Input Feedstock Research Articles

Characteristics of on-demand biogas production by using sugar beet silage

On-demand electricity generation can be achieved by just-in-time biogas production instantly utilized in co-generation units. For this goal, easily degradable substrates like sugar beet silage have a high potential.Potential for on-demand biogas production from co-digestion of sugar beet silage (SS) with grass silage (GS) was evaluated in two experiments at organic loading rates (OLRs) of 1.5 kgVS m−3 day−1 and 2.5 kgVS m−3 day−1, respectively. Each experiment was fed with intermittent feeding system at 8 hrs interval at the same feedstock ratios (volatile solids based) of GS:SS-1:0, 3:1 and 1:3, respectively. Modelling by Gaussian equation was performed in order to understand the effects of SS on biogas production.Addition of sugar beet silage led to maximum biogas production within a short time, but it differed significantly depending on feedstock ratios and OLRs, respectively. At OLR 1.5 kgVS m−3 day−1, during mono fermentation of grass silage maximum biogas production rate of 0.27 lN hr−1 was reached at 2.74 hrs. Production rate did not change at feedstock ratio of GS:SS-3:1 but increased to 0.64 lN hr−1 at GS:SS-1:3 within a shorter time span (1.58 hrs). On the contrary, at OLR of 2.5 kgVS m−3 day−1 time span between feedstock input and maximum biogas production did not differ significantly (p > 0.05) among the reactors. Biogas production rates were 0.60 lN hr−1 within 2.27 hrs and 0.82 lN hr−1 within 2.30 hrs at GS:SS-3:1 and GS:SS-1:3, respectively.Surprisingly, there was no time lag between maximum biogas and methane production rates, irrespectively of OLR. This implies that once the whole microbial community is adapted to intermittent substrate input, the metabolic products are instantly utilized through the all steps of anaerobic substrate degradation. Applying this finding opens new perspectives for on-demand biogas energy production.

Dry anaerobic digestion of cow manure and agricultural products in a full-scale plant: Efficiency and comparison with wet fermentation

For years, anaerobic digestion processes have been implemented for the management of organic wastes, agricultural residues, and animal manure. Wet anaerobic digestion still represents the most common technology, while dry fermentation, dedicated to the treatment of solid inputs (TS>20%) can be considered as an emerging technology, not in terms of technological maturity, but of diffusion. The first agricultural dry anaerobic digestion plant constructed in Italy was monitored from the start-up, for over a year. The plant was fed with manure and agricultural products, such as corn silage, triticale, ryegrass, alfalfa, and straw. Three Combined Heat and Power units, for a total installed power of 910kWe, converted biogas into thermal and electric energy. The monitoring included the determination of quality and quantity of input feedstocks, of digestate (including recirculation rate), of leachate, biogas quality (CH4, CO2, H2S), biogas yield, energy production, labor requirement for loading, and unloading operations. The results of the monitoring were compared to performance data obtained in several full scale wet digestion plants. The dry fermentation plant revealed a start-up phase that lasted several months, during which the average power resulted in 641kWe (70.4% of nominal power), and the last period the power resulted in 788kWe (86.6% of installed power). Improving the balance of the input, the dry fermentation process demonstrated biogas yields similar to wet anaerobic digestion, congruent to the energy potential of the biomasses used in the process. Furthermore, the operation of the plant required significant man labor, mainly related to loading and unloading of the anaerobic cells.

