Conventional Harvesting Methods Research Articles

A brief harvesting-freezing delay significantly alters the kidney metabolome and leads to false positive and negative results.

Abnormalities in distinct metabolic pathways have been associated with many forms of kidney disease. Metabolomics analyses can be used to determine organ-specific metabolic fingerprints. However, conventional harvesting methods depend on post-euthanasia tissue harvest, which results in ischemia conditions and metabolome changes that could introduce artifacts into the final studies. We optimized a clamp-freezing technique for kidney harvesting and freezing, significantly reducing ischemia and freezing times and granting a closer snapshot of in vivo metabolism. In this study, we characterized and compared the metabolome of kidneys harvested using our approach vs. traditional techniques to determine which metabolites are preferentially affected by a brief lapse of ischemia and freezing delay and which are more stable. We used Sprague Dawley rats as a model of wild-type (WT) kidneys and PCK, polycystic kidney disease (PKD) rats as a model of CKD kidneys. Finally, we compared the metabolic profile of clamp-frozen and delayed WT and PKD-kidneys to determine which metabolic changes are most likely observed in vivo in PKD and which could be subjected to false positive or negative results. Our data indicate that a short harvesting-freezing delay is sufficient to impart profound metabolic changes in WT and PKD kidneys. Interestingly, while the delay had a similar effect in WT and PKD, there were notable differences, leading to false positive and negative results when comparing these genotypes. The data obtained indicate that the quick clamp-freezing technique for kidney metabolomics provides a more accurate interpretation of the in vivo metabolic changes associated with the disease state.

A novel biomineralization-inspired flocculation approach for harvesting high quality microalgal biomass: Dual action of cationic polyelectrolytes and nanosilica

This study posed a novel biomimetic flocculation approach, aiming to efficiently harvest high-quality biomass of Scenedesmus quadricauda cultured with anaerobic digestate. Here, that poly(diallyldimethylammonium chloride) (PDADMAC) could serve as mimetic silicified proteins to spontaneously incorporate nanosilica onto microalgal cells, imparting diatom-like characteristics to S. quadricauda. Compared to the exponential growth phase (day 3), the highest harvesting efficiency (93.49%) was obtained at a lower dosage of PDADMAC (5 mg/g) in the stationary phase (day 6), which was attributed to changes in properties and composition of microalgal LB-EPS. On day 6, the hydrophobic functional groups in LB-EPS provided more binding sites during the flocculation process and formed a network structure of microalgal cells-flocculants-nanosilica. The resulting larger and more stable biomimetic silica shell promoted microalgal flocculation and sedimentation. Compared to conventional harvesting methods (centrifugation, polyacrylamide, alkaline flocculation), this method had the minimal negative impact on harvested biomass, with 9.95% of cell membranes damaged.

Ultra-high throughput microfluidic concentrator for harvesting of Tetraselmis sp. (Chlorodendrophyceae, Chlorophyta)

Microalgae are of commercial interest for their ability to produce high-value compounds and their potential to be used as feedstock across numerous industries. The production of algal biomass and other algal-based products involves different upstream and downstream processing steps, including cultivation, harvesting, and extraction. In particular, the harvesting process involves the extraction of a condensed algal slurry from a watery growth medium. This process accounts for 20 to 30 % of the biomass production costs, creating technological and economic barriers. The conventional harvesting methods suffer from high costs, cross-contamination, and low yield. This study explores the use of a microfluidic technique, in particular, the rigid spiral microchannel, for ultra-high-throughput algae harvesting. We have designed a novel spiral channel that enables microalgae separation at high flow rates and spatial resolution, taking advantage of inertial microfluidic principles. The results from trials with surrogate microparticles and algal cells reveal that the microchannel has the potential to operate at 12 mL/min with separation efficiency >99 %. Our inertial microfluidic device operates at high flow rates as a single channel, can be multiplexed, and shows excellent potential for large-scale processing of microalgae cultures. In addition, the lower number of loops provides the system with reduced back pressure, making it more desirable for operation using a range of different pumps. Since the overall cost of microalgae dewatering is substantial at the industrial scale, the design and fabrication of low-cost devices are of great importance, similar to the one we have developed in this study.

