysis will be used to release sugars from the cellulose which will pass through a semi-permeable membrane where they will be fermented by yeast (or other selected microbes) to yield bioethanol. This approach has multiple advantages; catalyst is low cost, non-toxic, self cleaning, recoverable and activated by harvested natural light (augmented by low energy LED's where required). This integrated work programme is led by the experts in microbiology (Professor Linda Lawton - RGU), engineering (Professor Peter Robertson-RGU) and chemistry (Professor John Irvine - St Andrews) all of whom have a proven track record in application driven research.
Key components of the work programme include; substrate targeted design and synthesis of novel catalysts, which will be screened for maximum liberation of fermentable sugars, screening of microbes for maximum production of bioethanol, design, fabrication, testing and optimisation of the parallel bench scale reactor. A key features of the reactor is the use of selective membranes to separate the liberated sugars from the catalyst. Under typical conditions the photocatalytic reaction would completely degrade compounds in contact with the catalyst hence liberated sugars will pass through the membrane where they will be available for microbial degradation. This novel reactor will be simple and scale-able facilitating implementation at local or municipal scale. For maximum versatility, the reactor will be optimised to produce bioethanol from an array of waste feed stocks from agriculture and industry.
This multidisciplinary project will address the challenge of renewable energy with the development of a sustainable, cost effective, low environmental impact process for conversion of low value fibrous waste into high value bioethanol.

Current trends on world's energy are unsustainable. Rapid depletion of fossil fuels coupled with increased global population, industrialisation and climate change, necessitate radical changes in strategy. Development of practical, renewable energy solutions is essential to secure a sustainable global energy supply.

To address this challenge, the project aims to develop and optimise a scale-able parallel reactor for the conversion of waste biomass from plants into bioethanol. The process will be cost effective with low environmental impact, exploiting the photocatalytic conversion of waste to produce sugars followed by fermentation into bioethanol. The potential of the proposed concept has been clearly demonstrated in a preliminary study at RGU by the photocatalytic release of fermentable sugars from cellulose using a photocatalyst (TiO2). The outcome of this 4-year project has been expected drive into potential socio-economic and environmental impacts for sustainable human life and environment, for both developed and developing countries. To meet this challenge, we have assembled a multidisciplinary team, of application driven researchers and developed a programme that reflects a clear pathway to impact in research, society and the environment.

Development of this novel approach for bioethanol production has multiple direct beneficiaries; industry (re-use of waste reducing carbon footprint), environmental organisations (reduction in pollutants from waste and current processes), governments (positive economical value, fuel and food security), communities (employment, rural income, infrastructure development).In addition to contributing to future renewables, the technology involved in the parallel reactor will have enormous potential for low cost/energy bio-processing applications with clear global benefit. The success of this reactor would provide a world leading technology with clear export value globally as the reactor design would be suitable for application in most countries.

This project provides opportunities for public communication and engagement; local and national media, podcasts, web pages, schools (projects for pupils, exhibitions and science festivals), covering areas on use of low value waste for biofuel production, harnessing natural light and smart bio-processing. The multidisciplinary nature of the work would make it particularly relevant to developing interest in SET subjects with school pupils encouraging students to pursue these topics to a higher level.

Close collaboration of PIs, co-Is and PDRAs is pivotal to success in this project and will clearly benefit development of the PDRAs by means of knowledge transfer, interdisciplinary training and exchange visits. Development of innovative young scientists is essential for a sustainable research and development capability.

Significant impact of this project is that it will involve high quality research at the forefront of science and technology. It is expected to lead to high impact publications, multiple technology patents and extensive public/industrial engagement activities. The ultimate impact is to deliver a sustainable, technological solution to meet the future energy challenges and demonstrate the UK's commitment to this important agenda.