Short Rotation Wood Crops in Latin American: A Review on Status and Potential Uses as Biofuel

Co-Fermentation of Glucose-Xylose Mixtures from Agroindustrial Residues by Ethanologenic Escherichia coli: A Study on the Lack of Carbon Catabolite Repression in Strain MS04

The production of biofuels, such as bioethanol from lignocellulosic biomass, is an important task within the sustainable energy concept. Understanding the metabolism of ethanologenic microorganisms for the consumption of sugar mixtures contained in lignocellulosic hydrolysates could allow the improvement of the fermentation process. In this study, the ethanologenic strain Escherichia coli MS04 was used to ferment hydrolysates from five different lignocellulosic agroindustrial wastes, which contained different glucose and xylose concentrations. The volumetric rates of glucose and xylose consumption and ethanol production depend on the initial concentration of glucose and xylose, concentrations of inhibitors, and the positive effect of acetate in the fermentation to ethanol. Ethanol yields above 80% and productivities up to 1.85 g_EtOH/Lh were obtained. Furthermore, in all evaluations, a simultaneous co-consumption of glucose and xylose was observed. The effect of deleting the xyIR regulator was studied, concluding that it plays an important role in the metabolism of monosaccharides and in xylose consumption. Moreover, the importance of acetate was confirmed for the ethanologenic strain, showing the positive effect of acetate on the co-consumption rates of glucose and xylose in cultivation media and hydrolysates containing sugar mixtures.

Wastewater-Fertigated Short-Rotation Coppice, a Combined Scheme of Wastewater Treatment and Biomass Production: A State-of-the-Art Review

Vegetated filters based on short-rotation coppice (SRC) can be used to treat various industrial and municipal wastewater while producing valuable biomass in an economical and sustainable way, showing potential in the field of pollution control and bio-based circular economy. This study provides an overview of the state of the art in wastewater-fertigated SRC systems (wfSRCs) worldwide. Different designs, wastewater sources, tree species and varieties, planting schemes, geographic locations, and climates for wfSRC implementation were identified after conducting a literature review. The performance review includes standard water quality parameters, BOD5, COD, nitrogen, phosphorous, and potassium, as well as the extent of pathogen and emergent contaminant removal and biomass production rates. Identified knowledge gaps and important factors to support the practical implementation of wfSRCs are highlighted. Europe leads the research of wfSRC, followed by North America and Australia. The available publications are mainly from developed countries (73%). The most applied and studied tree species in wfSRC systems are willows (32%), followed by eucalyptus (21%) and poplars (18%). Most of the reviewed studies used domestic wastewater (85%), followed by industrial wastewater (8%) and landfill leachate (7%). Most data show high BOD5 and COD removal efficiencies (80%). There are large differences in the documented total nitrogen and total phosphorus removal efficiencies (12%–99% and 40%–80%, respectively). Enhanced biomass growth in wfSRC systems due to wastewater fertigation was reported in all reviewed studies, and biomass production varied from 3.7 to 40 t DM/ha/yr. WfSRCs seem to have high potential as viable and cost-effective wastewater treatment alternatives to conventional treatment technologies.

The Utilization of Plum Stones for Pellet Production and Investigation of Post-Combustion Flue Gas Emissions

Agri-food waste is generated at various food cycle stages and is considered to be a valuable feedstock in energy systems and chemical syntheses. This research identifies the potential and suitability of a representative agri-food waste sample (i.e., plum stones) as a solid fuel. Ground plum stones containing 10, 15, and 20 wt.% of rye bran were subjected to pelletization. The pelletizer was operated at 170, 220, and 270 rpm, and its power demand for the mixture containing 20 wt.% of rye bran was 1.81, 1.89, and 2.21 kW, respectively. Such pellets had the highest quality in terms of their density (814.6 kg·m−3), kinetic durability (87.8%), lower heating value (20.04 MJ·kg−1), and elemental composition (C: 54.1 wt.%; H: 6.4 wt.%; N: 0.73 wt.%; S: 0.103 wt.%; Cl: 0.002 wt.%; O: 38.2 wt.%). Whole plum stones and pellets were subjected to combustion in a 25 kW retort grate boiler in order to determine the changes in the concentrations of NO, SO2, CO, CO2, HCl, and O2 in the post-combustion flue gas. Collected results indicate that plum stone–rye bran pellets can serve as effective substitutes for wood pellets in prosumer installations, meeting the Ecodesign Directive requirements for CO and NO.

Forest harvest byproducts: Use of waste as energy

Forest harvest waste is an attractive biomass feedstock for biofuel production. However, for better use it is necessary to understand the physical-energetic characteristics of the biomass which composes the waste. Therefore, this study aimed to evaluate the bark, wood and tree top characteristics from Eucalyptus urophylla × Eucalyptus grandis (called urograndis) and Acacia mangium harvest wastes. These species present fast-growing characteristics. The evaluations were carried out with waste generated in the forest harvest in central Brazilian plantations. Three fractions were studied: the Top, Wood and Bark. The energetic and physical characteristics of wastes and briquettes were determined. The top and bark of these species are not yet recognized for their energy potential. A. mangium presented better energetic and physical characteristics than urograndis, with a higher mean of fixed carbon (20.84%), a high heating value (20.34 MJ kg^-1), as well as high bulk and energy density (272.66 kg m^-3 and 5599.00 MJ m^-3). A. mangium bark and urograndis tree tops were the fractions with the best characteristics for energy purposes. Bark, wood and tree top waste generated after urograndis and A. mangium forest harvesting can be used as byproducts for energy purposes in their fresh form (as collected in field) or as briquettes, presenting an alternative for the waste.