Recent Advances in Cell Sheet Engineering: From Fabrication to Clinical Translation.

Cell sheet engineering, a scaffold-free tissue fabrication technique, has proven to be an important breakthrough technology in regenerative medicine. Over the past two decades, the field has developed rapidly in terms of investigating fabrication techniques and multipurpose applications in regenerative medicine and biological research. This review highlights the most important achievements in cell sheet engineering to date. We first discuss cell sheet harvesting systems, which have been introduced in temperature-responsive surfaces and other systems to overcome the limitations of conventional cell harvesting methods. In addition, we describe several techniques of cell sheet transfer for preclinical (in vitro and in vivo) and clinical trials. This review also covers cell sheet cryopreservation, which allows short- and long-term storage of cells. Subsequently, we discuss the cell sheet properties of angiogenic cytokines and vasculogenesis. Finally, we discuss updates to various applications, from biological research to clinical translation. We believe that the present review, which shows and compares fundamental technologies and recent advances in cell engineering, can potentially be helpful for new and experienced researchers to promote the further development of tissue engineering in different applications.

Microalgal wastewater recycling: Suitability of harvesting methods and influence on growth mechanisms

Wastewater recycling helps address the challenge of microalgae biomass commercialization by allowing for efficient resource recovery. In this study, three conventional harvesting methods, including centrifugation, microfiltration, and flocculation sedimentation, were investigated to explore the effects of harvesting methods on the characteristics of recycled wastewater and the growth of microalgae to select a suitable harvesting method for the microalgal wastewater recycling system. During the wastewater recycling process, the least amount of accumulated substances was exhibited in the wastewater recycled by microfiltration, followed by centrifugation, and the most by flocculation sedimentation. After 4 batches of cultivation, microalgal biomass harvested from centrifugation wastewater and microfiltration wastewater was 21.26 % and 13.54 % higher than that from flocculation wastewater, respectively. Lipids, carbohydrates and pigments were all increased by varying degrees. Additionally, flocculation sedimentation was not suitable for the microalgal wastewater recycling process since the low residual nutrients, high salinity, and excessive algal organic matter severely inhibited the growth of microalgae. Under the regulation of phytohormones, microalgae increased their energy reserves, enhanced photosynthesis, and improved their defense capability to resist the increasing abiotic stress. This study provides scientific support for the selection of suitable harvesting technology during the microalgal wastewater recycling process.

Design and experiment of a new mode of mechanized harvesting of raft cultured kelp

The conventional kelp culture rafts remains in extensive use into the present day. However, such rafts rely on manual harvesting and are associated with a number of problems: a lack of uniform quality standards and dimensions, inconsistent length and spacing between kelp ropes due to the mixed use of old and new ropes, the bending and warping of rafts, and difficulty in controlling harvesting vessels due to the large flow of water during the harvesting process. All of these limit the consistent use of mechanized harvesting practices. In order to enable the systemic mechanized harvesting of kelp, this study thoroughly reviewed a range of interrelated culture rafts and harvesting equipment, and a new, optimized mechanized kelp harvesting model was created, involving ropes connected in series along with harvesting cutter systems. Conventional rafts using kelp ropes connected in parallel were transformed and upgraded into serial-connected ones maintaining the original frame width and spacing between kelp ropes and connecting kelp ropes in a "▪" shape, while the harvesting equipment installed on the vessel is designed to lift the kelp ropes, cut kelp stipes and handholds, transport kelp, reel in and store kelp ropes, etc. Kelp ropes are designed to be quickly run through the hole in the cutting device, after which the stipes and holdfasts are cut off at high speed and separated from the kelp ropes. Sea tests showed that, after a single culture cycle, the average yield of kelp cultivated in series-connection rope rafts was 99.77 % compared to conventional parallel connection rope rafts. The cutting and harvesting equipment for kelp culture in series connection rope rafts had a yield of 12–15 t/h, and required 4 operators with a harvest yield of 3–3.75 t/h/person. However, the conventional manual harvesting method for kelp cultures grown on parallel-connected rope rafts had a yield of 8 − 10 t/h, and generally required a single harvesting team consisting of 16 operators. The yield of the mechanized harvesting system was 1.5 times that of manual harvesting, saving 3/4 of labor, while the per capita yield of mechanized harvesting was 6–7 times that of the manual harvesting system. Tests therefore showed that mechanized harvesting has greatly improved efficiency and significantly reduced labor intensity.