Anaerobic co-digestion of recalcitrant agricultural wastes: Characterizing of biochemical parameters of digestate and its impacts on soil ecosystem

Anaerobic digestion (AD) of organic wastes is a promising alternative to landfilling for reducing Greenhouse Gas Emission (GHG) and it is encouraged by current regulation in Europe. Biogas-AD produced, represents a useful source of green energy, while its by-product (digestate) is a waste, that needs to be safely disposal. The sustainability of anaerobic digestion plants partly depends on the management of their digestion residues. This study has been focused on the environmental and economic benefits of co-digest recalcitrant agricultural wastes such olive wastes and citrus pulp, in combination with livestock wastes, straw and cheese whey for biogas production. The aim of this work was to investigate the effects of two different bioenergy by-products on soil carbon stock, enzymes involved in nutrient cycling and microbial content. The two digestates were obtained from two plants differently fed: the first plant (Uliva) was powered with 60% of recalcitrant agricultural wastes, and 40% of livestock manure milk serum and maize silage. The second one (Fattoria) was fed with 40% of recalcitrant agricultural wastes and 60% of livestock manure, milk serum and maize silage. Each digestate, separated in liquid and solid fractions, was added to the soil at different concentrations. Our results evidenced that mixing and type of input feedstock affected the composition of digestates. Three months after treatments, our results showed that changes in soil chemical and biochemical characteristics depended on the source of digestate, the type of fraction and the concentration used. The mainly affected soil parameters were: Soil Organic Matter (SOM), Microbial Biomass Carbon (MBC), Fluorescein Diacetate Hydrolysis (FDA), Water Soluble Phenol (WSP) and Catalase (CAT) that can be used to assess the digestate agronomical feasibility. These results show that the agronomic quality of a digestate is strictly dependent on percentage and type of feedstocks that will be used to power the digester.

Numerical simulation of multi-rifled tube drawing – finding proper feedstock dimensions and tool geometry

Production of multi-rifled seamless steel tubes is quite a new technology in Železiarne Podbrezová. Therefore, a lot of technological questions emerges (process technology, input feedstock dimensions, material flow during drawing, etc.) Pilot experiments to fine tune the process cost a lot of time and energy. For this, numerical simulation would be an alternative solution for achieving optimal parameters in production technology. This would reduce the number of experiments needed, lowering the overall costs of development. However, to claim the numerical results to be relevant it is necessary to verify them against the actual plant trials. Searching for optimal input feedstock dimension for drawing of multi-rifled tube with dimensions Ø28.6 mm × 6.3 mm is what makes the main topic of this paper. As a secondary task, effective position of the plug – die couple has been solved via numerical simulation. Comparing the calculated results with actual numbers from plant trials a good agreement was observed.

English

A case study of an innovative medium sized commercial-industrial bioenergy plant is portrayed. This plant effectively runs on various agricultural waste feedstocks like; animal-manure, vegetable, poultry and sugar wastes etc. The plant design is based on anaerobic fixed dome triple digester system connected via underground lagoon. Thus system is facilitating continuous flow of the input feedstock capacity up-to four tonnes per day. This modern scheme is built on innovation with the inclusion of mechanical stirrers, gas scrubbers, filtration, compression and storage systems. This research paper highlighted the potential techno-economic impacts of such bioenergy plant for the energy stressed small-medium industrial sector in developing countries like Pakistan. It has the capability of 142 MWh energy generations per year; rate of return 15.42% and employment growth prospects in SME sector up-to 55%.

A review on the global warming potential of cleaner composting and mitigation strategies

With the rapid population growth and industrial development in the fast developing countries, there is a significant increase in the production of waste. For instance, the municipal solid waste in Malaysia is expected to exceed 9 Mt/y by 2020 based on the current production rate of 1 kg−1 person−1. Approximately 90% of the waste is channelled into the landfill that can release a significant amount of greenhouse gases, mainly the methane gas and nitrous oxide gases, due to the anaerobic decomposition of organic matter. Composting is a cleaner alternative to landfilling for managing organic waste. Its main advantage lies in its capability to recycle nutrients through compost utilisation. The life cycle assessment has been widely used as a mean of comparison for impact assessment, such as global warming potential, among different waste management technologies. The common inventories accounted for composting include transportation, operational machineries, fugitive emissions during maturation and curing as well as the end production utilisation. There is inconsistency in the methodology adopted to assess its environmental impact. This study discusses on the variations of life cycle assessment that contributed to the different global warming potential of composting. It also discusses on the mitigation strategies to reduce the global warming potential for composting. The highlight of the study is to examine the variation in the inventory analysis for composting, and its underlying mechanism and the critical inventory for a more representative assessment. The second part of the paper reviews the mitigation strategies for reducing the greenhouse gas emissions, i.e. the use of the bulking agent, aeration system, chemical additives and use of the cover material. This study found that the direct greenhouse gas emissions during composting contribute more significantly to the global warming potential than other direct emissions. The use of bulking agent is desirable to reduce the global warming potential. This study concludes that the assessment of the global warming potential for composting is dependent on the system boundary and the defined functional unit. The environmental impact should be assessed based on the operational mode and the input feedstock to generate a basis with minimised discrepancies among studies. Continuous effort is needed to quantify the long-term benefits of composting on environment, health and soil to further assess its impact as a cleaner process.

