Environmental performance assessment of retrofitting existing coal fired power plants to co-firing with biomass: carbon footprint and emergy approach

Co-firing of biomass and coal has drawn many attentions because it can reduce the amount of CO2 release of the coal power plant/incinerator. However, the higher amount of sulfur, chlorine, potassium and calcium in biomass could lead to a more serious corrosion. In this study, the high-temperature corrosion of Fe-Cr-Mo alloy at 400 °C to 600 °C in co-firing of biomass and coal was performed. The results show that the weight change of specimen tested in co-firing of biomass and coal is 1.7 to 2.4 times of that for specimen tested in dry air. Also, the weight change of specimen tested in co-firing increased with the tested temperature and time increased. For the specimen tested in co-firing with different ratio of biomass/coal, the weight change of specimen increased with the ratio of biomass/coal increased.

Methane emissions and climatic warming risk from hydraulic fracturing and shale gas development: implications for policy Robert W Howarth Department of Ecology and Environmental Biology, Cornell University, Ithaca, NY, USA Abstract: Over the past decade, shale gas production has increased from negligible to providing >40% of national gas and 14% of all fossil fuel energy in the USA in 2013. This shale gas is often promoted as a bridge fuel that allows society to continue to use fossil fuels while reducing carbon emissions since less carbon dioxide is emitted from natural gas (including shale gas) than from coal and oil per unit of heat energy. Indeed, carbon dioxide emissions from fossil fuel use in the USA declined to some extent between 2009 and 2013, mostly due to economic recession but in part due to replacement of coal by natural gas. However, significant quantities of methane are emitted into the atmosphere from shale gas development: an estimated 12% of total production considered over the full life cycle from well to delivery to consumers, based on recent satellite data. Methane is an incredibly powerful greenhouse gas that is >100-fold greater in absorbing heat than carbon dioxide, while both gases are in the atmosphere and 86-fold greater when averaged over a 20-year period following emission. When methane emissions are included, the greenhouse gas footprint of shale gas is significantly larger than that of conventional natural gas, coal, and oil. Because of the increase in shale gas development over recent years, the total greenhouse gas emissions from fossil fuel use in the USA rose between 2009 and 2013, despite the decrease in carbon dioxide emissions. Given the projections for continued expansion of shale gas production, this trend of increasing greenhouse gas emissions from fossil fuels is predicted to continue through 2040. Keywords: shale gas, natural gas, methane, greenhouse gases, global warming, bridge fuel

This report investigates the effect of increasing the number of wind turbine generators on carbon dioxide emission in the Australian National Electricity Market’s (NEM) existing transmission grid from 2014 to 2025. This report answers urgent questions concerning the capability of the existing transmission grid to cope with significant increases in wind power and aid emissions reductions. The report findings will help develop a coherent government policy to phase in renewable energy in a cost effective manner. We use a sensitivity analysis to evaluate the effect of five different levels of wind penetration on carbon dioxide emissions. The five levels of wind penetration span Scenarios A to E where Scenario A represents ‘no wind’ and Scenario E includes all the existing and planned wind power sufficient to meet Australia’s 2020 41TWh Large Renewable Energy Target (LRET). We also use sensitivity analysis to evaluate the effect on carbon dioxide emissions of growth in electricity demand over the projections years 2014 to 2015 and weather over the years 2010 to 2012. The sensitivity analysis uses simulations from the ‘Australian National Electricity Market (ANEM) model version 1.10’ (Wild et al. 2015). We find increasing wind power penetration decreases carbon dioxide emissions but retail prices fail to reflect the decrease in carbon dioxide emissions. We find Victoria has the largest carbon dioxide emissions and of the states in the NEM Victoria’s emissions respond the least to increasing wind power penetration. Victoria having the largest brown coal generation fleet in the NEM explains this unresponsiveness. Wind power via the merit order effect displaces the more expensive fossil fuel generators first in the order gas, black coal and brown coal. However, brown coal has the highest carbon dioxide emissions per unit of electricity. This is suboptimal for climate change mitigation and the reintroduction of a carbon pricing mechanism would adjust the relative costs of fossil fuels favouring the fuels with the lower emissions per unit of electricity. We find that uncertainty in electricity demand and the renewable energy target are hindering the deployment of wind power. Electricity demand uncertainty stems from permanent structural changes such as downward pressure on demand from the decline in manufacturing, price sensitivity, technological efficiency and meeting electricity demand behind the meter via solar PV and solar water heating. Electricity demand uncertainty also stems from cyclical uncertainty of the El Nino Southern Oscillation (ENSO). The recent reduction of the LRET from the 41 TWh to 20% of demand reflects both permanent and cyclic changes. Both the recent reduction and the annual review of the RET induces investment uncertainty for wind power generators. Introducing a 100% RET and making the percent a moving average of the demand of the last 10 years would encourage retailers to purchase the LRET certificates, help reduce investment uncertainty and accommodate the structural changes in electricity demand. We find transmission congestion is reducing wind power’s ability to reduce emissions. This is particularly noticeable in South Australia (SA) where there are negative wholesale prices inducing spillage of wind power. Factors causing this situation are SA large wind deployment and relatively small demand base plus interconnectors between SA and VIC that quickly exceed their maximum capacity. In further research, we (Bell et al. 2015b, 2015c) investigate augmenting the NEM’s transmission grid to reduce carbon dioxide emissions across the NEM and address the price differential between states under increasing wind power penetration.