Multi-year, post-harvesting impact assessment in a neotropical secondary Atlantic Forest

Subject to overexploitation in the past centuries, the Atlantic Forest is subject to very rigorous protection rules. However, the law is a controversial issue since landowners are not compensated for the limited choice of land use possibilities. We believe that, alternatively to a general timber harvest ban, sustainable forest management of the Atlantic Forest has the potential to generate income for the landowners while sustaining important ecological functions of the forest. Such choice would require better understanding of the potential effects of timber harvesting on the forest ecosystem and on species composition and succession over time. In this context, we assessed the harvesting impact of a conventional harvesting method (CM) and compared it to an alternative harvesting method (AM) in three different stands (stands A, B and C) of a secondary forest fragment in southern Brazil. Results from three comprehensive forest inventories over a period of two years were used to assess the timber harvesting impact. Measurements of species composition (i.e., number of species, life form, ecological group), forest structure (i.e., density, basal area, DBH, volume) and saplings density formed the basis of the impact assessment. The inventories were carried out before, immediately after and two years after harvesting. Intensities of damage on remnant trees immediately after harvesting and two years after harvesting were also measured. Before harvesting, a total of 114 tree species (trees, tree fern and palm tree) belonging to 49 families were identified in the study site’s three research stands. Palm trees and secondary species, such as Euterpe edulis, represented the majority of recruited individuals (DBH ≥ 5 cm) two years after harvesting. However, new saplings (DBH ≤ 5 cm) after two years were mainly pioneer woody tree species, such as Cecropia glaziovii and Schizolobium parahyba. On average, AM reduced damage to saplings by 5%. Most of the damages caused by CM were moderate to severe, while AM caused light to moderate damages. Binary logistic regression indicated dependency of the mortality rates on the independent variables “stand, stem and leaning damages.” On the other hand, the recovery rates of damaged trees were dependent on crown, stem and leaning damages. Therefore, two years after harvesting a higher mortality rate of low-dimensional trees was observed in stands with high density of smaller trees and high density of improvement felling. Although crown damages were not related to mortality rates, high intensity of crown damages reduced recovery rates over time.

Microalgae Harvesting by Self-Driven 3D Microfiltration with Rationally Designed Porous Superabsorbent Polymer (PSAP) Beads.

Microalgae are emerging as next-generation renewable resources for production of sustainable biofuels and high-value bioproducts. Conventional microalgae harvesting methods including centrifugation, filtration, flocculation, and flotation are limited by intensive energy consumption, high capital cost, long treatment time, or the requirement of chemical addition. In this study, we design and fabricate porous superabsorbent polymer (PSAP) beads for self-driven 3D microfiltration of microalgal cultures. The PSAP beads can swell fast in a microalgal suspension with high water absorption capacity. During this process, microalgal cells are excluded outside the beads and successfully concentrated in the residual medium. After treatment, the beads can be easily separated from the microalgal concentrate and reused after dewatering. In one PSAP treatment, a high concentration factor for microalgal cultures up to 13 times can be achieved in 30 min with a harvesting efficiency higher than 90%. Furthermore, microalgal cultures could be concentrated from 0.2 g L-1 to higher than 120 g L-1 with minimal biomass loss through multistage PSAP treatments. Therefore, the use of PSAP beads for microalgae harvesting is fast, effective, and scalable. It does not require any complex instrument or chemical addition. This technique potentially provides an efficient and feasible alternative to obtain high concentrations of functional biomass at a very low cost.

