Anaerobic digestion of the inedible oil biodiesel residues for value addition

Bioenergy Generation from Municipal Solid Waste and Glycerin Waste: Population Dynamics

“…According to a recent study, electricity generation from biogas in OECD countries grew from 3.7 TWh in 1990 to 78.8 TWh in 2015, making it the third fastest-growing renewable electricity source after wind and solar energy. Due to the advantages of AD, many research studies have sought to optimize the AD of MSW, including the interesting option of the codigestion process, which increases the load of biodegradable organic matter and produces a higher biogas yield. − Studies on AD of MSW have shown that the C:N ratio of this waste presents average values of 10:1, below the optimum for anaerobic digestion (25:1), while hydrogen production (HP) and methane production (MP) is reduced due to the washout of microorganisms, not to overloading. − Therefore, an increase in the loading rate employed in the AD process via the addition of readily biodegradable organic substances, such as glycerol, a major byproduct of biodiesel production, could constitute an ideal strategy. ,− Biodiesel manufacturing worldwide has gained in importance due to several factors: (i) the unavailability of fossil fuels due to demographics and political instability; (ii) modern methods of biodiesel production and new catalyst formulations producing higher biodiesel yields (iii) the breeding and cultivation of new varieties of oil crops with higher lipid yields (iv) an increase in the cultivation of inedible oilseed plants on waste land; (v) new engine designs that can use biodiesel and its admixtures as fuel; and (vi) stringent regulations to reduce GHG emissions. − Producing 100 kg of biodiesel yields approximately 10 kg of glycerin waste (GW) as a coproduct. Numerous sectors, such as the pharmaceutical, cosmetics, and food processing industries, use refined glycerol as a raw input material.…”

“…However, the GW generated as a coproduct of biodiesel production requires purification before being suitable for use in these industries. The problem is that the high costs of purifying glycerol from impure glycerol has reduced its demand in the market, in addition to the reduction in the cost of petroleum-derived glycerol to less than $20 per barrel. , Thus, GW is often considered a waste stream instead of a coproduct, which makes its disposal a fundamental environmental concern.…”

“…Several strategies have been reported in the literature to maximize energy recovery and generate value added products from this type of waste. These options include direct combustion and gasification and AD of waste glycerol to produce biogas (hydrogen or methane), as well as fermentation of glycerol to produce methanol, ethanol, citric acid, 1,3- propanediol, polyhydroxyalkanoates (PHA), and the like. ,,,− This paper focuses on the joint AD of waste glycerol together with MSW to obtain both hydrogen and methane. Recent studies have demonstrated the effectiveness of two-phase dry-thermophilic AD of actual MSW to produce HP and MP, as well as that of GW supplementation (1% v/v) to improve the hydrogen production steps in thermophilic-dry dark fermentation of actual MSW in batch mode .…”

A critical review of Pongamia pinnata multiple applications: From land remediation and carbon sequestration to socioeconomic benefits

“…Biodiesel production from Pongamia generates 7.88 kg of biomass waste per kg of biodiesel, mainly in the form of pods and seed cake. Total energy (expressed in megajoules) of the biomass waste has been estimated to be 3.46 times higher than the energy of 1 kg of biodiesel (Khuntia et al, 2017). This provides a great opportunity for an integrated valorisation pathway as the biomass waste can potentially be used as anaerobic digestor's feedstock for biogas production.…”

Sustainable Bioenergy from Biofuel Residues and Waste

“…Khuntia et al (2017) investigated biodiesel production from non-edible seeds, which generate significant residues that are energy rich. They evaluated methods to minimize inhibition in anaerobic digestion, which could be used to generate biogas.…”