Alchemy - Turning Wastes into Functional Soils: a Bio-Chemical and Physical Assessment from Lab to Field

Background:

Natural soil formation is the product of mineral and organic components mixing over a period of time, subject to the influence of local topography and climatic conditions. Thus the formation of good quality, fertile soils is a lengthy process. Conversely the destruction of such soils can occur rapidly. Urbanisation and effective sealing of soils by construction reduces soil function to virtually zero (Nehls et al, 2015). During cycles of deconstruction of the urban environment much material with potential mineral and/or organic value is often disposed of before that value can be fully extracted or exhausted.

In recent years, increasing efforts have been made to re-purpose urban by-products to manufacture fertile soil-like plant growth substrates (eg Molineux et al, 2009). These types of artificial substrates, whose characteristics and pedogenesis are dominated by their technical origin are sometimes called technical soils or ‘technosols’. Several studies have successfully employed various by-products to create such substrates with some properties analogous to ‘natural’ soil (eg Rokia et al, 2014), though these ‘soils’ often remain skeletal in nature, lack balanced macro-nutrient content and effective aggregation.

Hypothesis:

Basic functional soils can be produced by the combination of urban de-construction materials (mineral) and urban-sourced organic residues.

Project:

This project will utilise two basic components to manufacture soils, being mineral and organic residues from urban source (for example, greenwaste compost, food waste digestate, cement and brick [deconstruction] residues etc). The project’s aims, to address the hypothesis, are to:

(1) Create a selection criteria for urban by-products for soil manufacture (ie local availability, social perception of the material’s suitability, macro-nutrient status of materials, contamination and risk issues arising);

(2) Devise and conduct appropriate laboratory and field trials to test the performance of the manufactured soils to mimic a range of soil functions (eg support microbial biomass, store water, perform biochemical cycling, plant growth) as compared to a range of suitable natural reference soils; and

(3) Develop criteria to determine suitable base material selection for soil end usages (urban greening, bio-energy crop growth, other agricultural outlets, landscaping mine sites etc) based on stages 1 and 2.

Research training value of project:

Skills to be developed for the student include: liaison with industry partners, practical glass house and laboratory skills especially in the use of analytical chemistry techniques, field trial set-up and management, data gathering, data handling, mathematical modelling and statistical analysis including programming/coding; more generic transferable skills such as presentation and writing, teaching and mentoring, and stakeholder interaction.