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1.
Waste Manag ; 118: 667-676, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33011544

RESUMO

This paper compares the yield and composition of bio-oil derived through stepwise and continuous pyrolysis of agro-residues. The temperature steps were selected using thermogravimetric analysis. Groundnut shell, empty fruit bunch pellets, and rice straw were pyrolyzed at 305 °C in the first step and 600 °C in the second step and pinewood chips were pyrolyzed at 340 °C and 600 °C. The cumulated yields of bio-oil were lower in both continuous and stepwise pyrolysis for agro-residues in comparison with woody biomass, with a corresponding increase in biochar and pyrolysis gas yields. Approximately 50% of the pinewood and 31-40% of the agro-residues were converted to bio-oil through both methods. This trend is explained by the differing biochemical composition of biomasses, and concentrations of inorganic components. Bio-oil fractions were separated into water-soluble and water-insoluble compounds before characterization. Bio-oil obtained in the first step was richer in organic acids, anhydrosugars, and carbonyl compounds, while the later fraction of bio-oil was richer in unbranched phenolic compounds. Thus, compounds known to promote bio-oil aging were separated into different fractions. Further, stepwise pyrolysis proved to be most effective for groundnut shells in isolating chemicals with a minimum loss of yield compared to continuous pyrolysis. A preliminary economic assessment of bio-oil showed that the value of bio-oil for crop residues was improved by 2-2.5 times during stepwise heating while for pinewood it reduced by half. This study provides a good starting point for further research in optimizing the temperature steps for pyrolysis and separation of chemicals from bio-oil.


Assuntos
Biocombustíveis , Pirólise , Biocombustíveis/análise , Biomassa , Fenóis , Madeira/química
2.
Ambio ; 49(12): 1878-1896, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33044700

RESUMO

The bioeconomy is currently being globally promoted as a sustainability avenue involving several societal actors. While the bioeconomy is broadly about the substitution of fossil resources with bio-based ones, three main (competing or complementary) bioeconomy visions are emerging in scientific literature: resource, biotechnology, and agroecology. The implementation of one or more of these visions into strategies implies changes to land use and thus ecosystem services delivery, with notable trade-offs. This review aims to explore the interdisciplinary space at the interface of these two concepts. We reviewed scientific publications explicitly referring to bioeconomy and ecosystem services in their title, abstract, or keywords, with 45 documents identified as relevant. The literature appeared to be emerging and fragmented but eight themes were discernible (in order of decreasing occurrence frequency in the literature): a. technical and economic feasibility of biomass extraction and use; b. potential and challenges of the bioeconomy; c. frameworks and tools; d. sustainability of bio-based processes, products, and services; e. environmental sustainability of the bioeconomy; f. governance of the bioeconomy; g. biosecurity; h. bioremediation. Approximately half of the documents aligned to a resource vision of the bioeconomy, with emphasis on biomass production. Agroecology and biotechnology visions were less frequently found, but multiple visions generally tended to occur in each document. The discussion highlights gaps in the current research on the topic and argues for communication between the ecosystem services and bioeconomy communities to forward both research areas in the context of sustainability science.


Assuntos
Biotecnologia , Ecossistema , Biomassa
3.
Water Sci Technol ; 82(6): 1009-1024, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055392

RESUMO

In microalgae harvesting, flocculation is usually a compulsory preliminary step to further separation by sedimentation or flotation. For some microalgae species, and under certain growth conditions, flocculation can occur naturally. Natural flocculation presents many advantages as it does not require the addition of any flocculants to the culture medium and shows high efficiency rate. But because natural flocculation is so specific to the species and conditions, and thanks to the knowledge accumulated over the last years on flocculation mechanisms, researchers have developed strategies to induce this natural harvesting. In this review, we first decipher at the molecular scale the underlying mechanisms of natural flocculation and illustrate them by selected studies from the literature. Then we describe the developed strategies to induce natural flocculation that include the use of biopolymers, chemically modified or not, or involve mixed species cultures. But all these strategies need the addition of external compounds or microorganism which can present some issues. Thus alternative directions to completely eliminate the need for an external molecule, through genetic engineering of microalgae strains, are presented and discussed in the third part of this review.


