Euroimmun, Lübeck produces test systems with which antibodies can be determined in the serum of patients and thus autoimmune and infectious diseases (including COVID-19) as well as allergies. Chemical. Almost all chemical industry concentrate around Brunsbüttel. Covestro with 650 employee produced annually 400 000 tonnes methylene diphenyl diisocyanate, which using in synthesis of polyurethane. Yara (214 empl.) produce nitrogen fertilizers, but with special process instead of using natural gas, it use heavy oil, which allow also manufacture as byproduct vanadium oxide and sulphur. Heavy oil is source material to produce bitumen by Total Bitumen (130 empl.). Other plant is Sasol (520 empl.) produce fatty and Guerbet alcohols, paraffin and high-purity aluminum oxide, aluminum hydroxide and triethylaluminium. Other important location of chemical industry is Neumünster with EMS-Griltech which manufacture technical fibers from polyamides and polyesters, adhesives and powder coatings. Transport Kiel Canal The most important transport way in Schleswig-Holstein is Kiel Canal, which connect Brunsbüttel on North Sea with Kiel on Baltic Sea. Total cargo of ships reach peaks in 2007 and 2012, after that it continuous decline with 73.8 million tonnes in 2020. Ports The state has a total of 46 public ports and landing stages, four of which fulfill international transit functions: Kiel, Lübeck / Travemünde and Puttgarden on the Baltic Sea, Brunsbüttel on the North Sea. Kiel and Lübeck are also important for freight traffic to Scandinavia and Eastern Europe. Lübeck-Travemünde and Kiel are also important ferry and cruise ports. Puttgarden is the German port of the Vogelfluglinie to Denmark. Brunsbüttel is an important port for bulk goods and also serves as the basis for the offshore wind energy industry. Education Compulsory education starts for children who are six years old on 30 June. All children attend a "Grundschule", which is Germany's equivalent to primary school, for the first 4 years and then move on to a secondary school. In Schleswig-Holstein there are "Gemeinschaftsschulen", which is a type of comprehensive school. The regional schools, which go by the German name "Regionalschule" have been done away with as of 1 January 2014. The option of a Gymnasium is still available. During the schoolyear 2021/2022, there are 393 Grundschulen in Schleswig-Holstein educating 101.675 students. Combined with secondary schools, there are a total of 360.922 Students in Schleswig-Holstein. In a comparison of the federal states, Schleswig-Holstein has the highest student-to-teacher ratio in Germany at around 16.5:1 (national average: 15.2:1). In addition,