Dorota BURCHART-KOROL

Transcription

1 SUSTAINABILITY AND ECO-EFFICIENCY ASSESSMENT OF BIOMASS USE IN STEELMAKING Dorota BURCHART-KOROL CENTRAL MINING INSTITUTE, Plac Gwarkow 1, , Katowice, Poland, Abstract The conventional route for steel production produces high emissions of greenhouse gases (GHGs). Biomass as alternative fuel can be applied in steelmaking to reduce GHGs emission. Biomass use in steel industry was discussed in this paper. Evaluation of three dimension of sustainability assessment of biomass use was presented. The social, environmental and economic dimension of biomass use in steelmaking was shown with life cycle approach. This paper adapted LCSA (life cycle sustainability assessment) methodologies to undertake an analysis of the sustainability dimensions of steelmaking technology. Additionally eco-efficiency analysis of biomass use in steelmaking was discussed. Keywords: sustainability, LCSA, eco-efficiency, life cycle approach, biomass, iron and steel industry 1. INTRODUCTION According to the Intergovernmental Panel on Climate Change (IPCC) global CO 2 emissions have to be significantly reduced by The iron and steel industry accounts for approximately 6.7% of total global CO 2 emissions. The greenhouse gas of most relevance to the world steel industry is CO 2, as it makes up approximately 93% of all steel industry GHGs emissions [1]. Replacement of fossil carbon by biomass is one of the effective approaches to reduce the GHGs emission intensity of the iron and steel making process. According to World Steel Association [1] CO 2 emissions was 1.8 t CO 2 /Mg crude steel based on routespecific CO 2 intensities for three steel production routes: basic oxygen furnace, electric arc furnace and open hearth furnace; and weighted based on the production share of each route. Blast furnace process is the major GHGs emitting process in integrated steel mills. Recently research were concerned with environmental assessment of ironmaking [2,3], decreasing CO 2 and dust emission [4-6], reverse system [7] and harmful elements assessment in iron production [8]. Primary research of biomass materials (sunflower briquettes, almond nut shells, hazelnut shells, rape straw, rape seed and charcoal) use in ironmaking were shown in the papers [9,10]. The aim of this study was analyzed of sustainability and eco-efficiency of biomass use as alternative fuel in iron and steel industry. 2. METHODS Life cycle sustainability assessment (LCSA) enlarges the scope of life cycle assessment (LCA) by integrating additional social and economic aspects into the decision making process with the aim to have more sustainable products or technologies [11-13]. LCSA integrates the three components i.e. conventional LCA, social LCA (SLCA) and life cycle costing (LCC), only a few attempts of such an integrated assessment have been made so far [11]. All three components include a goal and scope definition, an LCI phase and an interpretation phase [14]. Life cycle impact assessment (LCIA) has not yet been described for LCC. LCSA is defined as a sustainability impact assessment technique that aims to assess the environmental, social and economic aspects of products and their potential positive and negative impacts along their life cycle encompassing extraction and processing of raw materials, manufacturing, distribution, use, re-use, maintenance, recycling and final disposal. The eco-efficiency concept was first defined in 1989 by The World Business Council for Sustainable Development (WBCSD) as being achieved by the delivery of competitively priced goods and services that