Changing old habits: The case of feeding patterns in anaerobic digesters

A non-linear programming model was developed to maximize the economic profit from an anaerobic co-digester. The model consists of a combination of technical and economic equations, linked through the biogas production variable. Five scenarios were simulated. These differed with regard to substrate inlet mass flow rate, organic loading rate and hydraulic retention time. The impact on biogas production was investigated and an economic analysis was undertaken based on the concepts of profitability and Net Present Value. The model results indicate that varying the substrate inlet mass flow rate and organic loading rate could have a positive impact on the profitability of co-digesters in Flanders. This can be achieved either by increasing the interval time between feedstock input, or by feeding individual streams of feedstock separately into the system, while at the same time reducing the hydraulic retention time.

Toxicological challenges to microbial bioethanol production and strategies for improved tolerance.

Bioethanol production output has increased steadily over the last two decades and is now beginning to become competitive with traditional liquid transportation fuels due to advances in engineering, the identification of new production host organisms, and the development of novel biodesign strategies. A significant portion of these efforts has been dedicated to mitigating the toxicological challenges encountered across the bioethanol production process. From the release of potentially cytotoxic or inhibitory compounds from input feedstocks, through the metabolic co-synthesis of ethanol and potentially detrimental byproducts, and to the potential cytotoxicity of ethanol itself, each stage of bioethanol production requires the application of genetic or engineering controls that ensure the host organisms remain healthy and productive to meet the necessary economies required for large scale production. In addition, as production levels continue to increase, there is an escalating focus on the detoxification of the resulting waste streams to minimize their environmental impact. This review will present the major toxicological challenges encountered throughout each stage of the bioethanol production process and the commonly employed strategies for reducing or eliminating potential toxic effects.

Impact of local conditions on bio‐based chemical process design: selection of input feedstock and production scale and scenario

Economic incentive is an important driving force for the implementation of bio‐based chemical industry. The economic performance of a bio‐based chemical process is influenced strongly by the input biomass feedstock and production scale and scenario that must be selected with respect to the local conditions, such as the availability, distribution, and transportation distance of biomass feedstocks, which differ according to regional productivity, regional production scale, and geographical distribution of biomass resources. In this study, by assessing the economic indicator, we examine the impact of local conditions on the selection of input feedstock and production scale and scenario on the design of bio‐based chemical processes. Considering the local conditions of Vietnam and Japan, the economic performance of a bio‐based chemical process producing ethyl acetate is evaluated. The results show that the conditions in Vietnam, which has low productivity and wide distribution of biomass feedstocks, have a stronger impact on the economic viability of bio‐based chemical plants. In Japan, fewer options for feedstock selection are provided, but larger production scale and lower production cost can be achieved. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 174–182, 2016

Solar Hybridized Coal-to-liquids via Gasification in Australia: Techno-economic Assessment

