This work aims at finding an alternative strategy to manage the waste generated by the winemaking industry to obtain a solid biofuel and phenolic compounds. The effect of temperature (180–260 °C), residence time (1–7 h), and biomass-to-liquid ratio (0.05–0.25) on the co-hydrothermal carbonization of vine pruning and exhausted grape pomace, by using vinasse as moisture source, is studied. The effect of the variables is investigated and optimized using the Box–Behnken design of response surface methodology to maximize mass yield, fuel ratio, energy densification yield and phenols extraction yield and to minimize energy consumption. The statistical analysis shows that the carbonization temperature is a crucial parameter of the process, decreasing the product yield on one hand and improving the quality of hydrochar on the other. At the optimal conditions (246.3 °C, 1.6 h, 0.066), an hydrochar yield of 52.64% and a calorific value of 24.1 MJ/kg were obtained. Moreover, the analysis of the H/C and O/C ratios of hydrochars demonstrates that carbonisation significantly improves the fuel properties of solid biofuel. Liquid by-products obtained from the HTC process are found to contain high concentrations of organic matter but the BOD/COD ratios suggest their potential valorization by biological methods.
On a global scale many countries are still heavily dependent on crude oil to produce energy and fuel for transport, with a resulting increase of atmospheric pollution. A possible solution to obviate this problem is to find eco-sustainable energy sources. A potential choice could be the use of biodiesel as fuel. The work presented aims to characterise the transesterification reaction of waste peanut frying oil using colour analysis and wavelet analysis. The biodiesel production, with the complete absence of mucilages, was evaluated through a suitable set of energy wavelet coefficients and scalograms. The physical characteristics of the biodiesel are influenced by mucilages. In particular the viscosity, that is a fundamental parameter for the correct use of the biodiesel, might be compromised. The presence of contaminants in the samples can often be missed by visual analysis. The low and high frequency wavelet analysis, by investigating the energy change of wavelet coefficient, provided a valid characterisation of the quality of the samples, related to the absence of mucilages, which is consistent with the experimental results. The proposed method of this work represents a preliminary analysis, before the subsequent chemical physical analysis, that can be develop during the production phases of the biodiesel in order to optimise the process, avoiding the presence of impurities in suspension in the final product.
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