A critical review on pretreatment and detoxification techniques required for biofuel production from the organic fraction of municipal solid waste

Bio-physical pre-treatments in anaerobic digestion of organic fraction of municipal solid waste to optimize biogas production and digestate quality for agricultural use

This study optimized the anaerobic digestion (AD) of separated collected organic fractions of municipal solid waste (OFMSW) to produce energy and digestate as biofertilizer. Due to OFMSW's partial recalcitrance to degradation, enzymatic (UPP2, MCPS, USC4, USE2, A. niger) and physical (mechanical blending, heating, hydrodynamic cavitation) pre-treatments were tested. Experimental and modeling approaches were used to compare AD performance regarding energy sustainability and digestate quality. Digestate was separated into solid and liquid fractions, and then chemically and physically characterized by investigating the nutrient release mechanisms. Principal Component Analysis was applied, equally weighing energy and digestate productions. Unlike previous studies focusing only on biogas, this study evaluated the effects of pre-treatments on both biogas and digestate production, viewing AD as a biorefinery process for urban waste valorization. Results showed that all pre-treatments were energetically sustainable, but enzymatic pre-treatments yielded digestates richer in nutrients (increase of 80% N, 200% P and 150% K as compared to OFMSW) and with greater organic matter degradation compared to physical pre-treatments. The liquid fraction of digestate from enzymatic pre-treatments had higher nutrient concentrations, while those from physical pre-treatments had more balanced nutrient content, making them more suitable for fertigation.

Bioprocesses for lactic acid production from organic wastes toward industrialization-a critical review

Lactic acid (LA) is a crucial chemical which has been widely used for industrial application. Microbial fermentation is the dominant pathway for LA production and has been regarded as the promising technology. In recent years, many studies on LA production from various organic wastes have been published, which provided alternative ways to reduce the LA production cost, and further recycle organic wastes. However, few researchers focused on industrial application of this technology due to the knowledge gap and some uncertainties. In this review, the recent advances, basic knowledge and limitations of LA fermentation from organic wastes are discussed, the challenges and suitable envisaged solutions for enhancing LA yield and productivity are provided to realize industrial application of this technology, and also some perspectives are given to further valorize the LA fermentation processes from organic wastes. This review can be a useful guidance for industrial LA production from organic wastes on a sustainable view.

Biobutanol production from underutilized substrates using Clostridium: Unlocking untapped potential for sustainable energy development

The increasing demand for sustainable energy has brought biobutanol as a potential substitute for fossil fuels. The Clostridium genus is deemed essential for biobutanol synthesis due to its capability to utilize various substrates. However, challenges in maintaining fermentation continuity and achieving commercialization persist due to existing barriers, including butanol toxicity to Clostridium, low substrate utilization rates, and high production costs. Proper substrate selection significantly impacts fermentation efficiency, final product quality, and economic feasibility in Clostridium biobutanol production. This review examines underutilized substrates for biobutanol production by Clostridium, which offer opportunities for environmental sustainability and a green economy. Extensive research on Clostridium, focusing on strain development and genetic engineering, is essential to enhance biobutanol production. Additionally, critical suggestions for optimizing substrate selection to enhance Clostridium biobutanol production efficiency are also provided in this review. In the future, cost reduction and advancements in biotechnology may make biobutanol a viable alternative to fossil fuels.

Efficient polymalic acid production from corn straw hydrolysate by detoxification of phenolic inhibitors

Inhibitory compounds generated from lignocellulose pretreatment would inhibit Poly (malic acid) (PMA) production by Aureobasidium pullulans, but the tolerance mechanism of A. pullulans to lignocellulosic inhibitor is poorly understood. In this study, the cellular response of A. pullulans to lignocellulosic inhibitor stress was studied. Among the three groups of inhibitors (furans, weak acids and phenolic aldehydes), phenolic aldehyde was the dominant inhibitor for PMA production. Phenolic aldehyde was mainly converted into phenolic alcohol by A. pullulans, and phenolic alcohol also exhibited severe inhibition on PMA production. Furthermore, the effect of detoxification methods on inhibitor-removal and PMA fermentation was investigated, both CaCO3 and overliming presented poor detoxification effect, whereas resin H103 could remove both furan derivatives and phenolic compounds efficiently, thereby producing 26.27 g/L of PMA with a yield of 0.30 g/g in batch fermentation. This study will be beneficial for the development of PMA production from lignocellulosic biomass.

Assessing the environmental footprints and material flow of 2,3-butanediol production in a wood-based biorefinery

This study aims to scrutinize and compare the environmental impacts of biobased 2,3-butanediol (BDO) and its fossil-based counterpart. BDO is a fundamental chemical in various industries, traditionally derived from petroleum sources. Wood residues, largely available in Nordic countries, are sustainable alternative feedstocks, offering potential environmental benefits. Material flow analysis followed by consequential life cycle assessment (LCA) were employed to quantify the potential environmental burdens associated with various biorefinery stages of wood-based BDO production. The findings indicated that refraining from wood combustion and, instead, utilizing wood in a biorefinery to produce BDO as the main product, with methane and fertilizer as coproducts from the waste residue, resulted in 125%, 52%, and 90% better environmental performance regarding human health, climate change, and resource scarcity, respectively, compared to fossil-based BDO production. The results offer valuable insights for technology developers and policymakers, empowering them to make informed decisions and support sustainable practices.

A strategic review on sustainable approaches in municipal solid waste management andenergy recovery: Role of artificial intelligence,economic stability andlife cycle assessment

The consumption of energy levels has increased in association with economic growth and concurrently increased the energy demand from renewable sources. The need under Sustainable Development Goals (SDG) intends to explore various technological advancements for the utilization of waste to energy. Municipal Solid Waste (MSW) has been reported as constructive feedstock to produce biofuels, biofuel carriers and biochemicals using energy-efficient technologies in risk freeways. The present review contemplates risk assessment and challenges in sorting and transportation of MSW and different aspects of conversion of MSW into energy are critically analysed. The circular bioeconomy of energy production strategies and management of waste are also analysed. The current scenario on MSW and its impacts on the environment are elucidated in conjunction with various policies and amendments equipped for the competent management of MSW in order to fabricate a sustained environment.