Enhancement of volatile fatty acid production by co-fermentation of food waste and excess sludge without pH control: The mechanism and microbial community analyses

Anaerobic process modelling is a mature and well-established field, largely guided by a mechanistic model structure that is defined by our understanding of underlying processes. This led to publication of the IWA ADM1, and strong supporting, analytical, and extension research in the 15 years since its publication. However, the field is rapidly expanding, in terms of new technology, new processes, and the need to consider anaerobic processes in a much broader context of the wastewater cycle as a whole. Within the area of technologies, new processes are emerging (including high-solids and domestic wastewater treatment). Challenges relating to these new processes, as well as the need to intensify and better operate existing processes have increased the need to consider spatial variance, and improve characterisation of inputs. Emerging microbial processes are challenging our understanding of the role of the central carbon catabolic metabolism in anaerobic digestion, with an increased importance of phosphorous, sulfur, and metals as electron source and sink, and consideration of hydrogen and methane as potential electron sources. The paradigm of anaerobic digestion is challenged by anoxygenic phototrophism, where energy is relatively cheap, but electron transfer is expensive. These new processes are commonly not compatible with the existing structure of anaerobic digestion models. These core issues extend to application of anaerobic digestion in domestic plant-wide modelling, with the need for improved characterisation, new technologies having an increased impact, and a key role for the linked phosphorous–sulfur–iron processes across the cycle. The review overall finds that anaerobic modelling is increasing in complexity and demands on the modeller, but the core principles of biochemical and physicochemical processes, metabolic conservation, and mechanistic understanding will serve well to address the new challenges.

Mathematical modelling of anaerobic digestion processes: applications and future needs

Anaerobic baffled reactor (ABR) for treating heavy oil produced water with high concentrations of salt and poor nutrient.

The palm oil industry generates significant amounts of solid wastes. The solid wastes, also known as oil palm biomass, includes the trunk (OPT) and fronds (OPT) from the plantation, and empty fruit bunch (EFB), mesocarp fibre (MF) and palm kernel shell (PKS) from the processing mills. Oil palm biomass is not effectively recycled for other applications, and existing disposal practices can cause adverse impacts on the environment. As oil palm biomass is a readily available lignocellulosic biomass, it has the potential to be a low-cost feedstock for conversion into higher value products. The first part of this study provides a comprehensive review of utilisation of oil palm biomass for the production of biofuels, chemicals and biomaterials through direct utilisation and physical conversion, biochemical conversion, thermochemical conversion and synthesis of lignin-based materials. The second part of this study discusses the opportunity for biorefinery development based on existing bioproducts from oil palm biomass, for the production of advanced fuels and platform chemicals that have not been explored in oil palm biomass research. This study proposes integrated biorefinery concepts via the integration of existing oil palm biomass biorefinery products with thermochemical process for upgrading the bioproducts into higher values products. The high-value products integrated biorefinery products include advanced biofuels, fuel additives and platform chemicals. The integrated biorefinery development for oil palm biomass processing is expected to improve the economics of the production of biomass-derived renewable energy and enhance the sustainability of palm oil industry.

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The outlook of the production of advanced fuels and chemicals from integrated oil palm biomass biorefinery

Removal of hydrogen sulfide by complete aerobic oxidation in acidic biofiltration

Effects of pH adjustment by parawood ash and effluent recycle ratio on the performance of anaerobic baffled reactors treating high sulfate wastewater

Effects of size and thermophilic pre-hydrolysis of banana peel during anaerobic digestion, and biomethanation potential of key tropical fruit wastes.

Low temperature hydrothermal treatment of palm fiber fuel for simultaneous potassium removal, enhanced oil recovery and biogas production

Co-fermentation of oil palm lignocellulosic residue with pig manure in anaerobic leach bed reactor for fatty acid production

Napier grass (Pennisetum purpureum) is a high yield tropical grass with great potential for anaerobic digestion. Two-phase anaerobic dry digestion (TADD), considered an alternative for anaerobic wet digestion system (AWD) with only front-end leach bed reactor (LBR), is added to existing liquid digester, was tested under different leachate circulations, and was compared with AWD. Leachate circulation frequency in LBR was found to highly influence hydrolysis rate and hence improved overall digestibility of the grass fiber. Additional methane yield of 32.5% was achieved when leachate circulation increased from 1 to 4 times per day and diminished to merely 13.7% more at continuous circulation. A shift in methane generation from leachate digester to LBR as digestion time progressed and important biochemical characteristics were discussed. In AWD, operation at an organic loading of 4 kgVS/m3 d gave the highest methane yield at 145.2 m3/tondry, which is 2.3 times higher than TADD due to an advantage in mass transfer in a total wet environment. This work had advanced our understandings on phase separation in anaerobic digestion system and the key methanation performance among dry and wet digestions of the prototypical lignocellulosic biomass.

Kanyarat Saritpongteeraka

Papers

Effects of pH adjustment by parawood ash and effluent recycle ratio on the performance of anaerobic baffled reactors treating high sulfate wastewater

Effects of size and thermophilic pre-hydrolysis of banana peel during anaerobic digestion, and biomethanation potential of key tropical fruit wastes.

Low temperature hydrothermal treatment of palm fiber fuel for simultaneous potassium removal, enhanced oil recovery and biogas production

Co-fermentation of oil palm lignocellulosic residue with pig manure in anaerobic leach bed reactor for fatty acid production

Anaerobic Digestion of Napier Grass (Pennisetum purpureum) in Two-Phase Dry Digestion System Versus Wet Digestion System