Assuntos
Microalgas , Bioensaio , Biomassa , Meios de Cultura , Floculação
4.
Water Sci Technol ; 82(6): 1044-1061, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055395

RESUMO

This study evaluates the feasibility of advanced biofilm microalgae cultivation in a twin layer (TL) system for nutrient removal (N and P) as the tertiary treatment in small wastewater treatment plants (WWTPs) located in sensitive areas. Furthermore, the potential valorisation of microalgae biomass as a component of bio-based fertilizers is assessed. Scenedesmus sp. was chosen among 33 microalgae strains for inoculation of TL due to its high growth rate and its nutrient uptake capacity. The tests carried out in the prototype were markedly efficient for total soluble and ammoniacal nitrogen removal (up to 66 and 94%, respectively). In terms of potential valorisation of microalgae, the nutrient content was 5.5% N (over 40% protein), 8.8% P2O5 and 1.5% K2O, high enzymatic activity, very low levels of heavy metals and no detectable pathogen presence. However, in the formulation of solid-state bio-based fertilizers, the microalgae proportions in blends of over 2% of microalgae led to negative effects on ryegrass (Lolium perenne L. ssp.) and barley (Hordeum vulgare ssp.). The obtained results demonstrate that TL represents a promising technology, which allows efficient tertiary treatment of urban wastewater and the production of high-quality bio-based fertilizer.


Assuntos
Microalgas , Scenedesmus , Biomassa , Nutrientes , Águas Residuárias
5.
Water Sci Technol ; 82(6): 1111-1119, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055401

RESUMO

Vinasse, an effluent generated during sugar and alcohol production, has great potential for soil and water pollution; however, it can be treated, used in biomass production and reused in sugarcane plantations. Thus, this work uses different types of biodigested vinasse to produce more biomass. The effect is the removal of ammonia nitrogen quickly and the end of the exponential growth phase of microalgae at different levels from the sixth day of cultivation. Among the concentrations used, the use of 50% biodigested vinasse showed the highest biomass concentration (255 mg L-1) after 10 days of growth, coinciding with the end of ammoniacal nitrogen availability and stabilization of effluent color removal. The addition of biodigested vinasse also provides an increase in Chlorophyll a (5.33 mg L-1) and b (4.66 mg L-1) levels, obtained on the sixth day with 40% of vinasse, as well as protein (40.50%) with 50% effluent. Therefore, with the obtained results we noticed the variation of the biomass composition according to the vinasse concentration and increase of the pigment concentration in the presence of the effluent with higher nutrient concentration. Thus, the higher concentration of vinasse was more productive of the cultivation of Chlorella vulgaris.


Assuntos
Chlorella vulgaris , Microalgas , Saccharum , Biomassa , Clorofila A
6.
Water Sci Technol ; 82(6): 1120-1130, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055402

RESUMO

As a byproduct of agriculture, rice bran can be a good alternative carbon source to mass-produce microalgae and increase lipid content. The purpose of this study was to investigate the effects of rice bran extract (RBE) on the mass culture and oil content of microalgae. Various parameters were applied to the growth rate model to explain the dynamics of substrate inhibition and growth of microalgae. The rice bran contains 46.1% of carbohydrates, in which is 38.3% glucose, and is very suitable as a carbon source for microalgae growth. The culture with RBE had a four times higher biomass production than microalgae cultured on Jaworski's medium (JM) with a small amount of 1 g/L. In addition, for RBE, the lipid content was three times higher and saturated fatty acid was 3% lower than were those of JM. According to the above results, when Chlorella vulgaris is cultured using RBE, a high amount of biomass and high lipid content can be obtained with a small amount of RBE. RBE is a discarded waste and has a high content of glucose, so it can be replaced by an organic carbon source to increase microbial biomass growth and lipid content at low cost.


