High temperature interactions between K-rich biomass ash and MgO-based refractories

MgO-based refractories are used in lime kilns to withstand the high temperature and chemical environment. Efforts to reduce CO₂ emissions have led to an increased interest to use bio-based fuels as alternatives to traditional fossil sources. The potential for refractory corrosion from a potassium-rich biomass ash was investigated by studying the infiltration of olive pomace ash into magnesia/spinel refractories. Refractory samples were exposed to the ash at up to 1400 °C for 15–60 min in a CO₂–rich atmosphere. Molten ash infiltrated the refractories through pores and grain boundaries to a depth of up to 9.6 mm, which was quantified with a new systematic procedure. The phase KAlO₂ was identified inside the refractories after exposure, indicating an attack of spinel components by potassium. Phases found in the ash residues also indicated the migration of refractory constituents. Thermochemical equilibrium calculations were also used to investigate the ash/refractory chemistry.     

Hydro-upgrading of bio-oils derived from pyrolysis of biomass with different H/Ceff ratios in tetralin over Pt/C and Ru/C

Pyrolysis oils with different effective hydrogen (H/C_eff) ratios are mixed with tetralin at a mass ratio of 1:1 and treated at 400 °C for 2 h under 6 MPa H₂ over Pt/C and Ru/C, respectively, to examine the effect of H/C_eff ratio on the yield and quality of the upgraded oil. Pyrolysis oil with higher H/C_eff ratios results in an upgraded oil with higher yield and H/C_eff ratios. The highest S and O reduction ratios of 96.11% and 56.26% are achieved with added Pt/C at an H/C_eff ratio of 1.39 of the feedstock. In comparison, the highest N reduction ratios of 34.50% is achieved with added Ru/C at an H/C_eff ratio of 1.38 of the feedstock. The N and S poison the catalyst's active sites and reduce the deoxygenation efficiency. Thus, we view that the H/C_eff plays a vital role in improving the properties of the bio-oil.     

Catalytic gasification of rice hull by dielectric barrier discharge non-thermal plasma over potassium catalyst

Dielectric barrier discharge (DBD) non-thermal plasma was used for gasification of rice hull. And the gasification efficiency, gas production performance and gasification productions of rice hull were studied in the different atmosphere of the DBD gasification. The effect of the potassium metal on DBD gasification of rice hull was investigated and the catalytic mechanism of potassium was studied by density functional theory calculation. It was found that the gasification efficiency of rice hull by DBD in CO₂ atmosphere is up to 87.14%, which is higher than that in the N₂ atmosphere. The implantation of the potassium metal can also improve the DBD gasification efficiency, and promote the generation of H₂ and CH₄. The rice hull loaded with 3% potassium had the best gasification in the CO₂ atmosphere. Almost no tar was found during the DBD gasification of rice hull. N₂ adsorption and desorption, scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) were used to investigate the properties of the carbon materials, which was generated from the rice hull gasification. The carbon material which was produced by DBD gasification in CO₂ atmosphere had large specific surface area and abundant functional groups. It can be used as catalyst carrier and other fields.     

Dual carbon source method to fabricate hierarchical porous carbon with three-dimensional interconnected network structure toward advanced energy storage device

Selective fabrication of carbon materials with developed specific surface area and hierarchical porous structure is essential for high-performance carbon-based supercapacitors. Direct carbonization of organic acid salts represents a strategy that can produce porous carbon with high specific surface area, but it is still hindered by low carbon yield, impeding its large-scale application. Herein, a biomass-derived hierarchical porous carbon with large specific surface area is prepared via a facile one-pot calcination method. The optimal SCPC-4 sample presents three-dimensional interconnected network structure and plentiful heteroatom content. Hence, it delivers a large specific capacitance of 321 F g^?1 at a current density of 1 A g^?1, and negligible capacitance loss after 10,000 cycles at 10 A g^?1. In addition, the assembled SCPC-4 based symmetric supercapacitor exhibits an energy density of 21.2 Wh kg^?1 at a power density of 900 W kg^?1. This cost-effective binary biomass carbon source route provides a great possibility for the mass production of high-yield porous carbon materials.     

Establishment of bioenergy crops on metal contaminated soils stimulates belowground fauna

Soils of contaminated agrosystems represent potential arable land surfaces for the production of non-alimentary crops. The aim of this study is to monitor changes in belowground biodiversity (Collembola), potentially occurring following establishment of perennial biomass crop systems on contaminated agricultural land. We selected, within an agricultural trial, two different biomass crops, miscanthus (Miscanthus x giganteus) and switchgrass (Panicum virgatum) and an annual wheat crop (Triticum sp.) used as a control. About 20-fold more individuals were found under miscanthus and switchgrass than under wheat. The highest mean number of species was found under miscanthus being 30% greater than in switchgrass and 424% than in annual wheat. Furthermore, abundance and species richness of the three collembolan life-forms (epedaphic, hemiedaphic, and euedaphic) differed between the crops leading to distinctly different assemblages.On metal contaminated soils, perennial bioenergy crops have the potential to increase belowground faunal diversity and abundance with the identity of crops as a critical factor driving soil animal assemblages.     

