Two Hong Kong hotels have partnered with a local manufacturer to create cement that uses limestone derived from oysters instead of extracting it from the ground in what is being called a pioneering effort to introduce renewable resources into one of the most carbon-intensive industries.
Eaton and Langham hotels joined forces with Hong Kong’s sole major cement producer, Green Island Cement, to collect eight tonnes of oyster shells and turn them into building material, according to Amie Lai Gor, the general manager of sustainability at the hotels’ parent company Great Eagle Holdings.
The project allowed them to source 80 per cent of the limestone needed to make cement from oysters.
Speaking to the press on Friday, Lai said she was inspired by studies and journal papers about reusing oyster shells, which are 91 per cent limestone, and wanted to do “a bit more beyond laboratory scale”.
“We brought together like-minded partners to repurpose oyster shells as a sustainable alternative raw material for cement production,” she said. “Our goal is to encourage more hotels and restaurants to participate, diverting more discarded oyster shells from landfills through upcycling.”
Cement and concrete production generates as much as 9 per cent of all human activity carbon dioxide emissions, making it the world’s third-largest contributor to global warming.
The planet-heating substance is produced during the excavation of limestone and the use of coal to convert it into quicklime.
Raymond Cheung Wai-man, a division manager at Green Island Cement specialising in operations and environmental business, said the company first thought about sourcing limestone from oyster shells 20 years ago.
But the company was initially reluctant to move ahead with the idea because of difficulties in separating impurities from the shells, such as mud and residual meat.
Eddy Tsang Pak-chung, the cement company’s chief executive, said the new project allowed them to develop a proper way of cleaning, storing and transporting the shells, which he called “the key success” in the project.
The city imported 3,300 tonnes of oysters last year, according to global food sourcing data analyst Tridge, with most leftover shells being sent to landfills.
Since 2021, the Airport Authority has cooperated with US-based NGO The Nature Conservancy to collect oyster shells in an attempt to rebuild an oyster reef around the airport island, in a bid to enhance the biodiversity of nearby waters, increase fishery resources and protect the coastline.
The authority said in June that 10 restaurants participated in the scheme, with the amount of shells collected increasing to 56 tonnes from 18 tonnes in 2021.
According to a joint study by the University of Hong Kong and The Nature Conservancy in 2021, a single oyster can filter up to 30kg of water per hour in summer and help clean seawater.
Lai said the hotels were discussing with local universities to quantify how much carbon could be reduced by using oyster shells instead of limestone to produce cement.
She added they would also explore the use of shells from other shellfishes.
Cheung said that while using oyster shells to produce cement was 10 times more expensive than using limestone, scaling up the project could help reduce the cost.