A set of technological interventions has been identified which are suitable for applications in the majority of existing UK dwellings and which would significantly reduce their carbon footprint. The dwelling types are semi-detached, detached and terraced. The paper considers two scenarios, viz. i) using present-best technologies and ii) looking at the likely-future technologies. The research has assessed the effectiveness of the selected technological interventions. These reduce heating demands and as a result there is a decrease in carbon dioxide emissions. It is concluded that the total CO2 emitted because of space and water heating can be reduced by up to 86, 87 and 86% respectively for the semi-detached, detached and terraced dwellings using likely-future technologies and by up to 78, 77 and 82% using present-best available technologies. This assumes that the proposed mechanical ventilation system used in conjunction with a heat-wheel heat recovery system (MVHW) runs on green electricity generated by a solar PV system.

A detailed economic evaluation was carried out to determine the impact of biomass and coal co-firing on power plant carbon capture by methods of plants equipment designing factors and performance, and the sum up of the associated breakdowns of CAPEX and OPEX. Based on the assumptions of the CO2 neutrality of biomass and likely governmental incentives to reduce CO2 emissions, the study results show that biomass and coal co-firing would result in both lower cost of carbon avoided (carbon capture) and lower incremental cost of electricity generation when MEA solvent carbon capture is applied. Two scenarios for co-firing with carbon capture, 30% biomass blending and 90% or 60% CO2 capture from stack, indicate different preference depending on lower or higher incentives.

With the increasing population and economic development of Mauritius, the demand of electricity increases each year. This has brought a significant rise in the consumption level of fossil fuels to meet these demands. Currently, the increasing prices of fossil fuels on the international market are having severe repercussion on the economy of the country.There are around 444, 570 tons of municipal solid waste (MSW) generated per year in Mauritius and this amount is giving rise to disposal problem. One of the disposal options could be the generation of electricity through combustion of the waste. At the same time, there are several coal power plant in the country that generate both heat and power. This study was, therefore, initiated to investigate the effect of co-firing MSW and coal. Proximate and ultimate analyses were conducted on both MSW and coal. The optimum blending ratio of MSW and coal was found to be 80 % MSW and 20 % coal by mass that is 1119 tons per day of MSW. The electrical output from the mixture of MSW and coal was 51 MW out of which 29.7 MW was generated from MSW only which represent around 58 % of the total produced power of the plant. Total cost saving from this co-firing project is estimated at 456 million Mauritian Rupees (MUR). The MSW has a lower heating value, however, it was seen that pollutant emission was reduced in the co-firing process. Gaseous pollutant emissions like CO2 was reduced significantly at this blending ratio compared to firing coal solely. Greenhouse gases (GHG) emissions were reduced on two counts: firstly reducing combustion of coal and secondly avoiding methane emission at the landfill site, which is equivalent to around 1.92 million Metric tonnes of CO2 equivalent annually.The findings from this study showed that MSW could be a good renewable fuel for co-firing with coal combustion. It reduces both the amount of land allocated annually for landfilling and the dependence on fossil fuels.Keywords: co-firing, municipal solid waste, coal, GHG reduction

Fossil fuels, the predominant energy source in the United States, have been identified as major contributors to environmental pollution through the release of harmful emissions. As a countermeasure, there has been an increasing focus on the exploration and development of cleaner energy alternatives to alleviate the environmental degradation caused by fossil fuels and to satisfy the growing energy needs. This study conducted scenario analyses to evaluate the impact of integrating solar energy into specific US power grids on reducing carbon emissions. The analysis encompassed electrical systems within California, New England, New York, and the Southwest, utilizing datasets from the Energy Information Administration and National Renewable Energy Laboratory. The Energy Information Administration dataset includes information on net generation according to each source and carbon emissions according to fuel type, whereas the National Renewable Energy Laboratory dataset provides hourly projections for 6000 theoretical photovoltaic installations and detailed solar energy output data every five minutes over a year. Our findings indicated a notable decrease in carbon dioxide emissions following the introduction of solar power facilities. The most significant reductions were observed in the Southwest and California, attributed to solar plant integration. Conversely, New York and New England were identified as regions requiring additional policy measures and incentives to meet the emission reduction goals.

