Optimization of microwave pretreatment of lignocellulosic waste for enhancing methane production: Hyacinth as an example

The effect of microwave pretreatment on the anaerobic degradation of hyacinth was investigated using response surface methodology (RSM). The components of lignin and the other constituents of hyacinth were altered by microwave pretreatment. Comparison of the near-infrared spectra of hyacinth pretreated by microwave irradiation and water-heating pretreatment revealed that no new compounds were generated during hyacinth pretreatment by microwave irradiation. Atomic force microscopy observations indicated that the physical structures of hyacinth were disrupted by microwave pretreatment. The yield of methane per gram of the microwave-irradiated substrate increased by 38.3% as compared to that of the substrate pretreated via water-heating. A maximum methane yield of 221 mL?g-sub^–1 was obtained under the optimum pretreatment conditions (substrate concentration (PSC) = 20.1 g?L^–1 and pretreatment time (PT) = 14.6 min) using RSM analysis. A maximum methane production rate of 0.76 mL?h^–1?g-sub^–1 was obtained by applying PSC = 9.5 g?L^–1 and PT = 11 min. Interactive item coefficient analysis showed that methane production was dependent on the PSC and PT, separately, whereas the interactive effect of the PSC and PT on methane production was not significant. The same trend was also observed for the methane production rate.

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Algal biomass valorization for biofuel production and carbon sequestration: a review

The world is experiencing an energy crisis and environmental issues due to the depletion of fossil fuels and the continuous increase in carbon dioxide concentrations. Microalgal biofuels are produced using sunlight, water, and simple salt minerals. Their high growth rate, photosynthesis, and carbon dioxide sequestration capacity make them one of the most important biorefinery platforms. Furthermore, microalgae's ability to alter their metabolism in response to environmental stresses to produce relatively high levels of high-value compounds makes them a promising alternative to fossil fuels. As a result, microalgae can significantly contribute to long-term solutions to critical global issues such as the energy crisis and climate change. The environmental benefits of algal biofuel have been demonstrated by significant reductions in carbon dioxide, nitrogen oxide, and sulfur oxide emissions. Microalgae-derived biomass has the potential to generate a wide range of commercially important high-value compounds, novel materials, and feedstock for a variety of industries, including cosmetics, food, and feed. This review evaluates the potential of using microalgal biomass to produce a variety of bioenergy carriers, including biodiesel from stored lipids, alcohols from reserved carbohydrate fermentation, and hydrogen, syngas, methane, biochar and bio-oils via anaerobic digestion, pyrolysis, and gasification. Furthermore, the potential use of microalgal biomass in carbon sequestration routes as an atmospheric carbon removal approach is being evaluated. The cost of algal biofuel production is primarily determined by culturing (77%), harvesting (12%), and lipid extraction (7.9%). As a result, the choice of microalgal species and cultivation mode (autotrophic, heterotrophic, and mixotrophic) are important factors in controlling biomass and bioenergy production, as well as fuel properties. The simultaneous production of microalgal biomass in agricultural, municipal, or industrial wastewater is a low-cost option that could significantly reduce economic and environmental costs while also providing a valuable remediation service. Microalgae have also been proposed as a viable candidate for carbon dioxide capture from the atmosphere or an industrial point source. Microalgae can sequester 1.3 kg of carbon dioxide to produce 1 kg of biomass. Using potent microalgal strains in efficient design bioreactors for carbon dioxide sequestration is thus a challenge. Microalgae can theoretically use up to 9% of light energy to capture and convert 513 tons of carbon dioxide into 280 tons of dry biomass per hectare per year in open and closed cultures. Using an integrated microalgal bio-refinery to recover high-value-added products could reduce waste and create efficient biomass processing into bioenergy. To design an efficient atmospheric carbon removal system, algal biomass cultivation should be coupled with thermochemical technologies, such as pyrolysis.

