Transition to zero pollution

By Maria Koulouri a PhD student in the Department of  Civil and Environmental Engineering and a member of the second Transition to Zero Pollution PhD cohort and the  Science and Solutions for a Changing Planet DTP

Today, approximately 3.1 billion people rely on improved on-site sanitation facilities, like pit latrines and septic tanks, to access sanitation services [WHO/UNICEF 2019]. The material that accumulates in such facilities, known as faecal sludge, can have detrimental environmental and public health impacts, if not safely managed.

The UN Sustainable Development Goal (SDG) 6 calls for universal access to sanitation services, as well as adopting sustainable management practices for the faecal sludge that is being contained and collected.  At the same time, there is a new paradigm of looking at faecal sludge as a source of valuable resources to be recovered rather than just waste to be safely discharged. In this context, sustainable sanitation systems can support progress towards multiple SDGs, through the recycling of water, carbon, energy and nutrients.

My PhD work places resource recovery at the centre of faecal sludge management, using a treatment process called pyrolysis (the thermochemical conversion of biomass in an oxygen-limited or oxygen-free environment), to treat and recover resources from faecal sludge. The end-products of pyrolysis, a solid output known as biochar, a bio-oil and gas products, offer several reuse opportunities, including energy and nutrient recovery.

I will be investigating faecal sludge-derived biochars as organic fertilisers that can contribute to global food security by replacing unsustainable mineral fertilisers, which depend on depleting phosphorus resources and costly synthetic nitrogen forms. By using organic fertilisers made from faecal sludge, we can contribute not only to SDG 6 (“Clean water and Sanitation”), but also others including “Zero hunger” (SDG2) and “Responsible consumption and production” (SDG12).

These interactions among SDGs make it evident that sanitation sits within a wider system of human interventions and natural ecosystems. Therefore, faecal sludge management choices can impact and be impacted by the environment around them. Investigating such interactions can be complex and requires the adoption of a systems approach to define the sanitation and faecal sludge management chain.

I am using systems thinking and life-cycle analysis tools to describe some of the key interactions among faecal sludge management components and study the integration of man-made sanitation systems to the natural and socio-economic environment in which they function, through resource recovery. My work will include assessing environmental impacts of real-world sanitation case studies to better understand the effects that sanitation interventions may have on their surrounding environment. I hope that this work will contribute to global sanitation and resource recovery efforts, ultimately helping developing countries meet the SDGs.

Read PhD Insights: A systems approach to sanitation & faecal sludge management in full

By Felix Richter a PhD student in the Department of Chemical Engineering and a member of the second Transition to Zero Pollution PhD cohort and the  Science and Solutions for a Changing Planet DTP

In the face of climate change, exploding world population and inevitable shortages in fossil resources within the next 50–100 years, it keeps getting harder and harder for agriculture to keep up with demand. Taken together with the fact that conventional chemical fertilisation destroys natural biomes, this calls for immediate action and alternatives.  

One such possible alternative dwells underground, well hidden from the eye. An illustrious circle of soil fungi have been found to associate with nearly every terrestrial plant on earth, rendering them one of the key players in ecosystem stability and carbon sequestration. They interact with the plant’s roots and form a symbiosis commonly known as the mycorrhiza. These mycorrhizal fungi span vast mycelial networks, exploring the soil for minerals, which they exchange with the plant for photosynthesis products, like sugars. Furthermore, the symbiosis increases the plant’s resistance against soil pathogens, heavy metals or drought, reduces nutrient leaching and improves the environment for the establishment of fresh seedlings. The fungus acts as an elongation to the roots and stores large amounts of carbon, even beyond the plant’s life, remaining in a state of quiescence just waiting for the next plant to team up with. 

In order to harness the fungus’ abilities, more basic research is needed. Their natural habitat is the intransparent soil, a complex environment with an enormous range of physical obstacles, nutrient and mineral gradients and numerous interacting species of each of nature’s kingdoms as well as their metabolites. In order to mimic these structures and simulate real-life conditions, which is impossible with conventional techniques, we set out to design our own microenvironment using so-called microfluidic technology. 

In the past decades microfluidic technology has arisen as a new promising tool. In general, the field of microfluidics deals with the behaviour of fluids in miniature dimensions down to picoliters and involves the fabrication of microdevices for all kinds of tasks in biology or chemistry, either for analytics or synthesis. We can specifically tailor microenvironments to the task at hand, implanting physical obstacles, introducing chemical gradients or facilitating co-habitation with beneficial, hostile or just co-existing character. The applications are vast, stretching over investigations involving all kinds of environmental cues, chemical or physical, and their influence on the fungus.  

With this new approach for basic mycorrhizal fungi research, we hope to understand these essential fungi and their symbiosis better, paving the way for new strategies in biofertilisation, as an alternative to conventional fertilisers based on fossil resources as well as sustainable forestry. 

Read PhD Insights: Fungi-on-a-chip: Tackling environmental problems on the microscale  in full