Effect of agitation speed on enzymatic saccharification of dry-pulverized lignocellulosic biomass

A vibration mill using cog-ring media, called a “tandem-ring mill”, was developed to achieve high-impact pulverization of lignocellulosic biomass for producing bio-ethanol. Instead of the ball medium in a conventional vibration mill, it has a cog-ring medium. Japanese cedar powder pulverized by the tandem-ring mill in a dry condition was pulverized to 20 μm particle diameter and 13% crystallinity index. Saccharification efficiency in enzymatic saccharification of Japanese cedar powder of greater than 70% was reached based on holocellulose. The Japanese cedar powder pulverized using the tandem-ring mill is suitable for bioethanol production. For this study, the Japanese cedar powder was prepared using a two-batch-type tandem ring mill in 60 min pulverization. Then, the agitation speed effect on Japanese cedar powder pulverization for enzymatic saccharification was investigated. Results show that the enzymatic saccharification efficiency of pulverized Japanese cedar powder increased continuously with decreasing agitation speed until 30 rpm. The best yields of 77% at 1 L and 75% at 3 L were obtained at 30 rpm agitation. The pulverized Japanese cedar powder produced by the tandem-ring mill was useful for enzymatic saccharification. Moreover, low agitation speed for saccharification of Japanese cedar powder pulverized by the tandem-ring mill might provide high saccharification efficiency.     

Design of a biomass power plant for burning date palm waste to cogenerate electricity and distilled water

Date palm trees (Phoenix dactylifera L.) produce approximately 40 kg of burnable waste including dried leaves, spathes, sheaths, and petioles annually. In this paper, the potential of date palm waste as a bioenergy source has been investigated. As a sample project, a power plant has been preliminary designed to simultaneously generate electrical power using a steam Rankine cycle and distilled water by the thermal desalination of seawater using a multiple effect evaporator. The results indicated that a small plant in Bushehr Province in southern Iran which burns 140,000 tons of waste annually can produce approximately 62 GWh of electricity in conjunction with 2.27 million tons of distilled water. This production is equivalent to 75 GWhe/year. Environmental assessments revealed that the use of this amount of biomass leads to a net green-house gas (GHG) reduction of 40,500 tCO₂/year.     

Self-sustainable electricity production from algae grown in a microbial fuel cell system

This paper describes the potential for algal biomass production in conjunction with wastewater treatment and power generation within a fully biotic Microbial Fuel Cell (MFC). The anaerobic biofilm in the anodic half-cell is generating current, whereas the phototrophic biofilm on the cathode is providing the oxygen for the Oxygen Reduction Reaction (ORR) and forming biomass. The MFC is producing electricity with simultaneous biomass regeneration in the cathodic half-cell, which is dependent on the nutrient value of the anodic feedstock. Growth of algal biomass in the cathode was monitored, assessed and compared against the MFC power production (charge transfer), during this process. MFC generation of electricity activated the cation crossover for the formation of biomass, which has been harvested and reused as energy source in a closed loop system. It can be concluded that the nutrient reclamation and assimilation into new biomass increases the energy efficiency. This work is presenting a simple and self-sustainable MFC operation with minimal dependency on chemicals and an energy generation system utilising waste products and maximising energy turnover through an additional biomass recovery.     

Where to produce rapeseed biodiesel and why? Mapping European rapeseed energy efficiency

Rapeseed is widely used to produce biodiesel, especially in Europe. In several studies, it has been shown that there is a good potential for growing this crop across the continent. However there is still little awareness that the energy efficiency of biofuel production from rapeseed is very low. Energy efficiency can be expressed in terms of Energy Return for Energy Invested (EROEI). We mapped EROEI values for all EU countries plus Switzerland based on expected yields derived from rapeseed suitability maps. We find that EU countries produce rapeseed biofuel with EROEI values of 2.2 and lower. We suggest that plans for biofuel cropping have to be supplemented by maps of EROEI. It is not only relevant to show where rapeseed can be grown, but we should also look at where its use for bioenergy can be efficient. In the area theoretically suitable for growing rainfed rapeseed (excluding unsuitable areas and water), 37.6% of the area can produce rape methyl ester (RME) biofuel only with an energy loss. We conclude that the energy efficiency of rapeseed biodiesel is low and spatially heterogeneous, and unless there are major technological improvements in the production process, replacing fossil fuels by biofuels from rapeseed is hardly a feasible option.     

Reed canarygrass (Phalaris arundinacea) outperforms Miscanthus or willow on marginal soils,brownfield and non-agricultural sites for local,sustainable energy crop production

Growing biomass on non-agricultural land could potentially deliver renewable energy services without displacing land from food production, avoiding the social and environmental conflicts associated with bioenergy. A variety of derelict underutilized and neglected land types are possible candidates, sharing a number of challenges for agronomy, including contaminants in soils, potential uptake and dispersion through energy use. Most previous field trials have grown woody biomass species during phytoremediation. Five one-hectare brownfield sites in NE England, were each amended with c.500 t ha⁻¹ of green-waste compost, planted with short-rotation coppice willow, Miscanthus, reed canarygrass and switchgrass,¹ and then harvested for 3–5 years.Critical issues for the economic and environmental viability of energy production on brownfield land were investigated: The yields achieved on non-agricultural land; the potential for fuel contamination; the suitability for use and potential markets for any biomass produced. RCG appears best suited to the challenging soil conditions found on non-agricultural land, outperforming other species in ease of establishment, cost, time to maturity, yield and contamination levels. Invasive spreading and low melting ash compositions were not observed. Annual yields of 4–7 odt ha⁻¹ from the second growth season were found consistently across a range of previously-developed, capped or former landfill sites, with a gross annual energy yield of 97 GJ ha⁻¹ at contamination levels acceptable for domestic pellets. The analogy with marginal agricultural land suggests that this species and approach could help boost biomass production while avoiding the natural capital “nexus” related to global food-fuel-land-water limits.