     

Nanomaterials for environmental burden reduction, waste treatment, and nonpoint source pollution control: a review

Nanomaterials are applicable in the areas of reduction of environmental burden, reduction/treatment of industrial and agricultural wastes, and nonpoint source (NPS) pollution control. First, environmental burden reduction involves green process and engineering, emissions control, desulfurization/denitrification of nonrenewable energy sources, and improvement of agriculture and food systems. Second, reduction/treatment of industrial and agricultural wastes involves converting wastes into products, groundwater remediation, adsorption, delaying photocatalysis, and nanomembranes. Third, NPS pollution control involves controlling water pollution. Nanomaterials alter physical properties on a nanoscale due to their high specific surface area to volume ratio. They are used as catalysts, adsorbents, membranes, and additives to increase activity and capability due to their high specific surface areas and nano-sized effects. Thus, nanomaterials are more effective at treating environmental wastes because they reduce the amount of material needed.     

Nanomaterials for water cleaning and desalination,energy production,disinfection, agriculture and green chemistry

Nanomaterials may help to solve issues such as water availability, clean energy generation, control of drug-resistant microorganisms and food safety. Here we review innovative approaches to solve these issues using nanotechnology. The major topics discussed are wastewater treatment using carbon-based, metal-based and polymeric nanoadsorbents for removing organic and metal contaminants; nanophotocatalysis for microbial control; desalination of seawater using nanomembranes; energy conversion and storage using solar cells and hydrogen-sorbents nanostructures; antimicrobial properties of nanomaterials; smart delivery systems; biocompatible nanomaterials such as nanolignocellulosis and starches-based materials, and methods to decrease the toxicity of nanomaterials. Significantly, here it is reviewed two ways to palliate nanomaterials toxicity: (a) controlling physicochemical factors affecting this toxicity in order to dispose of more safe nanomaterials, and (b) harnessing greener synthesis of them to bring down the environmental impact of toxic reagents, wastes and byproducts. All these current challenges are reviewed at the present article in an effort to evaluate environmental implications of nanomaterials technology by means of a complete, reliable and critical vision.     

Utilization of the waste phosphogypsum for the Portland cement clinker production

This paper presents the results of investigation on the utilization of the phosphogypsum for the Portland cement clinker production. Characterization of the phosphogypsum and raw materials for rotary kilns was performed. Phosphogypsum, in quantities of 1%, 2%, 3% and 5%, was added to raw meal from regular production of rotary kiln and then the homogenization of raw meals and their chemical characterization was done. High temperature DTA and thermo‐microscopic investigations have been performed also. Raw meals without and with the addition of phosphogypsum have been laboratory sintered. Chemical composition of Portland cement clinkers has been defined and potential clinker phase composition has been calculated according to Bogue's formula from the chemical composition. Results are very encouraging regarding the energy consumption and Portland cement clinker quality. Phosphogypsum could be successfully applied as mineralizer in cement production, because with its addition, better composition of Portland cement clinker at the same sintering conditions could be obtained.     

Nanomaterials for water pollution monitoring and remediation

Water shortage and pollution are serious challenges for many countries. Nanomaterials are promising new tools for water quality management due to unique physicochemical properties, high economic benefit, high removal efficiency and environmental friendliness. Here we describe four types of nanomaterials used for water treatment: nanofiltration membranes, photocatalytic nanomaterials, adsorption nanomaterials and reducing nanomaterials. We discuss their properties, applications and mechanisms for pollutant removal. We also review nanomaterials used for water quality monitoring, notably nanomaterials used for the detection of trace pollutants and pathogens. These nanomaterials include carbon nanotubes, magnetic nanoparticles, noble metal nanomaterials and quantum dots.     

Growth and amylase production by Aspergillus oryzae during solid state fermentation using banana waste as substrate

Aspergillus oryzae, isolated from the starch rich litter soil, produced amylase when banana fruit stalk was used as substrate in a solid state fermentation system. The effects of incubation period, pH, temperature and various carbon sources on the production of amylase were studied. A maximum yield of 380U/mg was recorded on 96th hour of incubation. The amylase is tolerant to wide range of initial culture pH values (3 to 8) and temperature (25 to 35 degrees C), with an optimum pH of 5 and temperature of 35 degrees C. In SSF addition of starch (1%) increased the amylase production, when compared with other carbon sources used.     

