Herøya Industrial Park was established by Norsk Hydro in 1928-29 as a site for the production of fertiliser. Over the years the area has undergone substantial changes, from being a purely Hydro production site to its current status as an open industrial park.
- Norsk Hydro is founded on 2 December by engineer Sam Eydes and Professor Kristian Birkeland, on the basis of their own inventions, vision and faith in the potential of Norwegian hydroelectric power.
- Fertiliser production starts at Notodden, using the Birkeland-Eyde method.
- Eidanger Salpetre Factory , now Herøya Industrial Park, is under construction at Herøya, the first sod being cut on 2 February 1928. The plant is intended for processing ammonia (produced by the HaberBosch method at Rjukan) into nitrogen fertiliser (calcium nitrate).
- Production of nitrogen fertiliser begins on 1 June.
- Commissioning of a new factory for production of complete fertiliser (NKP), with a capacity of 36,000 t per year.
- The German occupiers hope to start production of light metals and embark on an aluminium factory and a magnesium factory, also constructing a chlorine factory.
- The factories are bombed by the Allies on 24 July 1943.
- Establishment of separate research laboratory at Herøya, today called Herøya Research Park.
- The "German factories" are organised as a separate company, Herøya Electrochemical Factories (HEFA), with equal shares held by the Norwegian Government and Hydro. The aim is to kickstart production in the bombed-out factories.
- Start-up of chlorine factory, later closed in 1987.
- Construction of urea factory, with an annual capacity of 10,000 t. The factory closes in 1987, when it has reached an annual capacity of 200,000 t.
- HEFA starts up PVC production (2000 t per year).
- Start of magnesium production. Annual capacity of 1000 t. The planned "German capacity" of 10,000 t is reached in 1960, while the figure for 2001 is 40,000 t.
- The factory has a further capacity of 10,000 t for remelting of returned metal.
- Start of production of polyvinyl chloride (PVC) plastic, with an annual capacity of 2000 t. By 1995, capacity is approx. 90,000 t, based on raw materials (vinyl chloride – VCM) from Hydro Rafnes.
- The Norwegian Government and Hydro agree for Hydro to take over all shares in HEFA. Hydro takes over operational responsibility for the HEFA sites and integrates them into the operation and organisation of the Eidanger Saltpetre Factories.
- The legal processes surrounding the takeover of HEFA come to an end. Hydro takes over all shares in HEFA and dissolves the company.
- From now on, all HEFA activities are part of Hydro and the Eidanger Saltpetre Factories.
- Ammonia factory NI, oil-based. Annual capacity of 125,000 t.
- Pulled down in September 1986, following explosion the previous year.
- Start-up of complete fertiliser factory no. 2. Annual capacity of 170,000 t. Dry side closes down in December 1987, at a capacity of 320,000 t.
- The liquid side currently supplies raw materials for complete fertiliser factory no. 4.
- Complete fertiliser factory no. 3 starts up, the world's first full-scale prilling plant for NPK fertiliser. Annual capacity is 430,000 t, later increased to 750,000 t.
- Start-up of ammonia factory NII, with naphtha and wet gas as the raw materials. Annual capacity is 350,000 t, later increased to 420,000 t.
- The Norwegian Oil Age begins with the first discovery in the North Sea, the Ekofisk field, the fruit of Hydro's commitment to exploration, alone among Norwegian companies. A new epoch begins for Norsk Hydro, with significant effects on the company's total activities in its Grenland home region.
- Renewal of calcium nitrate production.
- A completely new magnesium technology, the magnesium chloride leaching process. The factory is taken out of production in 1991.
- New magnesium electrolysis technology.
- Complex fertiliser factory no. 4, the world's largest NPK factory, with a capacity of 1 million t per year, and at the time, Norway's highest building (110 m).
- New calcium nitrate factory with plate granulation.
- Closure of chlorine factory based on mercury electrolysis.
- Commissioning of new plant for cleaning water from magnesium production. It reduces emissions of chlorinated hydrocarbons by over 99 per cent. Cleaning effect and reliability exceed all expectations and attract international interest.
- A nitrogen cleaning plant is completed at complex fertiliser factory 3, a total investment of NOK 420 m.
