For over two decades, the Movement for the Survival of the Ogoni People (MOSOP) and the people of Ogoni kingdom continuously agitated for the clean up of their land polluted by years of careless oil drilling and exploration by foreign multinationals.

On Thursday, Vice President, Professor Yemi Osinbajo represented President Muhammadu Buhari to flag off the clean-up process of the polluted environment.

While it’s not yet uhuru for the process, here are 5 things to know about the clean-up exercise.

1. The Clean-up process was birthed by Obasanjo’s govt

The clean-up follows a 2006 request to the UN by the government for a scientific investigation into the level of pollution in Ogoniland. This led to a three-year, landmark Unep report in 2011 which exposed shocking levels of pollution caused by spills in the region. The report identified 41 grossly polluted sites where oil had entered wells and underground water supplies.

2. Eighteen months before work starts

It will be at least 18 months before full remedial work starts in Ogoniland in the Niger delta, and possibly 25 years before all the swamps, creeks, fishing grounds and mangroves are restored after decades of spills by Shell, the national oil firm and other oil companies.

3. $200m to be spent annually

$200m (£139m) will be spent annually for five years to clear up the devastated 1,000 sq mile (about 2,600km2) region in Rivers state near Port Harcourt. It will involve building a factory to process and clean tens of thousands of tonnes of contaminated soil. There will also be a mass replanting of mangroves.

4. Employment opportunities

Many young Ogoni will be offered jobs, with several hundred engineers possibly being trained abroad, middle-level jobs and monitors recruited, and a few thousand jobs for manual workers. The UN Environment Programme (Unep) aims to create a taskforce of Ogoni people able to clean up many other devastated areas of the delta. It is hoped this will kickstart development in a region where the youth in many communities resort to sabotaging oil infrastructure and illegally refining diesel.

5. Source of the money

Each member of the SPDC joint venture is expected to pay a pro-rata share of the $1bn. Members include the state-owned Nigerian National Petroleum Corporation (55% share), SPDC (30%), Total E&P Nigeria (10%) and Agip (5%).