• Energy Research

This research assesses the impacts of hydrothermal (120 °C for 30 min), dilute acid (2%(w/w) H2SO4 at 120 °C for 30 min) and alkali (6% (w/w) NaOH at 35 °C for 24 h)pretreatments on the methane yield from date palm waste “Takarboucht” cultivar. The pretreated and untreated date palm waste (DPW) were digested at mesophilic temperature (36 °C) for 20 days. The highest soluble chemical oxygen demand (sCOD) was obtained by DPW hydrolysate from alkali pretreatment. The highest methane yield of 161.86 ml/g VS was obtained from untreated DPW. Among all pretreatments, higher methane yield was obtained from hydrothermally pretreated DPW (153.35 ml/g VS), followed by acid pretreated DPW (141.65 ml/g VS) and alkali pretreated DPW (50.78 ml/g VS). Alkali pretreatment improved the solubilization of DPW, however, it may not necessarily provide an enhancement in the methane yield. The optimization of the conditions of each pretreatment is proposed.

Abstract This paper examined both experimental and a new modelling test for biogas production based on Co-Digestion Ratio (CDR) of vegetable peel (VP) with cow dung (CD) without external inoculum. For this, vegetable peel was used as a substrate and cow dung was used as a co-substrate. Reactors in triplicate were prepared. The vegetable peel concentrations were 12, 8, 6 and 4 g VS/l with the same cow dung concentration (4 g of VS/l) which corresponds to a CDR of 3:1, 2:1, 1.5:1 and 1:1. A new mathematical model corresponding to the biotech anaerobic digestion process based only on the (CDR) and (VS) was implemented under Matlab Simulink. The experimental results indicate that the optimal cumulative methane production (CMP) of 2000 ml was generated in the reactor containing a (CDR) of 3:1 which corresponds to a methane yield of 170 ml CH4/ g VS. i.e., an improvement between 23 and 26% comparing to all other CDRs . The experimental results were conformed by the new mathematical model. After applying the invented new idea by converting the constants (Rm, L and Gm) into functions (Rm =f1 (CDR), L=f2(CDR) and Gm = f3 (VS)) and relating them to each other using the Gompertz relation. The new model was able to predict the methane produced using only two inputs: VS and CDR. While in the literature studies, which were used Gompertz relationship for kinetic modelling, the constants must be recalculated each time as a new model, although the substrates used are the same, only the composition is different. Analysis of the variance (ANOVA) between the experimental and modelling results showed that there is no statistically significant difference, with a significance level of 0.05. Finally, the invented new idea can be a key to another different research that uses the same substrate.

Biogas is one of the most attractive renewable resources due to its ability to convert waste into energy. Biogas is produced during an anaerobic digestion process from different organic waste resources with a combination of mainly CH4 (~50 mol/mol), CO2 (~15 mol/mol), and some trace gasses. The percentage of these trace gases is related to operating conditions and feedstocks. Due to the impurities of the trace gases, raw biogas has to be cleaned before use for many applications. Therefore, the cleaning, upgrading, and utilization of biogas has become an important topic that has been widely studied in recent years. In this review, raw biogas components are investigated in relation to feedstock resources. Then, using recent developments, it describes the cleaning methods that have been used to eliminate unwanted components in biogas. Additionally, the upgrading processes are systematically reviewed according to their technology, recovery range, and state of the art methods in this area, regarding obtaining biomethane from biogas. Furthermore, these upgrading methods have been comprehensively reviewed and compared with each other in terms of electricity consumption and methane losses. This comparison revealed that amine scrubbing is one the most promising methods in terms of methane losses and the energy demand of the system. In the section on biogas utilization, raw biogas and biomethane have been assessed with recently available data from the literature according to their usage areas and methods. It seems that biogas can be used as a biofuel to produce energy via CHP and fuel cells with high efficiency. Moreover, it is able to be utilized in an internal combustion engine which reduces exhaust emissions by using biofuels. Lastly, chemical production such as biomethanol, bioethanol, and higher alcohols are in the development stage for utilization of biogas and are discussed in depth. This review reveals that most biogas utilization approaches are in their early stages. The gaps that require further investigations in the field have been identified and highlighted for future research.

The Adrar region (Algeria) has a total of 397,800 date palm trees (Phoenix dactylifera L.). Due to annual palm cleaning, large quantities of lignocellulosic biomass are produced. Depending on the variety, an average of 65 kg of biowaste is obtained per palm tree. Since the value of this biowaste is underrated, most of the palms are burned outdoors, causing air and visual pollution. This work explores the gasification potential of lignocellulosic waste from date palms (Phoenix dactylifera L. Takarbouche variety) into useful energy. The technology investigated is air updraft fixed-bed gasification, thanks to an originally designed and built reactor, with the capability to process 1 kg of feedstock. Four types of palm waste—namely, palms, petioles, bunch, and bunch peduncles—are first characterized (bulk density, proximate analysis, fixed carbon, elemental composition, and calorific value) and then used as feedstock for two gasification tests each. The syngas produced for the four date palm wastes is combustible, with an outlet temperature between 200 and 400 °C. The operating temperature inside the gasifier varies according to the feature of the biomass cuts (from 174 °C for the peduncles to 557 °C for palms). The experimental setup is also equipped with a cyclone, allowing for the recovery of some of the tar produced during the tests. Finally, the results show that the residence time has a positive effect on the conversion rate of date palm waste, which can significantly increase it to values of around 95%.