The concept of solar hybridised coal-to-liquids is to produce transportation liquid fuels from the syngas obtained from gasification ofcarbonaceous feedstocks with the integration of concentrated solar thermal power (CSP). In the present study, a techno-economic evaluation of a coal-to-liquids processes integrated with a solar hybridised, oxygen blown, atmospheric pressure vortex-flow gasifier (SCTL) is compared with that of a reference, non-solar, pressurised entrained flow gasifier (CTL) based on the solar and coal resources in Australia. In comparison with conventional gasification systems, the proposed SCTL system reduces the input feedstock by 18% while maintaining the Fischer-Tropsch (FT) liquids output.Furthermore, with the addition of CSP to the CTL plant, a reduction in mine-to-tank (MTT) CO2 emissions by 26% can be achieved. This is due to the fact that the heat required to meet the endothermic gasification reactions is supplied by CSP when the sun is available, thus more coal was converted to syngas subsequently higher FT liquids. To produce 1500 barrel per day of FT liquids,the total permanent investment cost for the SCTL plant was estimated to be around $467-$493 million, depending on the solar site and the coal compared with the CTL plant of around $377-$384 million if the plant was to be built in year 2020. The levelised cost of fuel (LCOF) for the CTL plants was found to be around $40-$41/GJLHV and $46-$49/GJLHV for the SCTL plants. The LCOF for the plants is very sensitive to the total permanent investment cost, load factor and cost of carbon capture and sequestration. Furthermore, the LCOF for the SCTL plant is also very sensitive to the cost of the syngas storage.

Heat transfer mechanisms in poplar wood undergoing torrefaction

Torrefaction, a thermal treatment process of biomass, has been proved to improve biomass combustible properties. Torrefaction is defined as a thermochemical process in reduced oxygen condition and at temperature range from 200 to 300 °C for shorter residence time whereby energy yield is maximized, can be a bridging technology that can lead the conventional system (e.g. coal-fired plants) towards a sustainable energy system. In efforts to develop a commercial operable torrefaction reactor, the present study examines the minimum input condition at which biomass is torrefied and explores the heat transfer mechanisms during torrefaction in poplar wood samples. The heat transfer through the wood sample is numerically modeled and analyzed. Each poplar wood is torrefied at temperature of 250, 270, and 300 °C. The experimental study shows that the 270 °C-treatment can be deduced as the optimal input condition for torrefaction of poplar wood. A good understanding of heat transfer mechanisms can facilitate the upscaling and downscaling of torrefaction process equipment to fit the feedstock input criteria and can help to develop treatment input specifications that can maximize process efficiency.

Assessing development and commercialization priorities for a novel hydrogen production process through technical-economic cost modeling

Technology management tools are needed to guide early-stage commercialization decisions and research and development (R&D) prioritization for the development of novel processes associated with materials innovations. We demonstrate the technical-economic cost modeling (TCM) methodology to model the economics of production scale-up of lab and pilot scale technology, and to analyse the feasibility of commercialization. We describe an innovative process for efficiently producing pure hydrogen—the fluidized bed membrane reactor (FBMR) process—and assess viable market segments and R&D priorities. Through TCM analysis, we find that small volume production (5000 kg d−1 or less) is viable for hydrogen production by FBMR today, and that future R&D should focus on increasing pressure handling capabilities rather than reducing the membrane thickness. Through sensitivity analysis, we find that unit cost is most sensitive to input feedstock costs and palladium membrane life rather than energy input or membrane flux. We demonstrate that the TCM methodology, through tighter integration of technical process limitations to production and cost variables, is useful to guide commercialization decisions for novel lab-scale production processes.

Effects of anaerobic digestion on soil carbon and nitrogen turnover, N emissions, and soil biological activity. A review

