• Energy Research

Anaerobic co-digestion is a promising alternative to manage agri-food waste rather than landfilling, composting or incineration. But improvement of methane yield and biodegradability is often required to optimize its economic viability. Biomethanization of agri-food solid waste presents the disadvantage of a slow hydrolytic phase, which might be enhanced by adding a readily digestible substrate such as glycerol. In this study, strawberry extrudate, fish waste and crude glycerol derived from biodiesel manufacturing are mixed at a proportion of 54:5:41, in VS (VS, total volatile solids), respectively. The mesophilic anaerobic co-digestion at lab-scale of the mixture was stable at loads lower than 1.85 g VS/L, reaching a methane yield coefficient of 308 L CH4/kg VS (0 °C, 1 atm) and a biodegradability of 96.7%, in VS. Moreover, the treatment capacity of strawberry and fish waste was increased 16% at adding the crude glycerol. An economic assessment was also carried out in order to evaluate the applicability of the proposed process. Even in a pessimistic scenario, the net balance was found to be positive. The glycerol adding implied a net saving in a range from 25.5 to 42.1 €/t if compared to landfill disposal.

Anaerobic co-digestion is a promising alternative to manage agri-food waste rather than landfilling, composting or incineration. But improvement of methane yield and biodegradability is often required to optimize its economic viability. Biomethanization of agri-food solid waste presents the disadvantage of a slow hydrolytic phase, which might be enhanced by adding a readily digestible substrate such as glycerol. In this study, strawberry extrudate, fish waste and crude glycerol derived from biodiesel manufacturing are mixed at a proportion of 54:5:41, in VS (VS, total volatile solids), respectively. The mesophilic anaerobic co-digestion at lab-scale of the mixture was stable at loads lower than 1.85 g VS/L, reaching a methane yield coefficient of 308 L CH4/kg VS (0 °C, 1 atm) and a biodegradability of 96.7%, in VS. Moreover, the treatment capacity of strawberry and fish waste was increased 16% at adding the crude glycerol. An economic assessment was also carried out in order to evaluate the applicability of the proposed process. Even in a pessimistic scenario, the net balance was found to be positive. The glycerol adding implied a net saving in a range from 25.5 to 42.1 €/t if compared to landfill disposal.

Recent research has demonstrated that orange peel waste is a potentially valuable resource that can be developed into high value products such as methane. Following a pre-treatment to extract D-limonene, the anaerobic digestion of orange peel waste was evaluated at laboratory and pilot scale under mesophilic and thermophilic conditions. D-limonene removals of 70% were reached with pre-treatment. The results showed the convenience of thermophilic conditions for treating this waste as the methane production rate and biodegradability were higher than at mesophilic temperature. At pilot scale, a thermophilic continuously stirred-tank reactor working in semi-continuous mode was employed. The OLR was found to be in the range of 1.20-3.67 kg COD/m(3) d; the most appropriate range for working under stable conditions at SRT of 25 d. The methane yield coefficient was found to be 0.27-0.29 L(STP)CH(4)/g added COD and the biodegradability 84-90% under these conditions. However, acidification occurred at the highest OLR.

Recent research has demonstrated that orange peel waste is a potentially valuable resource that can be developed into high value products such as methane. Following a pre-treatment to extract D-limonene, the anaerobic digestion of orange peel waste was evaluated at laboratory and pilot scale under mesophilic and thermophilic conditions. D-limonene removals of 70% were reached with pre-treatment. The results showed the convenience of thermophilic conditions for treating this waste as the methane production rate and biodegradability were higher than at mesophilic temperature. At pilot scale, a thermophilic continuously stirred-tank reactor working in semi-continuous mode was employed. The OLR was found to be in the range of 1.20-3.67 kg COD/m(3) d; the most appropriate range for working under stable conditions at SRT of 25 d. The methane yield coefficient was found to be 0.27-0.29 L(STP)CH(4)/g added COD and the biodegradability 84-90% under these conditions. However, acidification occurred at the highest OLR.

