Analysis of Biogas Production from Biomass Residue of Palm Oil Mills using an Anaerobic Batch Test

The Malaysian palm oil industry has grown rapidly due to Malaysia’s tropical weather and suitable terrain. Palm oil production is now categorized as the most significant agriculture-based industry in the country. Along with strong economic returns, the palm oil industry also generates an abundance of waste products, including empty fruit bunches (EFB) (23%), mesocarp fibre (12%), shells (5%) and palm oil mill effluent (POME) (60%) for every batch of fresh fruit bunches (FFB) processed in the mills. This study is meant to fill the gap from previous studies in terms of biogas productions from the POME or the combination of POME and EFB which normally been conducted under the thermophilic conditions. The appropriate mixture ratios between POME and EFB in anaerobic digestion will reduce time of treatment and space if been conducted in the low temperature (mesophilic conditions). Thus, this paper is focuses on the analysis of batch test design which consist of low temperature (mesophilic, 20-40 °C) conditions for evaluating the performance of biogas production from the combination of POME and EFB in anaerobic digestion. The aim was to determine the amount of biogas production based on different ratios of POME and EFB mixtures. Biogas 1, containing 160 mL of fresh POME mixed with 40 g of EFB, was shredded and blended with 1800 mL seed sludge. Biogas 2, containing 120 mL of fresh POME mixed with 80 g of EFB, was shredded and blended with 1800 mL seed sludge. Based on the analysis of the results, the total production of Biogas 1 was greater than that of Biogas 2. The findings also show that the ratio of POME and 20% EFB (Biogas 1) was more efficient in producing the biogas compared to the ratio POME and 40% EFB (Biogas 2) under the mesophilic conditions. Thus, the mesophilic conditions required energy saving and low-cost process, compared to the previous studies which used the high temperature (thermophilic, 41-122 °C) that definitely was costly and require more energy consumption. This study will serve as preliminary results for enhancing the treatment methods use in Malaysia and form the early basis for the development of a new technology incorporating a combination of POME and EFB.

Development of parameters for the production of biomass and biohydrogen from brewer’s grain

In this work, suitable pretreatment conditions have been studied to increase hydrogen production by dark fermentation of brewer’s grain (BG). All samples with different concentrations of raw materials were tested: treatment with sulfuric acid with a concentration of 1.5%, autoclaving at 121 ◦C, purification from impurities by filtration, centrifugation and calibration of the pH of the medium to 7.5 units. The choice of acid hydrolysis is due to the fact that this type of pretreatment is the most suitable for the further commercialization of this technology. Also, pretreatment performs the task of suppressing methanogens and creating conditions for the life of hydrogen-producing bacteria. Experiments were carried out under mesophilic conditions ( 37 ◦C) using wild-type and multiple mutant E. coli. The highest sugar yields were obtained at a 4% concentration of brewer’s grains and in the presence of a concentration of 1.5% sulfuric acid in the original substrate. The results of the experiments showed that brewer’s grains are a valuable product as a source of carbon and energy for microorganisms in the production of biohydrogen, as well as for the production of biomass for further production of value-added products.

Rigid and film bioplastics degradation under suboptimal composting conditions: A kinetic study

The present research investigates the degradation rate of bioplastics under various composting conditions, including suboptimal ones. Lab-scale tests were carried out setting three variables: temperature (37°C–58°C), humidity (30%–60%) and duration of the thermophilic and the maturation phases (15–60 days). The composting tests were carried out following modified guideline ISO 20200:2015 and lasted for 60 days. Bioplastics in the synthetic waste matrix consisted of Mater-Bi® film biobags and PLA rigid teaspoons. A kinetic study was performed, resulting in faster degradation rates for film bioplastics (first-order kinetics with k = 0.0850–0.1663 d−1) than for rigid (0.0018–0.0136 d−1). Moreover, film bioplastics reached a complete degradation within the 60 days of the test. Concerning the rigid products, 90% degradation would be achieved in 2–3 years for mesophilic conditions. Finally, in the undersieve of 0.5 mm some microplastics were identified with the ImageJ software, mainly relatable to rigid (PLA) bioplastics. Overall, the results disclosed that the combination of mesophilic temperatures and absence of moistening slowed down both the degradation and the disintegration process of bioplastics.

