Net CO2 Emission Reduction Research Articles

Toward a better understanding of 2-butanone oxidation: Detailed species measurements and kinetic modeling

In view of a desired transition from fossil fuels to sustainably produced biofuels that should contribute to a net reduction of CO2 emissions, promising fuel candidates have been identified including 2-butanone (methyl ethyl ketone, MEK) that is qualified for use in spark-ignition (SI) engines. To support a potential, rapid integration of such biofuels into the existing infrastructure, fundamental studies of their combustion and emission behavior are highly important. In the case of 2-butanone specifically, only very few fundamental combustion experiments have been performed to date, with a notable shortage of detailed speciation data. For predictive model development, accurate and reliable species measurements are needed to describe the oxidation and combustion of 2-butanone and to elucidate the kinetic mechanism.The present study relies on three different experiments: a laminar flow reactor coupled with molecular-beam mass spectrometry (MBMS, Bielefeld), a rapid compression machine (RCM, Aachen), and a shock tube using advanced laser absorption techniques (Stanford). This combination ensured coverage of a wide regime in temperature, pressure, and mixture composition while providing numerous species profiles. The species measurements in the flow reactor were performed at stoichiometric (Φ= 1.0) and fuel-rich (Φ= 2.0) equivalence ratios at temperatures between about 800–1100K with an argon dilution of 95%. Ignition delay times in the RCM were measured in air for equivalence ratios of 0.5, 2.0 in the temperature range of 840–945K to reflect application-relevant conditions. Shock tube measurements were performed at stoichiometric conditions at 1303–1509K in argon.To provide insight into the oxidation mechanism of 2-butanone, the newly measured experimental data was used to develop and validate a detailed chemical kinetic model. To this end, the reactions for the low-temperature regime, especially concerning early fuel consumption, radical formation, and subsequent low-temperature oxidation, were examined in detail, and used to extend and adapt an existing reaction mechanism (Burke et al., 2016 [23]) to more accurately predict the new low-temperature conditions studied. The resulting model that incorporates the latest theoretical kinetic calculations available in the literature was compared to the measurements presented here as well as validated using literature data. To the authors' knowledge, the present model represents the most robustly validated mechanism available for the prediction of 2-butanone combustion targets to date.

Switching to efficient technologies in traditional biomass intensive countries: The resultant change in emissions

This paper aims to quantify the benefits of switching from a system dependent on traditional biomass to systems running on more efficient fuels and technologies. It is estimated that even when open fires burning fuelwood are replaced by improved cooking stoves (ICSs) and liquefied petroleum gas (LPG) stoves, and biomass is processed in dedicated biomass power plants, a net reduction in CO2 emissions is still obtained. The ICS/LPG stove/biomass combustion power plant configuration could provide an average net reduction of 84 kg-Ce/tDM. Meanwhile, a net reduction of 105 kg-Ce/tDM could be obtained when implementing a ICS/LPG stove/biomass gasification power plant scheme. Main factors influencing the net reduction of CO2 emissions are technology efficiency and the fraction of non-renewable fuelwood use.The switch from traditional biomass to modern biomass in traditional biomass intensive countries must not only be done to reduce CO2 emissions but also to avoid indoor pollution and energy poverty. Health improvements should be more important than energy savings. Results also indicate that the use of modern biomass systems not only could provide a reduction of local environmental pollution, but also could boost the local economy by the creation of biomass infrastructures.

Dynamic Hybrid Life Cycle Assessment of CO2 Emissions of a Typical Biogas Project

Abstract Biogas project has been earmarked as an efficient way to achieve climate change benefits due to the comprehensive utilization of biogas products. However, CO2 emission would occur during the construction, operation and dispose stages of biogas project, and it requires a holistic and systematic accounting framework to evaluate both emissions and reductions over the lifetimes. In this study, a dynamic hybrid LCA model combining both process analysis and input-output analysis was proposed to dynamically characterize both direct and embodied carbon emissions and mitigation of a typical household biogas project. Moreover, the time-varying social-economic development factors are also taken into account to reduce the uncertainty and increase accuracy. Results show that biogas project is a good choice to achieve carbon emission reduction with 17.09 tons of net CO2 emission reduction over the lifespan. In addition, indirect CO2 emission (5.45 tons) plays significant part in the total emissions, in which the construction stages are the largest contributor due to the large amount of energy-intensive materials consumption. Moreover, with the CO2 emission intensity of fertilizer changing over years, the net emission reduction decreases 2.18 tons. The proposed dynamic hybrid LCA framework could unveil both direct and indirect carbon emission and reduction of the biogas project with consideration of technology development.