Abstract The recovery of squalene from deodorizer distillate derived from the physical refining of olive oil was evaluated by combining pressurized acidic esterification in a closed system with vacuum distillation. Esterification was carried out at 341, 359, 366, 391 and 395 K. The reaction at 395 K was found to be satisfactory as it decreased the acid value by 99.21% and generated a FAME concentration of 67.53% within 1 h. In order to demonstrate that the generation of FAME from deodorizer distillate was mainly due to the transformation of FFA, the reaction extent, which characterizes the reaction and simplifies calculations, was evaluated for FFA removal and the generation of FAME. Subsequent vacuum distillation allowed the separation of one fraction rich in FAME (94%), which can be used as a biofuel and accounted for 85% of the initial mass, and another fraction that was rich in squalene (78%) and may be used for manufacturing pharmaceutical products. The global squalene yield was 117 g kg−1 initial deodorizer distillate.

Abstract The recovery of squalene from deodorizer distillate derived from the physical refining of olive oil was evaluated by combining pressurized acidic esterification in a closed system with vacuum distillation. Esterification was carried out at 341, 359, 366, 391 and 395 K. The reaction at 395 K was found to be satisfactory as it decreased the acid value by 99.21% and generated a FAME concentration of 67.53% within 1 h. In order to demonstrate that the generation of FAME from deodorizer distillate was mainly due to the transformation of FFA, the reaction extent, which characterizes the reaction and simplifies calculations, was evaluated for FFA removal and the generation of FAME. Subsequent vacuum distillation allowed the separation of one fraction rich in FAME (94%), which can be used as a biofuel and accounted for 85% of the initial mass, and another fraction that was rich in squalene (78%) and may be used for manufacturing pharmaceutical products. The global squalene yield was 117 g kg−1 initial deodorizer distillate.

AbstractBanana and plantain (Musa spp.) are among the most popular crops especially in tropical and sub‐tropical zones. Musa spp. is a unique, perennial, single‐harvest plant that after fruit harvesting is decapitated and generates large amounts of waste and by‐products: leaves and pseudostem. Fruit processing also generates waste peels and discarded pieces. Recent research has demonstrated that this type of organic substrate represents a potentially valuable resource that can be developed into high‐value products. These developments are critically reviewed in this article, which includes a summary of the composition and biocompounds contained in pseudostem and peel, the use of Musa spp. waste in animal and human feed and the obtention of fiber to make paper, rope, handcrafts and combustion materials. On the other hand, the potential for polysaccharides to be fermented and transformed into ethanol, methane or hydrogen, the obtention of single‐cell protein (microbial protein) and the use of solid residues for composting or as a substrate for mushrooms cultivation have also been evaluated. The applications described represent great opportunities for economic benefits from this agro‐industrial waste. A scheme for the integrated utilization of Musa spp. waste in a biorefinery approach is presented as well.

AbstractBanana and plantain (Musa spp.) are among the most popular crops especially in tropical and sub‐tropical zones. Musa spp. is a unique, perennial, single‐harvest plant that after fruit harvesting is decapitated and generates large amounts of waste and by‐products: leaves and pseudostem. Fruit processing also generates waste peels and discarded pieces. Recent research has demonstrated that this type of organic substrate represents a potentially valuable resource that can be developed into high‐value products. These developments are critically reviewed in this article, which includes a summary of the composition and biocompounds contained in pseudostem and peel, the use of Musa spp. waste in animal and human feed and the obtention of fiber to make paper, rope, handcrafts and combustion materials. On the other hand, the potential for polysaccharides to be fermented and transformed into ethanol, methane or hydrogen, the obtention of single‐cell protein (microbial protein) and the use of solid residues for composting or as a substrate for mushrooms cultivation have also been evaluated. The applications described represent great opportunities for economic benefits from this agro‐industrial waste. A scheme for the integrated utilization of Musa spp. waste in a biorefinery approach is presented as well.