circularising the bioeconomy

the 英格兰vs美国谁会赢？ is undertaking a project entitled a sustainable future as part of our 75th anniversary, which aims to highlight the sustainable development goals (sdgs) to our members and empower them to use their research to evidence and impact the goals. earlier this year, we put a call out to our members to submit case studies in the following three areas: antimicrobial resistance, soil health and the circular economy.

this case study is written by louise horsfall, professor of sustainable biotechnology at the university of edinburgh, uk. it focuses on the circular economy; an alternative to a traditional linear economy (make, use, dispose), in which we keep resources in use for as long as possible, extract the maximum value from them while in use, then recover and regenerate products and materials at the end of each service life.

covid-19 has had a severe impact on the economy, with public debt now larger than the size of the uk’s economy. however, it has also provided us with a massive opportunity to effect real environmental change. calls to #buildbackbetter in a green recovery are gaining wide-spread public and political support. developing a circular economy would lead to a 48% reduction in carbon dioxide emissions by 2030 and provide a host of opportunities for the expanding bioeconomy.

stewardship of this growing bioeconomy requires both responsibly sourced feedstock and the circularisation of processes. the food and drink production industry is vital to the uk economy but creates unavoidable bio-based waste that largely goes to landfill, resulting in methane gas production, causing environmental pollution and contributing to climate change. food and drink manufacturing waste and by-products therefore constitute a vast resource that is currently underutilised. they have the potential to power a circularised bioeconomy, whilst also relieving tensions in the food-versus-fuel debate and supporting efforts to achieve targets in climate change, sustainability and food security.

the circular economy model may be bioinspired, but the biological cycles and cascades are somewhat under developed and over simplified. the reliance on anaerobic digestion for biogas production overlooks opportunities for employing biotechnology and synthetic biology to better meet all three foundational principles of the circular economy:

1. design out waste and pollution

2. keep products and materials in use

3. regenerate natural systems

what is needed is a multidisciplinary research approach that incorporates new technologies able to utilise the waste and by-products of food and drink production to their full potential. we propose three areas of technical development to improve resource flow and circularity within a bioeconomy powered by waste from the food and drink sector:

(i) separation of valuable by-products, e.g. the removal of proteins for animal feed

(ii) biological transformation of by-products into new products, with concomitant redesign of biological systems and processes to minimise waste, e.g. the production of high yields of enzymes using microbes engineered for increased lifespan, to reduce washing, sterilisation and waste.   

(iii) conversion of biomass, including that resulting from biological processes, into carbon products and chemicals through thermochemical processing or anaerobic digestion – thereby providing an alternative route, by which even the treated biomass of genetically modified micro-organisms could be used to regenerate natural systems through thermochemical conversion to useful soil additives.    

the interdisciplinary challenge of circularising the bioeconomy is clearly enormous and expertise in the field of microbiology is key to overcoming it. there are specific challenges associated with using complex industrial by-products and wastes as feedstocks, instead of comparatively pure commercial growth media for microbial growth. impurities that can accumulate in the growth medium to inhibitory or toxic levels, as well as unfavourable consequences of harsh raw material pre-treatment conditions, such as very low ph, represent chemical stresses for the microbial production strains. whether it be a source of new genes or as alternative ‘chassis’, we will be reliant on a diverse range of micro-organisms to adapt the current microbial production platforms to better tolerate unfavourable conditions and impurities. new bio-based products will be produced from food waste by moving away from our ‘go to’ hosts, escherichia coli and saccharomyces cerevisiae, and diversifying the pallet of tools available to biotechnology.

the success of technical developments must be assessed through techno-economic and environmental assessment to minimise the use of additional resources and maximise the benefits and/or limit the impact to the environment. this presents another set of challenges. although widely used by companies with a well-developed methodology governed by iso standards, life-cycle assessment (lca) is challenging to apply to biotechnology due to the complex nature of biological systems and its foundation within the barely related packaging industry. to demonstrate utility for auditing environmental impacts of biotransformation processes, lca must be extended to assess value chain impacts and dependencies on natural capital, to support a whole-system view when making bio-economies more circular. techno-economic analysis, (cost-benefit analysis, cost-effectiveness and risk assessment methods) aid with option appraisal, but feasibility is also dependent upon processing logistics, especially for nutrient-rich and high-water content wastes. for instance, a microbially-based process used by a company based in a city will look very different when applied to a remote location in scotland. as such, feedstock must be mapped to inform use and to highlight current tensions and dependencies, with all stakeholders consulted and considered.

as climate change imposes further stresses on land use, food security will depend on our ability to control our own supply chains. the uk currently imports 50% of its food and feed. a circular bioeconomy would reduce our demand for imports, lowering carbon footprints and environmental pollution. valorisation of waste is critical to the maintenance of our limited arable land and marine resources, while still protecting the uk’s natural environment.

about the author

professor louise horsfall is chair of sustainable biotechnology in the school of biological sciences at the university of edinburgh, uk. she is researching novel industrially-usable platforms for the sustainable production of improved enzymes, bio-based chemicals and other biomaterials. the cost-efficient and energy-saving innovations being developed will lead to unique and sustainable new products, derived from the wastes and by-products of industries that stretch from food & drink manufacturing to electric vehicles. more information about her work is available here.