• Energy Research
• 2016-2025close

he present study investigates the air-steam gasification of ten commercial and alternative lignocellulosic biomass fuels (pine sawdust, chestnut sawdust, torrefied pine sawdust, torrefied chestnut sawdust, almond shells, cocoa shells, grape pomace, olive stones, pine kernel shells and pine cone leafs) in order to evaluate the product gas composition and the process performance in a bubbling fluidized bed gasifier with focus on the different biomass properties. Accordingly, an effort to correlate the biomass characteristics with the gasification results has been done. Pine kernel shell (PKS) was used to test the effect of the gasification temperature (700, 800 and 900 °C), steam to air ratio in the gasifying agent (S/A = 10/90, 25/75, 50/50 and 70/30) and stoichiometric ratio (SR = 0.13 and 0.25) on the product gas composition, combustible gas (H2 + CO + CH4) production, H2/CO ratio, heating value, energy yield and cold gas efficiency of the obtained gas. Results showed that higher temperature and S/A ratio favored H2 production and gasification performance. A higher value of SR slightly affected the gas composition, but led to a higher process efficiency as a consequence of a higher biomass conversion into gaseous combustible products. All the biomass samples of different origin and characteristics were then gasified at the best experimental conditions found (900 °C, S/A = 70/30, SR = 0.25). Gasification of all the biomasses was feasible and H2 and combustible gas concentrations of 30–39 vol% and 59–78 vol% (inert gas-free basis), respectively, were obtained for the biomasses studied, with energy yields of 8–18 MJ/kgbiomass. Torrefied biomass showed similar combustible gas production than the corresponding raw biomass under the conditions studied, but it gave slightly higher H2 production and efficiency results. Possible correlations of the gasification performance parameters with biomass properties were also analyzed. The results showed positive effects of biomass volatile matter content, C content and high heating value (HHV) on the CO and combustible gas contents, calorific value of the product gas, as well as gas and energy yields. This work has received financial support from the Spanish MINECO (ENE2014-53515-P), cofinanced by the European Regional Development Fund (ERDF). M.P. González-Vázquez acknowledges a fellowship awarded by the Spanish MINECO (FPI program), cofinanced by the European Social Fund. Peer reviewed

Investigation into clean energies has been focused on finding an alternative to fossil fuels in order to reduce global warming while at the same time satisfying the world’s energy needs. Biomass gasification is seen as a promising thermochemical conversion technology as it allows useful gaseous products to be obtained from low-energy-density solid fuels. Air–steam mixtures are the most commonly used gasification agents. The gasification performances of several biomass samples and their mixtures were compared. One softwood (pine) and one hardwood (chestnut), their torrefied counterparts, and other Spanish-based biomass wastes such as almond shell, olive stone, grape and olive pomaces or cocoa shell were tested, and their behaviors at several different stoichiometric ratios (SR) and steam/air ratios (S/A) were compared. The optimum SR was found to be in the 0.2–0.3 range for S/A = 75/25. At these conditions a syngas stream with 35% of H2 + CO and a gas yield of 2 L gas/g fuel were obtained, which represents a cold-gas efficiency of almost 50%. The torrefaction process does not significantly affect the quality of the product syngas. Some of the obtained chars were analyzed to assess their use as precursors for catalysts, combustion fuel or for agricultural purposes such as soil amendment.

This study provides essential information related to the nutrient and carbon levels and the energy potential of Eucalytpus nitens (Deane & Maiden) Maiden bionenergy plantations located in northwestern Spain. Nutritional analysis showed that leaves and bark had the highest concentrations of N, P, K and Mg. Carbon concentration was constant for all above-ground tree components. Nutrients and carbon were analyzed at stand level according to plantation productivity. Stemwood, the main tree component at the end of the rotation, had the highest nutrient content, except for N and Ca, which were highest in leaves and bark respectively. Based on this study, the nutrient content per ha of above-ground biomass was 243-706 kg N, 44-122 kg P, 131-375 kg K, 121-329 kg Ca and 25-67 kg Mg at the end of the bioenergy rotation (6-12 years, depending on site quality) and 19-56 Mg C ha-1. Energy analysis showed a fairly constant Net Calorific Value for wood, 18.32 ± 0.19 MJ kg-1. The results obtained are valuable for selecting the most appropriate forest management system in these bioenergy plantations, and thereby promote the sustainable use of woody crops.

Traditional methods to develop biomass-based carbon adsorbents generally involve carbonization followed by chemical or physical activation. However, routes involving the hydrothermal treatment of biomass are receiving growing interest. In this work, two different strategies for the synthesis of sustainable CO2 adsorbents are compared, i.e., in situ ionic activation and hydrothermal treatment followed by activation with CO2. The latter is a green and simple procedure that does not require the addition of chemicals or acid-washing stages, and which leads to carbon adsorbents with relatively high CO2 adsorption capacity at low pressures, up to 0.64 mmol g−1 at 15 kPa and 50 °C, conditions relevant for postcombustion CO2 capture applications. On the other hand, in situ ionic activation can lead to carbon adsorbents with superior CO2 adsorption capacity in the aforementioned conditions, 0.78 mmol g−1, and with reduced cost and environmental impact compared to conventional chemical activation.