Sustainability in agriculture means the inclusion of several aspects, as sustainable agriculture systems must not compromise not only their ability to satisfy future needs by undermining soil fertility and the natural resource base but also sustainable agriculture has had to address a range of other issues including energy use, efficient use, and recycling of nutrients, the effects on adjacent ecosystems including the effects on water bodies and climate change. Organic manures are an important factor to keep the soil fertility level of soils. However, their management is often related to large emissions. In this context, anaerobic digestion is—similarly to composting—a treatment option for stabilization of biogenic wastes leading to a residual product called digestates, enabling the sanitation and the recycling and use as fertilizer. It is also a means to obtain energy from wastes as well as from dedicated energy crops. Therefore, anaerobic digestion potentially addresses several aspects of agricultural sustainability. This review discusses the current state of knowledge on the effects of anaerobic digestion on organic compounds in digestates and the most important processes influencing N emissions in the field, as well as the possible long-term effects on soil microbial biomass and soil fertility. The main findings are that (1) the direct effects of anaerobic digestion on long-term sustainability in terms of soil fertility and environmental impact at the field level are of minor relevance. (2) The most relevant effects of anaerobic digestion on soil fertility as well as on N emissions will be expected from indirect effects related to cropping system changes such as changes in crop rotation, crop acreage, cover cropping, and total amounts of organic manures including digestates. Furthermore, (3) the remaining organic fraction after anaerobic digestion is much more recalcitrant than the input feedstocks leading to a stabilization of the organic matter and a lower organic matter degradation rate after field application, enabling a similar reproduction of the soil organic matter as obtained by direct application of the feedstock or by composting of the feedstock. (4) Regarding emissions, the main direct effect of anaerobic digestion on a farm level is the influence on gaseous emissions during manure or digestate treatment and handling, whereas the direct effects of anaerobic digestion on a field level on emissions (NH3 − and N2O− emissions, NO3 - leaching) are negligible or at least ambiguous. (5) The main direct effects of anaerobic digestion on the field level are short-term effects on soil microbial activity and changes in the soil microbial community. Therefore, in terms of the effects on agricultural sustainability, potential cropping system-based changes induced by introduction of biogas plants are probably much more relevant for the overall performance and sustainability of the cropping system than the direct effects triggered by application of digestates in comparison to the undigested feedstocks. Furthermore, to get the full potential advances from implementation of biogas plants in terms of improvement of the nutrient use efficiency and reduction of greenhouse gas emissions, there is the need to introduce more sophisticated techniques to avoid counteracting effects by pollution swapping, e.g., by gas-tight closure of the digestate stores and direct soil incorporation of the field-applied digestates.

A Geographic Information Systems Program to Optimize Feedstock Logistics for Bioenergy Production for Mobile Pyrolysis Units

<abstract><title><italic>Abstract.</italic></title> A comprehensive decision-making tool was developed to optimize the use of a fleet of mobile pyrolysis units in the North Central region of the U.S. to produce bio-oil from agricultural feedstocks. The concept is to use mobile pyrolysis units to convert low-density biomass to high-density bio-oil to minimize the cost of feedstock logistics. The feedstocks evaluated in this project included corn stover, energy sorghum, and switchgrass. It was assumed that (1) energy sorghum would replace grain sorghum and (2) switchgrass would be grown on Conservation Reserve Program (CRP) land. A Geographic Information System (GIS) program was developed to optimize the movement of mobile pyrolysis units based on an analysis of transportation networks, cropping patterns, feedstock production rates, and oil refinery locations in the North Central region. The locations of existing corn, sorghum, and CRP fields in the North Central region were obtained from the USDA National Agricultural Statistics Service (NASS). Model Builder, a utility in ArcGIS, was used to automate the GIS procedures. Network Analysis, an extension of ArcGIS, was used to find the best route to move the mobile pyrolysis units to new locations and to identify the nearest refinery to receive the bio-crude oil. The feedstock input rate for each mobile pyrolysis unit was assumed to be 40 tons/day.