Pilot-Scale Operation of a Concrete Sludge Recycling Plant and Simultaneous Production of Calcium Carbonate

A pilot-scale plant to treat concrete sludge and produce calcium carbonate (CaCO3) and an environmental purification agent (phosphorus adsorbent derived from concrete sludge, PAdeCS®) was designed, constructed, and operated. Concrete sludge from a concrete pile and pole production plant, boiler gas containing CO2, and groundwater were used in the plant. The process involved calcium extraction from concrete sludge into water, followed by reaction of the calcium with CO2 to produce crystalline CaCO3. The pilot-scale plant was operated for 1 week, and the mass flows, conversion of CO2 to CaCO3, and net CO2 emissions of the process were estimated. High-purity CaCO3 (>97%) suitable for industrial use was obtained. Based on the power consumption of the process and the amount of CO2 sequestered into CaCO3, a net reduction in CO2 emissions can be achieved using this process. The produced PAdeCS can be used as an inexpensive substitute for calcium series environmental purification agents.

Analyzing the Prospects of Electroreduction of Carbon Dioxide to Value-Added Chemicals

Increasing evidence suggests that the unwanted effects of climate change, including global warming, rising sea levels, and erratic weather patterns are the result of the increasing concentration of carbon dioxide (CO2) and other greenhouse gasses in the atmosphere. Further development and integration of renewable but intermittent energy sources such as solar and wind, as well as enhancing energy efficiency in buildings and transportation applications will be critical to significantly reduce global CO2 emissions. An alternative strategy to reduce CO2 emissions is the capture and subsequent electrochemical reduction of CO2 into useful chemicals such as formic acid, carbon monoxide (CO), hydrocarbons, or alcohols. This approach has the additional advantage that it can enhance the utilization of renewable energy that is produced in excess of grid demand (too much solar or wind energy production) and currently wasted. Multiple research efforts over the last decade have developed increasingly better cathode catalyst for the efficient electrochemical reduction of CO2 to formic acid, CO, and other products. At the same time progress has been made on anode catalysts (typically for the oxygen evolution reaction), gas diffusion electrodes suitable for CO2 electrolysis cells, and on the optimization of electrolysis operating conditions. Despite this progress, it is still unclear whether this emerging electrochemical technology has the potential to achieve a net reduction in CO2 emissions and is economically feasible. We developed a gross-margin model for a first order estimate of the economic viability of CO2 electrolysis. Second, in a collaborative effort, we performed a techno-economic analysis of a process that starts with the flue gas from a 0.5 MW power plant, captures the CO2, converts that CO2 into CO, which then in combination with hydrogen from a water electrolyzer is converted into liquid fuels via the Fischer Tropsch process. The results of these models with respect to economic viability and their ability to reduce greenhouse gas emissions will be presented.

Methanol synthesis using captured CO2 as raw material: Techno-economic and environmental assessment

