In the late 1980s, Bermuda was in a similar situation to the one the Cayman Islands finds itself in today. With almost 80,000 tonnes of domestic and commercial waste being disposed of annually, Bermuda’s only landfill was nearing capacity. Located in the capital city of Hamilton, the landfill was creating serious problems for the local community.
The Government of Bermuda decided to develop an integrated solid waste management system that included waste-to-energy as the primary waste treatment facility, along with special wastes management and composting. Completed in 1994, the Tynes Bay Waste Treatment Facility treats about 70,000 tonnes of municipal solid waste annually and produces almost 5 per cent of the island’s average electricity needs.
As the Bermuda government’s solid waste manager from 2005 to 2010, Martin Edelenbos experienced the benefits of waste-to-energy firsthand. These days, Edelenbos works as engineering coordinator for the Decco
Consortium, the preferred bidder to implement Cayman’s proposed integrated solid waste management system.
Edelenbos says that one valuable lesson learned from Bermuda’s experience is that waste management systems developed for large industrial communities may not necessarily satisfy, in a sustainable manner, the needs of a small island nation.
Based on his experiences, Edelenbos says public discourse often pits recycling and waste-to-energy facilities against each other. However, both are important aspects of Grand Cayman’s waste management hierarchy with decisions on specific materials weighed on a case-by-case basis.
In absence of a local market for recycled materials, Edelenbos notes that Bermuda opted to recycle non-combustible products and recover energy from the plastics and paper materials that could be processed through the waste-to-energy facility.
“Tin, glass and aluminium do not add calorific value to a waste-to-energy facility, so it is better for those items to be recycled,” he says.
It is estimated that less than 5 per cent of the more than 90,000 tonnes of garbage produced annually on Grand Cayman is currently recycled. This recycled amount is composed mostly of scrap metal, end-of-life vehicles and tyres. Less than 1 per cent is attributed to the household recycling depots.
The Decco Consortium will be responsible for developing a public communication plan to increase waste diversion in support of the new waste management strategy and given the challenges facing recycling in a remote small island, two other “Rs” in the waste management hierarchy — reduce and reuse — will gain importance over recycling.
Although a modern waste-to-energy facility has little in common with the older smoke-belching incinerators of the past, many people still conflate the two.
“It doesn’t help some people to know that half of the energy produced is green or that emissions of heavy metals including mercury, lead and cadmium, and particulate matter have been dramatically reduced since the implementation in the U.S. of Maximum Achievable Control Technology in the early 1990s,” Edelenbos says. “It can become an emotional topic because there is so much misinformation out there.”
Even the Tynes Bay Facility got off to a rocky start, having been delayed due to environmental concerns about air emissions and ash disposal versus the perceived benefits of recycling.
“That was when waste-to-energy was still in its infancy,” Edelenbos says. “Now we have the benefit of a lot more information and the experiences of other countries like Bermuda to learn from.”
DEALING WITH ASH
Of the total tonnage managed through a waste-to-energy facility, about 25 per cent (10 per cent volume) is discharged in the form of bottom ash and 3 per cent is discharged as fly ash or air pollution control residue. Bottom ash contains ferrous and valuable non-ferrous metals that can be removed and sold to overseas buyers, while the remaining bottom ash can be used as secondary aggregate in construction.
Although fly ash on its own is classified as a hazardous material, with further treatment, the ash can be safely disposed of in an engineered landfill or made suitable for use in concrete or asphalt.
In Bermuda, the fly ash and bottom ash are mixed with cement and poured into molds to produce cubic yard concrete-ash blocks. These blocks are utilised — after they are tested to demonstrate that contaminants are locked into the cement matrix and do not leach out into the marine environment — in foreshore protection at the marine fill site where other non-combustible materials are disposed of.