Coal as a fossil fuel has long been used for a variety of industrial and domestic purposes. The worldwide distribution and widespread availability of coal resources have been a major contributor to the economic growth of many countries, either directly through their own resources or indirectly through access to the international coal trade. Alhough coal usage has continued to increase, environmental concerns and changes in the political climate have begun to give coal an unfavorable public image. Increasing concerns about coal utilization as a contributor to greenhouse gas emissions, particularly CO2, have led to more intense questioning of the role of coal and a renewed search for alternative energy sources. Despite this coal will remain the second largest energy source worldwide in the next years and a key feedstock for other industrial usages. Coal has been thoroughly researched over the years to the point where all its characteristics and properties that make it such a versatile product are known. This chapter describes and summarizes the general knowledge acquired about coal in relation to its formation, worldwide resources and reserves, composition and properties, and all the characteristics relevant for describing the quality of a coal when it is used in the main conversion processes: combustion, gasification, and cokemaking.

Woody biomass pellets' demand for primary energy production is increasing. To guarantee sustainable and cost-efficient pellet production the diversification of biomass feedstock is mandatory. In this work it is proposed to re-use the solid biochar obtained from pyrolysis of eucalyptus (PEc) at 700 °C as an additive to produce enhanced pine sawdust (PIN) pellets. The process required the addition of glycerol as a lubricant in a percentage of 1 and 2 wt% per 5 and 10 wt% of pyrolyzed eucalyptus in the blend, respectively. Small additions of PEc enhanced PIN pellets’ grindability and water-resistance, providing products with remarkable values of durability (up to 99%), net calorific value (up to 20 MJ/kg), energy density (up to 13.3 GJ/m3), and particle density (up to 1.24 g/cm3). N, S, chlorine, and heavy metals contents were also analyzed. The proposed pellets fulfill the A1/A2 and the I1/I2 quality classes for domestic and industrial wood pellets, respectively. A preliminary economic evaluation indicated that pellets made up from a mixture of 90% PIN and 10% PEc are competitive compared to raw PIN pellets, with expected savings in the costs of production, energy, transport, and construction of a storage site of 4, 13, 10 and 7%, respectively. This work was carried out with financial support from the Gobierno del Principado de Asturias (PCTI, Ref. IDI/2018/000115), co-financed by the European Regional Development Fund (ERDF). M.V. Gil acknowledges support from a Ramón y Cajal grant (RYC-2017-21937) of the Spanish Government and the Spanish State Research Agency, co-financed by the European Social Fund (ESF). Peer reviewed

Energy generation from non-hazardous waste streams, which are unfeasible to be reused or recycled, can help overcome some of the problems related to fossil fuel depletion, global increase in energy demand and waste generation management under restricted landfilling. One of the main drawbacks of waste-to-energy strategies is the poor combustion properties of waste, which densification could help to circumvent. This work studies the co-pelletization of refused derived fuel (RDF) and pine sawdust (PIN) in a continuous pilot pellet mill that resembles industrial pelletization. The effect of RDF contents up to 90 wt% on a set of parameters has been assessed: pelletization energy consumption, physical properties (durability, particle and bulk densities), net calorific value and energy density of the obtained pellets. In addition, slagging, fouling and corrosion, phenomena associated with combustion, were estimated from the ash composition. Results showed that obtaining pellets with a low RDF loading (2–9 wt%) was feasible. They accomplished ISO 17225-2 solid biofuels standard for industrial use, and presented low deposition and corrosion risks. On the other hand, pellets with 30–90 wt% RDF were also manufactured and complied with the UNE-EN 15359:2012 solid recovered-fuel standard for energy recovery in incineration and co-incineration plants. All the produced pellets presented durability and net calorific value above 96.9% and 10.7 MJ/kg, respectively. Energy density higher than 10.6 GJ/m3 was obtained for pellet formulations with RDF content up to 50 wt%. It was demonstrated that the blends of RDF and PIN can provide high-quality pellets with a high load of waste material, under the same operational conditions required for PIN pelletization. It is a versatile process that can be tailored to different product requirements depending on the end-use. It promotes energy recovery and generates value out of a waste fraction with no relevant use, adding economic and environmental benefits. This work was carried out with financial support from the Gobierno del Principado de Asturias (PCTI, Ref. IDI/2018/000115), co-financed by the European Regional Development Fund (ERDF) and from the CSIC (Project PIE, Ref. 202080E115). M.V. Gil acknowledges support from a Ramon y Cajal grant (RYC-2017-21937) of the Spanish Government and the Spanish State Research Agency, co-financed by the European Social Fund (ESF). Peer reviewed