Environmental and economic aspects of production and utilization of RDF as alternative fuel in cement plants: A case study of Metro Vancouver Waste Management

Municipal solid waste (MSW) disposal and management is one of the most significant challenges faced by urban communities around the world. Municipal solid waste management (MSWM) over the years has utilized many sophisticated technologies and smart strategies. Municipalities worldwide have pursued numerous initiatives to reduce the environmental burden of the MSW treatment strategies. One of the most beneficial MSWM strategies is the thermal treatment or energy recovery to obtain cleaner renewable energy from waste. Among many waste-to-energy strategies, refuse-derived fuel (RDF) is a solid recovered fuel that can be used as a substitute for conventional fossil fuel. The scope of this study is to investigate the feasibility of RDF production with MSW generated in Metro Vancouver, for co-processing in two cement kilns in the region. This study investigates environmental impacts and benefits and economic costs and profits of RDF production. In addition, RDF utilization as an alternative fuel in cement kilns has been assessed. Cement manufacturing has been selected as one of the most environmentally challenged industries and as a potential destination for RDF to replace a portion of conventional fossil fuels with less energy-intensive fuel. A comprehensive environmental assessment is conducted using a life cycle assessment (LCA) approach. In addition, cost–benefit analysis (CBA) has been carried out to study the economic factors. This research confirmed that RDF production and use in cement kilns can be environmentally and economically viable solution for Metro Vancouver.     

Life cycle assessment of clinker production using refuse‐derived fuel: A case study using refuse‐derived fuel from Tehran municipal solid waste

One of the techniques used to dispose of 4,000 tons per day (TPD) of non‐recyclable waste from Tehran is to burn it as an alternative fuel in cement kilns. This practice reduces emissions from landfills, prevents the loss of waste energy, and conserves fossil fuel resources. The aim of our study was to conduct a life cycle assessment (LCA) of clinker production in cement kilns using a combination of natural gas, mazut, a form of heavy, low‐quality fuel oil, and refuse‐derived fuel (RDF) from Tehran. We used SimaPro 7.1 software to perform an LCA of 1 kilogram (kg) of clinker produced using the following fuel combinations: the first scenario involved natural gas consumption alone, the second scenario involved a combination of natural gas and mazut, with the mazut providing 5% to 30% of the heating value needed to produce cement clinker in the kiln, and the third scenario involved a combination of natural gas and RDF (providing 5% to 30% of the heating needed in the kiln). The impact categories in the LCA of global warming, eutrophication, and acidification were assessed by the Center of Environmental Science of Leiden University (Centrum voor Milieukunde Leiden—CML) CML 2000 method. The results indicated that the third scenario, involving natural gas and RDF, reduced acidification by 2.14–11.5% and global warming by 0–1.3% relative to the first scenario involving the use of only natural gas. In addition, we observed a 0.65–3.81% reduction in acidification and a 0.9–3.8% reduction in global warming under the third scenario compared with the second scenario (co‐firing of natural gas and mazut). The amount of nitrogen oxides (NO_X) emitted from the combustion of the Tehran RDF was greater than that was emitted when burning mazut. Therefore, reduction of nitrogen from the RDF composition is necessary. This study indicates that the use of Tehran RDF (with reduced nitrogen) in Tehran cement kilns does not increase cement kiln NO_X, sulfur dioxide (SO₂), and carbon dioxide (CO₂) emissions; however, we need to conduct additional investigation into the chemical composition of the Tehran waste before using solid waste in place of fossil fuels.     

Optimal planning of co-firing alternative fuels with coal in a power plant by grey nonlinear mixed integer programming model

Energy supply and use is of fundamental importance to society. Although the interactions between energy and environment were originally local in character, they have now widened to cover regional and global issues, such as acid rain and the greenhouse effect. It is for this reason that there is a need for covering the direct and indirect economic and environmental impacts of energy acquisition, transport, production and use. In this paper, particular attention is directed to ways of resolving conflict between economic and environmental goals by encouraging a power plant to consider co-firing biomass and refuse-derived fuel (RDF) with coal simultaneously. It aims at reducing the emission level of sulfur dioxide (SO(2)) in an uncertain environment, using the power plant in Michigan City, Indiana as an example. To assess the uncertainty by a comparative way both deterministic and grey nonlinear mixed integer programming (MIP) models were developed to minimize the net operating cost with respect to possible fuel combinations. It aims at generating the optimal portfolio of alternative fuels while maintaining the same electricity generation simultaneously. To ease the solution procedure stepwise relaxation algorithm was developed for solving the grey nonlinear MIP model. Breakeven alternative fuel value can be identified in the post-optimization stage for decision-making. Research findings show that the inclusion of RDF does not exhibit comparative advantage in terms of the net cost, albeit relatively lower air pollution impact. Yet it can be sustained by a charge system, subsidy program, or emission credit as the price of coal increases over time.     