Energy Multiphase Model for Biocoal Conversion Systems by Means of a Nodal Network

The coal-producing territories in the world are facing the production of renewable energy in their thermal systems. The production of biocoal has emerged as one of the most promising thermo-energetic conversion technologies, intended as an alternative fuel to coal. The aim of this research is to assess how the model of biomass to biocoal conversion in mining areas is applied for thermal systems engineering. The Central Asturian Coal Basin (CACB; Spain) is the study area. The methodology used allows for the analysis of the resource as well as the thermo-energetic conversion and the management of the bioenergy throughout the different phases in a process of analytical hierarchy. This is carried out using a multiphase mathematical algorithm based on the availability of resources, the thermo-energetic conversion, and the energy management in the area of study. Based on the working conditions, this research highlights the potential of forest biomass as a raw material for biocoal production as well as for electrical and thermal purposes. The selected node operates through the bioenergy-match mode, which has yielded outputs of 23 MWe and 172 MWth, respectively.

Evaluation of Macaranga tanarius as a biomass feedstock for fermentable sugars production

Macaranga tanarius is a fast-growing tree species that could be potentially utilized as a biomass feedstock for biorefinery. The average productivity of M. tanarius biomass was estimated to be ~19.2 ton/ha if the above-ground biomass is harvested bi-annually. Different pretreatment approaches were investigated to increase the enzymatic digestibility of foliage and woody biomass. The results indicated that no pretreatment was required for the foliage biomass while sequential acid/alkali pretreatment was necessary for the woody biomass before enzymatic hydrolysis. For the woody biomass, the delignification was 34.5% after sequential dilute acid/alkali pretreatment. The reducing sugar yields from enzymatic hydrolysis of foliage and pretreated woody biomass were 0.31 and 0.42 g/g dry biomass, respectively. The results also showed that both hydrolysates were fermentable by lactic acid bacteria. Overall, the results suggested that M. tanarius could be a potential feedstock for biorefinery based on the findings and processes derived from this study.

Determination of Strength Properties of Energy Plants on the Example of Miscanthus × Giganteus, Rosa Multiflora and Salix Viminalis

Energy from biomass accounts for 70% of all renewables used for heat and electricity production. Such a significant share of biomass determines the need for the investigation of their mechanical properties, as most of the lignocellulosic material requires cutting, chipping or milling before its utilization for energy purposes. Therefore, the knowledge about cutting resistance, bending stiffness, and impact strength of the energy plants is very important. The values of these parameters are used in the proper selection of shredding machines and their elements, wrapping nets or determination of power demand during raw material conversion. This paper presents the results of research on the mechanical properties of selected energy plants. The scope of the research included three different plant species: Miscanthus × giganteus, Rosa multiflora, and Salix viminalis, investigated in terms of cutting resistance, bending stiffness and impact strength of stalks. The results showed that the average stalk cutting resistance for the rotation speed of 4200 RPM was 0.17 N·mm−2 for the Miscanthus × giganteus, 0.15 N·mm−2 for the Rosa multiflora and 0.2 N·mm−2 for the Salix viminalis. Meanwhile, for a rotation speed of 3200 RPM, the cutting resistance amounted to 0.15 N·mm−2 for Miscanthus × giganteus, 0.16 N·mm−2 for Rosa multiflora and 0.18 N·mm−2 for Salix viminalis. For the impact measurements, the Salix viminalis exceeded 40 J·mm−2 of absorbed energy. Meanwhile, the average impact strength value for the Rosa multiflora was 0.53 J·mm−2 and for the Miscanthus × giganteus was 0.22 J·mm−2. The bending stiffness of Miscanthus × giganteus at an average modulus of 3.44 GPa was 1.1 N·m2 for the basal zone, 0.78 N·m2 for the central zone, and 0.72 N·m2 of the apical zone. For the average Young’s modulus of 0.19 GPa, the bending stiffness of the Rosa multiflora reached a value of 0.64 N·m2 for the basal zone, 0.23 N·m2 for the central zone, and 0.28 N·m2 for the apical zone. The Salix viminalis, with an average modulus of elasticity of 0.23 GPa, achieved bending stiffness in the basal zone of 0.99 N·m2, the central zone 0.33 N·m2, and the tip zone 0.38 N·m2. This research makes it possible to expand our knowledge in the field of biomass processing and construction of agricultural machinery with higher processing efficiency.

The Use of Waste Biomass from the Wood Industry and Municipal Sources for Energy Production

Biomass can be used for the production of energy from renewable sources. Because of social resistance to burning crop plants, mixtures and pellets made from or including waste materials are a good alternative. The mixtures analyzed, prepared from wood and municipal waste, were characterized for their calorific values, 7.4–18.2 MJ·kg−1. A result, over 15 MJ·kg−1 was obtained for 47% of the quantities of mixtures being composed. It has been demonstrated that wood shavings and sewage sludge have a stabilizing effect on the durability of pellets. The emissions of acidic anhydrides into the atmosphere from the combustion of pellets from waste biomass were lower for NO, NO2, NOx and H2S than emissions from the combustion of willow pellets. Obtained emission results suggest the need to further optimize the combustion process parameters.