Estimation of Sustainable Bioenergy Production from Olive Mill Solid Waste

Olive mill wastes: from wastes to resources

Olive oil extraction has recently experienced a continuous increase due to its related beneficial properties. Consequently, large amounts of olive mill wastes (OMWs) derived from the trituration process are annually produced, causing serious environmental problems. The limited financial capabilities of olive mills make them usually unable to bear the high costs required for the disposal of their wastes. Alternatively, the valorization of OMWs within the framework of the so-called waste-to-resource concept and their recycling can represent a successful strategy for the implementation of circular economy model in the olive industry, which could have significant socioeconomic impacts on low-income Mediterranean countries. There is, however, no unique solution for OMWs valorization, due to the wide variety of the wastes' composition and their seasonal production. In this review, the potential of OMWs for being reused and the recent technological advances in the field of OMWs valorization are assessed. Special focus is given to the analysis of the advantages and limitations of each technology and to reporting the most significant issues that still limiting its industrial scale-up. The information collected in this review shows that OMW could be effectively exploited in several sectors, including energy production and agriculture. OMWs potential seems, however, undervalued, and the implementation of sustainable valorization strategies in large-scale remains challenging. More efforts and policy actions, through collective actions, encouraging subsidies, and establishing public-private collaborations, are still needed to reconcile research progress with industrial practices and encourage the large-scale implementation of the waste-to-resource concept in the olive sector.

Evolution of Hydroxytyrosol, Hydroxytyrosol 4-β-d-Glucoside, 3,4-Dihydroxyphenylglycol and Tyrosol in Olive Oil Solid Waste or "Alperujo"

The main by-product generated from the olive oil two-phase extraction system, or alperujo, is undoubtedly a rich source of bioactive components, among which phenolics are one of the most important. The evolution of four of its main phenolics: hydroxytyrosol (HT), hydroxytyrosol 4-β-d-glucoside (Glu-HT), 3,4-dihydroxyphenylglycol (DHPG) and tyrosol (Ty) was studied over two seasons and in ten oil mills under similar climatological and agronomic conditions, for the first time using organic extraction and high-performance liquid chromatography (HPLC-DAD) determination. The results show that HT (200-1600 mg/kg of fresh alperujo) and Ty (10-570 mg/kg) increase, while DHPG (10-370 mg/kg) decreases only in the last month of the season and Glu-HT (1400-0 mg/kg) decreases drastically from the beginning. This evolution is similar between different seasons, with a high correlation between Glu-HT, HT, and Ty. On the other hand, it has been verified that a mixture of alperujos from all the oil mills, which is what the pomace extractor receives, is a viable source of a liquid fraction which is rich in the phenolics studied through organic extractions and especially after the application of a thermal treatment, obtaining values of 4.2 g/L of HT, 0.36 g/L of DHPG, and 0.49 g/L of Ty in the final concentrated liquid fraction.

Potential of Renewable Energy in Jamaica’s Power Sector: Feasibility Analysis of Biogas Production for Electricity Generation

Jamaica is heavily dependent on fossil fuels to meet its energy demand and is currently seeking to reduce consumption. Accordingly, it is essential to investigate the expansion of renewable energy systems to achieve its 2030 renewable energy goal of 50%, with 70% diversification in energy types, as outlined in the National Energy Policy 2009–2030. This study explores biogas feasibility in Jamaica and discusses the potential for electricity generation from combinations of dairy cow and Swine feces with sugarcane bagasse. The study’s primary purpose is to assess the feasibility of biogas production from livestock manure and sugarcane bagasse for electricity generation and manure treatment. Findings reveal that biogas anaerobic digestion and the co-digestion of different varieties of animal manure with sugarcane bagasse can generate up to 122,607.68 MWh or 2.49% of Jamaica’s total electrical energy generation in 2019. The findings indicate a high potential for the installation of community-based plants. Moreover, considering all scenarios and the remaining feedstock, potential electrical energy increases to 222,868.60 MWh (4.53% of total energy generation). This power may be fed to the electrical grid network or consumed by local producers. In addition, electric power generation from animal manure and sugarcane bagasse is feasible with improved technical capability and human development. Additionally, anaerobic digestion and co-digestion of sugarcane bagasse plus animal manure offer an excellent solution to mitigate climate change.

Evolution of the Olive Oil Industry along the Entire Production Chain and Related Waste Management

The production of olive oil involves the sustainable management of the waste produced along the entire production chain. This review examines the developments regarding cultivation techniques, production technologies, and waste management, highlighting the goals to be achieved and the most reasonable prospects. The results show that cultivation and production technology have evolved to an almost final solution to meet economic feasibility, keeping the oil’s high quality. Continuous horizontal decanters will coexist with traditional mills in many countries with old olive oil production and consumption traditions. High-quality products have conquered markets, especially in the wealthiest countries. At the same time, the exploitation of dried pomace by solvent extraction is increasingly an obsolete practice. However, waste management is still looking for one or a few reasonable solutions that meet modern society’s constraints. The enhancement of some experienced technologies and the full-scale application of emerging technologies and strategies should solve this problem in the short–medium term. A short discussion is reported on the possibility of unifying the nature and the quality of the waste, whatever the olive oil production method is. Furthermore, modern thermochemical treatment for solid wet organic waste disposal is examined and discussed.