Assuntos
Chlorella vulgaris , Oryza , Agricultura , Biomassa , Carbono , Lipídeos
7.
Water Sci Technol ; 82(6): 1176-1183, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055407

RESUMO

The influence of the feeding regime on surfactant and nutrient removal and biomass production was evaluated in three high rate algal ponds for primary domestic wastewater treatment. Feeding times of 24, 12 and 0.1 h d-1 were studied in each reactor at a similar hydraulic retention time of 7.0 days and organic load of 2.3 mg m-2 d-1. Semi-continuous feeding at 12 and 0.1 h d-1 showed better microalgal biomass production (0.21-0.23 g L-1) and nutrient removal, including nitrogen (74-76%) and phosphorus (80-86%), when compared to biomass production (0.13 g L-1) and nitrogen (69%) and phosphorus (46%) removals obtained at continuous feeding (24 h d-1). Additionally, the removal efficiency of surfactant in the three reactors ranged between 90 and 97%, where the best result was obtained at 0.1 h d-1, resulting in surfactant concentrations in the treated effluent (0.3 mg L-1) below the maximum freshwater discharge limits.


Assuntos
Microalgas , Biomassa , Fósforo , Tensoativos , Águas Residuárias
8.
Water Sci Technol ; 82(6): 1217-1226, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055411

RESUMO

Flocculation is a common technique to harvest microalgae, where the negatively charged algal cells coalesce together to form larger flocs that settle under gravity. Although several inorganic flocculants have been applied for algal biomass recovery, the dosage varies depending on the algal strain-specific features. Thus, the selection of inorganic coagulant that can be applied at a low dosage for achieving the maximal biomass recovery under normal physiological conditions is necessary. The present study analyses the influence of different inorganic flocculants like ferric chloride (FeCl3), alum, calcium hydroxide, ferrous sulphate and copper sulphate on the biomass removal efficiency of a mixed microalgal consortium isolated from the open ponds of the National Institute of Technology Rourkela and further enriched with diluted human urine. Flocculation experiments were carried out with varying coagulant dosages, pH between 7.5 and 7.8, and 0.5 g L-1 algal concentration. The results revealed that FeCl3 at the dosage of 0.05 g L-1 and KAl(SO4)2 with the dosage of 0.04 g L-1 could be utilized to achieve the biomass recovery efficiency of 99.5% and 97.9%, respectively, within a duration of 5 min. An economic evaluation of the harvesting process showed KAl(SO4)2 to be the cheapest coagulant that could be feasibly used to recover algae at a large scale.


Assuntos
Microalgas , Biomassa , Floculação , Humanos , Tanques
9.
Water Sci Technol ; 82(6): 1237-1246, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055413

RESUMO

This study focused on the simultaneous recovery of carbohydrates (CHO) and phosphorus (P) from Desmodesmus sp. biomass cultivated in municipal wastewater, through a sequential pretreatment. The pretreatment consisted first of ultrasound to trigger cell disruption followed by ozonation to recover CHO and P. For ozone pretreatment, three different parameters were considered: ozone concentration (9, 15, 21, 27, 36, and 45 mg O3/L), contact time (15, 25 and 35 min), and pH (8 and 11). The maximum simultaneous release of 84% of CHO and 58% of P was achieved at the experimental parameters of ozone concentration of 45 mg O3/L, contact time of 35 min, and pH of 11. Also, P was concentrated in solution by 8- to 14-fold with respect to municipal wastewater. The sequential pretreatment was conducted at alkaline pH of 11 and atmospheric conditions, which may considerably reduce energy demand and reagents, in comparison to a traditional hydrolysis pretreatment. The results found suggest that the sequential pretreatment could be feasible on a large scale.