A spatially explicit techno‐economic assessment of green biorefinery concepts

AbstractBiorefineries are seen as a key component for the transition toward a resource‐efficient, low‐carbon bio‐economy. The green biorefinery (GBR) concept is promoted in several countries to create business and employment opportunities in rural areas. It aims at providing alternative utilization pathways for surplus grassland areas by producing bioenergy, biomaterials, livestock feed, and organic acids. We have developed a spatially explicit, mixed integer programming model that maximizes total producer surpluses of GBR supply chains subject to resource endowments by selecting optimal plant locations and sizes. The model is applied to assess the economic viability of three GBR concepts compared to biogas plants. Impacts of uncertain model input parameters on model outputs are analyzed by Monte‐Carlo simulations and regression analysis. The model results reveal that green biorefineries could utilize significantly more biomass than biogas plants, leading to higher regional feedstock prices. Furthermore, the Monte‐Carlo simulation results demonstrate that the economic viability of green biorefineries mainly depends on the selected process layout and the prices of the main products. Under favorable market conditions GBRs are economically viable even without policy support measures with average profits between Ä15 and Ä115 t–1 feedstock input. © 2013 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Strategic value optimization and analysis of multi-product biomass refineries with multiple stakeholder considerations

The commercialization of cellulosic biofuels has been plagued by multiple sources of market and technology uncertainty, and the lack of capital. It is conjectured that government support for renewable fuels’ has concealed the true market value of its producers, and its removal will lead to a slew of enterprise failures destroying significant private and tax-payer wealth. With such uncertainty, it is prudent to carefully evaluate capital investments in new facilities before actual investment is incurred. This paper presents a strategic optimization model for a multi-product biomass refinery that optimizes the long-term value of the facility to its stakeholders while yielding optimal decisions for input feedstock mix, product portfolio, conversion technology and process configuration, and capital structure for financing. The paper promotes the concept of stakeholder value, where actors at different supply chain nodes are included as a part of a co-operative enterprise, as a means to spread risks across the supply chain.

Analysis of Sustainable Cassava Biofuel Production in Nigeria

Nigeria's biofuels policy advocates the adoption of cassava as feedstock for a 10%-biofuel substitution option in Nigerian transport fuel demand. This policy option is expected to address energy security and environmental consequences of using fossil fuels as the sole source of transport energy in the country. This paper appraised the technological and economic factors necessary for achieving Nigeria's cassava-based biofuel initiative at different substitution levels of 5, 10, and 15% by the Year 2020. A multi-stage energy forecasting and project analysis framework adapted from Coate's structure for technology assessment, as well as engineering economy methodology was used for the study. Technological analysis entailed determining petrol consumption projection, R&amp;D capability, input feedstock requirements, environmental considerations and land requirement for feedstock crop production while engineering economy analysis evaluated the economic viability of the project. The results showed that petrol consumption in Nigeria and bioethanol substitution requirements were in the range of 18,285.7 – 19,142.84 thousand tons and 914.28 (5% low demand) – 2871.43 (15% high demand) thousand tons, respectively by 2020. Cassava feedstock and landmass requirements for bioethanol production were in the range of 4.64 – 14.53 million tons and 4.08 – 12.80 thousand sq. km, respectively while carbon dioxide savings were between 1.87 – 5.89 million tons by 2020. The recovery price for cassava bioethanol was estimated to be US$ 0.74/litre [Formula: see text]. Petrol being subsidised presently is harmful to the environment though it ‘oils’ the economy. Nigeria currently subsidizes petroleum products to the tune of 28% of 2011 budget. The government plans to remove this by 2012. Thus we conclude that weighing both economic and environmental benefits of bioethanol substitution in petrol consumption in Nigeria, the study showed that bioethanol production from cassava feedstock would be both technically and economically viable, provided subsidy, which depends on political will on the side of the government, is introduced for the first ten years of its implementation.

