1H Relaxometry and Quantitative Relaxation Tomography of compost during biodegradation and maturation

The collection and composting of organic waste both from families and from industrial production processes are considered as good practices for waste management. Composts made from sewage sludge, household waste, straw, bark, have successfully been employed in gardens, pot cultures, arable land, and even in forests. In general, composts contribute to the structure and nutrient supply of soils or artificial substrates for plant growth. Compost chemical and microbial properties, which define compost maturity, are important key factors for correct use in environmental and agricultural activities. Parameters such as the temperature, pH and C/N ratio can be observed to monitor the compost maturation and to decide on the compost quality and stability [1]. Proton Nuclear Magnetic Resonance relaxometry (1H-NMR) can be used to follow compost biodegradation during time, as it permits the monitoring of internal compositional and structural modifications, as already observed in many food types when they experience natural or not natural processes [2]. Since generally the parameters of biodegradation are volume averaged and little is known on the influence of local behaviour on the final overall biodegradation, a local investigation of the compost mixture is desirable [3]. Quantitative Relaxation Tomography (QRT), which gives spatial information on relaxation times combining 1H-NMR relaxometry with Magnetic Resonance Imaging, can be an innovative tool to monitor compost degradation and maturation. In this work a sample of compost has been monitored for two months by means of both T1 and T2 QRT maps [4]. In a first preliminary analysis, both kinds of maps seem to well describe a trend that follows the three phases of the composting process: mesophilic, thermophilic and maturation, moreover having information of the spatial distributions of these phases. [1] J. Forster, W. Zech, E. Wiirdinger, Biology and Fertility of soils, 16, 93-99, (1993). [2] M. F. Marcone, S. Wang, W. Albabish, S. Nie, D. Somnarain, A. Hill, Food Research International, 51(2), 729-747, (2013). [3] F. P. Duval, S. Quellec, A. Trémier, C. Druilhe, F. Mariette, Waste management, 30(4), 610-619, (2010). [4] G. C. Borgia, V. Bortolotti, P. Fantazzini, journal of Applied Physiscs, 90(3), 1155-1563, (2001).