Hybrid energy harvesting system under the electromagnetic induced vibrations with non-rigid ground connection

A hybrid energy harvesting system has been presented in this study by vibrating a beam element with an electromagnetic actuator. With the structure proposed in this article, two different types of energy harvesting concepts were provided with the piezoelectric patch attached to the fixed end of the cantilever beam and the electromagnetic device connected to the free end of the cantilever beam. Generally, in electromagnetic energy harvesting systems, the electromagnetic device is fixed from one end to the ground. The effects of vibration of this fixed surface on energy harvest are being neglected. Electromagnetic devices that provide energy harvesting and vibrate the beam element are of identical structure in the proposed hybrid system. Both devices are mounted at the same point of the beam to face each other. While one of these electromagnetic devices is fixed onto the ground, the other one is assembled to the main beam with a secondary parallel beam element. Therefore, the electromagnetic device that harvests energy or vibrates the beam element can be changed so that it can be either on the lower or upper side of the main beam element. With this designed structure, the behavior of electromagnetic energy harvesting elements and vibration actuators placed on the non-rigid ground has been investigated. Unlike conventional energy harvesting methods, the concept of displacement transmissibility has been discussed in this study. Experimental studies have performed the dynamic conditions to obtain optimum energy harvest in the proposed harvesting system for different frequency inputs. Experimental results revealed the effect of vibrations originating from the non-rigid ground on energy harvesting. It has been observed that the electromagnetic energy harvesting device connected to the non-rigid ground increases the amount of energy collected.

Recent advances and future prospects of electrochemical processes for microalgae harvesting

Over the years, algae have found wide scope of utility in a variety of environmentally beneficial processes like biofuel production, removal of heavy metals from wastewater sources for potential bioremediation, monitoring water pollution and source of animal nutrition. However, the conventional harvesting methods pose a set-back in terms of energy, cost and operational complications due to the small size of microalgae. Of all the processes, harvesting alone corresponds to approximately 30% of the total production costs. Recent advancements in the microalgal technology have brought many efficient techniques into use for improved recovery of microalgae. This review comprehends the development, principle, influencing parameters and directions to future research of one of the state-of-the-art approaches for harvesting microalgae, electrochemical technology. Though this area was previously explored for its application in wastewater treatment, it has lately gained momentum in the field of microalgae due to its economic efficiency. This paper highlights the three prime processes used to yield microalgae namely electroflocculation, electroflotation and a combined electrocoagulation-flotation (ECF) system. Several encroachments and strategies among these techniques have also been elucidated. The review focusses on the effect of most significant process controlling parameters such as reactor and electrode design, various surface properties of microalgae, current, pH, salinity and agitation that influence harvesting. In addition, the economy and energy aspects that emphasize the welfares of this technology over others have been extensively discussed. The overall work aims to provide an insight into the electrochemical methods, their challenges and opportunities that might be beneficial for carrying out further research and scope for industrial applications.

A self-powered analog sensor-data-logging device based on Fowler-Nordheim dynamical systems

Continuous, battery-free operation of sensor nodes requires ultra-low-power sensing and data-logging techniques. Here we report that by directly coupling a sensor/transducer signal into globally asymptotically stable monotonic dynamical systems based on Fowler-Nordheim quantum tunneling, one can achieve self-powered sensing at an energy budget that is currently unachievable using conventional energy harvesting methods. The proposed device uses a differential architecture to compensate for environmental variations and the device can retain sensed information for durations ranging from hours to days. With a theoretical operating energy budget less than 10 attojoules, we demonstrate that when integrated with a miniature piezoelectric transducer the proposed sensor-data-logger can measure cumulative “action” due to ambient mechanical acceleration without any additional external power.