The purpose of this paper is to assess via techno-economic and environmental metrics the production of methanol (MeOH) using H2 and captured CO2 as raw materials. It evaluates the potential of this type of carbon capture and utilisation (CCU) plant on (i) the net reduction of CO2 emissions and (ii) the cost of production, in comparison with the conventional synthesis process of MeOH Europe. Process flow modelling is used to estimate the operational performance and the total purchased equipment cost; the flowsheet is implemented in CHEMCAD, and the obtained mass and energy flows are utilised as input to calculate the selected key performance indicators (KPIs). CO2-based metrics are used to assess the environmental impact. The evaluated MeOH plant produces 440ktMeOH/yr, and its configuration is the result of a heat integration process. Its specific capital cost is lower than for conventional plants. However, raw materials prices, i.e. H2 and captured CO2, do not allow such a project to be financially viable. In order to make the CCU plant financially attractive, the price of MeOH should increase in a factor of almost 2, or H2 costs should decrease almost 2.5 times, or CO2 should have a value of around 222€/t, under the assumptions of this work. The MeOH CCU-plant studied can utilise about 21.5% of the CO2 emissions of a pulverised coal (PC) power plant that produces 550MWnet of electricity. The net CO2 emissions savings represent 8% of the emissions of the PC plant (mainly due to the avoidance of consuming fossil fuels as in the conventional MeOH synthesis process). The results demonstrate that there is a net but small potential for CO2 emissions reduction; assuming that such CCU plants are constructed in Europe to meet the MeOH demand growth and the quantities that are currently imported, the net CO2 emissions reduction could be of 2.71MtCO2/yr.

Sustainability and Economic Analysis of Propylene Carbonate and Polypropylene Carbonate Production Processes Using CO2 and Propylene Oxide

Currently, the industrially important polycarbonates are synthesized from bisphenol A and diphenyl carbonate, which are highly toxic and hence other feasible alternatives are preferable. Following the considerable advances on the catalyst for the synthesis of carbonates from CO2 and propylene oxide (PO), industrial scale processes for the productions of propylene carbonate (PC) and polypropylene carbonate (PPC) have been designed and simulated with sustainability and economic analyses. The CO2 is supplied by a nearby bioethanol plant, while the PO from a petrochemical process. The first part of the study is for the production of 200 million lb/year cyclic PC by using 9990 lb/ hr of CO2. Ionic liquid-1-n-ethyl-3-methylimidazolium chloride is used as a catalyst. The net CO2 emission reduction is around −0.318 lb CO2/lb PC, while the net cost of duty (heating+cooling) is around $1.92×10−3/lb PC. The second part is for the production of 261 million lb/year PPC by using 14523.2 lb/hr CO2. The process uses (salen) CrIIICl complex as catalyst. The net CO2 emission reduction is around −0.342 lb CO2/lb PPC, while the net cost of duty/lb PPC is around $7.978×10−3/lb PPC. Economic analyses show that the feasibility of the both production plants depends on the selling price of PC and PPC. Both the production plants for PC and PPC are sustainable as they use CO2 and avoid toxic feedstock. Beside the engineering economics, a focused sustainability analysis should also be considered in the feasibility evaluation of chemical process technologies.

The effect of increased extraction of forest harvest residues on soil organic carbon accumulation in Sweden

The demand and potential for increasing the use of bioenergy from harvest residues in Sweden are large. However, harvest residue (branches and tops) and stump extraction negatively affect soil organic carbon (SOC) accumulation. The main objective of this study was to assess the effects of increased harvest residue extraction on soil organic carbon (SOC) accumulation at national level. Further, the reduction in CO2 by substituting coal with biofuel from harvest residues and stumps was assessed. Several scenarios with increased harvest residue extraction were simulated with the forest management system HUGIN and the SOC decomposition model Q and the effects on SOC accumulation in Swedish coniferous forest soils were assessed. All scenarios resulted in decreased SOC accumulation. The decrease in SOC accumulation was largest for stump extraction, with 0.15 Mg C ha−1 y−1 loss on average over a 100-year simulation period. In all scenarios, the short-term effects on SOC accumulation were greater than the long-term effects. The effect of substituting coal with bioenergy was an immediate reduction of net CO2 emissions. An increase in the use of forest residues leads to CO2 mitigation in the atmosphere, even when SOC losses are accounted for.

