Efficiency of Low Temperature Chemical Pretreatment of Fruit and Vegetable Pomace

Subjecting lignocellulosic substrates to anaerobic digestion is a promising way of renewable energy obtaining. This method of generating energy is consistent with the sustainable development. In order to destroy the biodegradation-resistant structure of lignocellulosic materials before directing them to anaerobic decomposition, the use of pretreatment methods is required. The purpose of the present study was to assess the effect of temperature rise and a solvent type on the chemical pretreatment of fruit and vegetable pomace results. Biomass samples were placed in distilled water, 0.05 M NaOH and 0.05 M H2SO4 solutions and left for 20 h at 22°C and at 50°C (at room temperature and in a thermostated chamber). Concentrations of dissolved chemical oxygen demand (CODdissolved), volatile fatty acids (VFA) and phenols, as well as electrolytic conductivity (EC) values, in the obtained hydrolysates were analyzed. The most significant result of temperature rise on the increase of solubility of organic compounds contained in fruit and vegetable pomace, expressed by VFA, one of the pretreatment methods efficiency indicators, was noted in the samples soaked in alkaline solution. The highest VFA level was observed in the series of the experiment conducted at 50°C (868 mg·L-1). The process carried out under these conditions resulted also in the highest concentration of another important pretreatment indicator, CODdissolved. Hydrolysis conducted at 50 °C in a sodium hydroxide solution seems to be the most effective option for the pretreatment of fruit and vegetable pomace intended for energy production on biological way.