Evaluation of acid production potential of mining waste materials

The formation of acidic effluents from mining waste materials is discussed and the chemisry involved explained. The bacteriumThiobacillus ferrooxidans plays an important role in acid production due to its ability to rapidly oxidize reduced forms of iron and sulphur which can result in the generation of H₂SO₄. The sulphide mineral pyrite (FeS₂), often present in waste materials, is generally recognized as the chief source of acid mine drainage.A small-scale test procedure has been developed which rapidly evaluates a waste material's capability to produce an acidic effluent. If the material is assessed as a potential acid producer, then scale-up testing procedures are available which can be used to simulate the characteristics of the effluents produced from a commercial-size waste dump.During periods of little rainfall, localized biological activity may occur in wet areas of a waste dump, resulting in possible accumulation of soluble pollutants. The length of these dry periods greatly affects effluent characteristics during subsequent rainfalls.     

Agricultural waste from the tequila industry as substrate for the production of commercially important enzymes

Approximately 1 million tons of Agave tequilana plants are processed annually by the Mexican Tequila industry generating vast amounts of agricultural waste. The aim of this study was to investigate the potential use of Agave tequilana waste as substrate for the production of commercially important enzymes. Two strains of Aspergillus niger (CH-A-2010 and CH-A-2016), isolated from agave fields, were found to grow and propagate in submerged cultures using Agave tequilana waste as substrate. Isolates showed simultaneous extracellular inulinase, xylanase, pectinase, and cellulase activities. Aspergillus CH-A-2010 showed the highest production of inulinase activity (1.48 U/ml), whereas Aspergillus niger CH-A-2016 produced the highest xylanase (1.52 U/ml) and endo-pectinase (2.7U/ml) activities. In both cases production of enzyme activities was significantly higher on Agave tequilana waste than that observed on lemon peel and specific polymeric carbohydrates. Enzymatic hydrolysis of raw A. tequilana stems and leaves, by enzymes secreted by the isolates yielded maximum concentrations of reducing sugars of 28.2 g/l, and 9.9 g/l respectively. In conclusion, Agave tequilana waste can be utilized as substrate for the production of important biotechnological enzymes.     

MOF synthesis using waste PET for applications of adsorption,catalysis and energy storage

Polyethylene terephthalate(PET) as one of non-degradable wastes has become a huge threat to the environment and human health.Chemical Recycle of PET is a sustainable way to release 1,4-benzenedicarboxylic acid(BDC) the monomer of PET as common used organic linker for synthesis of functional Metal–organic-frameworks(PET-derived MOFs) such as UiO-66, MIL-101, etc. This sustainable and costeffective “Waste-to-MOFs” model is of great significant to be intensively investigated in the past years. Attributes of substantial porosity, specific surface area, exposed metal centers, uniform structure, and flexible morphology render PET-derived MOFs are well-suited for applications in adsorption, energy storage, catalysis, among others. Herein, in the present work, we have summarized recent advances in synthesis of PETderived MOFs using ex-situ and in-situ methods for typical applications of adsorption, catalysis and energy storage. Despite those improvements in synthesis methods and potential applications, challenges still remain in development of green and economical routes to fully utilize waste PET for massive manufacture of valuable MOF materials and chemicals. This review provides insights into the conversion of non-degradable PET waste to value-added MOF materials, and further suggests promising perspectives to develop the sustainable “Waste-to-MOFs” model in addressing environmental pollution and energy crises.     