’s (2012) conclusion that observed climate change is comparableto projections, and in some cases exceeds projections, allows further inferences ifwe can quantify changing climate forcings and compare those with projections.The largest climate forcing is caused by well-mixed long-lived greenhouse gases.Here we illustrate trends of these gases and their climate forcings, and we discussimplications. We focus on quantities that are accurately measured, and we includecomparison with fixed scenarios, which helps reduce common misimpressionsabout how climate forcings are changing.Annual fossil fuel CO

Ash deposition during the co-firing of bituminous coal with pine sawdust and olive stones in a laboratory furnace

The economy is not circular, it is increasingly entropic. Energy from the photosynthesis of the distant past, fossil fuels, is burned and dissipated. Even without further economic growth the industrial economy would need new supplies of energy and materials extracted from the “commodity frontiers”, producing also more waste (including excessive amounts of greenhouse gases). Therefore, new ecological distribution conflicts (EDC) arise all the time. Such EDCs are often “valuation contests” displaying incommensurable plural values. Examples from the Atlas of Environmental Justice are given of coal, oil and gas-related conflicts in several countries combining local and global complaints. Claims for climate justice and recognition of an ecological debt have been put forward by environmentalists from the South since 1991, together with a strategy of leaving fossil fuels underground (LFFU) through bottom-up movements. This could make a substantial contribution to the decrease in carbon dioxide emissions.

The cofiring of biomass and coal may be one of the most effective methods to improve energy utilization efficiency and reduce greenhouse gas emissions. This study aims to investigate combustion performance, interaction and synergistic effects in the cofiring of coal and three types of biomass. Blended fuel consisting of coal and three types of biomass such as sawdust, rice husk and solid recovery fuel was selected as the research object. Ultimate and proximate analysis and differential thermogravimetric analysis with heating rates of between 10°C and 40°C/minute are used to analyse combustion characteristics. Simulation of combustion in a 600-MWe steam power plant with a Carolina-type boiler is also carried out with the help of computational fluid dynamic (CFD) analysis to see the effect of the interaction and synergy of the mixed fuel on the performance of the steam generator. The effect on the combustion process in the combustion chamber of a steam power plant is also simulated. Based on the analysis of several test results of parameters such as ignition temperature, burnout temperature, calorific value of the fuel mixtures as well as CFD simulation, the results of the study show a strong indication of a positive synergy in mixing some of these biomasses as compared with a fuel mixture consisting only of coal and one type of biomass. Practically no power derating of the boiler occurs until the biomass content in the fuel mixture is ~30% on a mass basis. The reduction in greenhouse gas emissions also appears significant from the results of the CFD simulation of this study, which is characterized by a decrease in the fraction of CO2 in flue gas from 21.5% for coal alone as fuel to 15.9% in the case of cofiring excluding the CO2 attributed to the biomass.

Identifying drivers of farm-level greenhouse gas (GHG) footprints of crop production can reveal opportunities to improve farming practices and enable more targeted GHG mitigation strategies. Although many studies evaluated the GHG footprints of crop production, differences between and within crops have not been systematically evaluated for a large number of farms so far. Here, we evaluated possible sources of variability in GHG footprints (in terms of kg CO2-eq/kg crop produced) of 26 crops, grown in compliance with Unilever's Sustainable Agriculture Code, using data from 4565 farms in 36 countries from 2013 through 2016. We quantified crop-farm-specific GHG footprints based on four components: (i) emissions from electricity use, (ii) emissions from fossil fuel (petrol and diesel) use, (iii) emissions from crop and pruning residue application, and (iv) emissions from fertilizer use. On average, fertilizer use contributed most to the GHG footprint for 23 out of the 26 crops in our dataset. We further found that variability in GHG footprints was smaller between crops (45%) than within crops (55%). Regression modelling revealed that on average 44% of the GHG footprint variability within crops could be attributed to (a selection of) three explanatory variables, i.e., yield, area of production, and year of production. Of these, yield was the most important explanatory variable. Lower GHG footprints were associated with higher yields for 24 out of the 26 crops. Relationships with area and year of production were less clear, and directions of the relationships were more variable between crops. Strategies to improve fertilizer use efficiencies while maintaining or increasing yields are preferable in a GHG reduction programme.

Ash transformation by co-firing of coal with high ratios of woody biomass and effect on slagging propensity

Co-firing of biomass and coal and biomass reduces the emission of pollutants and the overall effects have been extensively studied, but many aspects of the detailed mechanism remain uncertain. A number of studies have been previously made by us of emissions from the combustion in a fixed-bed furnace of bituminous coal and wood, both individually and together, and it was observed that biomass produced less soot and lower NOX emissions. These data are combined with recent measurements of emissions of black carbon (BC) and organic carbon (OC), which are an important source of climate forcing, from the combustion of a number of solid fuels. Conclusion are drawn about the nature of the OC and how the values are dependent on the measurement technique used. Complementary analytical-scale combustion and pyrolysis experiments were also carried out. The results of the analysis of emissions and reaction products, mainly by gas chromatography–mass spectrometry (GC–MS), were interpreted so as to construct a model for pollutant formation during co-firing.There is a reduction of smoke from the combustion of torrefied biomass and this is considered in relation to the torrefaction processes.

Investigation on Co-combustion characteristics and NOx emissions of coal and municipal sludge in a tangentially fired boiler