Discoloration in the marine red algae Pyropia: causative factors and exploiting the biotechnological potential of a waste resource

AbstractPyropia (Porphyra, referred to as ‘Gim’ in Korea or ‘Nori’ in Japan), an economically valuable alga, has long been consumed as seafood, especially in north‐east Asian countries. Its well‐established conventional mass cultivation and harvesting methods in coastal areas widen the industrial availability of edible Pyropia sp. However, the unexpected discoloration derived from causative factors during the cultivation process gives rise to serious economic losses in the aquaculture industry. For the industrial use of discoloured laver waste (DLW), recent articles have suggested that DLW biomass could be used as a source of agar polysaccharide, porphyran, γ‐aminobutyric acid and other value‐added bioactive compound productions. Although DLW biomass has economic potential, the lack of integrated information and relevant studies still limits its industrial availability. Therefore, we discussed recent research concerning the functional ingredients, causative factors and potential availability of DLW to provide integrated information. Furthermore, this review suggested the potential industrial application of DLW as a source for other value‐added material production.

Effect of Harvesting Methods on Storage Behaviour of Mandarin (<i>Citrus Reticulata</i> Blanco) Under Cellar Condition

Mandarin (Citrus reticulata Blanco) is a premier fruit crop expanding rapidly in the hilly areas of Nepal. Most of the mandarin growers in Nepal are using conventional harvesting method which is responsible for deteriorating the fruit quality and shortening the postharvest shelf life. Thus, this experiment was conducted to evaluate the effect of different harvesting methods on quality and shelf-life of mandarin during storage under the Cellar condition (11±2°C and 85-90% RH). For this, mandarin fruits harvested by different methods i.e. hitting by sticks, direct pulling, twisting and pulling, and clipping were stored for 90 days and fortnight interval reading of different quality parameters were carried out. The experimental results revealed that fruits harvested by clipper with small pedicel intact recorded the minimum PLW (3.15%), decay loss (8.33%), and TSS (10.57° Brix) and retained the higher fruit firmness (3.30 kg/cm2), maximum juice recovery percentage (49.69), TA (0.85%) and vitamin C (25.50 mg/100 ml) during the storage under Cellar condition. The study concluded that fruits harvesting with clipper can be stored safely up to three months under the Cellar condition.

Impact Assessment of Timber Harvesting Operations for Enhancing Sustainable Management in a Secondary Atlantic Forest

Conservation and management of forest ecosystems are currently largely conflicting goals in the Brazilian Atlantic Forest biome. At present, all parts of the Atlantic Forest are protected and commercial logging is highly restricted. However, sustainable forest management systems can offer significant income opportunities for landholders, and thereby actively support the process of ecosystem rehabilitation and protection of the Atlantic Forest. This research is intended to contribute to enhancing the development of environmentally sound forest management alternatives in the Atlantic Forest biome. Through a case study, the harvesting impact of a conventional harvesting method (CM) was evaluated and compared with an alternative and improved harvesting method (AM), performed by a well-trained professional chainsaw operator experienced in reduced impact logging techniques, and included the use of a snatch block and a skidding cone. Following a full pre-harvest inventory, 110 different tree species were identified. The harvesting impact on the residual stand was classified and evaluated through a successive post-harvest inventory. Damage maps were developed based on interpolation of tree damage intensities with the triangular irregular networks (TIN) methodology. Our results showed noticeable high rates of tree hang-ups, observed for both harvesting methods. Furthermore, the harvesting damaged trees mainly in the lower diameter at breast height (DBH) classes. In comparison to winching, the felling process caused most of the damage to remnant trees for both methods, at 87% (CM) and 88% (AM). The number of damaged trees (above 11.9 cm DBH) per harvested tree, for CM, ranged from 0.8 trees to 2.5 trees and, for AM, ranged from 0.6 trees to 2.2 trees. Improvements of the AM method (operator skills, skidding cone and snatch block) over CM allowed for a reduction of the damaged basal area, a reduction of the “high damaged area” per plot, and a reduction of the winching disturbed ground area. Nonetheless, a suitable harvesting system should consider further improvements in the felling technique, and additionally integrate the local knowledge of CM regarding forest and tree species with the technical improvements of AM.

An Enhanced Multiplication of RF Energy Harvesting Efficiency Using Relay Resonator for Food Monitoring.