Assuntos
Ozônio , Águas Residuárias , Biomassa , Carboidratos , Fósforo
10.
Water Sci Technol ; 82(6): 1247-1259, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33055414

RESUMO

The transformation of residual biomass from bioremediation processes into new products is a worldwide trend driven by economic, environmental and social gain. The present study aimed to evaluate the potential for obtaining bioproducts of technological interest from the remaining periphytic biomass formed during a bioremediation process with an algal turf scrubber (ATS) system installed in a lake catchment. Different methodologies were used according to the target bioproduct. Analyses were performed by high performance liquid chromatography with diode array detector (HPLC/DAD), gas chromatography mass spectrometry (GC-MS), ultraviolet-visible spectroscopy (UV-VIS) and inductively coupled plasma optical emission spectrometry (ICP-OES). The results demonstrated that the periphytic biomass presented potential since protein (17.7%), carbohydrates (22.4%), total lipids (3.3%) with 3.6 mg mL-1 of fatty acids, antioxidants (144.5 µmol Trolox eq. g-1) and chlorophyll a, chlorophyll b and carotenoids (1,719.7 µg mL-1, 541.2 µg mL-1 and 317.7 µg mL-1, respectively) were obtained. Inorganic analysis presented a value of 42.3 ± 2.58% of total ash and metal presence was detected, indicating bioaccumulation. The properties found in periphyton strengthen the possibility of its application in different areas, ensuring bioremediation efficiency.


Assuntos
Clorofila A , Biodegradação Ambiental , Biomassa , Cromatografia Líquida de Alta Pressão , Cromatografia Gasosa-Espectrometria de Massas
11.
Water Sci Technol ; 82(7): 1416-1429, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33079720

RESUMO

This study aims to investigate the feasibility of treating olive mill waste water (OMWW) by activated sludge pilot (AS) after its high dilution (1%) by urban waste water (UWW) and to study the effect of polyphenol compounds on the biomass during the treatment. Specific oxygen uptake rate (SOUR), mixed liquor volatile suspended solids (MLVSS), chemical oxygen demand (COD) and total polyphenols, were followed up over 100 days. In spite of the polyphenols' high concentration (up to 128 mg·L-1), successful biomass growth of 7.12 g MLVSS.L -1 and activity were achieved. Most of the bacteria (Pseudomonas sp., Klebsiella oxytoca, Citrobacter fereundii, Escherichia coli and Staphylococcus sp.) and fungi (Trichoderma sp., Rhizopus sp., Aspergillus niger, Penicillium sp., Fusarium sp., Alternaria) identified in the aerobic basin during the stabilization stage were known to be resistant to OMWW and showed effective adaptation of the biomass to polyphenols in high concentration. COD and polyphenols were highly eliminated (90%, 92% respectively). The sludge volume index in the pilot settling tank was almost constant at around 120 mL.g -1. This suggests the possibility of managing OMWW by simple injection at a given percentage in already functioning conventional AS treating UWW.


Assuntos
Olea , Águas Residuárias , Biomassa , Polifenóis , Esgotos
12.
J Environ Qual ; 49(1): 97-105, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33016356

RESUMO

Cover crops are often recommended as a best management practice to reduce erosion, weed pressure, and nutrient loss. However, cover crops may be sources of phosphorus (P) to runoff water after termination. Two greenhouse trials were conducted to determine the effects of cover crop species, termination method, and time after termination on water-extractable P (WEP) release from crop biomass. Treatments were structured in a 3 × 3 × 3 factorial and arranged in a randomized complete block design with six replicates. Treatments included three cover crop species (triticale [× Triticosecale; Triticum × Secale 'Trical'], rapeseed [Brassica napus L. 'Winfred'], and crimson clover [Trifolium incarnatum L.]); three termination methods (clipping, freezing, and herbicide); and three WEP extraction times (1, 7, and 14 d after termination). Rapeseed consistently resulted in the least WEP when exposed to the same method of termination and at the same extraction time as the other species. For both trials, terminating crop tissue via freezing increased concentrations of WEP compared with other termination methods. The WEP release from cover crop tissue increased as the time after extraction increased, but the effect was greater for herbicide- and freeze-terminated cover crops and less for clipping-terminated cover crops. Future studies on WEP release from cover crops should pay close attention to the effects of extraction timing. Producers may be able to reduce P loss from cover crop tissue by selecting cover crop species with low WEP and minimizing the amount of biomass exposed to freezing conditions.