Alternativas energéticas para o transporte público urbano no Rio de Janeiro: uma análise utilizando Inventário de Ciclo de Vida (ICV)

For the period 2003 to 2009 in Brazilian municipalities of over 60,000 inhabitants, buses accounted for more than 25% of urban trips, which is a trend that is not expected to change in the medium term. Worldwide, buses rely on petroleum diesel oil as fuel. In Brazil, alternative fuels such as biodiesel, natural gas and ethanol are available, and the choice between them should depend on an evaluation of the entire life cycle of such fuels. The present study uses a Life Cycle Inventory (LCI), which is essential to the implementation of a Life Cycle Analysis (LCA), to analyze 6 energy alternatives: petroleum diesel oil (D100), pure biodiesel (B100), biodiesel mixed with petroleum diesel (B5), compressed natural gas (CNG), CNG in conjunction with B5 (B5CNG) and additive hydrous ethanol (E95). In saving total energy consumption, D100, B5 and B5CNG stand out, in that order. If the use of renewable energy and the reduction of net CO2 emissions are the goals, E95 and B100 should be given preference.

Alkaline digestion of dunite for Mg(OH)2 production: An investigation for indirect CO2 sequestration

The sequestration of CO2 by carbonating natural minerals has a great potential for secure reduction of net CO2 emissions. Feedstock Mg–silicate minerals are usually converted into Mg rich solutions or Mg(OH)2 before the carbonation process, due to the slow reaction kinetic of direct carbonation. The present work studied the alkaline digestion of Mg–silicate minerals into Mg(OH)2 for CO2 sequestration. Powdered dunite containing ∼73±2wt% of forsterite (Mg2SiO4) was dissolved using highly concentrated NaOH aqueous systems at 90 and 180°C with varied NaOH concentration and duration of reaction. Thermal analysis and Rietveld Refinement Quantitative Phase Analysis (QPA) confirmed that an effective digestion of dunite was possible at 180°C achieving 80wt% of Mg(OH)2. It was found that NaOH concentration in solution, temperature and duration of reaction significantly influence the progress of digestion.

Analysis of environmental and economic benefits of integrated Exhaust Energy Recovery (EER) for vehicles

Differing from those traditional vehicle exhaust heat recovery systems which just provided thermal energy directly for cabin warming, integrated Exhaust Energy Recovery (EER) which is researched and developed mainly in recent years aims to convert exhaust thermal energy to mechanical or electric energy for increasing the total thermal efficiency and the total power of powertrain. In the study presented in this paper, an analytic model was built for examining the environmental and economic benefits of integrated EER systems. Then the improvement on the total powertrain efficiency and net reduction of CO2 emissions were investigated, in terms of the average vehicle used in the UK. Results show that, for light duty vehicles fitted with thermal cycle EER system, the cost increase could be paid back in 10.1years and CO2 emission could be paid back in just 1.9years, compared to Hybrid Electric Vehicle’s (HEV’s) 11.9years and 1.4years for cost and CO2 emission, respectively. When the annual fuel price increase is considered, the cost pay-back is reduced to 8.1years for EER vehicles and 8.9years for HEVs. Higher mileage vehicles will have more obvious advantage for fitting EER system. When doubled annual mileage is considered, EER system can reduce the cost and CO2 emission pay-back times to 2.7years and 0.6years, compared to HEV’s 8.5 and 2.7years, respectively.

Bench-Scale Operation of a Concrete Sludge Recycling Plant

A bench-scale plant for waste concrete sludge recycling was designed, constructed, and operated. Real concrete sludge generated from a pile and pole production plant and groundwater were used for the experiments. The process mainly consists of the extraction of calcium ions from the concrete sludge into the aqueous phase and the crystallization of calcium carbonate from the solution with CO2. The CO2 was supplied from boilers installed in the plant, where heavy oil is combusted. High-purity calcium carbonate (>99%) was obtained in the process, with particle sizes distributed in the range of 3–30 μm (volume-based), peaking at about 10 μm. A net reduction in CO2 emissions can be achieved based on the process power consumption and the amount of product. The effects of operating conditions on process performance data such as calcium extraction rate and calcium carbonate crystallization rate were examined, which can lead to scaling-up of the plant.