Recently, radio frequency (RF) energy harvesting (RFEH) has become a promising technology for a battery-less sensor module. The ambient RF radiation from the available sources is captured by receiver antennas and converted to electrical energy, which is used to supply smart sensor modules. In this paper, an enhanced method to improve the efficiency of the RFEH system using strongly coupled electromagnetic resonance technology was proposed. A relay resonator was added between the reader and tag antennas to improve the wireless power transmission efficiency to the sensor module. The design of the relay resonator was based on the resonant technique and near-field magnetic coupling concept to improve the communication distance and the power supply for a sensor module. It was designed such that the self-resonant frequencies of the reader antenna, tag antenna, and the relay resonator are synchronous at the HF frequency (13.56MHz). The proposed method was analyzed using Thevenin equivalent circuit, simulated and experimental validated to evaluate its performance. The experimental results showed that the proposed harvesting method is able to generate a great higher power up to 10 times than that provided by conventional harvesting methods without a relay resonator. Moreover, as an empirical feasibility test of the proposed RF energy harvesting device, a smart sensor module which is placed inside a meat box was developed. It was utilized to collect vital data, including temperature, relative humidity and gas concentration, to monitor the freshness of meat. Overall, by exploiting relay resonator, the proposed smart sensor tag could continuously monitor meat freshness without any batteries at the innovative maximum distance of approximately 50 cm.

Soil Carbon Storage in Douglas‐Fir Forests of Western Oregon and Washington Before and After Modern Timber Harvesting Practices

Core Ideas Nine forest stands in the Pacific Northwest were selected to detect at least a 5% change in mineral soil carbon. Change in mineral soil carbon content following harvest was negligible (+2% ns). There was an increase of 184% in forest floor carbon resulting from harvest residue inputs. Conventional methods of timber harvesting do not cause substantial short‐term loss in mineral soil carbon. Forest soil carbon represents a large, but slowly changing pool of carbon in forests. Understanding the response of soil carbon to forest management, including harvesting, is critical for determining overall stand and/or landscape carbon balance. This longitudinal study on nine randomly selected sites was designed to detect a 5% or greater change in mineral soil carbon storage following harvest. Soil samples were collected both pre‐harvest and 3 to 3.5 yr post‐harvest at 300 sample points on a fixed grid from each stand. A forest floor sample and mineral soil samples in depth increments of 0 to 15 and 15 to 30 cm were collected at every point. A soil sample at 30 to 100 cm (or 30–60 cm at two sites) was collected at 200 points. Each mineral soil depth fraction was separated into size fractions of <2 mm and 2 to 4.75 mm for analysis. At each site, these samples were spatially grouped into 25 composites by depth and size for the efficient analysis of carbon concentration. Soil mass and carbon concentrations were multiplied to calculate the carbon content in the soil per unit area. Across all sites combined, we found negligible change (+2% ns) in mineral soil carbon content following harvest and a 184% increase in forest floor carbon resulting from harvest residue inputs. This indicates that conventional timber harvesting methods in the Pacific Northwest do not cause substantial short‐term losses in mineral soil carbon, but the longer‐term trajectory of soil carbon storage following harvest remains to be investigated.

Productivity assessment of timber harvesting techniques for supporting sustainable forest management of secondary Atlantic Forests in southern Brazil