Reject management from a Mechanical Biological Treatment plant in Bangkok, Thailand

The potential reuse of rejects from upstream and downstream process of Mechanical-Biological-Treatment (MBT) plant for the production refuse derived fuel (RDF) was investigated in the present study. Since, the rejects were characterized with the high calorific values of approximately 21 kJ/kg for upstream process and 29.5 kJ/kg for downstream process, both can be considered for RDF production. Further, heavy metal contents were also not exceeding the European standards for using it as RDF is additional benefit. But, RDF production from upstream process rejects showed maximum energy supply of 3.20 × 10⁶ MJ/d with less ash (11.8%), chlorine (0.6%) and sulfur (0.2%) contents than the downstream process rejects. Among the three potential RDF users surveyed, the cement industries showed positive interest to burn RDF in their cement kiln with the energy supply cost of <2.1 USD/GJ. Few technical, economical and safety barriers were also identified with the RDF end users and potential suggestions were discussed for thriving RDF market in Thailand.     

The implementation of wood waste ash as a partial cement replacement material in the production of structural grade concrete and mortar: An overview

The timber manufacturing and power generation industry is gradually shifting towards the use of biomass such as timber processing waste for fuel and energy production and to help supplement the electrical energy demand of national electric gridlines. Though timber processing waste is a sustainable and renewable source of fuel for energy production, the thermal process of converting the aforementioned biomass into heat energy produces significant amounts of fine wood waste ash as a by-product material which, if not managed properly, may result in serious environmental and health problems. Several current researches had been carried out to incorporate wood waste ash as a cement replacement material in the production of greener concrete material and also as a sustainable means of disposal for wood waste ash. Results of the researches have indicated that wood waste ash can be effectively used as a cement replacement material for the production of structural grade concrete of acceptable strength and durability performances. This paper presents an overview of the work carried out by the use of wood waste ash as a partial replacement of cement in mortar and concrete mixes. Several aspects such as the physical and chemical properties of wood waste ash, properties of wood waste ash/OPC blended cement pastes, rheological, mechanical and the durability properties of wood waste ash/OPC concrete mix are detailed in this paper.     

Recycling contaminated soil as alternative raw material in cement facilities: Life cycle assessment

Volcanic soil can be used to remove metals from wastewaters. Once used, it is disposed in landfills. The utilization of this material in the cement industry as an alternative raw material was evaluated using life cycle assessment (LCA) methodology. This possibility has been studied from an environmental point of view in a Chilean cement facility, representative of the current operation state of art, including both technical and economic analysis. Two scenarios were compared: Scenario 1, which corresponds to the existing cement production process, and Scenario 2, which represents cement production using spent volcanic soil. With the exception of the categories of carcinogens (C) and minerals (M), the comparative results are favourable to Scenario 2, specially regarding to the category of ecotoxicity (E), mainly due to the avoided landfilling emissions of the volcanic soil. When considering the damage assessment, damage to human health (HH), ecosystem quality (EQ) and resources (R) are lower in Scenario 2. In addition, sensitivity analyses were performed to study the influence of particular parameters (i.e., transport of spent volcanic soil, CO₂ emissions from the clinkerization process and heavy metals leaching from the spent volcanic soil) on the results of the assessment. The use of alternative raw materials (in this case, spent volcanic soil), which present the advantage to be wastes from other technical systems, appear to allow the development of cement production in a more sustainable way, slightly improving the economy of the process. The spent volcanic soil can be treated with zero cost for the wastewater treatment plant with savings of 0.23€ for each tonne of clinker production. Establishing a sound management way for the spent volcanic soil could foment its possible use as mineral adsorbent in industrial wastewater treatment facilities.     