2 satisfy human needs and bring quality of life, while progressively reducing ecological impacts and resource intensity throughout the life cycle to a level at least in line with the earth s carrying capacity [15]. According to ISO 14045:2012 [16] eco-efficiency is an aspect of sustainability relating the environmental performance (measurable results related to environmental aspects) of a product system (collection of unit processes with elementary and product flows, performing one or more defined functions, and which models the life cycle of a product) to its product system value. Eco-efficiency indicator is measured relating environmental performance of a product system to its product system value. An eco-efficiency is a relative concept and a system is only more-or-less eco-efficient in relation to another system. Environmental assessment in ecoefficiency evaluation shall be based on Life Cycle Assessment (LCA) according to ISO 14040:2006 [14]. Development of eco-efficiency and eco-effectiveness in steel industry in Poland was presented in [17]. 3. RESULTS AND DISCUSION 3.1. Sustainability aspects assessment of biomass use in steel industry Sustainability dimensions of biomass use as alternative fuel for steelmaking was listed in Table 1 and aspects of fossil fuels was listed in Table 2. Social life cycle assessment (SLCA) of alternative fuels was shown in [18]. Social aspects indicators were analyzed included land-use, employment, workplace health and safety. The scale effects of a shift to biomass technologies on land-use were significant. Biomass (charcoal produced from Radiata pine plantation forestry) alternatives represented a 3.84% increase in land use compared to metallurgical coal. Production of pine plantation forestry in Australia would be required to increase by 67% to accommodate the full substitution of coal (an additional 1.35 million hectares under plantation forestry). Biomass alternatives were significant generators of direct employment at that regional level (2.9 x 10-3 per Mg of steel for Pine biomass as compared to 2.66 x 10-4 for metallurgical coal). There was also a potential for employment created from processing by-products such as bio-oil from eucalypts and in particular biomass residues. However, sourcing energy from biomass was identified as having concomitantly higher rates of workplace injuries (6.28 x 10-5 per Mg of steel for pine compared to 3.23 x 10-6 per Mg of steel for coal). The supply of land of this magnitude presents a stern challenge given land-use conflicts associated with plantation forestry expansion. However, local level conflicts have manifest from the community health and amenity impacts, and subsidence effects associated with metallurgical coal mining despite the relatively less significant scale of land (5 x 10-3 hectares per Mg of steel) used [18]. Wood pellets were examined to support ironmaking from a life cycle analysis perspective [19]. Comparison of GHGs emissions in different ironmaking pathways (conventional ironmaking, charcoal bio-ironmaking and wood pellet bio-ironmaking) was presented. The functional unit of this analysis is defined as one Mg of hot metal produced. The total emission of the systems was expressed in g CO2eq/Mg HM based on IPCC method. The pathway charcoal bio-ironmaking process included in the analysis consist of the growth and collection of raw biomass material for pellet production, pelletization of raw biomass, pyrolysis/carbonization of wood pellets and the associated transportation of materials Results of the analysis showed that GHG emission in the carbon life cycle of bio-ironmaking via this pathway was kg CO2eq/ MgHM (Mg of hot metal) compared to 1552 kgco2eq/mghm in the conventional blast furnace process. The high reduction, 83%, arises from the GHG neutral characteristic of renewable biomass materials. This would result in a reduction of GHG emission associated with Canadian hot metal production from 12 Mt/yr to 2 Mt/yr. The low charcoal yield in wood pyrolysis imposes the most significant technical challenge on bio-ironmaking. The charcoal bio-ironmaking pathway involved the collection of forestry residues as raw materials and their conversion into charcoal prior to long-range transportation. The use of side products or residues from forestry operation as raw materials leads to emissions associated with their growth and harvesting. The transportation of high-carbon density charcoal also lowers emission related to long-range transportation of materials. As a result, the total emission of the charcoal bio-ironmaking process is 62.8 kg CO2eq/ MgHM. In the pathway wood pellet bio-ironmaking, raw materials are purposely grown for pellet production. Therefore, emissions associated with the growth of raw biomass materials and harvesting should be included, which