Overcoming business model uncertainty in a carbon dioxide capture and sequestration project: Case study at the Boise White Paper Mill

Carbon capture and storage (CCS) is one of a suite of technology options that might play a significant role in reducing greenhouse gas emissions. However, outside of traditional enhanced oil and gas recovery operations with a well established business model, CCS project deployments are struggling with adoption of a federal or international climate policy driver appearing unlikely for the foreseeable future. As part of a feasibility study for an industrial CCS project at the Boise White Paper mill in Washington State, a business model and CCS system design was developed that provided financial surety for the project developers while recognizing that uncertainty in revenue forecasts for CO2 storage would persist for the foreseeable future. Key to the business model was installation of a new 37MWe biomass-fueled power island at the plant that would replace antiquated boilers and that could still supply the necessary steam to run pulp and paper production operations when capturing CO2 emissions under favorable market conditions for monetizing CO2 storage credits. Under unfavorable market conditions, CO2 capture would be suspended and excess power generated from the plant would reduce external electrical energy purchases required for paper mill operations. The net CO2 reduction for the project versus current operations is 1.0MMT of CO2 per year with the CCS system online, and 139ktons per year with the CCS system offline due to reduced natural gas co-firing. So, both operational modes offered a significant net reduction in CO2 emissions. Based on assumptions regarding electricity and natural gas pricing, and CO2 storage revenue generated through an open market mechanism priced at $15 per metric ton CO2, the payback period for the project capturing 0.5MMT/yr (62% of total CO2 production) was estimated at 6.7 years versus 7.4 years with the CCS system offline. Geologic storage was evaluated in the deep flood basalt formations that dominate the storage capacity in Eastern Washington. Sub-basalt sediments were also examined at the site to provide alternative or supplemental storage capacity in the event that storage in the basalt sequences did not prove technically or economically feasible.

Effect of Change of Forest Carbon Storage on Net Carbon Dioxide Balance of Wood Use for Energy in Japan

Summary This study analyzed the net carbon dioxide (CO2) emission reductions between 2005 and 2050 by using wood for energy under various scenarios of forest management and energy conversion technology in Japan, considering both CO2 emission reductions from replacement of fossil fuels and changes in carbon storage in forests. According to our model, wood production for energy results in a significant reduction of carbon storage levels in forests (by 46% to 77% in 2050 from the 2005 level). Thus, the net CO2 emission reduction when wood is used for energy becomes drastically smaller. Conventional tree production for energy increases net CO2 emissions relative to preserving forests, but fast-growing tree production may reduce net CO2 emissions more than preserving forests does. When wood from fast-growing trees is used to generate electricity with gas turbines, displacing natural gas, the net CO2 emission reduction from the combination of fast-growing trees and electricity generation with gas turbines is about 58% of the CO2 emission reduction from electricity generation from gas turbines alone in 2050, and an energy conversion efficiency of around 20% or more is required to obtain net reductions over the entire period until 2050. When wood is used to produce bioethanol, displacing gasoline, net reductions are realized after 2030, provided that heat energy is recovered from residues from ethanol production. These results show the importance of considering the change in carbon storage when estimating the net CO2 emission reduction effect of the wood use for energy.

Environmental impacts of a German CCS strategy

Abstract In this presentation it is analyzed how the replacement of out-dated power plants can be combined with a German CCS strategy and which environmental impacts this will cause. Although the application of CCS results in net reduction of CO2 emissions, a broader environmental analysis is necessary to show the overall environmental impacts. Based on Life Cycle Assessment (LCA) methodology and a simulation of capacity replacement from today up to 2030 the environmental effects of power generation of coal-based steam power plants are examined. Future environmental impacts of German electricity production are projected.

A tool for creating energy market scenarios for evaluation of investments in energy intensive industry

The energy intensive industry can be a major contributor to CO2 emissions reduction, provided that appropriate investments are made. To assess profitability and net CO2 emissions reduction potential of such investments, predictions about future energy market conditions are needed. Energy market scenarios can be used to reflect different possible future energy market conditions. This paper presents a tool for creating consistent energy market scenarios adapted for evaluation of energy related investments in energy intensive industrial processes. Required user inputs include fossil fuel prices and costs associated with policy instruments, and the outputs are energy market prices and CO2 consequences of import/export of different energy streams (e.g. electric power and biomass fuel) from an industrial process site. The paper also presents four energy market scenarios for the medium-term future (i.e. around 2020) created using the tool.