Genotoxicity and mutagenicity of electronic waste leachates using animal bioassays

Human exposure to electronic waste (e-waste) is increasing, especially in developing nations. This has potential short and chronic adverse health risks. Information is currently scarce on potential genotoxicity of e-waste leachate. In this study, the potential mutagenic and genotoxic effects of leachates from e-waste dumpsites at two electronic markets in Lagos, Nigeria, were investigated. The assays utilized were: bone marrow micronucleus (MN) and chromosome aberration (CA), spermatogonia CA, sperm morphology, and sperm count in mice. Experiments were carried out at concentrations of 1%, 5%, 10%, 25%, and 50% (v/v; leachate: distilled water) of leachate samples. MN analysis showed a concentration-dependent induction of micronucleated polychromatic erythrocytes (MNPCE) across the treatment groups. In the CA tests (bone marrow and spermatogonia), there was concentration-dependent significant reduction in mitotic index and induction of different types of CA. Assessment of sperm shape showed a significant increase in sperm abnormalities with significant decrease in mean sperm count in treated groups. Heavy metals analyzed in the tested samples are believed to contribute significantly to the observed genetic damage. This indicates that e-waste contains potential genotoxic agents; and constitutes a genetic risk in exposed human population.     

Simulating fish production using exponential smoothing

The variation over time of the total annual production of pe and the United Kingdom has been described quantitatively using the exponential smoothing technique. The exercise was repeated on annual mackerel landings for the same two countries. It is suggested that in some cases, the production figure for the current year can be used to simulate the following year's value. The greater variations in South Africa's annual production probably gave rise to the poorer results for these data.     

Air pollution protection by waste amorphous SiO2 utilization in Portland cement production

This papers deals with waste amorphous silica obtained from AlF₃ production. This is a waste material that could be used as additive in cement production. Results are encouraging although there are no large quantities of this material available (about 4000 t/yr). Experiments were performed with the addition of 2.5%, 5.0%, 7.5% and 10.0% mass of amorphous silica obtained from AlF₃ production. Flexural and compressive strengths of the prepared mortar samples with w/c = 0.50 and with the constant flow were determined. Experiments show that optimal quantity for the amorphous silica addition is 5% of the cement mass.     

钢铁工业固废应用于水泥生产的降耗与减排

运用物质流分析法定量比较原生水泥与再生水泥生产过程中的物能代谢和环境负荷,并采用生命周期分析进行环境影响评价。结果表明：生产1 t原生水泥需要的直接物质投入是1.637 t;消耗原煤0.086 t/标准煤,消耗电力0.067 t/标准煤。利用钢铁工业固废生产功能单位再生水泥,可减少资源投入0.16 t;减少能源消耗0.036 t;环境排放SO2减排0.000 2 t;粉尘减排0.001 t;烟尘减排0.000 12 t;NOx减排0.000 34 t;CO2减排0.231 t。水泥生产潜在的各类环境影响中以废气排放引起的温室效应最大;其次依次是酸化效应和不可再生资源消耗;光化学烟雾和人体健康损害在水泥生产过程中的影响都相对较小。与原生水泥相比,再生水泥各环境负荷均呈下降趋势,两者总体环境负荷差值为6.93E-15。研究结果充分说明钢铁工业固废资源化可以明显的降低水泥生产的总体环境负荷,是促进水泥行业循环经济发展的有效手段。     

Stabilization of Cu-contaminated army firing range soils using waste oyster shells

A stabilization/solidification (S/S) process was used to immobilize Cu in contaminated soils obtained from two army firing ranges sites (A and B) with total Cu concentrations of 520 and 380 mg/kg, respectively. Both waste oyster shells (WOS) and pretreated oyster shells (POS) were used to immobilize Cu in the contaminated soils. Waste oyster shells passing the #10 mesh and #20 mesh were used for the Sites A and B, respectively. WOS- and POS-treated soil samples cured for 28 days were evaluated for Cu leaching by the Korean Standard Leaching Test (KSLT) method. Slurry suspensions were prepared to investigate the Cu immobilization mechanism using X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) energy dispersive X-ray spectroscopy (EDX) analyses. The treatment results showed that the POS treatment was more effective than the WOS treatment of 28 days. For Site A, 10 wt% WOS and 3 wt% POS dosages were required to pass the Korean warning standard of 50 mg/kg, while 10 wt% WOS and 5 wt% POS dosages were required for the Site B treatment. The XRPD and SEM-EDX results showed that Cu immobilization was strongly linked to both CSH/CAH and ettringite. Overall, the POS treatment was effective at immobilizing the Cu in the contaminated soils, very likely due to its CaO content.     