Conditions for a 100% renewable energy supply system in Japan and South Korea

In the wake of the Fukushima nuclear accident, alternative energy paths have been discussed for Japan, but except for a few studies the assumption is usually made that Japan is too densely populated to be suited for a near-100% sustainable, indigenous energy provision. The studies emphasizing renewable energy have proposed the use of photovoltaic power as the main source of electricity supply, in combination with diurnal battery storage and supplemented by other renewable sources such as wind, hydro, and geothermal power. Here, an alternative approach is explored, with wind and derived hydrogen production as the main energy source, but still using solar energy, biofuels, and hydropower in a resilient combination allowing full satisfaction of demands in all sectors of the economy, i.e., for dedicated electricity, transportation energy as well as heat for processes and comfort. Furthermore, the possible advantage of establishing a regional energy system with energy interchange and coordinated management of the mix of renewable energy resources across a wider region is discussed. As the closest neighbor, the energy system of South Korea is considered, first regarding the possibility of a similar full renewable energy reliance, and then for possible synergetic effects of connecting the Korean and the Japanese energy systems, in order to be able to better cope with the intermittency of renewable energy source flows.     

UK electricity requirements and the environmental and economic aspects of the development of the combined cycle power station

In the space of three to four years, gas has changed from being a premium fuel, not to be utilized in power stations, to virtually the only fuel being considered for future electricity generation in the UK. This paper reviews the growth in the use of gas for electricity generation within the UK, with particular regard to the adoption of the gas-fired combined cycle power station. The environmental, economic and strategic issues associated with the proposed development of approximately 27 GW of new gas-fired plant are analysed and the resulting effects on existing base load power plant within the UK are considered.Dr James W.S. Longhurst is Director of the Atmospheric Research and Information Centre, ARIC, at Manchester Metropolitan University He is an environmental scientist who has specialized in the air quality impacts of transport and energy. He holds a BSc, MSc and PhD in Environmental Science from, Plymouth Polytechnic, Aston University and Birmingham University, respectively. He has written numerous papers, consultancy reports, books and technical reports since 1986.Jane Bantock joined ARIC in 1992 with a degree in Environmental Studies from Manchester Polytechnic. She jointly manages ARIC's information and education programmes. Her research interests include the inter-relationship of UK energy policy and emission control in the electricity generating sector, the subject of her part time PhD, and urban air quality issues.     

Emissions study of co-firing waste carpet in a rotary kiln

Post-consumer carpet represents a high volume, high energy content waste stream. As a fuel for co-firing in cement kilns, waste carpet, like waste tires, has potential advantages. Technological challenges to be addressed include assessing potential emissions, in particular NO emissions (from nylon fiber carpets), and optimizing the carpet feed system. This paper addresses the former. Results of pilot-scale rotary kiln experiments demonstrate the potential for using post-consumer waste carpet as a fuel in cement kilns. Continuous feeding of shredded carpet fiber and ground carpet backing, at rates of up to 30% of total energy input, resulted in combustion without transient puffs and with almost no increase in CO and other products of incomplete combustion as compared to kiln firing natural gas only. NO emissions increased with carpet waste co-firing due to the nitrogen content of nylon fiber. In these experiments with shredded fiber and finely ground backing, carpet nitrogen conversion to NO ranged from 3 to 8%. Conversion increased with enhanced mixing of the carpet material and air during combustion. Carpet preparation and feeding method are controlling factors in fuel N conversion.     

CO2-free paper?

Black liquor gasification–combined cycle (BLGCC) is a new technology that has the potential to increase electricity production of a chemical pulping mill. Increased electricity generation in combination with the potential to use biomass (e.g. bark, hog fuel) more efficiently can result in increased power output compared to the conventional Tomlinson-boiler. Because the BLGCC enables an integrated pulp and paper mill to produce excess power, it can offset electricity produced by power plants. This may lead to reduction of the net-CO₂ emissions. The impact of BLGCC to offset CO₂ emissions from the pulp and paper industry is studied. We focus on two different plant designs and compare the situation in Sweden and the US. The CO₂ emissions are studied as function of the share of recycled fibre used to make the paper. The study shows that under specific conditions the production of “CO₂-free paper” is possible. First, energy efficiency in pulp and paper mills needs to be improved to allow the export of sufficient power to offset emissions from fossil fuels used in boilers and other equipment. Secondly, the net-CO₂ emission per ton of paper depends strongly on the emission reduction credits for electricity export, and hence on the country or grid to which the paper mill is connected. Thirdly, supplemental use of biomass to replace fossil fuel inputs is important to reduce the overall emissions of the pulp and paper industry.     

