Jean-Louis Lanoisellé

This study investigates the influence of inoculum to substrate ratios, substrate length, and freezing on the anaerobic digestion of the brown macroalga Sargassum muticum through batch experiments. Methane production optimisation was performed using response surface methodology with a central composite design. Biochemical methane potential tests conducted on frozen algae underscore the significant impact of the inoculum to substrate ratio, revealing that a ratio of 2 enables a high hydrolysis rate without apparent phenomena that limit methane production. In terms of modelling, the first-order model provided more accurate biochemical methane potential estimations than the Gompertz model. Furthermore, using fresh algae resulted in a 21% increase in methane production per kilogram of volatile solids compared to frozen samples. The study also confirms that high endogenous methane production can compromise BMP assay reliability. A methane potential range of 170-270 NL CH₄·kg VS^-1 was established allowing an initial assessment of energy production. The examination of Sargassum muticum contributes to the understanding of marine biomass anaerobic digestion processes and demonstrates its potential as a renewable energy source.

Coasts are home to one-third of the human population. In the process of energy transition, local biomass and waste resources represent a renewable fuel that can substitute fossil fuels in order to reduce greenhouse gas emissions, hence including marine resources as part of the eligible feedstock for renewable energy production. Gasification regroups different technologies that aim to convert a solid fuel into a useful gas, and has several applications, such as heat production, power generation, and chemical synthesis. Gasification technologies regroup the traditional “dry” processes that use relatively dry fuels, but recent developments have been made with “wet” processes such as hydrothermal gasification, in sub- or supercritical conditions for the water, which can accept wet fuel. This review focuses on scientific articles that performed gasification of marine resources in order to produce a syngas. First, a definition of marine resources is made, followed by the presentation of marine resources studied in the literature. Secondly, this review presents the different types of gasification reactors and their operating conditions, followed by a summary of the different syngas produced with their composition as a performance indicator. Finally, this review exposes the limitations of the current literature and concludes with perspective propositions.

Poultry waste is rich in organic matter, which allows its treatment by the process of anaerobic digestion (AD) to reinforce economic and environmental green strategies. The aim of this study is to assess the technical feasibility of poultry waste AD in semi-continuous mode and to intensify methane production by co-digestion with physico-chemical sludge, i.e., the product of the primary treatment of wastewater after the slaughtering process. First, the AD of poultry droppings is conducted in a continuous stirred anaerobic digester (CSAD) at 37 °C. A volume of 0.791 and 0.623 Nm³·Nm⁻³ reactor·days⁻¹ of biogas and methane, respectively, were produced during the entire process stabilization period. Biochemical characterization of the substrate and the final digestate show high reduction rates of the biochemical fractions, which corroborates with methane yield. In addition, the co-digestion of poultry droppings with two different ratios of physico-chemical sludge (20% and 40% added sludge considering the amount of volatile solids) shows an increase in methane production versus droppings alone, with a higher increase of 54% with a sludge ratio of 40%. Altogether, these promising results were obtained in stable processes, highlighting the pertinence of our study.

The objective of this study was to assess the impact of pulsed electric field (PEF) treatment on the extraction of polyphenolics and antioxidant activity from downgraded date palm fruits. The PEF pretreatments (frequency: 30 Hz, time: 50 μs, pulse number: 240, the electric field strengths were found to be 1, 2, and 2.5 kV.cm⁻¹, and methanol (50%) and temperatures (20, 40, 50 °C)) were optimized and applied before extraction to produce an extract of date fruits with a high content of bioactive compounds. The extracts obtained immediately after pretreatments were analyzed for total polyphenolic content, antioxidant activity, and phenolic profiles. The results revealed that the PEF-assisted extracts at 2.5 kV.cm⁻¹ at T₅₀ °C exhibited higher polyphenol content (+27%) and antioxidant activity (+31%) and notably improved phenolic profiles compared to untreated extracts. PEF treatment processing significantly enhanced the bioactive components and antioxidant activities of date fruits over time, regardless of the treatment applied and the extraction’s temperature. Hence, the application of PEF combined with thermal processing can be an appropriate alternative treatment for a better extractability of bioactive compounds from fruit of dates and food byproducts. These biomolecules could be consumed as new food technology, incorporated as food additives, and nutraceuticals products.

Poultry waste are rich in organic matter, allowing its use as substrates for biogas production by anaerobic digestion (AD). The major difficulty in the anaerobic digestion of this protein-rich waste is the ammonia inhibition. Different results of biochemical methane potential (BMP) were obtained after the mesophilic anaerobic digestion of different avian waste in batch mode. It was shown that using two different inoculum (Liger and Saint-Brieuc) sources and different substrate to inoculum (S/I) ratios does not have a significant effect on the biochemical methane potential of organic laying hen droppings (OLHD); an average of 0.272 Nm³ CH₄ · kg^-1 VS was obtained with both inocula. Otherwise, it affects the hydrolysis constant K_H, it decreases when substrate to inoculum ratio increases. Furthermore, Liger is the most suitable inoculum for our substrate because it shows a stability during the process even with different organic load. Comparing the biochemical methane potential of multiple avian waste such as organic laying hen droppings and different slaughterhouse waste highlights the importance of slaughterhouse waste in the anaerobic digestion process because of the high methane yield observed specially with the viscera (0.779 Nm³ CH₄ · kg^-1 VS, SD = 0.027 Nm³ CH₄ · kg^-1 VS). Moreover, methane production was affected by increasing the ammonia concentrations; when [N-NH₃] > 9.8 g N-NH₃ · L^-1 the biochemical methane potential decreases and the lag phase increases (λ > 30 days); a total inhibition of the process was observed when ammonia concentration is above 21.8 g · L^-1. GRAPHICAL ABSTRACT

Seaweeds represent a promising and sustainable feedstock for biofuel production which raises increasing research interests. Their high availability, easy fermentable composition, and good degradation potential make them a suitable candidate for alternating fossil fuels as an advantageous energy resource. This comprehensive review aims to summarize and discuss data from the literature on the biochemical composition of seaweeds and its potential for biomethane and biohydrogen production, as well as to investigate the effect of the common pretreatment methods. Satisfactory yields comparable to terrestrial biomass could be obtained through anaerobic digestion; concerning dark fermentation, the challenge remains to better define the operating conditions allowing a stable production of biohydrogen. Finally, we propose a potential energy production scheme with the seaweed found by the Caribbean Islands of Guadeloupe and Martinique, as well as current techno-economic challenges and future prospects. An annual energy potential of 66 GWh could be attained via a two-stage biohythane production process, this tends to be promising in terms of energetic valorization and coastal management.