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We assessed the suitability of various biogenic materials for development of a gradient packed bed bio-filter to mitigate the methane (CH 4 ) emission from landfills. Five different biogenic materials (windrow compost-WC; vermicompost-VC; landfill top cover-LTC; landfill bottom soil-LBS; and river soil sediment-SS) were screened. Among these materials, the VC showed a better CH 4 oxidation potential (MOP) of 12.6 μg CH 4 g dw −1 h −1 . Subsequently, the VC was used as a packing material along with wood chips in proto-type bio-filters. Wood chips were mixed at 5–15% to form three distinct gradients in a test bio-filter. Under the three different CH 4 loading rates of 33, 44 and 55 gCH 4 m −3 h −1 , the achieved MOPs were 31, 41, and 47gCH 4 m −3 h −1 , respectively. The gradient packed bed bio-filter is effective for landfill CH 4 mitigation than the conventional bio-filter as the latter shows gas channeling effects with poor MOPs. [ABSTRACT FROM AUTHOR]

Polyhydroxyalkanoates (PHAs) are group monomers/heteropolymers that are biodegradable and widely used in biomedical applications. They are considered as alternatives to fossil derived polymers and accumulated by microbes including extremophilic archaea as energy storage inclusions under nutrient limitations. The use of extremophilic archaea for PHA production is an economically viable option for conventional aerobic processes, but less is known about their pathways and PHA accumulation capacities. This review summarized: (a) specific adaptive mechanisms towards extreme environments by extremophiles and specific role of PHAs; (b) understanding of PHA synthesis/metabolism in archaea and specific functional genes; (c) genetic engineering and process engineering approaches required for high-rate PHA production using extremophilic archaea. To conclude, the future studies are suggested to understand the membrane lipids and PHAs accumulation to explain the adaptation mechanism of extremophiles and exploiting it for commercial production of PHAs. [ABSTRACT FROM AUTHOR]

Food waste (FW) is a valuable resource which requires sustainable management avenues to reduce the hazardous environmental impacts and add-value for better economy. Anaerobic digestion (AD) is still reliable, cost-effective technology for waste management. Conventional AD was originally designed for sewer sludge digestion, is not effective for FW due to mainly high organics and volatile fatty acid (VFA) accumulation, hence better technical aptitudes and biochemical inputs are required for optimal biogas production. Besides, to overcome these challenges, FW co-digestion with complementary organic waste e.g. sewage sludge (SS) mixed which complement each other for better process design. The main aim of this article is to summarize the recent updates and review different holistic approaches for efficient anaerobic co-digestion (AcoD) of FW and SS to provide a comprehensive review on the topic. Moreover, to demonstrate the status and perspectives of AcoD at present scenario for Hong Kong and rest of the world. [ABSTRACT FROM AUTHOR]

• Genetic modification reduces O 2 -sensitivity and increase bio-H 2 yield. • Combination of photo and dark-fermentation increases total bio-H 2 yield. • Wastewater utilization reduces the microalgae cultivation cost for H 2 production. • Advanced strategies can improve efficiency of bio-H 2 production and reduce cost. The reliance of fossil fuel for industrial and energy sectors has resulted in its depletion. Therefore, enormous efforts have been considered to move-out from fossil fuels to renewable energy sources based industrial process developments. Recently, biohydrogen (bio-H 2) has been recognised as a clean source of fuel with high-energy efficiency, which can be produced via different routes. Among them, biological fermentation processes are highly recommended due to eco-friendly and economically viable approaches compared to that of thermochemical processes. However, the low H 2 yield and high production cost are major bottlenecks for commercial scale operations. Thus, this review proposed an integrated microalgae-based H 2 production process, which will provides a possible route for commercialization in near future. Furthermore, process integration to improve efficiency and implementation of advanced strategies for the enhancement of bio-H 2 production, economic viability, and future research needs are discussed. [ABSTRACT FROM AUTHOR]