Assuntos
Agricultura , Fósforo , Biomassa , Produtos Agrícolas , Congelamento
13.
J Environ Qual ; 49(1): 140-151, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33016365

RESUMO

Watershed managers generally focus on P reduction strategies to combat freshwater eutrophication despite evidence that N co-limits primary production. Our objective was to test the role of P in limiting stream periphyton biomass within the Buffalo River watershed in Arkansas by conducting a 31-d streamside mesocosm experiment. To represent potentially different starting states, cobbles were transplanted from two different tributary streams and initially exposed to a range of P (0, 0.012, 0.025, 0.05, 0.1, and 0.2 mg L-1 P) to assess benthic ash-free dry mass (AFDM) and chlorophyll-a (chl a) and responses during a P only enrichment period. Later, the experiment was continued under a N/P (10:1 molar ratio) enrichment gradient to examine co-limitation. Mean AFDM was higher on Day 31 of the N+P enrichment compared with Day 17 of the P-only enrichment (p < .001). Overall differences in AFDM and chl a were observed between cobbles from different stream sites. Phosphorus enrichment stimulated benthic chl a biomass, but enrichment effects were greater when streams were enriched with N+P (p < .001). Chlorophyll-a increased (4.4-57.9 mg m-2 ) with increasing P concentrations (p < .001) after P enrichment but was threefold greater after N+P enrichment, increasing from 13.3 to 171.1 mg m-2 across the enrichment gradient. Results support the need to consider both N and P limitation in freshwater systems and demonstrate that potential increases in nutrient concentrations may influence accumulation of algae on cobble substrates from the Buffalo River watershed.


Assuntos
Nitrogênio/análise , Fósforo/análise , Arkansas , Biomassa , Nutrientes
14.
J Environ Qual ; 49(4): 1044-1053, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33016485

RESUMO

Duckweed has been recognized for its potential of producing biomass on nutrients from waste streams. Our research has shown that strains of duckweed can be successfully cultivated on anaerobically digested (AD) dairy manure under controlled levels of nitrogen (N) and phosphorus (P). The objective of this study was to explore the maximization of starch accumulation in Landoltia punctata (Mey.) Les & Crawford strain 0128 under different cultivation conditions using AD dairy manure as the nutrient source. Experimental results have shown that the most influential factors for starch accumulation in L. punctata were the nutrient concentration and the appropriate scheduling of nutrient starvation at the right growth stages. In our study, nutrient starvation for starch accumulation in L. punctata was achieved by incorporating nutrient addition of appropriately diluted AD dairy manure sequentially in a controlled manner under a constant light intensity of 3,000 lx. It was observed that a starch concentration of 30% (w/w) within the L. punctata biomass was achieved with an initial total N of 57.1 mg L-1 and a total P of 6.7 mg L-1 after a 30-d cultivation. Under the abovementioned cultivation conditions, the duckweed L. punctata recovered 16.3% (±4.0%) of total N and 25.9% (±6.6%) of total P from AD manure into its biomass. It is concluded that L. punctata can be successfully cultivated on nutrients from dairy manure for starch production, which would achieve well-being for dairy farmers by producing a feedstock for biofuels while treating dairy wastewater in an environmentally friendly manner.