The economics of tire remanufacturing

The world market for tires is described to identify the current material flow from raw materials to tires and the used tire disposal problem. Then, I describe the value-adding operations in the tire production process and in the tire retreading process. Once retreading is identified as the only recovery alternative that maximizes tire utilization, I explain why heat generation is the only recovery alternative, when retreading is not technically feasible. The economic values of heat generation in electric plants and in cement kilns are discussed. The paper culminates with the case of retreading, the tire remanufacturing process and the recommendation of a simple decision rule for selecting the number of times a tire should be retreaded to maximize its utilization.     

The living banana plant as a long-lasting battery cell

Among citrus fruits, lemon is widely used as a low-power electrical source. Although, it can generate a potential difference, this phenomenon is only sustainable for few days, and no other alternative organism has been reported to provide a similar potential with longer duration. This study reports the discovery of living banana plant as an inexpensive, reliable, stable, and long-lasting power. A Zn anode and Cu cathode are inserted into banana plant to extract electricity, and the organic compounds of plant act as electrolyte. This new discovery may introduce an era of providing renewable energy to who live in proximity to banana plantations.     

An analysis of the use of life cycle assessment for waste co-incineration in cement kilns

Life cycle assessment, LCA, has become a key methodology to evaluate the environmental performance of products, services and processes and it is considered a powerful tool for decision makers. Waste treatment options are frequently evaluated using LCA methodologies in order to determine the option with the lowest environmental impact. Due to the approximate nature of LCA, where results are highly influenced by the assumptions made in the definition of the system, this methodology has certain non-negligible limitations. Because of that, the use of LCA to assess waste co-incineration in cement kilns is reviewed in this paper, with a special attention to those key inventory results highly dependent on the initial assumptions made. Therefore, the main focus of this paper is the life cycle inventory, LCI, of carbon emissions, primary energy and air emissions. When the focus is made on cement production, a tonne of cement is usually the functional unit. In this case, waste co-incineration has a non-significant role on CO₂ emissions from the cement kiln and an important energy efficiency loss can be deduced from the industry performance data, which is rarely taken into account by LCA practitioners. If cement kilns are considered as another waste treatment option, the functional unit is usually 1 t of waste to be treated. In this case, it has been observed that contradictory results may arise depending on the initial assumptions, generating high uncertainty in the results. Air emissions, as heavy metals, are quite relevant when assessing waste co-incineration, as the amount of pollutants in the input are increased. Constant transfer factors are mainly used for heavy metals, but it may not be the correct approach for mercury emissions.     

四川省新型干法水泥行业发展概况及其环境问题分析

本文简述了四川省“十一五”期间新型干法水泥工业发展概况和取得的环境效益,分析了新型干法水泥工业发展中面临的环境问题,提出利用新型干法水泥回转窑处理有机废物和危险废物是今后水泥行业可持续发展的一个重要方向。     

The economic and environmental benefits of increased use of pfa and granulated slag

It is commonly claimed that increased use of pulverised fuel ash (pfa) and ground granulated blast-furnace slag in concrete as partial replacement for Portland cement can have economic, amenity and technical advantages. Many factors need to be considered is such an analysis and this paper is offered as a contribution to the debate of this issue, and not as a definite solution. In the long-term the major benefit may be in the savings of the energy that would otherwise be required for increased production of Portland cement.     

Toward energy and livelihoods security in Africa: Smallholder production and processing of bioenergy as a strategy

The past few years have seen a phenomenal rise in the production and consumption of biofuels and biodiesel at the global level. This development is of special significance to Africa, where about 550 million people (75% of the total population in Sub‐Saharan Africa) depend on traditional biomass (wood, charcoal, cow dung, etc.) and lack access to electricity or any kind of modern energy service. Derived from plants and agricultural crops, biofuels and biodiesel represent modern forms of bioenergy and more efficient use of biomass energy. Beyond efficiency, modern bioenergy offers tremendous opportunities to meet growing household energy demands, increase income, reduce poverty, and mitigate environmental degradation. In the African setting, energy and livelihoods security are indeed inseparable. This paper argues economic, social, and environmental benefits of modern bioenergy can be realized through a strategy that centres on smallholder production and processing schemes and pursuit of a livelihood approach to energy development. Such a scheme opens up new domestic markets, generates new cash incomes, improves social wellbeing, enhances new technology adoption, and lays the ground for rural economic transformation and sustainable land use. The paper concludes by underlining the vital importance of considering sound property rights and strategic planning of sustainable development as tools for sustainable energy and livelihoods security.     

