technologyComment of kaolin production (RER, RoW): There exist two different processes for the production of market kaolin - a dry and a wet process. The first one - the dry process - is relatively simple but yields therefore also a lower quality product, reflecting the quality found in the crude kaolin. The wet process on the other hand side is used to produce filler and coating grades. It is this process that is modeled in this dataset. The most important four steps of the wet process are the following: - Mining: Nowadays most of kaolin mining is done in open pit mining. Depending on the composi-tion, either mining with shovels, draglines, motorized scrapers and front-end loaders is done (e.g. Georgia, USA) or mining with high-pressure hydraulic monitors (e.g. Cornwall, UK) is done. In the second case, a stream of water is washing out the fine particle kaolin and is leaving the coarse quartz and mica residues within the soil. - Mineral separation (degritting): Kaolin beeing a mineral, it is obvious that there are always also other minerals (the grit) in the kaolin deposits, which have to be separated. To separate two miner-als, either physical or chemical differences between the two substances are taken as base. In gen-eral, the mined kaolin is mixed therefore with water and a dispersing chemical to form a slurry that is then degritted (by e.g. rake classifiers, hydrocyclones or screens). - Kaolin benefication: When the separated kaolin fullfills not the specification asked a benefication process is added to improve e.g. the brightness (either by magnetic separation or by bleaching with ozone or hydrogen peroxide), the rheology (by blending different kaolins), the purity (either by blending or by magnetic separation) or the grain size distribution (again blending as a possibility). In this step, the producer is also deciding the form of delivery (bulk, powder, slurry). - Storage & transport: The storage is done either in silos (bulk and powder) or in tanks (slurries). Due to the fact that customers more and more apply for the 'just in time' principle, the storage ca-pacities of the producers are increasing and the transports are done more and more by lorry to the customer (more flexible than other means of transport). References: Hischier R. (2007) Life Cycle Inventories of Packagings & Graphical Papers. ecoinvent report No. 11. Swiss Centre for Life Cycle Inventories, Dübendorf, 2007.
technologyComment of cryolite production, from fluosilicic acid (GLO): The main production of cryolite involves hydrofluoric acid or fluosilicic acid. In both cases, the reactants can be combined with a variety of materials, such as Al2O3 · 3 H2O, Al2O3 · x NaOH, NaOH, NaCl, and Na2SO4. During the present reaction, fluosilicic acid is neutralised with sodium hydroxide. Then it reacts with Al2O3 to produce cryolite and silica. The reaction process is shown below: Al2O3 + 2H2SiF6 + 6 NaOH --> 2 Na3AlF6 + 2 SiO2 + 5 H2O It is difficult to predict how much of the cryolite is produced with the present reaction, since many production routes exist. The present inventory serves as an illustration of the cryolite production from fluosilicic acid. The alternative production route with HF is still considered to be the main production route (source: Ullmann encyclopedia, Cryolite, 2005). technologyComment of silica sand production (DE, RoW): Generally there are no differences in the quarrying process of silica sand compared to the “normal” sand process. An important difference is that silica sand is dried. It is assumed that the content of moisture before drying is about 5% and afterwards around 1%. Another difference is based on the high content of SiO2, which makes the raw material rarer. Losses in the conveyor belt transportation are taken into account.
technologyComment of bentonite quarry operation (DE, RoW): The technology used in the modelled German mine is probably state-of-art (first mining company in Europe taking part at an eco-audit based on EG-eco-audit requirements). The assumed thickness of the bentonite layer is 3 m. The thickness of overburden material is estimated to be 30 m. Digging and transportation is made by heavy diesel machines. Reference: Kellenberger D., Althaus H.-J., Jungbluth N., Künniger T., Lehmann M. and Thalmann P. (2007) Life Cycle Inventories of Building Products. Final report ecoinvent Data v2.0 No. 7. EMPA Dübendorf, Swiss Centre for Life Cycle Inventories, Dübendorf, CH.
technologyComment of gravel and sand quarry operation (CH): The typical technology for swiss gravel and sand mining was assumed.
technologyComment of fluorspar production, 97% purity (GLO): Open cast mining of resource. Separation by crushing, grinding and flotation. technologyComment of scandium oxide production, from rare earth tailings (CN-NM): See general comment.
technologyComment of gravel and sand quarry operation (CH): The typical technology for swiss gravel and sand mining was assumed.