Assuntos
Araceae , Amido , Biomassa , Esterco , Nutrientes
15.
Mar Environ Res ; 160: 104980, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32907718

RESUMO

While the effects of industrial contamination in coastal areas may persist for years in benthos communities, plankton should not show permanent impairments because of their high spatial dynamics, fast turnover times and pronounced seasonality. To test this hypothesis, in 2019 we conducted five surveys in the Bay of Pozzuoli (Gulf of Naples, Mediterranean Sea), in front of a dismissed steel factory and in the adjacent inshore coastal waters. High seasonal variability was observed for bacteria, phytoplankton and mesozooplankton, whereas plankton spatial gradients were relatively smooth during each survey. Plankton biomass and diversity did not reveal any effects of past industrial activities not even at the innermost stations of the Bay, which however showed some signals of present anthropogenic pressure. Hydrodynamic and morphological features likely play a prominent role in maintaining a relatively good status of the plankton of the Bay, which hints at the relevance of coastal circulation and meteorological dynamics to revitalize areas impacted by human activities.


Assuntos
Baías , Fitoplâncton , Plâncton , Biomassa , Mar Mediterrâneo
16.
Mar Environ Res ; 160: 104986, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32907724

RESUMO

Although eutrophication is considered a major driver for global seagrass loss with aquaculture effluents being a main factor, little is known about the effect on seagrass meadows in eastern Asia and their resilience to long-term nutrient impact. Seagrass meadows impacted by land-based aquaculture since the 1990s, were visited in 2008/2009 and revisited after another 9 years of effluent exposure. During that period seagrass aboveground biomass declined by 87%. Species diversity decreased with increasing effluent exposure. A δ15N of 9.0‰ of seagrass leaves and additional biogeochemical and biological indicators identify pond effluents as the driver of the observed eutrophication. When continuously exposed to dissolved inorganic nitrogen (DIN) concentrations exceeding a calculated threshold of 8 µM DIN seagrass meadows will disappear. Chronic nutrient pollution from aquaculture effluents can lead to a reduction of biodiversity and ultimately to a complete loss of seagrasses along the aquaculture-dominated coasts in E and SE Asia.


Assuntos
Aquicultura , Eutrofização , Nitrogênio , Biodiversidade , Biomassa
17.
Mar Environ Res ; 160: 105023, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32907734

RESUMO

In the present study, using in-situ and satellite observations, we investigate the influence of physical processes on the enhancement of phytoplankton biomass in the eastern Arabian Sea (EAS). Water column measurements were carried out from 9°N to 21°N (stations II-2 to II-14) along 68°E transect in the EAS during the beginning of fall intermonsoon (FIM) of 2014. Both in-situ and satellite-derived chlorophyll a (Chl a) showed higher biomass at 15°N (station II-8) compared to northern and southern stations. We explored the possible physical processes which can lead to high biological productivity at this station. Our study shows that nearly two times enhancement in Chl a at station II-8 was contributed by an open-ocean front, which occurred two days before the measurement. Based on phytoplankton marker pigments, it was evident that haptophytes were abundant at II-8 with a minor contribution from diatoms and dinoflagellates. This condition also led to a high concentration (4.9 nM) of dimethylsulphide (DMS), an anti-green house gas with a net flux of 3.76 µmol m-2d-1 at this site. Among the picophytoplankton, Synechococcus were abundant at this station, however Prochlorococcus were absent as confirmed by both marker pigment and flow cytometric counts. The case study presented here demonstrates the dynamic nature of open ocean fronts and their overall contribution to the productivity of the eastern Arabian Sea during the oligotrophic inter-monsoon period.


Assuntos
Diatomáceas , Fitoplâncton , Biomassa , Clorofila A , Oceanos e Mares , Tempo (Meteorologia)
18.
J Environ Manage ; 263: 110353, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883472

