Global warming concerns have driven developments in carbon neutral energy, pulling initiatives on biofuels production. However, the low bulk density and low specific energy of biomass refrain its ...widespread use due to logistic costs comprising harvesting and collection, storage, pretreatments and transportation. This work approaches increasing land energy productivity by thermochemical conversion of residual biomass to energy products, identifying the best options in terms of energy efficiency and economic indicators. Techno-economic performance of three corncob-to-energy pathways is investigated: gasification to methanol, fast pyrolysis to bio-oil and combustion to electricity. Fast pyrolysis allows higher energy recovery in its products (79%) than biomass gasification to methanol (53%), with biomass densification (volume reduction) of 72.7% and 86.2%, respectively. The combustion route presents net efficiency of 30.2% of biomass low heating value (LHV). All alternatives are economically feasible provided biomass cost is lower than US$75.5/t. The minimum allowable product prices for economic attractiveness of gasification, combustion and pyrolysis routes are US$305/t methanol, US$80.1/MWh electricity and US$1.47/gasoline-gallon-equivalent bio-oil. Despite its vulnerability to price volatility, gasification presents the highest net present value, seconded by the combustion route, which has lower medium-term payback and investment than gasification due to its process simplicity.
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•Three thermochemical processes for energy densification of corncob are compared.•Pyrolysis has highest energy efficiency, lowest CO2 emissions and shorter payback.•Net Present Values decrease from combustion to gasification and then pyrolysis.•All Net Present Values are positive provided biomass costs below US$75.50/t.•Bio-oil price above US$18/t renders pyrolysis the best economic alternative.
Biomass is the only source on earth that can store solar energy in the chemical bond during its growth. This stored energy can be utilized by means of thermochemical conversion of biomass. ...Gasification is one of the promising thermochemical conversion technologies, which converts biomass to burnable gases, often termed as producer gas. Major components of this gas are hydrogen, carbon monoxide and methane. Depending on the purity, this gas can be used in the furnace for heat generation and in the internal combustion engine and fuel cell for power generation or it can be converted to liquid hydrocarbon fuels and chemicals via the Fischer–Tropsch synthesis method. Despite numerous applications of the biomass gasification gas, it is still under developing stage due to some severe technological challenges. Impurities such as tar, particulate matters and poisonous gases including ammonia, hydrochloric acid and sulfur gases, which are unavoidably produced during gasification, create severe problems in downstream applications. Therefore, the cleaning of producer gas is essential before being utilized. However, the conventional physical filtration is not a technically and environmentally viable process for gasification gas cleaning. The utilization of catalyst for hot gas cleaning is one of the most popular technologies for gas cleaning. The catalyst bed can reform tar molecules to gas on the one hand and destroy or adsorb poisonous gases and particulates on the other hand, so as to produce clean gas. However, numerous criteria need to be considered to select the suitable catalyst for commercial use. In this review, the advantages and disadvantages of different gas cleaning methods are critically discussed and concluded that the catalytic hot gas cleaning with highly efficient catalyst is the most viable options for large-scale production of clean producer gas.
This work contrasted gaseous emissions of carbon, sulfur and nitrogen oxides from combustion of several types of biomass including woody, herbaceous and crop-derived wastes, pulverized in the size ...range of 75–150μm. Both raw and torrefied biomass were exposed to high heating rates (104–105K/s) in a laboratory-scale electrically-heated drop-tube furnace, operated at 1400K. Combustion occurred under fuel-lean conditions. Torrefied biomass has lower volatile matter content, higher fixed carbon content and higher heating value than raw biomass. Results revealed that (a) CO2 emission factors from torrefied biomass were higher than those from raw biomass, reflecting the higher carbon content of the former, however there was no uniform trend in emission factors (kg/GJ); (b) SO2 emission factors of torrefied biomass were lower than those from raw biomass, even if some torrefied biomass types contained higher sulfur mass fractions than their raw biomass precursors. All raw and torrefied biomass, with one exemption, generated lower SO2 emission factors than a typical sub-bituminous coal; (c) torrefied biomass has higher fuel-nitrogen mass fractions than their raw biomass precursors; however, there was no clear trend in NOx emission factors between raw and torrefied biomass, as torrefied herbaceous and woody biomass types generated higher while torrefied crop biomass types generated lower emission factors than their raw biomass precursors. Comparing with the sub-bituminous coal, some raw and torrefied biomass types generated lower and some higher NOx emission factors. Overall, combustion of most types of biomass, either in raw or torrefied state, can result in lower SO2 and NOx emissions factors than those of typical western US sub-bituminous coals while, in principle, generating minimal net emissions of carbon.
•A model based minimizing Gibbs free energy was developed.•The downdraft biomass gasification process has been modeled with Aspen Plus.•The model was successfully validated with the experimental ...data.•Sensitivity analysis and error analysis was also performed.
Thermo-chemical conversion of biomass has been regarded as one of attractive routes of producing the clean and environmental friendly bio-fuels. Downdraft biomass gasification process has been served as a key technology to provide the bio-syngas with high quality, which can be used to produce the renewable liquid transportation fuels through Fischer Tropsch Synthesis in Mississippi State University. In order to provide the performance data of the integrated Biomass to Liquid system and future process optimization, a comprehensive model of the downdraft biomass gasification process based on Aspen Plus by minimizing Gibbs free energy with restricting chemical reaction equilibrium in the gasification reduction zone has been developed. The model was successfully validated with the experimental data from the hardwood chips gasification. Sensitivity analysis was also performed to investigate the effects of gasification temperature, equivalence ratio, and biomass moisture content on the quality of bio-syngas. All the investigated factors have been found with a significant effect.