The Atlantic Forest in southern Brazil has been subject to overexploitation in the past prompting the formulation of a rigorous conservation orientated policy by the government including a strict ban of timber harvesting. In the region, the forestland is owned by farmers. The economic value of the forest is rather limited for those farmers, because of the prohibition of commercial timber harvesting as a source of income. Sustainable forest management systems can offer great potential as new income opportunities for land holders, and further actively support the process of ecosystem rehabilitation and protection for these ecosystems. Yet, successful implementation of such sustainable management systems requires feasible and adapted timber harvesting systems. In order to develop such harvesting systems, a regional comparative case study was conducted at a typical smallholder forestry venture with the objective to analyze and evaluate harvesting methods supporting sustainable management of the Atlantic Forest. This study assessed production rates and associated costs of a common conventional timber harvesting method (CM) and a proposed alternative method (AM). CM was performed by a selected, typical forest landowner who had only basic training in chainsaw operations, but 20 years of experience at the wood yard of his small sawmill. In contrast, the AM employed a professional chainsaw operator from the Amazon forest, trained and experienced in reduced impact logging techniques using state of the art equipment, supplemented by a snatch block and a skidding cone for improved extraction. Time study based models identified tree volume, winching distance and skidding distance to the landing as the most significant independent variables affecting productivity. Total net productivity ranged from 4.9 m³ PMH0-1 for CM to 3.1 m³ PMH0-1 for AM. Corresponding gross-productivity ranged from 3.0 m³ SMH-1 to 1.9 m³ SMH-1 with an overall mean utilization rate of 60.8 % and 60.9 %, respectively for CM and AM. Associated harvesting costs ranged from 12.05 € m-3 to 20.94 € m-3 with an estimated annual production of 4000 m³ and 2700 m³, respectively. Although AM showed overall lower productivity and higher costs, it represented an important improvement in terms of occupational health and safety. In conclusion, a suitable harvesting system should integrate local experiences of CM and proposed technical improvements of AM.

Electric-Field Energy Harvesting in Wireless Networks

Electric-field energy harvesting (EFEH) can be considered as an emerging and promising alternative for self-sustainable next-generation WSNs. Unlike conventional harvesting methods that rely on ambient variables, EFEH provides more reliable and durable operation as it is operable with any voltage-applied conductive material. Therefore, it is better suited for advanced throughput and applications requiring a certain QoS. In this article, we introduce this newly emerging WSN paradigm, and focus on enabling EFEH technology for smart grid architectures, such as home, building, and near area networks, where the field intensity is relatively low. To this end, a practical methodology and a general use implementation framework have been developed for low-voltage applications by regarding compelling design issues and challenging source scarcity. The proposed double-layer harvester model is experimentally evaluated. Its performance in terms of implementation flexibility, sensor lifetime, and communication throughput is investigated. In addition, current challenges, open issues, and future research directions are discussed for the design of more enhanced EFEH wireless networks.

Electro-flotation of Chlorella sp. assisted with flocculation by chitosan

Harvest of algal biomass from dilute culture medium at low cost remains a major hurdle to industrial scale processing. Conventional harvesting methods are not only costly, but also affect any later downstream processes partly because of the metal ions contamination by flocculants. This work constructed an electro-flotation technique including two steps of flocculation by chitosan first and then sequential bubbling flotation by non-sacrificial graphite electrodes. Laboratory work has been carried out to investigate the influences of chitosan dosage, pH value, cell density of algal culture, stirring rate and mixing time on flocculation efficiency, and the voltage and current intensity imposed on electrodes and the space between electrodes on flotation efficiency. Moreover, a 1000L pilot bench of electro-flotator constructed to harvest Chlorella sp. was tested. Around 90% of total recovery efficiency and 50 times concentration rate have been reached, and only 23.7g chitosan and 0.43kWh of electricity are required to harvest 1kg biomass. Above results proved electro-flotation by graphite electrodes assisted with chitosan is a safe and cost effective approach for microalgae harvesting.

Comparison of harvest-related removal of aboveground biomass, carbon and nutrients in pedunculate oak stands and in fast-growing tree stands in NW Spain

In northern Spain, the use of biomass to produce bioenergy has led to increased exploitation of both natural pedunculate oak (Quercus robur L.) stands and fast-growing plantations of natural or exotic species. In this study, we developed a model for estimating aboveground biomass, carbon and nutrient contents in different pedunculate oak components at individual-tree and at stand level. Six harvesting methods were simulated in an average stand, ranging from whole-tree to stem wood extraction (stem without bark) and including the conventional harvesting method used in the region (extraction of stem plus branches of diameter >7cm). The biomass and macronutrients extracted were compared with those removed during harvesting of fast-growing tree species (Eucalyptus globulus Labill., Pinus radiata D. Don and Pinus pinaster Ait.) on the same temporal basis (mean annual values). Harvesting pedunculate oak stands generally extracted lower amounts of nutrients than harvesting fast-growing species, although the differences depended on the species, macronutrients and harvesting regime considered.