Cascade processes for integrated bio-refining of agricultural waste in India and Vietnam

Managing the water, energy and food requirements of a constantly-rising world population, in the context of climate change, is a key global challenge. Significant growth in proven and predicted fossil fuel reserves mean that achieving the Paris COP21 target for a 1.5 degree Celsius increase in mean global temperature relative to the pre-industrial level is at risk if we remain dependent upon these reserves.

Biomass derived from agricultural and forestry residues is a low carbon feedstock for transportation fuels and organic chemicals. Integrating conversion processes so that biofuels, chemicals and energy are co-produced maximises the economic viability of waste biomass utilisation; an approach analogous to current petroleum refineries that deliver high volume/low value (fuels and commodity chemicals) and low volume/high value (fine/speciality chemicals) products in tandem. The potential for agricultural waste as a feedstock for low carbon fuels and chemicals is vast, even allowing for sustainable land management practices. In the EU alone, 16% of road transport fuel could be produced from waste by 2030 which would deliver green-house gas savings of greater than 60%.

In Asia rice is the single most important crop, annually yielding >250 million tonnes of waste rice residues. Current practices of "at-site" burning of these waste residues in developing nations have serious detrimental effects on the environment and human health; improved waste management is therefore essential. To employ rice residues as sustainable feedstocks for transportation fuels and organic chemicals requires improved processes for their pre-treatment and conversion. This project proposes to develop an alternative, environmentally-benign process to utilise waste rice residues for the production of fuels and bio-derived agrochemicals, which will impact on renewable energy, climate change and environmental pollution by seeking to transform a plentiful waste resource into (1) an economically-viable, sustainable energy source for transportation fuels; and (2) a sustainable feedstock for the production of organic chemicals, while mitigating emissions of carbon dioxide and atmospheric particulates from "at-site" burning.

We will exploit recently-established demonstrator plant facilities at ICT-Mumbai in India (ICTM) which offer cost-effective waste rice residue fractionation into lignin and cellulose, with a focus on bioethanol production. Our aim is to develop underpinning science to offer a wider range of high-value products from lignin, sugars and other extracted components thereby future-proofing the process to combat the fragile economics of bioethanol production. We propose an innovative and flexible conversion platform building on current expertise of the UK partners. A multidisciplinary team with expertise in plant cell wall deconstruction and simultaneous saccharification (Institute of Food Research; IFR), green extraction methods (The VN-UK Institute, University of DaNang), enzyme expression, tandem bio- and chemo-catalytic conversion technologies (Aston), bio-chemo routes to depolymerising lignin (Vietnam National University, Ho Chi Min City), process engineering and catalysis (Ha Noi University of Science & Technology) and photocatalytic water depollution (Aston and The Vietnam Academy of Science and Technology) will tackle the challenge of value-added product production while also ensuring sustainable water management practices are adopted.

Enhanced research capacity in the Indian and Vietnamese institutes will be facilitated by interdisciplinary researcher training exchange visits to the partner research institutes at Aston and IFR, building a platform for sustainable agricultural waste management.

This project will exploit waste rice residues in the production of chemicals by delivering the following aims:

1 - Waste rice residue pre-treatment processes will be investigated to enable extraction of rice bran oil and high-protein products from rice bran; fractionation of rice straw and husk; and assessment of downstream saccharification. Comparison of the economic and environmental viability of UK and LMIC processes will provide insight into how cellulose disruption, enzymatic saccharification and lignin quality is affected by treatment conditions and rice straw/husk composition.

2 - The production of malic acid (and derivatives) from glucose and the depolymerisation of lignin using enzymatic and catalytic cascades will be investigated. A "one pot" route to malic acid via the co-factor-balanced, consolidated action of 5 enzymes from thermophilic bacteria has been devised. Recombinant enzymes will be heterogenised for continuous operation via surface chemisorption or in-pore cross-linking approaches using macroporous supports. Heterogeneous catalysts for selective hydrogenation/hydrodeoxygenation/dehydration of malic acid to succinic, maleic or 2,4 dihydroxybutyric acids will be developed. For the latter, pore dimensions (exploiting confinement effects) and surface polarity will be explored to direct chemo-selectivity. Tandem chemo-biocatalytic exploitation of lignin will be investigated using immobilised enzymes that depolymerise lignin together with Ni-based chemo-catalytic aryl ether bond cleavage.

3 - Photo-catalysis will be employed for the remediation of low concentrations of organic pollutants in fermentation waste-water that will be pre-treated with duckweed. We will nano-engineer semiconductor photo-catalysts to enhance mineralisation of organic residues from fermentation broths to enable recycling of waste water in bio-catalytic processes.

Overall, the project will generate a sustainable biotechnological route to waste management in LMICs.

This project will rapidly advance knowledge in the fundamental science and engineering of agricultural waste usage as a feedstock in biorefineries. Routes to cost-effective and sustainable biofuels and chemicals will contribute to the global transition to a low carbon economy.

Improved processing economics will result from the development of methods to extract high-value components from biomass. Processing steps that use state-of-the-art biotechnology to generate enzymatic systems for cascade bio-/chemo- catalytic transformations will underpin lignocellulosic biomass biorefining technology in the UK, India and Vietnam.

The consequences of chemical processes on the environment are a cause of increasing concern. There is a particular need to find sustainable, economically-viable routes to chemicals for a range of applications. The project will therefore benefit a wide range of stake-holders including the public, companies who are establishing low carbon processes in LMICs, scientists seeking employment in the UK, India and Vietnam, and the environment.

Research results will be implemented in the field in India and Vietnam to obtain data for a future techno-economic analysis of the process. The know-how of the resulting technologies will be transferred appropriately to Indian and Vietnamese partners, including academic researchers, industrial enterprises and farmers. The research capabilities of India and Vietnam will be enhanced significantly through the collaboration and capacity building exercises. Capacity building in the LMICs will result from exchange visits of PhD students, researchers and academic staff between India/Vietnam and UK research groups to better understand the challenge and stimulate knowledge transfer. The collaborations will facilitate (i) knowledge transfer at the interface of bio-/chemo- transformations and physics/engineering and (ii) provide young researchers in India and Vietnam with unrivalled access to expertise spanning the whole biorefining field.

Our published data on bio- and chemo-catalysis approaches to the synthesis of agrochemical intermediates will lead to the development of greener, more cost effective, safer products. This will be seen as a benefit by an increasingly demanding and well-informed customer base, who are aware of the impact on the environment. It will also benefit industrial stakeholders interested in low carbon chemicals who will have access to methodology to produce a range of new glucose-derived additives for use in commercial applications. A significant benefit of this project will be the production of malic acid derivatives for use as surfactants in agrochemical formulations; developing and expanding new markets for low carbon products has potential to create new jobs.

A key focus of the project is the development of new technology for the valorisation of agri-waste within India and Vietnam for sustainable agrochemical production. The partners have expertise in complementary skills spanning biomass characterisation, biochemistry and enzymatic conversion, materials synthesis and bioprocess
engineering. A series of approximately 6 month exchange visits from Indian and Vietnamese partners as well as return visits will be planned during the project for training of researchers in key skills as well as on-site development of processes. All these activities will ensure the lasting impact of the project and the sustainability of the resulting technologies. This will be further reinforced by the current partnership between Aston University and the University of DaNang with the creation of the new University VN-UK Institute for Research and Executive Education (IREE) which will act as a hub to support training activities.