Biogas upgrading and utilization from ICEs towards stationary molten carbonate fuel cell systems

Biogas production from anaerobic digestion has increased rapidly in the last years, in many parts of the world, mainly due to its local scale disposition and to its potential on greenhouse gases (GHG) emissions mitigation. Biogas can be used as fuel for combined heat and power systems (CHP), in particular for internal combustion engines (ICEs). In recent investigations, fuel cells have been considered as alternative CHP systems. In the present article, two different energy conversion systems are compared: a 1.4 MW class MCFC system, running on pipeline natural gas, and an in situ ICE, running on biogas. In the first case, biogas is considered as a source fuel to obtain upgraded gas to be injected in the natural gas grid. In such scenario, the location of the fuel cell power plant is no longer strictly connected to the anaerobic digester site. Several energy balances are evaluated, considering different upgrading techniques and different biogas methane/carbon dioxide ratios.     

新型垃圾衍生燃料制备工艺

介绍了一项新型垃圾衍生燃料RDF制备技术。该技术通过改变现有焚烧炉工作状况入手,利用专有技术对南方高湿混合生活垃圾进行预处理制成衍生燃料后再进行焚烧,降低了垃圾焚烧处理对原料、热值及水分的要求,提高了焚烧法处理垃圾的适用范围,减少了能耗及成本,提高了处理能力和热能输出,极大降低了焚烧尾气所造成的二次污染,实现了重要技术突破。     

A concept for simultaneous wasteland reclamation, fuel production, and socio-economic development in degraded areas in India: Need, potential and perspectives of Jatropha plantations

The concept of substituting bio‐diesel produced from plantations on eroded soils for conventional diesel fuel has gained wide‐spread attention in India. In recent months, the Indian central Government as well as some state governments have expressed their support for bringing marginal lands, which cannot be used for food production, under cultivation for this purpose. Jatropha curcas is a well established plant in India. It produces oil‐rich seeds, is known to thrive on eroded lands, and to require only limited amounts of water, nutrients and capital inputs. This plant offers the option both to cultivate wastelands and to produce vegetable oil suitable for conversion to bio‐diesel. More versatile than hydrogen and new propulsion systems such as fuel cell technology, bio‐diesel can be used in today's vehicle fleets worldwide and may also offer a viable path to sustainable transportation, i.e., lower greenhouse gas emissions and enhanced mobility, even in remote areas. Mitigation of global warming and the creation of new regional employment opportunities can be important cornerstones of any forward looking transportation system for emerging economies.     

Biomass use in chemical and mechanical pulping with biomass-based energy supply

The pulp and paper industry is energy intensive and consumes large amounts of wood. Biomass is a limited resource and its efficient use is therefore important. In this study, the total amount of biomass used for pulp and for energy is estimated for the production of several woodfree (containing only chemical pulp) and mechanical (containing mechanical pulp) printing paper products, under Swedish conditions. Chemical pulp mills today are largely self-sufficient in energy while mechanical pulp mills depend on large amounts of external electricity. Technically, all energy used in pulp- and papermaking can be biomass based. Here, we assume that all energy used, including external electricity and motor fuels, is based on forest biomass. The whole cradle-to-gate chain is included in the analyses. The results indicate that the total amount of biomass required per tonne paper is slightly lower for woodfree than for mechanical paper. For the biomass use per paper area, the paper grammage is decisive. If the grammage can be lowered by increasing the proportion of mechanical pulp, this may lower the biomass use per paper area, despite the higher biomass use per unit mass in mechanical paper. In the production of woodfree paper, energy recovery from residues in the mill accounts for most of the biomass use, while external electricity production accounts for the largest part for mechanical paper. Motor fuel production accounts for 5–7% of the biomass use. The biomass contained in the final paper product is 21–42% of the total biomass use, indicating that waste paper recovery is important. The biomass use was found to be about 15–17% lower for modelled, modern mills compared with mills representative of today's average technology.