3 significantly increases emissions associated with the collection and transportation of raw materials compared to the charcoal bio-ironmaking process. The carbon density of wood pellet was relatively low compared to charcoal [19]. According to [22-24] wood chips is suitable biomass for ironmaking. Forest chip is cheap fuel and has increasing potential in the market. Depending on the fossil fuel substitution rate in blast furnace, needed wood amount could reach 3 million cubic meters [22,24]. The most studied bio-based reducing agent is charcoal. Depending on the raw material, charcoal production cost could be in the range of /Mg with charcoal production capacity of Mg. Currently the prices of fossil reducing agents were lower than the ones produced from biomass. However the future carbon restrained world might make them more competitive. Task relating to evaluation of life cycle impacts of using biomass in ironmaking is still in progress [22-24]. Charcoal can be used as a alternative fuel for coke charge to smaller blast furnace (BF) due to its insufficient strength. Charcoal Powder Injection (CPI) was used in mini-bfs in Brazil at injection rates from kg/ MgHM [24,25]. Table 1 Compare of sustainability aspects of biomass use for steelmaking Biomass Category Indicator Amount Reference Land use Biomass production 1.97 x 10-1 hectares/mg of steel Direct Biomass 2.6 x 10-3 per Mg of steel Charcoal Indirect Biomass 2.8 x 10-3 per Mg of steel Employment (pine biomass) Direct Charcoal 2.95 x 10-4 per Mg of steel [18] Indirect Charcoal 2.95 x 10-4 per Mg of steel Health and Lost time injuries safety (biomass) 6.28 x 10-5 per Mg of steel Charcoal bioironmaking IPCC Carbon footprint 62,8 kg CO 2 eq/mg HM Wood pellet (bioironmaking) IPCC Carbon footprint 261,8 kg CO 2 eq/mg HM [19] Biomass Cost Production cost 386 US$/Mg Biomass cost (Australia) 260 US$ [20] Production cost US$/Mg Biomass cost (Brazil) 91.6 US$ [21] IPCC Carbon footprint kg CO 2 eq/mj Wood logs Land use Land occupation m 2 a/mj Human health Human toxicity kg 1.4-DB eq/mj IPCC Carbon footprint kg CO 2 eq/mj [27] Wood chips Land use Land occupation m 2 a/mj Human health Human toxicity kg 1.4-DB eq/mj Source: own analyses Table 2 Compare of aspects of fossil fuels use for steelmaking Fossil fuels Category Indicator Amount Reference Land use Coal production 5 x 10-3 hectares/mg of steel Direct Coal 1.34 x 10-4 per Mg of steel Metallurgical Indirect Coal 2.7 x 10-4 per Mg of steel Employment coal Direct Coke 1.3 x 10-4 per Mg of steel [18] Indirect Coke 1.3 x 10-4 per Mg of steel Health and Lost time injuries safety (coal) 3.23 x 10-6 per Mg of steel Coke Ironmaking IPCC Carbon footprint 1552 kg CO 2 eq/mg HM [19] Hard coal coke Source: own analyses IPCC Carbon footprint kg CO 2 eq/mj Land use Land occupation m 2 a/mj Human health Human toxicity kg 1.4-DB eq/mj [27]

4 The HIsmelt iron-making process could potentially be run on 100% wood charcoal instead of coal in steelworks. Wood charcoal does not have the physical strength to support the iron ore burden in large BFs, but can replace all of the coke in small ones. Charcoal can also be fed into EAFs. But the sustainable production of charcoal from planted trees needs large amounts of land. Producing 500 Mt of hot metal requires over hectares (400 km 2 ). There is also the competition with land for food production and with other industrial users, such as the power generating industry, that will lead to increased biomass costs. These factors limit the role of biomass in CO 2 abatement [26]. In this paper the percentage share of emissions of GHGs in the different stages of ironmaking pathways with coke, charcoal and wood pellets (Table 3) was carried out. Table 3 Share of GHGs emission of alternative ironmaking pathways, % Coke Charcoal Stages Conventional ironmaking Bio-ironmaking Residues First stages Coal mining collection and transport 80 km Transportation Production 1.68 (rail: 46km, barge: 434 km) 8.57 Cokemaking (truck: 1200 km) 2.39 Charcoal making Wood Pellet Bio-ironmaking Harvesting and transport-115 km (rail:180 km, vessel:890 km) Peller production and pyrolysis Ironmaking Source: Own analyses based on [19] It was found that in the case of coke using the highest impacts of GHGs emissions occurs during ironmaking - in a blast furnace (88.85%). In the case of charcoal using, the highest impact of GHGs is generated in transportation of charcoal (65.29%). In the case of wood pellet using, the highest GHGs emission is at the stage - harvesting and transport (55.08%) Eco-efficiency of biomass use in steelmaking Eco-efficiency considers two aspects of sustainable development economic and environmental assessment. In order to eco-efficiency assess of biomass use in steelmaking it should be taken into account environmental and economic impact assessment indicators. The higher cost and environmental impacts cause the lower eco-efficiency indicator. In this paper environmental assessment (ecological fingerprint) of chosen conventional and alternative fuels for ironmaking was carried out. The system boundary was from cradle to gate of fossil fuels and alternative fuels production. The results could be useful to the steel producers and interested to compare the relative environmental impacts by different prospective fuels. The results of environmental LCA were expressed in different units. Therefore in order to comparative analysis of LCA, results were presented in relative values (Fig. 1). LCA analysis allowed obtaining the following conclusions: the highest carbon footprint and fossil fuels depletion had coke, however wood logs have the highest agricultural land occupation and wood chips had the highest energy demand of renewable, biomass. Agricultural land occupation Non renewable, fossil 1 0,8 0,6 0,4 0,2 0 Carbon footprint Renewable, biomass Human toxicity Hard coal Anthracite Coke Wood logs Wood chips

