Impact of lignocellulosic waste-immobilised white-rot fungi on enhancing the development of 14C-phenanthrene catabolism in soil

In this study, an investigation was carried out to explore the the impact of white-rot fungi (WRF) on enhancing the development of phenanthrene catabolism in soil over time (1, 25, 50, 75 and 100 d). The WRF were immobilised on spent brewery grains (SBG) prior to inoculation to the soil. The results showed that SBG-immobilised WRF-amended soils reduced the lag phases and increased the extents of ¹⁴C-phenanthrene mineralisation. Greater reductions in the lag phases and increases in the rates of mineralisation were observed in immobilised Trametes versicolor-amended soil compared to the other WRF-amendments. However, the presence of Pleurotus ostreatus and Phanerochaete chrysosporium influenced biodegradation more strongly than the other fungal species. In addition, fungal enzyme activities increased in the amended soils and positively correlated with the extents of ¹⁴C-phenanthrene mineralisation in all soil amendments. Maximum ligninolytic enzyme activities were observed in P. ostreatus-amended soil. Microbial populations increased in all amended soils while PAH-degrading fungal numbers increased with increased soil-PAH contact time and strongly positively correlated with fastest rates of mineralisation. The findings presented in this study demonstrate that inoculating the soil with these immobilised WRFs generally enhanced the mineralisation of the ¹⁴C-phenanthrene in soil. This has the potential to be used to stimulate or enhance PAH catabolism in field-contaminated soils.

Circular economy and the matter of integrated resources

A circular economy offers solutions for global sustainability challenges through the transition from the linear take-make-use-dispose economy to a better organisation of resources. However, realising a circular economy has ran into various biophysical constraints. Circular economy implementation is shaped by the Ellen MacArthur Foundation's butterfly diagram that depicts 'biological' and 'technical' flows as separate cycles, subsequently interpreted as organic materials circulating in open loop systems via the environment and inorganic materials circulating in closed loop systems within society. Conversely, in our view, resource flows often contain tightly bound combinations of organic and inorganic materials either due to their natural composition or due to their technical design. Building on this observation, a new diagram is proposed that broadens the scope of the circular economy to cover extractive sectors and the return of materials from anthropogenic use to natural reserves, thereby reshaping the conceptual space within which solutions such as effective zero-waste-residue technologies, business models, and policies can be developed for the optimal management of integrated resources from a whole-system perspective. The diagram offers a realistic outlook on the biophysical limitations of circularity and endeavours to inspire discussion that supports the transition towards a sustainable circular economy.