The company, which was named by the Financial Times as one of this year's Europe's Climate Leaders, also supplies urban landscaping materials for prestigious landmarks such as Trafalgar Square in London.
Dezeen's acting US Editor India Block interviewed Harrop about Marshalls' approach to sustainability, focussing on the company's concrete bricks, which Harrop claims are less carbon-intensive than traditional clay bricks.
"Due to the way we manufacture our products, they have significantly less embodied carbon than clay bricks – almost 50% less over their whole lifecycle," said Harrop.
Alongside his role at Marshalls, Harrop is also a non-executive director of Fair Tax Mark, a non-profit that gives certification to companies paying the correct amount of corporation tax.
Prior to working at Marshalls, Harrop was chairman of United Nations Global Compact Network UK, which helps businesses and non-businesses to engage in areas of human rights, labour, environment and anti-corruption.
From January 2011, Harrop was a non-executive director of the Ethical Trading Initiative, which seeks to promote workers' rights globally.
Harrop was appointed Officer of the British Empire by The Queen in the 2019 New Year Honours List for his services to the prevention of modern slavery and exploitation.