Imperial College London

Sarah Kakadellis

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Publication Type

6 results found

Benton J, Jimenez Zarco J, Banks A, Kakadellis S, Lee KY, Lee PH, Romain C, Wright S, von Holstein Iet al., 2024, Using microbes to remove microplastics from wastewater and sewage sludge, London, Publisher: Institute for Molecular Science and Engineering, Briefing paper No. 11

Microplastics are a widespread form of plastic pollution. There is increasing evidence that they are a threat to human health and the environment. Microplastics in domestic and industrial wastewater become concentrated in sewage sludge during wastewater treatment processes. In 2020, water companies in England produced more than 800,000 tonnes of sewage sludge from urban wastewater. More than 90% of UK sewage sludge is spread on agricultural land as a fertilizer and soil conditioner. This provides a pathway for microplastics to enter the terrestrial environment. There is currently no UK legislation defining safe limits for microplastics in sludge and soils but future regulation is a possibility. There is currently no technology available to remove microplastics from wastewater treatment processes or the resulting sludge. Safe limits for microplastics in treated sewage sludge, soils and water bodies should be identified. This will require a survey of the extent of microplastic pollution throughout the UK, including concentration, identity and characteristics of microplastics in each environmental reservoir, and understanding how microplastics affect different living organisms. Microbes or fungi that break down plastic could be added to existing wastewater treatment process to remove microplastics and prevent their release into the environment. Alternatively, only the active enzymes (rather than the live microorganisms) could be added to the process. Currently, only polyester microplastics (11% of the total microplastic burden) could be treated in this way. Different microorganisms would have to be discovered or developed to tackle other common microplastic polymers such as polypropylene or polyethylene.


Kakadellis S, Lee P-H, Harris ZM, 2022, Two birds with one stone: bioplastics and food wase anaerobic co-digestion, Environments, Vol: 9, Pages: 9-9, ISSN: 0711-6780

Following the BBC’s Blue Planet II nature documentary series on marine ecosystems, plastic packaging has come under public fire, with consumers demanding greener alternatives. The biodegradable properties of some bioplastics have offered a potential solution to the global challenge of plastic pollution, while enabling the capture of food waste through anaerobic digestion as a circular and energy-positive waste treatment strategy. However, despite their increasing popularity, currently bioplastics are being tested in environments that do not reflect real-life waste management scenarios. Bioplastics find their most useful, meaningful and environmentally-sound application in food packaging—why is there so little interest in addressing their anaerobic co-digestion with food waste? Here, we provide a set of recommendations to ensure future studies on bioplastic end-of-life are fit for purpose. This perspective makes the link between the environmental sustainability of bioplastics and the role of food waste anaerobic digestion as we move towards an integrated food–energy–water–waste nexus. It shines light on a novel outlook in the field of bioplastic waste management while uncovering the complexity of a successful path forward. Ultimately, this research strives to ensure that the promotion of bioplastics within a circular economy framework is supported across waste collection and treatment stages.

Journal article

Kakadellis S, Rosetto G, 2021, Achieving a circular bioeconomy for plastics, Science, Vol: 373, Pages: 49-50, ISSN: 0036-8075

Journal article

Kakadellis S, Woods J, Harris ZM, 2021, Friend or foe: Stakeholder attitudes towards biodegradable plastic packaging in food waste anaerobic digestion, Resources, Conservation and Recycling, Vol: 169, Pages: 1-10, ISSN: 0921-3449

Consumers are becoming increasingly attuned to sustainability issues in the food supply chain and demanding retailers to keep pace with their changing expectations. The visual nature of plastic pollution has strengthened public awareness of the environmental impact of plastic packaging. Against this backdrop, biodegradable plastics have been promoted as an alternative to conventional polymers, offering the potential to tackle hard-to-recycle plastics while being compatible with food waste recycling. Given increased recognition of food waste as an untapped resource worldwide and the incoming policy mandating separate collections for household and commercial food waste across the EU from 2023, anaerobic digestion is a particularly promising strategy and can make an important contribution to the transition to circular waste management practices. However, currently no industrial standard exists for ‘digestible’ packaging. Our research addresses stakeholder attitudes towards the treatment of biodegradable plastic packaging in food waste anaerobic digestion. We conducted 19 semi-structured interviews with a range of stakeholders, including the biowaste recycling sector, retail, governmental bodies and environmental charities. Qualitative data were categorised into thematic nodes based on inductive and deductive strategies. Content analysis showed significantly divergent views on biodegradable plastics. Though most respondents acknowledged the merits of biodegradable plastics, concerns over their compatibility with the current anaerobic digestion infrastructure (e.g. systematic depackaging, retention times) and their ultimate biodegradability were raised. In light of these issues, potential solutions are discussed and the role that legislation and consumer education can play in ensuring that the anaerobic digestion sector can accommodate these novel materials are highlighted.

Journal article

Kakadellis S, Harris ZM, 2020, Don’t scrap the waste: The need for broader system boundaries in bioplastic food packaging life-cycle assessment – A critical review, Journal of Cleaner Production, Vol: 274, Pages: 1-14, ISSN: 0959-6526

The increasing amount of plastic waste generated each year, fuelled by the growing consumption of single-use plastics in food packaging applications, threatens the integrity of our ecosystems while creating an unprecedented waste management crisis. The biodegradable properties of some bioplastics have been identified as a promising solution to divert food and food packaging waste from landfill while avoiding plastic leaking into the environment. However, such bio-based biodegradable alternatives may not necessarily provide an improvement in overall environmental impact, especially when considering their efficacy at preventing food waste. This is the first systematic review to investigate the relationship between food packaging and food waste, based on conventional and biodegradable plastic food packaging life-cycle assessments (LCAs). It focuses on the trade-offs that may occur between food packaging production, end-of-life management and food waste prevention across the entire food packaging life-cycle. Following a review of 111 papers, 19 were identified for further investigation and data extraction. Quantitative analysis for five LCA impact categories, as well as hotspot analysis and end-of-life scenario analysis for global warming potential were conducted. The resulting picture is conflicting and suggests that though bioplastics display environmental benefits for global warming potential and non-renewable energy use, these are often negated by the agricultural inputs required for bioplastics raw material production. While the LCAs included in this study do not provide enough evidence to state which polymer is best at reducing food waste, they emphasise the environmental footprint associated with food production and food waste, and highlight the importance of including the food itself in food packaging LCAs. Therefore, focusing on food packaging performance in food waste minimisation is critical. We found that bioplastics provide the benefit of diverting biodegra

Journal article

Stagkourakis S, Smiley KO, Williams P, Kakadellis S, Ziegler K, Bakker J, Brown RSE, Harkany T, Grattan DR, Broberger Cet al., 2020, A Neuro-hormonal Circuit for Paternal Behavior Controlled by a Hypothalamic Network Oscillation, CELL, Vol: 182, Pages: 960-+, ISSN: 0092-8674

Journal article

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