•Composition of eight biomass ashes (BAs) produced at 500 and 900 °C was characterized.•Carbonation and decarbonation of BAs were described.•3Extra CO2 capture and storage by carbonation of BAs was ...elucidated.
Eight biomass ashes (BAs) produced at 500 and 900 °C were studied to definite their composition, phase transformations, carbonation-decarbonation behavior, and CO2 capture and storage (CCS) potential. Light microscopy, powder X-ray diffraction, scanning electron microscopy, as well as differential-thermal, thermo-gravimetric and chemical analyses were used for that purpose. It was found that most of the BAs studied have high contents of alkaline-earth and alkaline elements represented by carbonates, bicarbonates, oxyhydroxides, chlorides, sulphates, phosphates, and inorganic amorphous material, and such minerals and phases have a key role for CCS by BA. There is an intensive formation of newly formed carbonates as a result of solid–gas reactions between alkaline-earth and alkaline oxyhydroxides and volatile CO2 formed during biomass combustion. Subsequently, additional post-combustion carbonates and bicarbonates are formed by both solid–gas and solid-liquid reactions between the unreacted oxyhydroxides and carbonates in BA and CO2 occurring in air and water during BA storage. The decomposition temperature of carbonates is mostly at 600–900 °C and the mass loss measured in this temperature range approximately determines the CO2 volatilization from the carbonates in BAs. The measured CO2 volatilization (or CCS) for the BAs studied is between 1 and 27% (mean 11%). It was emphasized that the biomass energy can be not only carbon-neutral, but also with some extra CCS potential due to fixation and immobilization of atmospheric CO2 in BA. Therefore, the future large-scale bioenergy production can contribute enormously for reducing CO2 emissions and can decrease or eliminate the application of expensive technologies for CCS.
Biomass combustion is technologically difficult. It is also problematic because of the necessity to manage the ash that is generated in the process. The combustion of biomass pellets is optimum when ...their moisture is 6–8%. The calorific value of pellets made from straw and willow wood (4:1) was 17.3–20.1 MJ∙kg−1. There were serious problems with burning this material caused by the accumulation and melting of bottom ash on the grate, which damaged the furnace. These problems with optimizing the biomass combustion process resulted in increased CO emissions into the atmosphere. It was shown that pelletization could also be used to consolidate the ash generated during the combustion process, which would eliminate secondary dust during transport to the utilization site. For this purpose, it was suggested to add binding substances such as bentonite and bran. The analysis showed that an optimum material for pelletization should contain, on average, 880 g of ash, 120 g of bentonite, 108 g of bran, and 130 g of water.
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•Biomass processing using advanced thermochemical conversion techniques.•Properties of fuels for energy production from biomass have been discussed.•For energy generation, different ...types of waste are discussed comprehensively.•The merits and demerits of thermochemical conversion techniques summarized.
The commercial conquest of the ethanol industry has raised curiosity within operations that transform biomass into biofuels. The energy production from biomass, bioenergy, is an outlook conception to substitute fossil fuels in the coming days, as it is productive, pure, and carbon dioxide neutral. Biomass may be combusted instantly to cause heat and power and employ advanced thermochemical techniques. It can be restored within bio-fuels in solid, liquid, and gas constitutions that may be utilized additionally towards heat and energy production. Here, in this review article, we have discussed the properties of biomass fuels, sustainability attention towards energy production from biomass along with different types of wastes to energy generation, and the advanced thermochemical conversion technologies that can be used for energy production from wastes. In the last, we have compared the advantages and drawbacks of these technologies and concluded our article with current challenges and future perspectives in this field.
Elevated nitrogen (N) deposition may increase net primary productivity in N‐limited terrestrial ecosystems and thus enhance the terrestrial carbon (C) sink. To assess the magnitude of this N‐induced ...C sink, we performed a meta‐analysis on data from forest fertilization experiments to estimate N‐induced C sequestration in aboveground tree woody biomass, a stable C pool with long turnover times. Our results show that boreal and temperate forests responded strongly to N addition and sequestered on average an additional 14 and 13 kg C per kg N in aboveground woody biomass, respectively. Tropical forests, however, did not respond significantly to N addition. The common hypothesis that tropical forests do not respond to N because they are phosphorus‐limited could not be confirmed, as we found no significant response to phosphorus addition in tropical forests. Across climate zones, we found that young forests responded more strongly to N addition, which is important as many previous meta‐analyses of N addition experiments rely heavily on data from experiments on seedlings and young trees. Furthermore, the C–N response (defined as additional mass unit of C sequestered per additional mass unit of N addition) was affected by forest productivity, experimental N addition rate, and rate of ambient N deposition. The estimated C–N responses from our meta‐analysis were generally lower that those derived with stoichiometric scaling, dynamic global vegetation models, and forest growth inventories along N deposition gradients. We estimated N‐induced global C sequestration in tree aboveground woody biomass by multiplying the C–N responses obtained from the meta‐analysis with N deposition estimates per biome. We thus derived an N‐induced global C sink of about 177 (112–243) Tg C/year in aboveground and belowground woody biomass, which would account for about 12% of the forest biomass C sink (1,400 Tg C/year).
To estimate whether nitrogen addition leads to additional carbon sequestration in forests, we performed a meta‐analysis of forest fertilization experiments that measure woody biomass increment following nitrogen addition. We found that nitrogen addition leads to additional carbon sequestration in tree aboveground woody biomass in boreal and temperate forests (13–14 kilogram carbon per kilogram nitrogen), but not in tropical forests. Younger forests generally responded more strongly to nitrogen addition than older forests. Using an upscaling approach, we estimate that nitrogen deposition globally leads to additional C sequestration in forest woody biomass of about 177 Tg C/year.
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