Digested Sludge Quality in Mesophilic, Thermophilic and Temperature-Phased Anaerobic Digestion Systems

Anaerobic digestion (AD) technology is commonly used to treat sewage sludge from activated sludge systems, meanwhile alleviating the energy demand (and costs) for wastewater treatment. Most often, anaerobic digestion is run in single-stage systems under mesophilic conditions, as this temperature regime is considered to be more stable than the thermophilic one. However, it is known that thermophilic conditions are advantageous over mesophilic ones in terms of methane production and digestate hygienisation, while it is unclear which one is better concerning the digestate dewaterability. Temperature-phased anaerobic digestion (TPAD) is a double-stage AD process that combines the above-mentioned temperature regimes, by operating a thermophilic digester followed by a mesophilic one. The aim of this study is to compare the digestate quality of single-stage mesophilic and thermophilic AD and TPAD systems, in terms of the dewaterability, pathogenic safety and lower calorific value (LCV) and, based on the comparison, consider digested sludge final disposal alternatives. The research is conducted in lab-scale reactors treating waste-activated sludge. The dewaterability is tested by two methods, namely, centrifugation and mechanical pressing. The experimental results show that the TPAD system is the most beneficial in terms of organic matter degradation efficiency (32.4% against 27.2 for TAD and 26.0 for MAD), producing a digestate with a high dewaterability (8.1–9.8% worse than for TAD and 6.2–12.0% better than for MAD) and pathogenic safety (coliforms and Escherichia coli were not detected, and Clostridium perfringens were counted up to 4.8–4.9 × 103, when for TAD it was only 1.4–2.5 × 103, and for MAD it was 1.3–1.8 × 104), with the lowest LCV (19.2% against 15.4% and 15.8% under thermophilic and mesophilic conditions, respectively). Regarding the final disposal, the digested sludge after TAD can be applied directly in agriculture; after TPAD, it can be used as a fertilizer only in the case where the fermenter HRT assures the pathogenic safety. The MAD digestate is the best for being used as a fuel preserving a higher portion of organic matter, not transforming into biogas during AD.

Bioemulsification and Microbial Community Reconstruction in Thermally Processed Crude Oil

Utilization of low-cost, environmental-friendly microbial enhanced oil recovery (MEOR) techniques in thermal recovery-processed oil reservoirs is potentially feasible. However, how exogenous microbes facilitate crude oil recovery in this deep biosphere, especially under mesophilic conditions, is scarcely investigated. In this study, a thermal treatment and a thermal recurrence were processed on crude oil collected from Daqing Oilfield, and then a 30-day incubation of the pretreated crude oil at 37 °C was operated with the addition of two locally isolated hydrocarbon-degrading bacteria, Amycolicicoccus subflavus DQS3-9A1T and Dietzia sp. DQ12-45-1b, respectively. The pH, surface tension, hydrocarbon profiles, culture-dependent cell densities and taxonomies, and whole and active microbial community compositions were determined. It was found that both A. subflavus DQS3-9A1T and Dietzia sp. DQ12-45-1b successfully induced culture acidification, crude oil bioemulsification, and residual oil sub-fraction alteration, no matter whether the crude oil was thermally pretreated or not. Endogenous bacteria which could proliferate on double heated crude oil were very few. Compared with A. subflavus, Dietzia sp. was substantially more effective at inducing the proliferation of varied species in one-time heated crude oil. Meanwhile, the effects of Dietzia sp. on crude oil bioemulsification and hydrocarbon profile alteration were not significantly influenced by the ploidy increasing of NaCl contents (from 5 g/L to 50 g/L), but the reconstructed bacterial communities became very simple, in which the Dietzia genus was predominant. Our study provides useful information to understand MEOR trials on thermally processed oil reservoirs, and proves that this strategy could be operated by using the locally available hydrocarbon-degrading microbes in mesophilic conditions with different salinity degrees.

Investigating the effect of temperature gradient on biogas production from pretreated maize straw and rice husk using multistage anaerobic bioreactor

The share of biogas in renewable energy sources is increasing as variety of feedstocks are now used for biogas production among which lignocellulosic biomass is emerging feedstock that can be used after proper pretreatment under best suited temperature. Although lot of pretreatments and temperature combinations have been tested but still there is a gap that can be filled by the current study focused on the effect of the temperature gradient (mesophilic and thermophilic) on biogas production potential of maize straw and rice husk using a modified Gompertz equation. Pretreatment was done by using alkali (NaOH and Ca(OH)2) and acids (HCl and H2SO4) each at 2, 4 and 6%.The pretreatment of crop residue with 6% NaOH degraded lignin contents significantly. The pretreated crop residue was further used for biogas production. A multistage anaerobic bioreactor containing three diagonally inline reactors provided with one water bath connected to reactors for better utilization of energy was used for biogas production. The temperature of water bath was adjusted to that the first reactor achieved 37°C and 55 °C for different experiments. The working temperatures found to be 31-37°C and 46-55°C were achieved to maintain the internal temperature of the reactors within mesophilic and thermophilice temperature ranges, respectively. The 36 days incubation time was equally divided for three reactors. The biogas production rate was297 mL/g-VSadded and 244.07 mL/g-VSadded from maize straw and rice husk under mesophilic conditions, respectively. The results showed an increased biogas yield for both feedstocks under mesophilic conditions as compared to thermophilic conditions. The central reactor showed better production as compared to other two rectors in all experiments.