RESUMO

Nowadays, as the world population is in need of creating alternative materials that can replace conventional plastics, microalgae biomass may be identified as a viable source for producing more environmentally friendly materials. Scenedesmus sp and Desmodesmus sp are the main components (~80%) of a microalgae consortium (MC) that first has been used to remove Nitrogen and Phosphorus from wastewater. The potential to develop bioplastic materials from MC considering its relatively high protein content (~48%) has been assessed in the present manuscript, using as a reference a commercial biomass rich an Arthrospira specie (AM) also present in the studied consortium. Bioplastics were obtained through injection moulding of blends obtained after mixing with different amounts of glycerol, and eventually characterized using Dynamic Mechanical Thermal Analysis (DMTA), water immersion and tensile tests. All bioplastics displayed a glass transition temperature around 60 °C, showing a thermoplastic behavior which is less pronounced in the CM based bioplastics. This would imply a greater thermal resistance of bioplastics produced from the biomass harvested in wastewater. Moreover, these bioplastics showed a lower ability to absorb water when immersed, due to the lower deformability displayed in the tensile tests. The mechanical properties of all samples, independently of the nature of the biomass, were improved when the presence of the biomass was higher. Therefore, results here presented prove the potential of valorisation of microalgae consortia used in the effective treatment of wastewater through the development of bioplastic materials.


Assuntos
Microalgas , Scenedesmus , Biomassa , Nitrogênio/análise , Fósforo , Águas Residuárias
19.
J Environ Manage ; 263: 110373, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883475

RESUMO

Long-term data regarding soil properties and crop growth are powerful resources substantially contributing to our knowledge of soil-forming processes of reclaimed sandy desertification land. Generalized ecological principles derived from long-term observations that help to maintain or improve soil quality and productivity is critical for guiding field management practices while suitable for newly reclaimed sandy desertification land still need to be evaluated. Here, a 14-yr old experiment showed that soil quality index (SQI) had an "increase-decline-recovery" tendency in irrigation and fertilizer addition desertification lands while it remained at constantly low levels in desertification land with only irrigation. Stably decent yield and net incomes were obtained after 3-4 years' consecutive irrigation and fertilizer addition management. Correlation between crop productivity and SQI followed a saturation characteristic curve with threshold at 0.5, corresponding to soil organic carbon (SOC) ~5.0 g kg-1, below which crop productivity was linearly declined. 60% of observed inter-annual variations in SQI were explained by quantity of leaf litter, which was three times higher than explanatory power of root residue. No substantial changes occurred in soil mechanical components while the soil microbial biomass carbon, water-stable aggregate and heavy carbon pool in SOC were significantly improved by 2-9 folds in reclaimed desertification lands. Results revealed that increased biomass production with abundant residue retention is crucial for ameliorating soil quality, stabilizing high yield and economic gains, supporting the "High Biomass Cropping System" ecological hypothesis. Ecological limitations and opportunities to sustainable utilization of sandy desertification land were discussed.


Assuntos
Carbono , Solo , Biomassa , Conservação dos Recursos Naturais , Areia
20.
J Environ Manage ; 263: 110292, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883484

RESUMO

This article analyzes different forest management strategies to meet the increasing demand of biomass for bioenergy and assesses the resulting global warming implications. Applied to maritime pine forest plantations in Portugal, the assessed strategies are: full harvest of residues (FULL); sustainable and proactive management (SMART); expansion of forest plantations on abandoned farmland (EXP); and biomass import (IMP). A dynamic CO2 inventory was obtained for each scenario using a parametric stand-level C-flux model adapted to Portuguese conditions, which was then extended to the landscape-level and coupled to a dynamic climate model. The time-adjusted absolute global warming potential (AGWP) was then calculated at both stand and landscape levels, considering the timing of all CO2 emissions and uptakes (both fossil and biogenic). To test the robustness of the findings, a sensitivity analysis was performed. Results show that, in a supply-constrained context like Portugal, SMART and EXP management strategies can provide important global warming mitigation benefits (GWPbio < 0), although their supply-response is slow (long-term strategies). On the other hand, FULL and IMP management strategies show moderate to null AGWP reduction potential (0 < GWPbio < 1), while involving other possible risks (e.g., exacerbated soil erosion, nutrient depletion or uncertain impacts abroad), but their supply-response is fast (short-term strategies). National forest regulations and energy policies should be revised to address the drawbacks related to all management strategies and to unleash the multiple environmental benefits they can provide in the short- and long-term.


Assuntos
Florestas , Aquecimento Global , Biomassa , Clima , Portugal
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