Nitrogen In the Circular Economy (NICE): The valorisation of nitrogenous waste

Project background (identification of the problem and its importance and relevance to sustainability)



Nitrogen containing molecules are ubiquitous and form the basis of many essential agrochemicals, pharmaceuticals, additives, textiles, and performance materials. The synthesis of nearly all nitrogen containing molecules requires ammonia, which is derived from the Haber-Bosch (HB) process. The HB process has a large detrimental environmental impact: it uses around 2% of global energy and contributes an estimated 2% to global carbon dioxide emissions. Consequently, the production of nitrogen containing compounds comes at a high environmental cost. Additionally, these resources are overconsumed and then discarded as waste once their initial purpose has been fulfilled. This is a symptom of our linear economy; fortunately, the circular economy provides a solution.



To transition from a linear to a circular economy, processes need to be developed that enable waste to be transformed into useful, high value products and materials. Protein-rich biomass waste streams are abundant, yet the nitrogenous fraction remains undervalued and underused. The valorisation of such protein-rich waste streams into useful, high value, nitrogenous chemicals is one approach to improve the sustainability of their synthesis.



The development of chemoselective disconnections for unactivated C-N bonds, particularly in underexplored transformations will enable the synthesis of small nitrogen containing compounds from nitrogenous waste, reducing both our dependence on the HB process and the environmental cost of producing such chemicals.



Proposed solution and methodology



This research project strives to develop methods to valorise nitrogenous waste streams that are abundant, currently underused, and for which valorisation into fine chemicals will not disrupt the food chain or require the growth of more crops. Through research into selective C-N sigma bond cleavage of various nitrogenous substrates, this project is envisioned to develop methods to valorise these waste streams to improve the flow of nitrogen containing compounds through the nitrogen cycle and to enable the transition towards a more circular economy.



The current state of the art for selective C-N sigma bond cleavage requires incredibly forcing conditions and/ or activated substrates which limit the current applications of these methods. There is also a lack of mechanistic understanding in the literature, which can impede the development of novel approaches. This project seeks to address these issues by developing novel catalytic systems for selective C-N bond cleavage.



Catalyst screening will be performed to find catalysts which can facilitate C-N sigma bond activation and cleavage using model N-compounds to explore and compare catalyst reactivities and selectivities, selected according to their activity towards C-N bond cleavage, commercial availability, ease of synthesis, and their scale-up potential. In particular, complexes of first row transition metals will be prioritised due to their sustainable credentials, low cost, and research group expertise. Upon the identification of a suitable catalyst system, optimisation will be carried out focusing on delivering high product yield and selectivity, whilst considering reaction sustainability in accordance with the 12 Principles of Green Chemistry. Substrate scope will be expanded by testing a large range of substrates with a variety of properties to gain insight into the limitations of the catalyst system. Data collected throughout this project will be continually analysed to gain insight into the catalyst mechanism of action, including isolation of potential reaction intermediates, along with detailed kinetic investigations; together this insight will enable a plausible catalytic cycle to be proposed.

This CDT will deliver impact aligned to the following agendas:

People
A2P will provide over 60 PhD graduates with the skill sets required to deliver innovative sustainable products and processes into the UK chemicals manufacturing industry. A2P will inspire and develop leaders who will:
- understand the needs of industrial end-users;
- embed sustainability across a range of sectors; and
- catalyse the transition to a more productive and resilient UK economy.

Economy
A2P will promote a step change towards a circular economy that embraces resilience and efficiency in terms of atoms and energy. The benefits of adopting more sustainable design principles and smarter production are clear. For example, the global production of active pharmaceutical ingredients (APIs) has been estimated at 65,000-100,000 tonnes per annum. The scale of associated waste is > 10 million tonnes per annum with a disposal cost of more than £15 billion. Consequently, even a modest efficiency increase by applying new, more sustainable chemical processes would deliver substantial economic savings and environmental wins. A2P will seek and deliver systematic gains across all sectors of the chemicals manufacturing industry. Our goals of providing cross-scale training in chemical sciences with economic and life- cycle awareness will drive uptake of sustainable best practice in UK industry, leading to improved economic competitiveness.

Knowledge
This CDT will deliver significant new knowledge in the development of more sustainable processes and products. It will integrate the philosophy of sustainability with catalysis, synthetic methodology, process engineering, and scale-up. Critical concepts such as energy/resource efficiency, life cycle analysis, recycling, and sustainability metrics will become seamlessly joined to what is considered a 'normal' approach to new molecular products. This knowledge and experience will be shared through publications, conferences and other engagement activities. A2P partners will provide efficient routes to market ensuring the efficient translation and transferal of new technologies is realised, ensuring impact is achieved.

Society
The chemistry-using industries manufacture a rich portfolio of products that are critical in maintaining a high quality of life in the UK. A2P will provide highly trained people and new knowledge to develop smarter, better products, whilst increasing the efficiency and sustainability of chemicals manufacture.
To amplify the impacts of our CDT, effective public engagement and technology transfer will become crucially important. As a general comment, 'sustainability' styled research is often regarded in a positive light by society, however, the science that underpins its effective implementation is often poorly appreciated. The University of Nottingham has developed an effective communication portfolio (with dedicated outreach staff) to tackle this issue. In addition to more traditional routes of scientific communication and dissemination, A2P will develop a portfolio of engagement and outreach activities including blogs, webpages, public outreach events, and contribution of material to our award-winning YouTube channel, www.periodicvideos.com.

A2P will build on our successful Sustainable Chemicals and Processes Industry Forum (SCIF), which will provide entry to networks with a wide range of chemical science end-users (spanning multinationals through to speciality SMEs), policy makers and regulators. We will share new scientific developments and best practice with leaders in these areas, to help realise the full impact of our CDT. Annual showcase events will provide a forum where knowledge may be disseminated to partners, we will broaden these events to include participants from thematically linked CDTs from across the UK, we will build on our track record of delivering hi-impact inter-CDT events with complementary centres hosted by the Universities of Bath and Bristol.