Waste and Biomass Valorization

Oil palm industry is the largest contributor of biomass in Malaysia. Oil palm biomass are constantly generated in large quantities annually with a small fraction being converted into value added product while a large percentage are left underutilized. Several researchers have reported the various technologies available for the conversion of oil palm biomass into useful bio-products, including bio-fuel, biogas, bio-fertilizers, bio-composite and briquettes. In general, these technologies are either underutilized or inadequate for full conversion of these abundantly available biomass, hence, there is an urgent need for upgrading of such technologies. This review article highlights the availability of oil palm biomass in Malaysia, the chemical compositions, as well as a brief description of current technologies for converting oil palm biomass into value added products. The review also outlines a summary of the various products obtained from oil palm biomass. Steps to achieve maximum utilization of biomass from oil palm industry are also proposed.

Trigonella foenum-graecum, is a widely used medicinal and culinary plant. The antioxidant compounds extracted from the seeds of this plant exert antioxidant, anti-inflammatory, and hypoglycemic effects. In this study, antioxidant compounds from the seeds of Trigonella foenum-graecum were obtained using the deep eutectic solvent (DES) assisted and β-cyclodextrin assisted extraction method. The process was optimized by implementing a response surface methodology that took into consideration the following independent variables: β-cyclodextrin concentration (Cβ-CD) or DES concentration, solid-to-liquid ratio, and temperature. Based on the results from single-factor experiments, response surface methodology was used to optimize the extraction conditions. The scavenging activity of Trigonella foenum-graecum antioxidant compounds on DPPH*, the total phenolic yield (YTP) and total flavonoid yield (YTF) was determined. Using the optimized conditions for DES extractions, the yields were 0.019 mmol TRE/g seed, 14.73 mg GAE/g seed and 0.092 mmol QE/g seed for AAR, YTP and YYF respectively. For β-cd assisted extraction, using the optimized conditions, the yields were 0.1213 mmol TRE/g seed, 12.89 mg GAE/g seed and 0.1602 mmol QE/g seed for AAR, YTP and YYF respectively. However, based on regression analysis and optimization based on solvent type it is observed that the extraction yield with β-cyclodextrin solutions is statistically significantly (P < 0.05) higher than the corresponding yield with solutions of deep eutectic solvent mixtures.

Abattoir waste methanization has historically focused on cattle, swine and poultry wastes. The main objective of the present work is the determination of biomethane potential of organic wastes from arid-region, i.e. animal dung: camel, sheep, goat, cattle; and mixed blood waste. Biomethane potential was determined for the five untreated wastes. In addition the investigated wastes were thermally pretreatment at 120 °C for 30 min and the biomethane potentials of the pretreated wastes were in addition determined. The thermal pretreatment increased the biomethane potential by 30–150%, achieving a maximum of 442 ml CH4/g VS for the thermally pretreated mixed blood waste. The results highlight the potential of using abattoir wastes in arid-regions for biomethane production. Two mathematical models, Gompertz, and modified Gompertz, were used to analyze the experimental data and determine the maximum biomethane production rate. The analysis showed that the modified Gompertz model is more accurate than the Gompertz model giving at biomethane production rate up to 56 ml CH4/g VS/day.

The aim of this study was to investigate the effect of the composting process, conducted with the addition of various substrates, on the biological and ecotoxic properties of composts. Composts were prepared on the basis of plant material amended with biochar, sewage sludge, coffee grounds, or yeast effluent. The composting process was carried out for 140 days. The biological activity of mixtures was determined in the process, while microorganism abundance and ecotoxicity, in the final product. The addition of biochar had no significant effect on the rate of the composting process measured by temperature; however, biochar-amended treatments showed a smaller loss of dry matter and higher C:N ratio. Compared to the control, reduced biological activity measured by the germination capacity of seeds was identified in treatments with maize straw composts and composts enriched with coffee grounds and yeast effluent. The inhibitory effect on the germination capacity was alleviated in treatments with biochar. The addition of biochar to compost with sewage sludge decreased the abundance of Escherichia coli and Salmonella ssp. and increased the total number of bacteria and fungi. In the case of composts with coffee grounds, biochar had an opposite effect to that observed for composts with sewage sludge. Biochar to sewage sludge and coffee grounds reduced ecotoxicity of composts to test organisms: Vibrio fischeri, Sianpis alba, Triticum L. and Eisenia fetida.