Cold flow model investigations of the countercurrent flow of a dual circulating fluidized bed gasifier

A novel fluidized bed gasification concept with enhanced gas–particle interaction combining two circulating fluidized bed reactors is proposed. Cold flow model results show the feasibility of the concept with regard to fluid dynamics. The aim of the design is to generate a nitrogen (N2) free product gas with low tars and fines contents. Therefore, the system is divided into an air/combustion and a fuel/gasification reactor. Two gas streams are obtained separately. The two reactors are interconnected via loop seals to assure the global circulation of bed material and to avoid gas leakages from one reactor to the other. The global circulation rate is driven by the gas velocity in the air/combustion reactor. Furthermore, the fuel/gasification reactor itself is a circulating fluidized bed with the special characteristic of almost countercurrent flow conditions for the gas phase and bed material particles. By simple geometrical modifications, it is possible to achieve well-mixed flow conditions in the fuel/gasification reactor along the full height. The gas velocity and the geometrical properties in the fuel/gasification reactor are chosen in such a way that the entrainment of coarse particles is low at the top. Due to the dispersed downward movement of the bed material particles and the feedstock input at defined locations of the fuel/gasification reactor, no volatiles are produced in the upper regions and the problems of insufficient gas phase conversion and high tar contents are avoided.

Impacts of co‐location, co‐production, and process energy source on life cycle energy use and greenhouse gas emissions of lignocellulosic ethanol

AbstractThe performance of lignocellulosic ethanol in reducing greenhouse gas (GHG) emissions and fossil energy use when substituting for gasoline depends on production technologies and system decisions, many of which have not been considered in life cycle studies. We investigate ethanol production from short rotation forestry feedstock via an uncatalyzed steam explosion pre‐treatment and enzymatic hydrolysis process developed by Mascoma Canada, Inc., and examine a set of production system decisions (co‐location, co‐production, and process energy options) in terms of their influence on life cycle emissions and energy consumption. All production options are found to reduce emissions and petroleum use relative to gasoline on a well‐to‐wheel (WTW) basis; GHG reductions vary by production scenario. Land‐use‐change effects are not included due to a lack of applicable data on short rotation forestry feedstock. Ethanol production with wood pellet co‐product, displacing coal in electricity generation, performs best amongst co‐products in terms of GHG mitigation (−109% relative to gasoline, WTW basis). Maximizing pellet output, although requiring import of predominately fossil‐based process energy, improves overall GHG‐mitigation performance (−130% relative to gasoline, WTW). Similarly, lower ethanol yields result in greater GHG reductions because of increased co‐product output. Co‐locating ethanol production with facilities exporting excess steam and biomass‐based electricity (e.g. pulp mills) achieves the greatest GHG mitigation (−174% relative to gasoline, WTW) by maximizing pellet output and utilizing low‐GHG process energy. By exploiting co‐location opportunities and strategically selecting co‐products, lignocellulosic ethanol can provide large emission reductions, particularly if based upon sustainably grown, high yield, low input feedstocks. © 2011 Society of Chemical Industry and John Wiley &amp; Sons, Ltd

Top Fuel Injection Design in an Entrained-Flow Coal Gasifier Guided by Numerical Simulations

A computational fluid dynamics scheme is employed to simulate the effects of potential fuel injection techniques on gasification performance. The objective is to help design the top-loaded fuel injection arrangement for an entrained-flow gasifier using coal water slurry as the input feedstock. Two specific arrangements are investigated: (a) coaxial dual jet impingement with slurry coal in the center and oxygen in the outer jet and (b) four jet impingement with two single slurry coal jets and two single oxygen jets. When the heterogeneous finite-rate solid-gas reaction scheme is implemented, it is discovered that the particle collision model cannot be implemented with the heterogeneous gasification scheme in the present computational model. The instantaneous gasification model is later employed to examine the particle collision phenomenon by implementing the particle collision model, in which the coal (consisting of carbon and volatiles) is injected as gas, and the water is injected as droplets. The result of droplet tracks shows that the droplets are not bounced around, as speculated, at the intersection where the jets meet, and majority of the droplets pass through the jet impingement section and hit the wall as in the finite-rate case. This implies that the results of the finite rate are acceptable even though the particle collision model is not implemented. The finite-rate result actually presents a worst-case scenario for predicting wall erosion. The particle tracks for both the two concentric and four separate injection configurations show that the coal particles hit the wall and can accelerate the deterioration of the refractory bricks. The case employing two concentric injections provides better fuel-oxidant mixing and higher heating values than the case using four separate injections.