ABSTRACT
A novel thermal digester for converting food waste (FW) into nutrient-rich soil conditioner was designed and explored. The process variables, that is, temperature, the volume of the digestion chamber and the rotational speed of the digester were optimised using response surface methodology (RSM). The study revealed that the digester temperature of 150°C and rotational speed of 40 RPM required minimum time (180 minutes) for attaining the equilibrium moisture with a minimum energy consumption of 0.218 kWh kg-1. The process resulted in 80 ± 2.5% reduction in total volume of the FW. Detailed characterisation revealed that the end product was comparable to the organic fertiliser as per the Fertiliser Association of India norms. The digestion helps in breakdown of cellulose content of FW into hemicellulose which supports formation of primary and secondary walls, seed storage carbohydrates, and facilitates plant growth. 1H-Nuclear magnetic resonance (1H-NMR) spectra of the end product revealed mineralisation of organics during digestion. Decrease in ultraviolet (UV) absorbance value at 280 nm also revealed the humification of the end product. X-ray diffraction (XRD) analysis disclosed extremely low crystallinity and non-recalcitrant nature of the end product. A low humification index value (HI-3.43), high fertilising index (FI-4.8), and clean index (CI-5.0) revealed that the end product could safely be utilised as an organic fertiliser. The cost-benefit analysis revealed that thermal digestion technique is profitable and economically viable with benefit-cost ratio (BCR) of 1.35. The study offers a unique approach for the rapid and hassle-free production of value-added soil conditioner from FW.
Subject(s)
Refuse Disposal , Anaerobiosis , Food , Soil , Fertilizers , Bioreactors , MethaneABSTRACT
The fuzzy leachate pollution index (FLPI) was established to classify the landfill sites on the basis of their leachate pollution potential by considering the limitations of traditional methods. The FLPI was developed adopting 9 critical input parameters, i.e., TDS, pH, Cl, Cu, Pb, Cr, Zn, BOD, and COD, from 22 major landfill sites across India. Using these critical parameters, 3 groups, i.e., inorganic leachate strength (INLS), organic leachate strength (ORLS), and heavy metal leachate strength (HMLS), were generated to estimate the FLPI. The regression analysis, ANOVA, and sensitivity analysis were also performed to determine the significance and uncertainty of the index. The results showed that among all MFs, the triangular with overlapping open ends (TOO) MF was best fitted (R = 0.90) for FLPI estimation. Accordingly, 41% of the landfill sites showed less treatment while the others (59%) required moderate degree of treatment. The regression (R2 = 0.92) and ANOVA (F value = 15.003, p = 0.000031) analyses described that the developed tool was significant (p < 0.05). The sensitivity analysis showed that Zn (R = 0.99) was the most influencing factor followed by BOD > COD > pH > Cr > Cu > Cl > Pb > TDS. The study provides an important tool that can also be used by researchers and scientists for investigating and evaluating various environmental problems.