Critical parameters in cost-effective alkaline extraction for high protein yield from leaves

Leaves are potential resources for feed or food, but their applications are limited due to a high proportion of insoluble protein and inefficient processing. To overcome these problems, parameters of alkaline extraction were evaluated using green tea residue (GTR). Protein extraction could be maximized to 95% of total protein, and, after precipitation by pH adjustment to 3.5, 85% of extracted protein was recovered with a purity of 52%. Temperature, NaOH amount, and extraction time are the protein yield determining parameters, while pH and volume of extraction liquid are critical parameters for production cost. The cost of energy and chemicals for producing 1 t GTR proteins is minimized to 102€, and its nutritional value is comparable to soybean protein. Furthermore, this technology was successfully applied to other sources of biomass and has potential to be used as a part of an integrated bio-refinery process.     

Reactivity investigation on biomass chemical looping conversion for syngas production

Chemical looping gasification (CLG) is regarded as an innovative and promising technology for producing syngas. In this work, CLG of straw was conducted in a fixed bed reactor with Fe₂O₃ as the oxygen carrier, whose results led to conclusions that Fe₂O₃, the oxygen carrier, proved advantageous to the secondary gasification reaction and the formation of CO and CO₂. It was also found that CO was further oxidized to CO₂ at high Fe₂O₃/C molar ratio, which resulted in a decreased gasification efficiency and low heat value of syngas. Therefore, a conclusion was drawn that the most optimized Fe₂O₃/C molar ratio was 0.2. In addition, the alkali metals in the biomass evaporated as chlorine salts into gas phase and retained as alkali metal oxide at high temperature, resulting in coking, slagging and heating surface corrosion. In the mean time, the oxygen carrier mainly converted to Fe and sintering phenomenon was serious at high temperature despite the fact that high temperature promoted gas yield, carbon conversion efficiency and gasification efficiency. Therefore, the most optimized temperature was set to 800 °C in order to maximize gas yield and gasification efficiency.     

Experimental investigation on co-gasification of coffee husk and sawdust in a bubbling fluidised bed gasifier

Energy can be extracted from biomass through gasification. The gasification process is influenced by the physico-chemical nature of the biomass selected for gasification. Ash content and composition of the biomasses are likely to affect the gasification process. Clinker formation in the reactor bed caused by melting and agglomeration of ashes will affect the gasification process in fluidised bed gasifiers. The agglomeration tendency of the biomass is examined by carrying out the Energy Dispersive X-ray Spectroscopy analysis on biomass ash to identify the presence of elements like potassium and sodium responsible for agglomeration. Experimental investigations on the gasification of coffee husk revealed that coffee husk is prone to agglomeration even though the hydrogen yield is more. However, gasification of saw dust is not vulnerable to agglomeration. Co-gasification of coffee husk with sawdust (which is less prone to agglomeration) is investigated experimentally.     

Study of synthesis gas composition,exergy assessment,and multi-criteria decision-making analysis of fluidized bed gasifier

A system based a fluidized bed gasifier with steam as a gasifying agent is investigated in details. Comparing the synthesis of gas compositions with experimental data available in the literature is used to validate the model. The synthesis of gas composition and efficiencies of the system is investigated respect to different biomasses considered as gasification fuels. The results indicate that the molar fractions of hydrogen and carbon dioxide are increased and the molar fraction of carbon monoxide is reduced with steam to biomass ratio (STBR). The hydrogen and cold gas efficiencies are improved with decreasing STBR. Hydrogen, cold gas, and exergy efficiencies are enhanced with temperature. The results illuminate that pine sawdust and straw have the highest hydrogen production and legume straw produces the lowest CO molar fraction. Straw has the highest hydrogen efficiency, eucalyptus and straw have the highest cold gas efficiency, and eucalyptus has the highest exergy efficiency. A systematical analytical hierarchy process (AHP)/technique for order preferences by similarity to ideal solution (TOPSIS) couple method are utilized to select the best alternative. The results illuminate that eucalyptus, straw, and pine sawdust are the best candidates, respectively as gasification fuel based on the considered criteria.     

Solar thermochemical gasification of wood biomass for syngas production in a high-temperature continuously-fed tubular reactor

Biomass gasification is an attractive process to produce high-value syngas. Utilization of concentrated solar energy as the heat source for driving reactions increases the energy conversion efficiency, saves biomass resource, and eliminates the needs for gas cleaning and separation. A high-temperature tubular solar reactor combining drop tube and packed bed concepts was used for continuous solar-driven gasification of biomass. This 1 kW reactor was experimentally tested with biomass feeding under real solar irradiation conditions at the focus of a 2 m-diameter parabolic solar concentrator. Experiments were conducted at temperatures ranging from 1000 °C to 1400 °C using wood composed of a mix of pine and spruce (bark included) as biomass feedstock. This biomass was used under its non-altered pristine form but also dried or torrefied. The aim of this study was to demonstrate the feasibility of syngas production in this reactor concept and to prove the reliability of continuous biomass gasification processing using solar energy. The study first consisted of a parametric study of the gasification conditions to obtain an optimal gas yield. The influence of temperature, oxidizing agent (H₂O or CO₂) or type of biomass feedstock on the product gas composition was investigated. The study then focused on solar gasification during continuous biomass particle injection for demonstrating the feasibility of a continuous process. Regarding the energy conversion efficiency of the lab scale reactor, energy upgrade factor of 1.21 and solar-to-fuel thermochemical efficiency up to 28% were achieved using wood heated up to 1400 °C.     