technologyComment of rare earth oxides production, from rare earth oxide concentrate, 70% REO (CN-SC): This dataset refers to the separation (hydrochloric acid leaching) and refining (metallothermic reduction) process used in order to produce high-purity rare earth oxides (REO) from REO concentrate, 70% beneficiated. ''The concentrate is calcined at temperatures up to 600ºC to oxidize carbonaceous material. Then HCl leaching, alkaline treatment, and second HCl leaching is performed to produce a relatively pure rare earth chloride (95% REO). Hydrochloric acid leaching in Sichuan is capable of separating and recovering the majority of cerium oxide (CeO) in a short process. For this dataset, the entire quantity of Ce (50% cerium dioxide [CeO2]/REO) is assumed to be produced here as CeO2 with a grade of 98% REO. Foreground carbon dioxide CO2 emissions were calculated from chemical reactions of calcining beneficiated ores. Then metallothermic reduction produces the purest rare earth metals (99.99%) and is most common for heavy rare earths. The metals volatilize, are collected, and then condensed at temperatures of 300 to 400°C (Chinese Ministryof Environmental Protection 2009).'' Source: Lee, J. C. K., & Wen, Z. (2017). Rare Earths from Mines to Metals: Comparing Environmental Impacts from China's Main Production Pathways. Journal of Industrial Ecology, 21(5), 1277-1290. doi:10.1111/jiec.12491 technologyComment of sodium chloride production, powder (RER, RoW): For the production of dry salt, three different types of sodium chloride production methods can be distinguished namely, underground mining of halite deposits, solution mining with mechanical evaporation and solar evaporation. Their respective products are rock salt, evaporated salt and solar salt: - Underground mining: The main characteristic of this technique is the fact that salt is not dissolved during the whole process. Instead underground halite deposits are mined with traditional techniques like undercutting, drilling and blasting or with huge mining machines with cutting heads. In a second step, the salt is crushed and screened to the desired size and then hoisted to the surface. - Solution mining and mechanical evaporation: In this case, water is injected in a salt deposit, usually in about 150 to 500 m depth. The dissolution of the halite or salt deposits forms a cavern filled with brine. This brine is then pumped from the cavern back to the surface and transported to either an evaporation plant for the production of evaporated salt or transported directly to a chemical processing plant, e.g. a chlor-alkali plant. - Solar evaporation: In this case salt is produced with the aid of the sun and wind out of seawater or natural brine in lakes. Within a chain of ponds, water is evaporated by sun until salt crystallizes on the floor of the ponds. Due to their natural process drivers, such plants must be located in areas with only small amounts of rain and high evaporation rates - e.g. in the Mediterranean area where the rate between evaporation and rainfall is 3:1, or in Australia, where even a ratio up to 15:1 can be found. There are some impurities due to the fact that seawater contains not only sodium chloride. That leads to impurities of calcium and magnesium sulfate as well as magnesium chloride. With the aid of clean brine from dissolved fine salt, these impurities are washed out. As a fourth form on the market, the so-called 'salt in brine' may be found, which is especially used for the production of different chemicals. In this case, the solution mining technique without an evaporation step afterwards is used. This dataset represents the production of dry sodium chloride by underground mining (51%) and by solution mining (49%) with modern solution mining technology (thermo compressing technology). References: Althaus H.-J., Chudacoff M., Hischier R., Jungbluth N., Osses M. and Primas A. (2007) Life Cycle Inventories of Chemicals. ecoinvent report No. 8, v2.0. EMPA Dübendorf, Swiss Centre for Life Cycle Inventories, Dübendorf, CH.
technologyComment of salt production from seawater, evaporation pond (GLO): No comment present
technologyComment of graphite production (RoW): Data approximated with data from lime mining, crushing and milling. technologyComment of graphite production (RER): Technology for limestone mining, crusching and milling assumed as a first approximation. Overall yield of 95% is assumed.
technologyComment of boric acid production, anhydrous, powder (RER, RoW): This dataset models the production of boric acid from colemanite minerals (calcium borates) with the aid of sulfuric acid, with process yield of 95%. As by-product, gypsum (CaSO4) is produced. The production of boric acid can be summarized with the following reaction equation: (2CaO.3B2O3.5H2O) + 2 H2SO4 → 3 (B2O3.3H2O) + 2 CaSO4