Nanomaterials for agriculture,food and environment: applications,toxicity and regulation

Nanotechnology is expected to have a beneficial influence on agriculture, food and environment, due to the unique properties of nanomaterials. However, little is known about their safety and potential toxicity. Here we review metal nanoparticles, nanometal oxides, carbon nanotubes, liposomes and dendrimers. We present the application of these nanomaterials in agriculture, food and environment for plant protection; disease treatment; packing materials; development of new tastes, textures and sensations; pathogen detection; and delivery systems. We discuss risk assessment of nanomaterials and toxicological impacts of nanomaterials on agriculture, food and environment. We then provide regulatory guidelines for the safer use of nanomaterials.     

Removal of congo red dye from water using carbon slurry waste

A cheaper adsorbent has been prepared from carbon slurry waste obtained from National Fertilizer Limited (NFL), Panipat and investigated for the removal of congo red, an anionic dye. Its adsorption on prepared carbonaceous adsorbent was studied as a function of contact time, concentration and temperature. The results have shown that carbonaceous adsorbent adsorbs dye to a sufficient extent (272 mg g^-1). A comparative study of adsorption results with those obtained on activated charcoal shows that the carbonaceous adsorbent is ~95% efficient as compared to activated charcoal. Thus, it can be fruitfully used for the removal of dyes from wastewaters.This work has been presented at the National Symposium on Biochemical Sciences: Health and Environmental Aspects (BSHEA—2003), Agra, India (2003).     

Photobiological production of hydrogen by the waste water treatment with anaerobic photosynthetic Purple bacteria

In this paper selected references about experience gained with photosynthetic bacteria in anaerobic process for either water treatment or hydrogen production are given. In particular experimental data about the hydrogen evolution rate, hydrogen yield and substrate efficiency in relationship to the nutrient conditions as well as about the behavior of some different species are presented. The limiting role of the nitrogen source is being discussed.     

Photoelectrochemical water splitting using post-transition metal oxides for hydrogen production: a review

Environmental Chemistry Letters - Dihydrogen (H2), commonly named ‘hydrogen,’ is considered as a promising renewable fuel that does not emit carbon dioxide upon combustion. Nonetheless,...     

The production of lumber using chainsaws in Guyana

SUMMARY

The structure, conduct and performance, and the environmental impacts of the chainsaw lumber production sector in Guyana are investigated. Chainsaws are a highly mobile lumber technology that is used to rip or produce lumber within the forest. Chainsaw lumbering operations have become the dominant lumber producer for the domestic market. Production costs are only 53% of wholesale lumber prices. On a ms basis, chainsaw operations' net profit is 80% of the gross price paid for logs at sawmills and more than twice the profit of firms engaged in the harvesting and transportation of logs to sawmills. Sawmills recognize this cost advantage and are increasingly using chainsaws in the production of lumber.

The handling and transportation of chainsawn lumber within the forest is environmentally less damaging than log production. The log recovery rate is 10–15% for chainsaw operations, as compared to the sawmill average of 40–45%. Log residue from chainsaw operations is left within the forest which promotes faster forest regrowth, while that at sawmills is wasted. Chainsaw operations harvest immature trees, engage in the harvesting of selective species, over-harvest trees per unit area of land, and engage in frequent reentry of the forest. Because of these practices, the chainsaw lumber sector is not environmentally sustainable and will require regulation. Policies that follow a non-market solution will be required in regulation.