5 Fig.1 Ecological Fingerprint of chosen fuels for steelmaking Source: Own analyses based on calculations in SimaPro In the assessment of the biomass use should be taken into account not only the production system but also biomass preparation and transportation impacts associated with land use, greenhouse gases emission and other impact categories. For evaluation of the use of biomass, costs are derived primarily from the costs of transporting biomass. Supply cost is the significant determinants of eco-efficiency of biomass use in steelmaking. The price of the charcoal is critical factor for industry. In recent years, biomass became an attractive alternative source of energy to traditional fossil fuels such as coal and coke and potential of biomass use in steelmaking increase. It was demonstrated that biomass use in steelmaking is method to decrease of GHGs of steelmaking. Lower GHGs emissions and lower cost production of biomass compare to conventional fuel (coke) means that biomass has a higher eco-efficiency than conventional fuels. However to holistic eco-efficiency assessment should be taken into account the whole life cycle of biomass and conventional fuel as well as other categories related to biomass chain (land use, transportation, cost supply etc.). 4. CONCLUSIONS In this paper biomass use in steelmaking was proposed as one of possibilities of replacement of fossil fuels to significantly reduce GHGs emissions from iron and steelmaking. Biomass can be used as alternative fuels in ironmaking sinter plant and blast furnace. However biomass use should be evaluated accurately taking into account all aspects of sustainable development. Sustainability assessment of biomass use including environmental, economic and social aspects. In order to select the optimal alternative fuel for iron and steelmaking, should be evaluate three dimensions of sustainability (environmental, economic and social aspect), the properties and availability of biomass use. Supply cost and selection of environmental impact categories of biomass are the significant determinants of eco-efficiency analysis. Further research of eco-efficiency assessment of biomass use in steelmaking is essential. Further reducing the ecological footprint of steelmaking, promoting life-cycle perspective and further improving steel end-of-life are needed to make sustainable steel. LITERATURE [1.] Worldsteel LCA Methodology report, ( ) [2.] BURCHART-KOROL D.: Evaluation of environmental impacts in iron-making based on life cycle assessment. 20th Anniversary International Conference on Metallurgy and Materials (METAL), Tanger Ltd Brno 2012, [3.] BURCHART-KOROL D.: Fossil fuels consumption evaluation in blast furnace technology based on different life cycle impact assessment methods. 21 International Conference on Metallurgy and Materials (METAL), Tanger Ltd Brno 2013 (in print) [4.] ROUBÍČEK, V., PUSTĚJOVSKÁ, P., BILÍK, J., JANÍK, I. Decreasing CO 2 Emissions in Metallurgy. Metalurgija, 2007, 46 (1), pp , ISSN [5.] PUSTĚJOVSKÁ, P., BROŽOVÁ, S. JURSOVÁ, S. Environmental benefits of coke consumption decrease. METAL 2010:19th International Conference on Metallurgy and Materials Brno, Czech Republic, Tanger, Ltd., pp ISBN [6.] BURCHART-KOROL D., KOROL J., FRANCIK P.: Application of the New Mixing and Granulation Technology of Raw Materials for Iron Ore Sintering Process, Metalurgija, 2012, 51, [7.] GRACZYK M., BURCHART-KOROL D., WITKOWSKI K.: Reverse Logistics Processes in Steel Supply Chains, 21 International Conference on Metallurgy and Materials (METAL), Tanger Ltd Brno 2013 (in print)

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