Energetic recovery of biomass in the region of Rabat,Morocco

Morocco has a potential of considerable biomass with a forest estate around nine million of hectares, and a herd around seven million units of large cattle. In particular, in the Rabat region, the amount of waste is about 714 350 Kg in 2014, who is equivalent to 0.96 Kg/inhabitant/day. In this document, we present, in the case of the Rabat, the Current situation of the electricity production from waste incineration. The data will be processed by statistical methods (Environmental Protection Agency (EPA) model and Solid Waste Association of North America (SWANA) model). The objective behind using these models is to introduce data for future years' estimates. We will show that the amount of electricity generated by incineration of waste in Rabat is in the order of more hundreds of Giga-watt-hours. This alternative allows a reduction in tonnage of accumulated waste and avoids its negative impact on the environment. It also provides energy independence. This involves, necessarily, construction of landfills and integration of neighbourhoods' population.     

Yield,water use efficiency and economic analysis of energy sorghum in South Texas

Yields, water use efficiency and economic returns (net farm revenues) of biomass sorghum [Sorghum bicolor (L.) Moench] were investigated over two years (2012 and 2014) under limited water resource conditions. Energy sorghum was grown under four water supply regimes: rain-fed (or dry-land, level 1), 50% (level 2), 75% (level 3) and 100% (level 4) of crop evapotranspiration rates (% ET_c). Biomass yields ranged from 5.8 to 16.6 Mg ha⁻¹ (dry weight) after 126 days of growth. Average water use efficiencies ranged from 3.95 kg m⁻³ to 23.4 kg m⁻³. Net return was approximately 410 $ ha⁻¹ with water depths above 400 ha-mm. These results suggest that it is possible to obtain more than 60 Mg ha⁻¹ of sorghum biomass (wet basis) with at least 425 mm of water. While biomass yield under irrigation was greater than rain-fed conditions, there were no significant differences among irrigation treatments. Biomass chemical composition did not differ significantly among water treatments suggesting that biofuel quality would not be affected by water deficits.     

Experimental investigation of the primary combustion zone during staged combustion of wood-chips in a commercial small-scale boiler

In this work the primary combustion zone of a modified, commercial, small-scale boiler was investigated during staged combustion of wood-chips. Experimental research on thermal conversion of biomass in fixed beds is necessary to supply reliable data for gas phase combustion model validation and optimization. Furthermore, scruting of pollutant emission formation and combustion efficiency enhancement can be conducted. Two different fuel moistures were used while the primary combustion zone of a small-scale boiler was investigated as a function of the primary air ratio. The combustible products leaving the fuel layer were analyzed under continuous operation by an extractive method. This approach is new in the field of small-scale biomass combustion research and considers the strong coupling between the products leaving the fuel bed and the heat fluxes emitted by the flame of the secondary combustion zone. Additionally, fine particulate matter emissions were quantified to study the effect of varying primary air ratio and different fuel moisture on particulate formation. Results show that the primary air ratio and the fuel moisture have a significant influence on the primary combustion products composition, on the fuel bed behavior and on fine particulate matter emissions. At low primary air ratios, tars constitute a significant part of the heating value of primary combustion products. The smallest amount of particulate emissions was found at low primary air ratio and low fuel moisture. Experimental data was validated with an elemental balance, which showed perfect accordance.     

Torrefaction of pine in a bench-scale screw conveyor reactor

Numerous works are reported in the literature regarding the torrefaction of biomass in batch processes. However, in industrial applications, continuous reactors and processes may by more interesting as this allows for the integration of continuous mass and heat flows. To shed light on the operation of continuous torrefaction processes, this work presents the findings of continuous, bench-scale (2.5 kg h⁻¹) torrefaction experiments using pine wood particles as a feed material in a screw conveyor reactor. The shifts in product mass yields were in line with theoretical expectations for changes in reactor temperature and reactor residence times whereas the degree of filling within the screw reactor and the flow of the nitrogen purge gas were found to be negligible. The process allowed for the measurement of the particle surface temperatures throughout the length of the reactor and significant temperature differences where measured between the wall of the reactor and the reactor screw. The proximate composition and the higher heating value of the torrefied biomass were found to be correlated to the ratio of the mass of dry biomass feed to the mass of the torrefied biomass produced. Important observations regarding the operability of such a process, also relevant to larger-scale processes, include the need to prevent the occurrence of torrefaction vapour condensation (which leaves the torrefaction reactor in the form of a saturated vapour) in the presence of fine, solid particles as this leads to rapid particle agglomeration and process blockage.     

Sampling procedure in a willow plantation for estimation of moisture content

Heating value and fuel quality of wood is closely connected to moisture content. In this work the variation of moisture content (MC) of short rotation coppice (SRC) willow shoots is described for five clones during one harvesting season. Subsequently an appropriate sampling procedure minimising labour costs and sampling uncertainty is proposed, where the MC of a single stem section with the length of 10–50 cm corresponds to the mean shoot moisture content (MSMC) with a bias of maximum 11 g kg⁻¹. This bias can be reduced by selecting the stem section according to the particular clone. The average difference in MSMC between the largest and smallest shoot in a stump was 31 g kg⁻¹. This variation is only marginally smaller than the variation found in MC between stumps. The MC of individual stem sections may vary as much as 190 g kg⁻¹ in one shoot. Variation in whole shoot moisture content was primarily influenced by the shoot diameter, but in addition significant effects of clone and shoot age were found.