Biofuels and biomaterials are gaining increased attention because of their ecofriendly nature and renewable precursors. Biochar is a recalcitrant carbonaceous product obtained from pyrolysis of biomass and other biogenic wastes. Biochar has found many notable applications in diverse areas because of its versatile physicochemical properties. Some of the promising biochar applications discussed in this paper include char gasification and combustion for energy production, soil remediation, carbon sequestration, catalysis, as well as development of activated carbon and specialty materials with biomedical and industrial uses. The pyrolysis temperature and heating rates are the limiting factors that determine the biochar properties such as fixed carbon, volatile matter, mineral phases, surface area, porosity and pore size distribution, alkalinity, electrical conductivity, cation-exchange capacity, etc. A broad investigation of these properties determining biochar application is rare in literature. With this objective, this paper comprehensively reviews the evolution of biochar from several lignocellulosic biomasses influenced by pyrolysis temperature and heating rate. Lower pyrolysis temperatures produce biochar with higher yields, and greater levels of volatiles, electrical conductivity and cation-exchange capacity. Conversely, higher temperatures generate biochar with a greater extent of aromatic carbon, alkalinity and surface area with microporosity. Nevertheless, this coherent review summarizes the valorization potentials of biochar for various environmental, industrial and biomedical applications.

The research aims to investigate the potential of using Ag/PMAc-g-CNT as a high-efficient catalyst for overall water splitting and supercapacitor applications. The results of Tafel slope measurements for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed that the Ag/PMAc-g-CNT catalyst had a lower Tafel slope of 22.62 mV dec−1 and 62.74 mV dec−1, respectively, compared to the other electrocatalysts. Additionally, the capacitance value of the Ag/PMAc-g-CNT catalyst was found to be 41.87 F at 0.5 A/g current density which is much higher than that of the Ag/PMAc catalyst. These results demonstrate that the Ag/PMAc-g-CNT catalyst has superior properties in terms of electrochemical activity, stability and energy storage capacity, making it a promising material for both water splitting and supercapacitor applications.

In this work we studied two approaches for the revalorization of corn stover (CS): Feedstock for bioethanol generation and substrate for the production of biocatalysts. The practical application of two of these biocatalysts (laccases and cellulases) was also evaluated. The hydrolysis of CS was improved through a pretreatment with the thermotolerant fungus Fomes sp. EUM1; simultaneously, enzymatic extracts enriched with laccases or cellulases were obtained and applied for the pretreatment or hydrolysis of untreated CS. After 7 days, the fungal pretreatment promoted a significant increase in the release of reducing sugars (60%) and in the hydrolysis rate (50%). Lignin content decreased 61.2%, while holocellulose remained practically unchanged; a significant positive correlation (r = 0.948, p = 0.01) was found between laccase production and lignin degradation. Regarding biocatalysts application, the cellulases of Fomes sp. EUM1 showed catalytic properties similar to those of commercial enzymes; in addition, the pretreatment with laccases reduced 70% the processing-time (compared to the fungal treatment), and improved the release of reducing sugars and the hydrolysis rate by 26 and 29%, respectively. The pretreatment of CS with Fomes sp. EUM1 produces two valuable products: saccharificable biomass useful for bioethanol production and highly active enzymes applicable in bioconversion processes.

This study aimed to elucidate the effect of preheat-treatments and bleaching agents on molecular characteristics and bioavailability of obtained bio-calcium. Bio-calcium from Asian sea bass backbone was prepared using different preheat-treatment methods (boiling at 100 °C for 30 min or autoclaving at 121 °C for 90 min). Subsequent bleaching was carried out using 2.5% sodium hypochlorite, followed by 2.5% hydrogen peroxide or using 2.5% hydrogen peroxide alone. Bio-calcium powder from autoclaved bone had higher calcium content (35.9 ± 0.2%) than that produced from boiled bone (25.7 ± 1.2%). Particle size of bio-calcium from autoclaved bone (16.71 ± 16.71 µm) was lower than that from boiled bone (52.85 ± 43.16 µm). Highest whiteness index (92.26 ± 0.21) was observed for autoclaved bone bio-calcium when hydrogen peroxide alone was used as bleaching agent. FTIR study confirmed that Ca-hydroxyapatite was present in both bio-calcium from boiled and autoclaved bones but the amount was higher in the latter. Boiling or boiling/autoclaving could be alternative pre-treatment for bio-calcium production to reduce chemical or alkali used and to soften the bone. However, solubility of autoclaved bone bio-calcium was lower than boiled bone counterpart. Enhancement of solubility is still needed to improve bio-availability of bio-calcium from Asian sea bass backbone.