This work aimed to study anaerobic digestion of a new substrate made from the waste of Algerian date palm (Phoenix dactyliferaL.) in order to evaluate its biogas production capacity. The lignocellulosic component biodegradability and the process stability were also tested. Two reactors were launched with the same concentration of 20g total solid (TS)/L. A physical pre-treatment (grinding) of dried leaves lowered the substrate size below 2 mm. The theoretical methane yield (499 - 538 mL CH4/g of Volatile Solids (VS)) indicated a high substrate methanogen potential. The tested methane and biogas yield reached 130±6 mL CH4/gVS and 197±6 mL/g VS respectively. The biodegradability through the volatiles solid reduction was 29%. The total alkalinity (TA) value increased from the beginning to the end, due to the substrate nature which gave a high buffering capacity of the medium. During the stable process, a higher Chemical Oxygen Demand (COD) removal was reached with a value of 77.58%. The majority of the biogas yield was generated during the same period, which confirmed that the anaerobic digestion process stability is indispensable. Finally, this study was an opportunity to better exploit local by-products for the bioenergy production.

© 2022 Elsevier LtdThis paper aims to study the effect of stirring speed on biodiesel yield using an innovative oscillating reactor compared to the conventional stirring tank reactor. The efficiency of the invented reactor was compared with the conventional system, employing two catalysts (a homogeneous catalyst and a heterogeneous bio-catalyst). The obtained results showed that under low agitation speed of 50 rpm, the invented oscillating reactor is more efficient than the conventional system with a biodiesel yield of 93% compared to 90.13% using the heterogeneous catalyst and 93.53% compared to 92.7% using the homogeneous catalyst respectively. As for the higher stirring speeds, the conventional system was found to be slightly more efficient than the oscillating reactor when using the heterogeneous biocatalyst (96.03% against 94.42%) while the contrary was observed when using the homogeneous catalyst (94.43% against 95%). However, this slight increase in the biodiesel yield at higher speeds results in increasing production costs. This indicates that biodiesel production using the innovative oscillating reactor at low speeds is more economically viable. The characteristics of the produced biodiesel using the invented reactor were in agreement with the ASTM D6751 biodiesel standards. Moreover, a two-way ANOVA analysis was conducted to compare between groups that have been split on two independent variables as reactor type and stirring speed. The statistical analysis proved that the invented oscillating reactor performs better when using heterogeneous catalysts at low stirring speed levels. This study suggests that the biodiesel yield of the innovative reactor can be further enhanced by introducing a baffle system which provides a relatively larger contact surface area. Similarly, synthesis of other heterogeneous bio-catalysts derived from the date seed of another date palm cultivar can be tested to further improve the biodiesel yield.

This article discusses the biochemical methane potential (BMP) test of the alkali pretreated “dry leaflets of Algerian date palm (Phoenix dactylifera L.) Hmira cultivar”. The anaerobic digestion (AD) experiments are performed in 4 digesters at 37 °C for 50 days. Digesters with one liter capacity for each one and a working volume of 600 mL are prepared with 10 g volatile solids (VS) of the substrate. A 6%, 12% and 18% weight/weight (w/w) NaOH (based on substrate VS) are used for alkaline pretreatment. During the performed experiments, the CH4 volume is monitored in order to evaluate the alkaline pretreatment influences. The obtained results show that a 12% NaOH is the best concentration, with a 135 mL CH4/gVS that represents an increase of methane production to 133.55% compared to the control test. A biodegradability (BD) improvement of 48.64% through the chemical oxygen demand (COD) removal is recorded with the same concentration of 12% NaOH. The technical digestion times (T80) of 22 and 32 days are recorded for both, the 12% NaOH concentration and the control test respectively, this clearly shows a shortening of 36.78% in T80. Finally, the results obtained in this experimental study show that, based on the increase of pretreatment range of the NaOH concentration (6%, 12% and 18%) before AD of the “dry leaflets of Algerian date palm (Phoenix dactylifera L.) Hmira cultivar”, an improvement of methane yield and biodegradability in shortening digestion time were registered.

EnergyVolume 269, 15 April 2023, 126774Anaerobic digestion of dry palms from five cultivars of Algerian date palm (Phoenix dactylifera L.) namely H'mira, Teggaza, Tinacer, Aghamou and Takarbouchet: A new comparative studyAuthor links open overlay panelMohammedDjaafriabLiborŠtěpanecehttps://doi.org/10.1016/j.energy.2023.126774Get rights and contentHighlights•The biomethane yield is massively influenced by the date palm cultivars.•The highest CH4 yield (231.87 ml CH4/g VS) was obtained with the Aghamou (Ag) cultivar.•The lowest CH4 yield (142.04 ml CH4/g VS) was obtained with the Takarbouchet (Tk) cultivar.•FTIR analyses confirm these findings with the highest transmittance (96.35%) with the Ag cultivar.•This study allows to better perform techno-economic studies and helps to make correct decisions.AbstractThe lignocellulosic properties of date palm waste (dry palm) differ significantly from one cultivar to another, which affects the anaerobic digestion (AD) process. This study is believed to be amongst the first to evaluate the influence of date palm cultivars on the biomethane yield in order to offer an annual, continuous and cost-effective biogas production model. In this work, 5 cultivars from date palm waste namely; H'mira (H), Teggaza (Tg), Tinacer (Ti), Aghamou (Ag) and Takarbouchet (Tk) were evaluated for biogas production. All experiments were performed for 45 days with 5 reactors in triplicate under mesophilic conditions (37 °C). The highest methane yield of 231.87 ml of CH4/g of Volatile Solid (VS) was obtained with the Ag cultivars with a difference that varied between 37% and 62% depending on the cultivar type. These results indicate that the date palm cultivars massively influence the biomethane yield, it may give an opportunity for researchers to select the most suitable cultivars for methane production and provide opportunities to valorize other cultivars on other beneficial uses, such as adsorption, thermal insulation, or charcoal production etc.