- Start-up of world's largest nitric acid factory in June, with a capacity of 2000 t per day.
- Nitric acid production goes up from 950,000 t to 1.2 million t per year.
- Completion of new quay facilities for ro-ro shipping, thus rationalising transport of raw materials and finished goods to and from Herøya.
- Certification processes underway in all parts of Hydro's activities at Herøya, in order to meet international quality requirements (ISO standard).
- Hydro Support is established to offer operating and maintenance solutions to businesses in Herøya Industrial Park, and to external customers in industry, services and public administration.
- All production sections are certified according to ISO requirements.
- Upgrading and expansion of PVC factory.
- Construction starts on new factory for production of potassium nitrate fertiliser and technical hydrochloric acid.
- Magnesium remelting works under construction.
- The Research Centre is ISO-certified
- The ammonia factory is reconstructed, modernised and expanded. Capacity goes up to 530,000 t and ammonia emissions to water are significantly reduced.
- On 25 October, the Hydro Corporate Assembly votes to cease production of magnesium metal at Herøya due to difficult market conditions. It is decided to continue operation of the remelting plant under Hydro control.
- The company ScanWafer enters into agreement with Hydro to build a new factory for silicon wafers for solar cell panels at Herøya.
- Svenska Mineral contracts to take over parts of the magnesium line for production of various calcium products.
- On 5 April, Hydro Magnesium Norge shuts down production of magnesium metal after five months of gradual winding down.
- Hydro establishes Herøya Industrial Park, opening it for external industrial establishments.
- REC's first wafer factory starts production.
- Hydro demerges the fertiliser activities as an independent company. Formerly Agri Porsgrunn, it becomes part of Yara International, established on 1 March 2004.
- The company is approved for quotation on the Oslo Stock Exchange on 25 March of the same year.
- REC starts construction of wafer factory no. 2.
- SIC Processing decides to build a factory for recovering cutting fluid from REC.
- Hydro Magnesium's remelting works closes.
- There are now about 90 tenants on the industrial park area, several of whom are large processing companies.
- REC Wafer decides to build two new wafer factories at Herøya.
- SIC Processing starts up its first factory.
- Statoil and Hydro merge their oil and gas activities, forming the company StatoilHydro. Many of the previous employees in the industrial park, including employees at Hydro's Research Centre, are transferred to StatoilHydro (the name is later changed to Statoil).
- Hydro sells out its petrochemical activities to the UK based chemical company INEOS.
- REC's second wafer factory starts production.
- IS Partner (a fully-owned subsidiary of StatoilHydro) is sold to EDB Business Partner ASA.
- Hydro Production Partner AS and Produksjonstjenester AS (fully-owned Hydro companies) are sold to the German Bilfinger Berger Industrial Services AG (BIS).
- REC's third wafer factory starts production.
- REC's fourth wafer factory starts production.
- SIC Processing starts up its second factory.
- EDB merges with Ergo Group to form EDB ErgoGroup.
- Norsk Jernbanedrift decides to build a new office building on a fill site at Gunneklev.
- REC decides to close wafer factories 1 and 2.
- SIC Processing decides to close factory 1.
- RHI acquires company SMA Magnesia and decides to build a factory for melted MgO.
- RHI’s new factory for melted MgO, fused magnesia, starts production.
- Herøya Industripark AS and Herøya Nett AS are established as wholly owned Hydro companies.
- REC Wafer Norway AS turn bankruptcy
- Proventia AS, a business incubator for start-ups and growth is established at Herøya Industrial Park
- Nokas Beredskap AS takes over the industrial safety and emergency call-out services in the park
- Yara Norge builds a new fertilizer terminal at Herøya
- Yara announce expantion of the fertilizer production and a new nitric acid plant amount to NOK 2,25 billion
- Hydro enter into an agreement with Industriarbeidermuseet in Rjukan to take over historical objects, documents and photographs from Herøya Industrial Park
- Norsk Hydro ASA enter into an agreement with Oslo Pensjonsforsikring regarding the sale of Herøya Industripark AS
- Elkem Solar has decided to start production of silicone blocks at Herøya
- RHI Normag closes down the fused magnesia plant
- The sale of Herøya Industrial Park AS to Oslo Pensjonsforsikring AS (OPF) is completed