DIALYSIS AND THE ENVIRONMENT: COMPARING HOME AND UNIT BASED HAEMODIALYSIS

Dialysis, with its high dependence upon technology, disposable products and transport requirements, presents an unusual perspective for environmental management. This study considers and compares the environmental aspects arising from the provision of haemodialysis (HD) in the hospital and home setting. Resource items were measured at two levels of aggregation--unit and individual patient. Unit level items applied to common resources used for HD and require apportioning appropriately with patient level items that could be attributable to individuals. The data was measured in standard units such as hours and number of treatments or apportioned appropriately. With equivalent emissions calculated as CO2 annually per patient for standard HD. The findings indicate that HD in the home offers a net reduction in CO2 emissions per patient annually compared to hospital based HD, and provides an overview of how healthcare provision and the use of resources can be measured, enabling refinement in environmental management plans.

97/03876 Combustion of residual biosolids from a high solids anaerobic digestion/aerobic composting process

Prospects are examined for utilizing renewable energy crops as a source of liquid fuel to mitigate greenhouse gas emissions from mobile sources and reduce dependence on imported petroleum. Fuel-cell vehicles would provide a promising technology for coping with the environmental and economic effects of an expanding vehicle fleet and a decreasing petroleum supply. Fueled with methanol or hydrogen derived from biomass, fuel cells can also effectively address the problem of CO2 emissions from that fleet. The extent to which this combination might affect petroleum displacement depends on the amount of biomass that could be produced and the efficiency of its conversion to a fuel compatible with fuel cells. Reduction of net CO2 emissions by the best current bio-fuel technology will be limited by biomass supply. Biomass conversion efficiency, petroleum displacement and overall net CO2 emission reduction can be improved, and the cost of fuel minimized, by use of natural gas as a co-feedstock. The extra hydrogen provided by natural gas allows these improvements by eliminating the partial shift of CO to CO2 that is otherwise necessary; elimination of that step and additional in situ leveraging of fuel yield by conventional reforming reactions also reduce the production cost. A thermochemical process utilizing both biomass and natural gas as co-feedstocks is compared with other options for methanol production and CO2 mitigation using either biomass or natural gas alone. Use of natural gas as co-feedstock makes possible the additional environmental advantage of utilizing waste methane from landfills and waste-water treatment facilities, as well as the carbonaceous solid wastes and sludge from those facilities, for conversion to clean transportation fuel. Greenhouse gas emissions from these important municipal sources can thus be concurrently reduced, together with landfill disposal requirements.

The Carnol process for CO2 mitigation from power plants and the transportation sector

Abstract A CO2 mitigation process is developed which converts waste CO2, primarily recovered from coal-fired power plant stack gases with natural gas, to produce methanol as a liquid fuel and coproduct carbon as a materials commodity. The Carnol process chemistry consists of methane decomposition to produce hydrogen which is catalytically reacted with the recovered waste CO2 to produce methanol. The carbon is either stored or sold as a materials commodity. A process design is modelled and mass and energy balances are presented as a function of reactor pressure and temperature conditions. The Carnol process is a viable alternative to sequestering CO2 in the ocean for purposes of reducing CO2 emissions from coal burning power plants. Over 90% of the CO2 from the coal burning plant is used in the process which results in a net CO2 emission reduction of over 90% compared to that obtained for conventional methanol production by steam reforming of methane. Methanol as an alternative liquid fuel for automotive engines and for fuel cells achieves additional CO2 emission reduction benefits. The economics of the process is greatly enhanced when carbon can be sold as a materials commodity. Improvement in process design and economics should be achieved by developing a molten metal (tin) methane decomposition reactor and a liquid phase, slurry catalyst, methanol synthesis reactor directly using the solvent saturated with CO2 scrubbed from the power plant stack gases. The benefits of the process warrants its further development.